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RADIOTELEM ETRY N ETWO R KrNsrRuciloN MANUAL

9/95

CAMPBELL SCIENTIFIC, INC.

WARRANW AND ASSISTANCE

The RADIOTELEMETRY NETWORK is warranted by CAMPBELL SCIENTIFIC, lNC. to be free fromdefects in materials and workmanship under normal use and service for twelve (12) months f rom date ofshipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, lNC.'sobligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, lNC.'soption) defective products. The customer shall assume all costs of removing, reinstalling, and shippingdefective products to CAMPBELL SCIENTIFIC, lNC. CAMPBELL SCIENTIFIC, lNC. will return suchproducts by surface carrier prepaid. This warranty shall not apply to any CAMPBELL SCIENTIFIC, lNC.products which have been subjected to modification, misuse, neglect, accidents of nature, or shippingdamage. This warranty is in lieu of all other warranties, expressed or implied, including warranties ofmerchantability or fitness for a particular purpose. CAMPBELL SCIENTIFIC, lNC. is not liable for special,indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. To obtain a Returned Materials Authorization(RMA), contact CAMPBELL SCIENTIFIC, lNC., phone (435)753-2342. Atter an applications engineerdetermines the nature of the problem, an RMA number will be issued. Please write this number clearly onthe outside of the shipping container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC. INC.RMA#-815 West 1800 NorthLogan, Utah 84321-1784

CAMPBELL SCIENTIFIC, lNC. does not accept collect calls.

Non-warranty products returned for repair should be accompanied by a purchase order to cover the repair.

c^A.lvlPEtELL =iclENTlFlG, ll\c.a15 W. 1AOO N.Logan, UT 44321-1744USAPhone (435) 753-2342FAX (435) 7sO-954Oww.campbellsci.com

Edmonton, Alberta T5M 1W7CANADAPhone (4O3) 454-2505FAX (4O3) 454-2655

Shepshed, Leics. LE12 gALENGLANDPhone (44)-50960-1141FAX (44)-50960-1O91

Campbell Scientilic Canada Corp. Campbell Scientific Ltd.1 1564 - l 49th Street 14-20 Field Street

RADIOTELEM ETRY N ETWORK APPLICATIONSTABLE OF CONTENTS

PAGE

1. INTRODUCTION

1.1 lntroduction1.2 Field Station """""1-21 '3 Base station "

:.:::::::::....:.::.:::::.:.::.:..::::::::.:......::l:l-?1.4 Repeater

2. ASSEMBLTNG THE RADIOTELEMETRY NETWORK

2.1 Final Layout """""'2-12.2 lnstafl Base Station """""""""2-12.2.1 Base Station Hardware """"""2-12.2.2 PC2OB Datalogger Support Software.'... ""'2-12.g Install NearesiRepeaier/Field Station """"2-22.4 Test the Radiotelemetry Link """""""""""2-32.4.1 A SuccessfulTest.......... """""2-32.4.2 An UnsuccessfulTest """""""2-32.5 Troubleshooting Unsuccessf ul Communication Attempts .........'....'. """""""""'2-32.5'1Troub|eshootingPhysica|LinkBetweenBaseandFie|dStation2.5.2 Error Messages............. """""'2-42.5.g Troubleshooiing Communication with GT...... """"""""2-4

3. RADIOTELEMETRY NETWORK COMPONENTS

3.1 RF95 Modem............... """"""3-1g.2 RF100/RF200 Radios """""""3-53.3 Antennas and Cables. """""""3-7g.4 Tripods, Towers, Enclosures, and Power Supplies """'3-93.5 RF2g2 Base Station """""""'3-11

4. OPERATION OF THE RADIOTELEMETRY NETWORK

4.1 Monitoring and Collecting Data - PC2O8 RF Notes.'.' '.""""""""""'4-14.1.1 Collecting Data - Telcom-. """"'4-14.1.2 Generaldommunication - GT..'. """"""""'4-2

4.2 Datalogger lnitiated Communications........... """"""""'4-3

APPENDIX A. SETTING THE STATION 1D....'...'...... ..""""""""' A-1

APPENDIX B. ALTERNATE BASE STATION CONFIGURATIONS

8.1 The Portable Base Station """"' B-18.2 Phone-to-RF Base Station """"' B-18.3 Phoneto-RF Base Station with Measurement capability ....'.'........'... B-2

APPENDTX C. POWER CALCULATJObI.S..'..........'.'.'.. """"""""'c-1

RF MANUAL TABLE OF CONTENTS

APPENDIX D. FUNDAMENTALS OF RADIOTELEMETRY

D.1 Radio Waves................. ..........D-1D.2 Antennas .............. D-1D.3 RF95 Modem............... ...........D-2D.4 Transceiver ..........D-2

APPENDIX E. RF95 STATES

E.1 RFgs-ME States......... ............. E-1E.2 RF9S-SDC State.......... ........... E-1

APPENDIX F. EQUIPMENT COMPATIBILITY

F.1 Compatibility of Current and Past RF Equipment............... ............. F-1F.2 The "U" Command .................. F-1

APPENDIX G. PsO RADIO

G.1 P50 Radio Setup and Specificaitons................. ............G-1G.1.1 Volume Control ....G-1G.1.2 Squelch Control.. .....................G-1G.1.3 Frequency Switch........ ............G-1G.1.4 P50 Specifications................. .....................G-1G,2 AdditionalTroubleshooting for P50 Radios. ..................G-2

GLOSSARY ............. ... cLossARyLIST OF FIGURES

1-1 A Basic Radiotelemetry Network. ................1-11-2 A CR10 Field Station ................1-21-3 A Radiotelemetry Base Station ...................1-31-4 A Typical Repeater Station........ ..................1-43-1 The RF95 Modem ....................3-13-2 Setting the Station |D............... ...................3-23-3 RF100 On Bracket With Connector............ ...................3-63-4 The PD237 Crossover Plate Antenna Mount...... ...........3-73-5 The PD46 Clamp Mount......... .....................3-83-6 Type-NM (male), BNC, and Type-NF (female) Connectors. .............3-83-7 The RF232 Base Station ........3-113-8 Top View of the RF232 Base Station ........3-12B-1 Portable Base Station .............. B-1B-2 Phoneto-RF Base Station ......B'-2B-3 Phone-to-BF Base with Measurement Capability .........B'-2G-1 P50 Radio"Settings.....-... .........G-1

LIST OF TABLES

3-1 A Sample of Station lD Numbers and the Corresponding Switch Settings.............................3-23-2 RF95 Command Character Summary ........3-43-3 Summary of the Shutdown 8|ock...................i.i....;j.;.......... ..............3-53-4 Serial l/O Connector Description. ................3-53-5 RF100/RF200 Radio Specifications................. ..............3-6

RF MANUAL TABLE OF CONTENTS

3-6 Radio to RF Modem Pin Descriptions......'...'. """"""""'3-7g-7 Common Antennas and Characteristics ""'3-83-8 PS12LA Battery and AC Transformer secifications............... .........3-103-9 Pin Descriptionfor RF232's 25-Pin Port .....'...... """""3-113-10 RF2g2 Power conversions ""'3-11F-1 Different RF Setups.. """""""' F-1

LIST OF EXAMPLES

2-1 TELCOM Station File - RFTEST......'.'....... """"""""""2-23-1 A sampre setup Brock.......... ..

:..::.::::.:.:..:.::.:.:...:.::.:.:.::::.::.:.:.:.:.:.3:13-2 SampleShutdownBlock...'.'.'..4-1 Sample RF Path Destination. """""""""""4-24-2 Script File - Attended Data Collection..'.'........ """""""'4-24-g Script File - Unattended Data Collection ""'4-2F-1 Useof the "U" Command'. '""""""""" F-1

||t

SECTION 1. GENERAL RADIOTELEMETRY NETWORK

1.1 INTRODUCTIONData retrievalfrom a remote site can be difficult.To accomplish data collection from isolatedsites Campbell Scientific, Inc. utilizes aradiotelemetry network. Dataloggers can beaccessed by radiotelemetry which requires nophysical connection from the computer to thedatalogger. The radiotelemetry link reduces thenumber of visits to a remote site for datacollection.

The radiotelemetry network is designed forcomplete computer control. One computer canestablish communication with up to 254 remotesites. The PC208 Datalogger Support Softwareallows data collection from the datalogger,transmitting datalogger programs, anddisplaying current readings from the datalogger.

The requirements specific to a radiotelemetrynetwork include:

FIELD STATION

BASI STATTON (OFFTCE)

. The distance between radio stations shouldnot be greater than approximately 25 miles.

o The stations should not have majorobstacles between them, therefore, theyshould be within line-of-sight of each other.

The stations communicate over a radiofrequency which is specified in Megahertz(MHz). A data communication network musthave its own specific frequency to preventinterference from other sources. Typical radiofrequencies are either VHF (Very HighFrequency) ranging from approximately 130 to174 MHz or UHF (Ultra High Frequency)ranging from approximately 403 to 512 MHz. Atypical RF system is shown in Figure 1-1.

Telemetry network's three basic componentsare:

. Field Station

. Base Stationo Repeater Station

REPEATER

STATI ON

FIGURE 1-1. A Basic Radiotelemetry Network

1-1


1.2 FIELD STATIONPurpose: The field station is where the

measurements are made. TheCampbell Scientific dataloggerresides at this station taking thedesired measurements. Any fieldstation can also operate as arepeater. The only requirement isthat the station's antenna must beable to communicate in alldesireddirections. This may require anomnidirectional antenna.

ANTENNA

12X14 ENCLOSURE

Equipment Required:

PSl 2

CRl O

RF95

l\|\|\i i cRouNDlNC RoD

FIGURE 1-2. ACRl0 Field Staiion

o Radio. RF Modemo Antenna and antenna cableo Dataloggero Power supply, enclosure,

sensors, and mounting needs

LA

1-2

SECTION

1.3 BASE STATIONPurpose: A base station utilizes a computer

to collect data from the fieldstation(s). NormallY, allcommunication to the field stationsoriginate at the base station. Dataretrieval, remote Programming, andsystem analYsis can all be donefrom the bhse station.

FIGURE 1-3. A Radiotelemetry Base Station

1. GENERAL RADIOTELEMETRY NETWORK

Equipment Required:

o Radio. RF Base Stationo Computer with PC208 softwareo Antenna and antenna cable. AC Power

ANTENNA

PC2OB DATALOGGTRSUPPORT SOFTWARE

R5232CABLE

otr trtrtrtrtrtrtrctrBDDOOtr trDOtrDE -DEOtrtrODOtrtrD0f-l trtrDtrOO EtrtrtrOOtrOOtrtrO-J trtrtrtroo E=trtrtrtrooBEoo-l trtrnonn m m trCtrO

1-3


1.4 REPEATERPurpose: To act as relay between two

communicating stations separatedby too long of a distance or anobstacle which impedes directcommunication. A repeater is notalways required in a radiotelemetrynetwork. A field station can alsofunction as a repeater.

RF95

FIGURE 1-4. A Typical HepeaterStation

Equipment Required:

. Radio

. RF Modemo Antenna and antenna cableo 'l2V and 5V power supply

(PSs12M). Enclosure and other mounting

needs

TO ANTENNA

trctrtrtrtrtrD

DDtrtrODtrC

trtrtrtrotrtrDntrtrDtrotrDoo

1-4

l

SECTION 2. ASSEMBLING THE RADIOTELEMETRY NETWORK

This section provides a togical order for RF network assembly and deployment. Details of specific

components in the system are described in Section 3 "Radiotelemetry Network Components." Thiscomponent section is cross-referenced throughout this assembly section.

2.1 FINAL LAYOUTThe initial locations of the base, field, andrepeater stations have likely been determinedalready. Locate RF stations on an area map,preferably a topographic map. Draw a linealong every communication path. Each fieldstation must have a path connecting it back tothe base station. No path can be going througha mountain or large obstacle;this would negatethe line-of-sight requirement. A station mayneed to be moved or a repeater station mayneed to be added if this requirement is not met.

At each station there is an RF modem. Eachmodem requires a unique lD number (StationlD). The number may range from 0 to 255. Onthe map, labelthe base station as 254. Labelthe remaining stations with different lDnumbers. Later, each modem will be set withthe corresponding lD number. The Station lD,similar to a phone number, allows the basestation to call many different field stations.

2.2 INSTALL BASE STATION2.2.1 BASE STATION HARDWARE

The major component of the base station is theRF232 Base Station. Referto Section 3.5 forlocational drawings and a description of theRF232 Base Station.

1. Remove the top of the RF232 bYunscrewing the four screws on the sides.

2. Remove the radio and its cable from itsmounting bracket. Mount the radio directlyonto the bottom of the RF232. Secure theBNC connector from the radio's cable to itshole on the back of the RF232. See Figure3-7 tor assistance.

3. Connect the radio to 12 V, ground, and theRF Modem. The RF modem is locatedbehind the front panel above the "POWERON" light. See Figure 3-8 for assistance.

CAUTION: Radio transmission without anantenna connected can damage radio.

4. Mount the base station antenna in alocation that is higher than any surroundingbuildings or obstacles. Refer to Section 3.3for more information oh mounting theantenna.

5. After the antenna is mounted, connect thecoax cable between the antenna and theBNC connector mounted in SteP 2.

6. Replace the cover of the RF232.7. Connect a large gauge (approximately 8

AWG) copper wire from the antenna to agood earth ground. This is for lightningprotection. This is required for anyantenna, especially if the coax cable fromthe antenna goes inside a building.

8. Connect a 25-pin RS232 cable Jrom the .computer serial port to the RF232.

9. After verifying that the RF232 power switchis otf, plug in the RF232's walltransformer.

2.2.2 PC2O8 DATALOGGER SUPPORT SOFTWARE

Once the base station hardware is installed, thePC208 software must be setup to allowcommunications. lf PC208 is not installed onthe computer, you will need to install it byplacing the PC208 Disk 1 in the drive and typingINSTALL, preceded by the disk drive. Refer tothe PC208 Manual if you have questions aboutthe installation procedure or details on specificprograms included with PC208.

There are five main programs in PC208:

o TELCOM - Collects data from field stations.o GT - Used to troubleshoot, look at current

readings, and download programs.

. SPLIT - Generates repofts and reduces' data stored'ontomputer.

o EDLOG - Editor to aid in writing dataloggerprograms.

o SMCOM - Communicates with Campbell'sStorage Modules.

2-1


Ultimately, a TELCOM Station File is needed foreach field station to establish the communicationpaths and conditions for calling a particular fieldstation. Procedures for creating an RF TestStation File are explained in this section.

To set up a TELCOM Station File, type"TELCOM'at your DOS prompt. Enterthe filename "RFTEST/E" when asked for a station orscript file name. The "/E" is used to edit theStation File named "RFTEST." A menu ofparameters will then appear on the screen listingdatalogger type, collection method, etc. Thedefault values will be automatically listed after theparameter description. When the cursor is on avalue, pressing the space bar will toggle ditferentoptions for that particular parameter.

Following the Station File Example 2-1, changethe default values of the listed parameters tomatch your system. Some of the parametersrequire a number entry (e.9. the parameter'Primary call interval' simply needs a number ofminutes that is desired between calls). For theseparameters, just type over the default value whichis shown. After completing Station File RFTEST,your display should be similar to Example 2-1.Exceptions would include the datalogger type,date and time after'Next time to call.' Also,COMl under'lnterface Devices' may be COM2,3, or 4, depending on the address of the intendedserialpoft.

The RF Path at the bottom of the Station Filedesignates which field station to call. In theexample shown, the base station willcallthe fieldstation with a Station lD of 10. lf a repeater isneeded to contact Field Station 10, the repeater lD

must also be specified. For example, "RF Path:10F," would call Field Station 10 through awith a Station lD of 5. The "F" at the end of thePath will be explained later. The base station isnow ready to communicate with a field station.

2.3 INSTALL NEAREST REPEATEH/FIELD STATION

Now to install the nearest field station. lf itcommunicates with the base station via arepeater, the repeater station must also beinstalled.

Following is the order in which a general RFfield station should be installed. A repeaterstation is installed in the same order. Forinstructions on installing any particularcomponent, refer to either Section 3 of thismanual or the Weather Station Manual.

1. Tripod or tower2. Enclosure and datalogger - Turn on

datalogger.

3. Antenna - Orientate correctly; rememberdirection and polarization.

4. Solar Panel5. Power Supply6. Sensors7. RF Modem - Set the Station lD according to

the map.

8. Radio - Make sure to connect to RF Modemand to power supply.

Example 2-1. TELCOM Station File - RFTEST

Station File name: RFTESTDatalogger or Command Type: CR10 Security Code: 0

Fix Datalogger Clock Using PC Clock: NoFinal Storage Area to Collect From: 1st Area

Data Collection Method: Since Last Call; Append File;Nbr of arrays to Backup on First Call: 1

Data File Format: Comma Delineated ASCIIPrimary Call Interval (rninutes): 1

Recovery Call Interval#1 (minutes): 1Repetitions of Rdcovery Int€tval #1: ' 1Recovery Call lnterval#2 (minutes): 1

Maximum Time CallWillTake (minutes): 3Next Time to Call: 1'1118/93 0:13:10

Interface Devices:COM1 Baud Rate:9600RF Modem RF Path: 10 FEnd

^O = Save/Resume nP = Save/Done ESC = Abandon Edit

2-2

2.4 TEST THE RADIOTELEMETRY LINKWith the field station installed, return to thebase station for initial testing of thecommunication link. An RF link can also betested at the field site with a portable basestation; hardware requirements for the portablebase station are described in Appendix B.

The Station File RFTEST must first contain theproper RF path. Edit the Station File RFTESTby typing "TELCOM RFTEST/E", typing

u/E" '

after "RFTEST" puts you directly in the StationFile for editing. Repeatedly press [ENTER] untilthe cursor reaches the RF path. Enter theproper RF path to communicate with thedesired station. For help, refer to Example 4-1or the PC208 Manual.

After entering the'RF Path', press [CTRL] "P" tosave the Station File. TELCOM willautomatically call the field station after it issaved. lf evefihing is set up properly, the basestation willcallthe field station, receive adatalogger status line on the computer, collectany data that is in the datalogger, and receiveRLQA quality accumulators. The RLQAnumbers are explained in Section 3.1 "RF95Modem."

2.4.1 A SUCCESSFUL TEST

Two files are created by calling the station if theRF link was setup properly. One file isRFTEST.CQR which includes the RLQAnumbers (RF Link Quality Accumulators), andthe other is a data file named RFTEST.DAT.RFTEST.CQR willconsist of one line ofnumbers for each time the station was called.The first two numbers are the Julian date andtime of call, followed by three numbers for eachmodem in the link. lf there is no repeater in thelink, there will be eight numbers: one for date,one for time, three for the field station RFmodem, and three for the base station modem.The first number from each modem should besmall (close to 0), the second and thirdnumbers should be 102 (t70).

RFTEST.DAT willcontain the data, if any, thatwas collected from the datalogger' To callthesame field station again, simply type'TELCOMRFTESTiC." After the successful test, set upthe next nearest field station and test thatradiotelemetry link.


2.4.2 AN UNSUCCESSFUL TEST

When an RF test is unsuccessfulthere arethree ways to troubleshoot the system:

1. Verify everything is connected properly.See Section 2.5.1 lor more suggestions.

2. Use the error messages in the error file toidentify where the link is breaking down.See Section 2.5.21or more information.

3. Try communicating from the base station to' the field station, one step at a time to try toidentify where the link is breaking down.See Section 2.5.31or more information.

2.5 TROUBLESHOOTING UNSUCCESS-FU L COMMUNICATION ATTEMPTS

2.5.1 TROUBLESHOOTING PHYSICAL LINKBETWEEN BASE AND FIELD STATION

When communication is not established,troubleshooting begins with the simplest RF linkin the system, which is usually communicationwith the nearest field station. There is NOsubstitute for first checking the hardware 'connections, Station lDs, and everything listedin the previous section. Below are a fewadditional items to check:

1. Antenna is used in proximity of metal.2. Transmitting inside a building.3. Damaged or shorted cables.4. Bad or improper connections.5. Antenna frequency does not match the

radio frequency.

6. Base and field station radios aren't usingsame frequency.

7. Datalogger power drops below 9.6 Voltsduring RF transmission. Use dataloggerlnstruction 10 or volt meter.

lf the field station's RF95 Modem's CarrierDetect light goes on, then at least a signal isreaching the site. lf this occurs, check thefollowing:

1. RF modem's lD matches lD in the RF Path'2. Field station's radio and datalogger have

sufficient power.

3. Radio is connected to RF modem'4. RF modem is the only thing connected to

datalogge/s 9-Pin connector.


2.5.2 ERROR MESSAGES

An error file is created as a result ofcommunication problems. Each time acommunication error occurs, the message isstored in a file called FILENAME.ERR. Thefilename is the name of the Station File, in thiscase RFTEST.ERR. Listed in the error file willbe the date and time the error occurred alongwith the error message. As errors occur, theyare appended to the existing error file.

One possible error message is "Communicationnot established with RF Modem." In this casecheck the following items:

1. RF232 Base Station plugged into computerand walloutlet?

2. RF232 Power Switch turned on?3. Does the TELCOM Station File match

Example 2-1?

4. ls the proper COM port specified in theStation File?

5. ls the SC12 9-pin ribbon cable inside theRF232 connected from the smallcircuitboard to the RF95 Modem?

Another possible error message is "RF ModemSet Link Failed" which is seen after the softwareattempts to establish communication threetimes. In this case, check the following items:

1. Are the radios plugged into the RFmodems?

2. Are the radios connected to power?3. Verify that nothing else but an RF modem is

connected to the datalogger's 9-pinconnector.

4. Are Station lDs set properly in the RFModems?

5. ls the 'RF Path' in the Station File correct?6. Are the antennas oriented correctly?7. Check all antenna cable connections.8. Turn radio otf. Unplug the SC12 9-pin

ribbon cdble from lheHF95 in the RF232,'reconnect the SC12 cable and watch thecarrier detect light. Does the light stay onfor one second, off for one second, on forone second, and then off? lf not, the RF95could have bad RAM or ROM. Also checkthe field/repeater station modems.

9. ls the field station datalogger turned on anddoes it have sutficient power?

The error message "RF Modem Does NotRespond" can occur if communication is notreturned to the base station. Check thefollowing items:

1, Are all RF Modems connected to radios anddataloggers?

2. Are the antennas oriented properly?3. ls the SDC switch open?4, ls the proper COM port being specified?

2.5.3 TROUBLESHOOTING COMMUNICATIONWITH GT

GT is the general purpose communicationpackage. Unlike TELCOM, GT does not alwaysautomatically set up or shut down an RF link.The advantage of GT is that it is possible to tryand retry the individual steps successively byusing the Terminal Emulator option.

GT uses portions of the Station File alreadysetup in TELCOM. To edit the GT Station Filetype "GT name/E" where "name" is the StationFile name; in this case it is RFTEST. Be surethe correct COM port and RF path are entered.After corrections are made, save the StationFile and a list of options will appear. Option T(Terminal Emulator) is the option to use fortroubleshooting.

A general understanding of the communicationsequences is necessary to properly trouble-shoot an RF link. The base station RF modem(RF95) is called the Start Of Link modem, orSOL modem. The field station RF modem iscalled the End Of Link modem, or EOL modem.When powered up,lhe SOL modemimmediately goes into a Wait Mode. The RF95Modem has five different modes of operation;these are described in Section 3 of this manual.

At the main GT menu, chose Option T to go into....the Terminal.Emulator Mode. Once you are in

Terminal Emulator Mode, try the followingTASKs in order.

TASK A: Press [ENTER] a few times, to setthe baud rate between the Base Station's RFmodem and the computer. This baud rate canbe set at 300, 1200, or 9600 baud.

2-4

RESPONSE lF SUCCESSFUL: "!" PromPtgiven, SOL modem is now in the LocalCommand Mode.

Things to check if TASK A is unsuccessful:

1. Communication port (COM port) could beconf igured improPerlY.

2. The wrong COM port may be specified inthe Station File.

3. Computer mouse driver could be intederingwith COM port.

4. The base station or radio may not bepowered sufficiently.

5. The radio and RF modem maY not beconnected properlY.

TASK B: The RF link must first be set up; enterthe 'RF Path' for communication with that fieldstation. For example, uss 8F'communicates toa field station with a Station lD of 8 through arepeater with an lD of 5. After typing the 'RFPath', press [ENTER].

RESPONSE lF SUCCESSFUL: "$" promptgiven.

Things to check if TASK B is unsuccessful:

1. lmproper antenna orientation.2. Bad connections on the antenna cables.3. Insufficient current supply at the base

station.

4. Field station radio and RF modem may notbe connected properlY.

5. Field station radio is not connected topower.

6. Field station RF modem is not receiving 5Volts from datalogger connection on pin 1of the 9-pin cable.


TASK C: Establish link and baud rate betweenRF Modem and Datalogger by slowly pressing

IENTERI a few times.

RESPONSE lF SUCCESSFUL: "*" fromdatalogger.

Things to check if TASK C is unsuccessful:

1. Datalogger is on and has sutficient power.2. Datalogger does not think it is still com-

municating with some other device like akeyboard or phone modem.

3. Datalogger and RF Modem are the onlydevices connected together on the 9-pinconnections.

Upon successfulcompletion of TASK C, thedatalogger is now in standard Telecom-munications Mode. See Section 5 of thedatalogger manualfor more information aboutthe Telecommunication mode. At this point theSOL modem and EOL modem willbe in theTransparent Mode of operation. Type I'A," wait,and then type [ENTER]to receive a dataloggerstatus sequence from the datalogger. lfeverything is successful, type [CTRL] "-" ot[ESC], then "Q" to quit.

2-5

SECTION 3. RADIOTELEMETRY NETWORK COMPONENTS

3.1 RF95 MODEMThe RF95 is an interface between the computerand the radio when used at a base station, andan interface between the radio and the data-logger at a field station. In a repeater station,the RF95 is an interface between two othercommunication stations.

The RF95 replaces CampbellScientific's oldDC95 and SDC RF Modems. The RF95 iscompatible with both the DC95 and SDCModems. Refer to Appendix F "EquipmentCompatibility" for cornpatibility considerations.

3.1.1 PHYSICAL DESCRIPTION

The front panel of the RF95 is shown in Figure3-1. There are two ports for intedacing externaldevices. The port labeled TRANSCEIVERconnects to the radio, and the port labeledSERIAL l/O connects to the datalogger,PS512M or CH512R in the case of a repeater orphone-to-RF base station. The red light labeledCARRIER DETECT is used primarily to indicatewhen a carrier frequency has been detected bythe radio. This is explained later in furtherdetail.

3.1.2 RF95 STATES

The RF95 Modem operates in one of twoseparate states. The RF95 can be utilized ineither the RF95-ME (Modem Enable) state orthe RF95-SDC (Synchronous Device Com-munication) state. The proper state must bedetermined before employing the RF95 in thefield. A switch inside the RF95 needs to be setaccordingly.

The RF95-ME state is always used with 21Xand CR7 dataloggers. The RF9S-ME state isnormally used with CR10s, also. The CR10 canalso use the RF95-SDC state. The CR10combined with the RF95 in the RF95-SDC statehas the advantage that a phone-to-RF basestation can have measurement capability. Only'the RF95 at a phone-to-RF base station needsto be switched to the RF9S-SDC state.

A switch with nine different dip switches isinside the RF95;the RF95 cover must beremoved to locate the switch. The ninth switchsets the RF95 state. The RF95-ME state ischosen by setting the ninth dip switch open,represented by 1. The RF95-SDC state ischosen by setting the ninth dip switch closed,represented by 0. Refer to Figure 3-2.

FIGURE 3-1. The RF95 Modem!4_;r:r:ii-

3-1


TABLE 3-1. A Sample of Station lD Numbersand the Corresponding Switch Settings

StationID

0102030405060708090

100110120130

000001010010011100010100001 101 10000001010010011100010100

0000x0000x1000x1000x0100x1 100x1 100x0010x1010x1010x01 10x01 10x1110X0001x

Switch Settings1234 56789

* Station lD 255 is reserued forphone-to- RF base stations.

The RF95 is shipped with the switch set for theRF95-ME state.

Further information on the RF95 compatibilitywith older CampbellScientific equipment can befound in Appendix F "Equipment Compatibility."

3.1.3 SETTING STATION ID

Each RF95, including the one in the RF basestation, must have a unique Station lD. Thestation lD is similar to a phone number. Thisallows one base station to communicate withany one particular field station.

The Station lD can be any number from 1 to255, the Station lD is set with the switch insidethe RF95. The first eight dip switches are usedto set the Station lD. Table 3-1 shows theswitch settings for several Station lD numbers,Appendix A shows all possible Station lDnumbers. The dip switches can either be open,represented by 1, or closed, represented by 0;X in Table 3-1 refers to "donlt care.'1 The ninthdip switch is set according to the desired RF95state, see Section 3.1.2 "RF95 States." AllRF95s are shipped with a Station lD of 1 andare set in the RF95-ME state. RF95s inside theRF base station ship with a station lD of 254.

3-2

BINARY I.D. SWITCH BITSSTATE SWITCH BIT 9

O SYNCHRONOUS,I MODEM

LEAST SIGNIFICANT BI

g-l

il

t\t)_s'

-bt(

_l1

12J4

!TITTL]L]i

5

ntlnLl

OPEN

678tnltHnILIL]

FIGURE 3-2. Setting the Station lD

3.1.4 THE CARRIER DETECT LIGHT

The Carrier Detect light on the front panel of theRF95 has several purposes. The primaryfunction of the light is to indicate when data isbeing received or transmitted. The light will stayon when a network frequency originating fromanother RF95 is detected. lf a signal isdetected which isn't intended for that station, thelight will shut off after about two-tenths of asecond.

The Carrier Detect light can also be used tocheck the RAM (Random Access Memory) andROM (Read Only Memory) of the RF95. Withthe radio disconnected and the datalogger inthe LOG (*0) Mode, connect the datalogger tothe RF95 Serial l/O Port with a 9-pin ribboncable. The sequence of the light flashing afterconnection indicates the RAM and ROM status.

Both the RAM and ROM are good if the lightgoes on for one second, off for one second, andthen back on for one second. The RAM isfaulty if the light is on for one half second andoff for one half second, continuously. The ROMis faulty if the light goes on for one second, offfor one half second, on for one half second, andthen off for one half second, continuously.

3.1.5 DATA TRANSFER RATE

The data transfer rate is the time it takes to getdata from the datalogger to the computer. In' 'general, datacan'betransfened at a rate ofabout 30 data points/second (60 bytes/second)without a repeater. lf a repeater is used, anapproximate data transfer rate is 22 datapoints/second.

3.1.6 RF95 MODEM COMMUNICATIONPROTOCOL

Comprehension of this section is notnecessary for routine operation of the RF95Modem. The PC208 Datalogger SupportSoftware accounts for the necessarycommu nication Protocol.

There must be an RF95 Modem at both thecalling (or computer) end of the transmissionlink, and at the answer (or datalogger) end ofthe transmission link. The modem at the callingend is the Start Of Link (SOL) modem, and themodem at the answer end is the End Of Link(EOL) modem.

RF95 Modems must also be used at repeaterstations. These RF95 Modems are termedMiddle Of Link (MOL) modems.

Five general modes of operation of the RF95Modem are:

o Wait Mode. LocalCommand Mode. Repeater Mode. End of Link Modeo Transparent Mode.The RF95 is in the Wait Mode of operationwhen it is waiting to enter one of the four othermodes of operation. The Wait Mode is entered1) after the power-up sequence is completed, 2)following the "T" command when in the LocalCommand Mode, and 3) when the system isreset by the Time-out Timer. The Time-outTimer is a 60-second timer which is set everytime a valid transmission block is received onthe RF link. The datalogger, being inTelecommunications Mode, will override theTime-out Timer.

The Local Command Mode is used to set upand shut down an RF link. The LocalCommand Mode is entered when thedatalogger goes into Telecommunications Modeafter being in the Wait Mode. ln this mode theRF95 responds to command charactersreceived on the Serial liO Port.

The RF95 is in the Transparent Mode after theRF link has been established. In theTransparent Mode, any data received on theSerial l/O port are organized into data blocks fortransfer through the RF link.


The Repeater Mode is entered by MOL RF95Modems. The function of the Repeater Mode isto receive and then transmit data blocks. Thesignature of each data block is checked beforebeing sent to the next RF station. The block isdiscarded if the signature of the data block isincorrect. The RF95 enters the Repeater Modewhen it receives a valid setup block that setsthe RF95 as a repeater.

The End Of Link Mode is entered when theRF95 receives a valid setup block that sets theRF95 as the EOL modem. Upon entering theEOL Mode, the RF95 brings the Serial l/O Ringline high which raises the datalogger ME line,thus causing the RF95 to enter the TransparentMode. The Ring line is reset after the ME linecomes high.

3.1.7 RF95 Modem and the RF Link

The RF link is the communication path which isopened between the Start Of Link modem andthe End Of Link modem, along with any MiddleOf Link modems. Any RF link must first beestablished, then maintained, and finally shutdown.

When collecting data, TELCOM establishes,maintains, and shuts down the RF link asdiscussed below.

3.1.7.1 Establishing the RF Link

The SOL RF95 is first brought into the LocalCommand Mode of operation. In the RF95-MEState, this is done when the ME line is high onthe Serial l/O port and the SOL modem is in theWait Mode of operation. After the ME line isbrought high, the baud rate of the SOL modemis set by repetitively pressing [ENTER]. TheSOL modem can operate at 300, 1200, or 9600baud. When the baud rate is set, the SOLmodem will respond by sending a carriagereturn line feed (CR-LF) and an exclamationpoint (!). In the RF95-SDC State, the Loca'Command Mode is entered after addressing.Some explanation is contained in Appendix E..xFlF95€tates."'

In the Local Command Mode, the SOL modemresponds to command characters received fromthe terminal or computer. The commandcharacters are summarized in Table 3-2. Allcommand characters must be capital letters.

3-3

CommandE


TABLE 3-2. RF95 CommandCharacter Summary

xxx and Wy are numbers from 1 to 255,inclusive. The user can have up to 12 repeatersin any RF link. Example 3-1 shows the setupblock for an RF link which will communicatethrough three repeaters to an EOL modem, withStation lD numbers of 10, 25, 50, and 30,respectively. The Fast Command is used tospeed data transfer.

EXAMPLE 3-1. A Sample Setup Block

s10 25 50 30F

Notice that it is not necessary to include thestation lD of the SOL modem.

Press [ENTER]following the setup string ofstation lDs to transmit the setup block. Whenthe RF link is established, a verification block issent from the EOL modem to the SOL modem.Upon receiving this verification block, the SOLmodem and EOL modem have entered theTransparent Mode of operation. At this point,the dollar sign prompt "$" will be returned to thecomputer screen. The datalogger connected tothe EOL modem is now in the Telecommuni-cations Mode and will respond to the standarddatalogger telecommunications commands. lfthe verification block does not return shortly,pressing IENTER]will cause the SOL modem toreturn to the Local Command Mode.

3.1.7.2 Maintaining the RF Link

Data can be transferred once the RF link isestablished. Data blocks are created andtransmitted by the SOL and EOL modemsto the following two rules. First, characters receion the Serial l/O port are placed into data blocks238 characters each. The block is then closedtransmitted. Any remaining or new charactersreceived at this point are placed into a new datablock. Second, if during this loading process aof 290 ms occurs between characters, the datawillbe closed and transmitted.

Most of the time, the SOL modem will becommand strings which will be answered by themodem and the datalogger. The response fromdatalogger is not instantaneous. lf a command

',sentbefore tlre response from the previouscommand has been received, the currentwill be sent and a possible collision of the RF simay occur. This results in a loss of the responseand the current command. The general rule isthe person sending characters should wait forresponse to come back before issuing lurthercommands.

DescriotionExit Link Command. The "E"command causes the dataloggerto drop its ME line and shutdown the RF link.Fast Command. The "F"Command is placed at the endof the string of setup numbers.In the RFgs-ME State, the Seriall/O port of the EOL modem willcommunicate with thedatalogger at 9600 baud with the"F" Command. In the RF95-SDC State, the baud rate fromthe computer to the SOLmodem will be 9600.Read Command. The "R"Command reads back theShutdown Block.Link Setup Command. The LinkSetup Command is followed bya string of setup numbersrepresenting the lD numbers ofthe modems in the RF link.Terminate Command. The "T"Command will reset the SOLmodem to the Wait Mode ofoperation.Old Link Command. The "U"Command willforce RFcommunication between radiosto 2400 baud rather than 3000baud. DC95s purchased beforeFebruary 1989 can only be usedal 24Q0 baud. For furtherinformation see Appendix F.Wait Command. The "W"Command willforce the RFmodem to wait unit there is nocarrier detect bef ore transmitting.

F

R

T

U

W

where:

XXX =

The first step in setting up an RF link, once inthe Local Command Mode, is to create a setupblock using the "S" command. The setup stringis entered via the computer as follows:

W=

3-4

Sxxx yyy

lD number of the RF95 which isacting as the repeater in the link.lf no repeater is used then xxx isomitted.

lD number of the EOL modem.

I

3.1.7.3 Shutting Down the RF Link

Sending the "E" character to a dataloggercauses the datalogger to drop its ME line, whichcauses a shutdown of the RF link.

A shutdown block is created by the EOLmodem which can be sent to the computer asan indicator of communication quality. Theshutdown block consists of three RF LinkQuality Accumulators (RLQA). Each RF95 inthe link will have three RLQAs which areappended to the shutdown block. The RLQAfrom each RF95 are representative of the activeperiod of the link. The first three RLQAsrepresent the EOL modem connected to thedatalogger, the following sets of numbers will befor any MOL modems (in order of occurrencefrom the EOL modem), and last will be the SOLmodem. A description of the shutdown block iscontained in Table 3-3.

TABLE 3-3. Summary of the ShutdownBlock

xxxxYw zzzz

= Number ofcommunication failures.

= Noise level indicator.= Noise level indicator.

A communication failure occurs when asignature of a block of data doesn't match itsoriginal signature. These blocks aresubsequently retransmitted. The noise levelindicators should be 102 (170) at the standard3.OK baud rate, or 124 (!7O) at 2.4K baud.

The noise level indicators are reset andsubsequently become active in the respectiveEOL and SOL modems as the TransparentMode is entered (immediately after setup). TheMOL modems are reset and become activewhen the setup block is propagated to the nextstation in the RF link.

After the "E" character is received by thedatalogger a CR-LF is sent through the RF linkto the SOL modem. The shutdown blockfollows after a one second delay. When theshutdown bloik is rdceived and veffied thd'SOL'"modem will leave the Transparent Mode and re-enter the Local Command Mode, indicated bysending an exclamation point (!) to thecomputer.

The shutdown block can be viewed by sending ...the "R" command. Example 3-2 illustrates ashutdown block for three RF95s.

SECTION 3. RADTOTELEMETRY NETWORK COMPONENTS

EXAMPLE 3-2. Sample Shutdown Block

!REOL modem - > 0004 0110 0097MOL modem - > 0002 0108 0090SOL modem - > 0000 0105 0093!

The first line of numbers, which are the firstthree RLQAs, represent the EOL modem. TheSecond line repiesents a MOL modem, and lastis the RLQAs for the SOL modem. The 0004indicates that four interruptions occurred on theEOL modem while the link was active.Interruptions are non-data blocks such as voicetransmissions on the same carrier frequency.All noise level indicators are within acceptablebounds in this example.

The "T" command should now be used to resetthe SOL modem to the Wait Mode of operation.This step should not be done if further calls aregoing to be made through a phone modem.

3.1.8 RF95 CONNECTIONS

The 9-pin Serial l/O connector is normally usedto connect the RF95 to the datalogger, PS512Mor CH512R. Table 3-4 describes the 9-pinconnections. The 1O-pin rectangular connectoris for connection to the transceiver. Table 3-6contains the pinout for the radio to modemcable descriptions.

TABLE 3-4. Serial UO Connector Description

Yfwzzzz

Pin

1

23456789

Description

+5 V: Supply from external sourceGND: GroundRing: Ring to dataloggerRXD: Transmit from RF95ME: Modem Enable from dataloggerPrinter Enable: Not usedUnload Enable: Not usedTape Enable: Not usedTXD: Received by RF95

3.2 RFlOO/RF2OO RADIOS3.2:1'RADIO'tlESeRlPTlON

The RF100 and RF200 are used in CampbellScientific's RF applications to transmit andreceive data blocks. The radios are shippedfrom Campbell Scientific secured on a mountingbracket designed to fasten on the top of the RFmodem (see Figure 3-3).

3-5


FIGURE 3-3. RF100 On Bracket With Connector

The mounting bracket also supports a BNCJack connector from the radio. The coax cablethat is required to connect the radio to itsantenna should be connected to the radio at thisBNC connector. See Section 3.3 for moreinformation on the antenna cable.

The RF100/RF200 Radios are connected to theRF modem by a special radio cable. The first1O-pin connector on this radio cable has a redand black wire coming out of the connector.This is the 1O-pin connector (labeled "radio")that should be connected to the radio. The red

and black power wires should be connected to12V and Ground respectlully. The second 10-pin connector (labled "RF modem") should beconnected to the RF modem. Table 3-6contains the pin out of this radio cable.

3.2.2 RADIO SPECIFICATIONS

The RF100 and RF200 radios are manu-factured by E.F. Johnson. Campbell Scientificmodifies the radios to work with the RF95Modem. Table 3-5 contains a list of the mainradio specifications.

Rr1 00OR

RT2OO

E.F. Johnson Model No.Power OutputFrequency (MHz).

Channel CapabilityDimensions (w/o mounting)Operating Temperature RangeEmissions DesignatorDeviation

Current DrainQuiescentActive

TABLE 3-5. RFl00/RF200 Radio Specitications

RFlOOVHF

34204W132-142, 142-150,150-162, 162-1741

3.6" x2.9" x2.2"-30"C to +60"C16KOF2D+ 2.5 kHz

30mA1.7 A

RF2OOUHF

34105W403-430, 430-450,450-470,470-5121

3.6" x2.9" x2.2"-30"C to +60"C16KOF2D+ 2.5kHz

30mA1.5 A

. DOC Compliance tor 138-174 MHz and 403-470 MHz only.

3-6

TABLE 3€. Radio to RF Modem PinDescriptions

RF100/RF200Radio 1O-pin

1

23 +12V (Red)4567I9 GND (Black)

10

RF95 RFModem 1O-oin

73

open (4)6I925

open (10)1

3.2.3 RADIO INSTALLATION

The RF100 and RF200 Radios are shippedfrom CampbellScientific mounted on a specialbracket with a cable going from the radio to aBNC connector (see Figure 3-3). The followingsteps will install a radio for a field or repeaterstation.

1. Secure the radio and its bracket using thefour screws from the RF95 Modem's lid.

2. Connect the 1O-pin connector (with the redand black power leads coming out of it) ofthe radio/RF modem cable into the radio.

3. Connect the second 1O-pin connector of thecable into the RF modem.

4. Connect the red and black power leadsfrom the radio cable to the 12V and Ground.

5. Route the BNC end of the antenna cablethrough the enclosure conduit. Connect thecable to the BNC Jack connector securedon the radio mounting bracket.

3.3 ANTENNAS AND CABLESAntennas radiate and receive the radio signals.Each radio in a radiotelemetry system musthave an antenna. Coax cable is used toconnect the antenna to the radio.

3.3.1 ANTENNA.MOUNTS

Antennas must be mounted above anysurrounding buildings or obstacles. Antennasmust be properly oriented in relationship to theother antennas for RF communications to work.Antennas have various mounting options.Table 3-7 lists mounting specifications forseveral common Celwave antennas. Specificquestions regarding antennas can be directed


to Campbell Scientific, Inc. or Celwave.Celwave's address and phone numbers are:

CelwaveRoute 79Marlboro, NJ 07746(908) 462-1880 or (800) 321-4700FAX (908) 462-6919

3.3.2 ANTENNA ORIENTATION

Antennas must be oriented correctly to allowcommunication between RF sites. Firstdetermine if your antenna is omnidirectional orunidirectional.

An omnidirectional antenna will transmiUreceive in a full 360 degree circle. Generally, anomnidirectionalantenna will be a straightcylindrical rod which is to be mounted verticallyat the top of a tripod.

A unidirectional antenna is designed totransmiUreceive in a particular direction, or in aspecified sector. There are various shapes ofunidirectional antennas. The most common isthe Yagiantenna (see Figure 1-2). Theelements of a Yagiantenna can be mountedeither veftically or horizontally, corresponding toeither vertical or horizontal polarization.

FIGURE 3-4. The PO237 Crossover PlateAntenna Mount

Normally, allantennas will be mounted withvertical polarization. Whichever polarization isused, be sure to keep antennas at all sitesidentically polarized.

3-7


3,3.3 ANTENNA CABLES AND CONNECTORS

The most common cable type to connect aradio to the antenna is a coaxial RG-8A/Ucable. Two connectors are required for eachlength of cable. The connector for the radio is aBNC type connector. The connector for theantenna is usually either a Type-NM or Type-NF. The BNC, Type-NM, and Type-NFconnectors are shown in Figure 3-6. The Type-NM (male) connector is for antennas with afemale receptacle, and Type-NF (female) forantennas with male receptacles.

A CampbellScientific antenna cable completewith connectors is specified as either COAXNM-L or COAX NF-L. COAX NF-L is a coaxialRG-8A/U cable with a BNC connector on oneend and a Type-NF connector on the other.See Table 3-7 for cable requirements forcommon antennas.

Due to power loss through the cable, the lengthof coax cable cannot be extended to anydesired length. The amount of power loss isdependent on the radio frequency. RG-8A/U willlose approximately 3.1 dB/100 ft. at 200 MHzand 5.0 dB/100 ft. at 400 MHz. Power losscalculations are reviewed in Appendix C.

TABLE 3-7 Common Antennas and Characteristics

FIGURE 3-5. The PD46 Clamp Mount

TYPT_NM BNC CONNICTOR TYPE-NFFIGURE 3-6. Type-NM (male), BNC, and

Type-NF (female) Connectors

AntennaVHF orUHF Cable

Pipeo.D.

MountingT

8A10108A1012BA13128A60128A61 1 0

8A6312PD2OOPD2O1PD22OPD344

PD39OSPD4OOPD688SPD1 107PDI 121

Omni VHFOmni VHFOmni VHFOmni UHFOmni UHFOmni UHFOmni VHFOmni UHFOmni 'VHFDipole VHFYagiOmniYagiOmni

U-BoltsU-BoltsU-BoltsU-BoltsU-Bolts

U-BoltsPD46 (Fig 3'5)PDa6 (Fig 3-5)PD46 (Fig 3-s)Clamps

PD37 (Fig 3-a)PDa6 (Fis 3-s)U-BoltsPDa6 (Fis 3-s)Clamps

VHFVHFUHFVHFVHF

Coax NM-L UnityCoax NM-L UnityCoax NM-L 3.0Coax NM-L UnityCoax NM-L UnityCoax NM-L 3.0Coax NF-L 5,8Coax NF-L 5.0Coax NF-L ' "'5.2ttCoax NF-L 4.5Coax NF-L 8.0Coax NM-L 7.5Coax NF-L 10.0Coax NF-L 3.0Coax NF-L 3.0

314', - 2118',1" - 2114"1',-2114',1', - 2114',314" -2118"

'l' - 2'll4'1" - 2314"1" - 23/4',1" - 23/4"2112',

1 5/16, 21/4, or 23181', - 2314',1 5/16" -2114"1', - 2314',2112"

3-8

3.4 TRIPODS, TOWERS, ENCLOSURES,AND POWER SUPPLIES

There are several methods of mounting andhousing sensors and other equipment for astation.

3.4.1 TRIPODS AND TOWERS FOR MOUNTING

For the different mounting requirements,Campbell Scientific offers the CM6 Tripod,CM10 Tripod, UT3 Tower, and UT930 Tower.All mounting options available from CampbellScientific are rugged instrument mounts thatprovide sturdy support for Campbell Scientificsensors, enclosures, and measurementelectronics. The CM6 and CM10 Tripods canbe used as a portable instrument mount in avariety of applications. The UT3 and UT930Towers provide a more sturdy long-termsupport

3.4.2 ENCLOSURES

Enclosures are needed to keep water anddebris from damaging the data acquisitionequipment. Campbell Scientific, Inc. enclosuresare designated as "raintight," and are designedto mount on a tripod. Following is a descriptionof the standard enclosures.

3.4.2.1 CRl0 and 21X Enclosures

Campbell Scientific offers two enclosures forhousing a CR10 or 21X and peripherals. Thefiberglass enclosures are classified as NEMA4X (water-ti g ht, d ust-tight, corrosion- resistant,indoor and outdoor use). A 1.25" diameterentry/exit port is located at the bottom of theenclosure for routing cables and wires. Theenclosure door can be fastened with the claspfor easy access. The enclosure's clasp doorcan be secured with a basic lock. Bothenclosures are white for reflecting solarradiation, reducing the internal temperatu re.

The Model ENC 12l14 fiberglass enclosurehouses the CR10 and power supply, and one ormore peripherals. Inside dimensions of theENC 12/14 are 14" x 12" x 5.5", outsidedimensions are 18" x'13.3'x 8.13" (withbrackets); weight is 11.16 lbs.

The model ENC 16/18 fiberglass enclosurehouses the CR10 and power supply, and two ormore peripherals. Inside dimensions of theENC 16/18 are 18" x 16" x 8.5." Outsidedimensions are21.75" x21" x 11" (withbrackets); weight is 17.2 lbs.


3.4.2.2 CR7 Enclosures

Most CR7 radiotelemetry applications havespecial needs depending on the individualsystem. The ENC-24 is normally used in CR7RF applications. Contact Campbell Scientific'scustomer seruice department for specialapplications.

3.4.3 POWER SUPPLY

A radiotelemetry network requires a reliablepower supply at each station. A solar panel or11Ol22O VAC charging source is normallyrequired due to the large current drain of theradio.

3.4.3.1 Lead Acid Batteries

Lead acid batteries are designed to be floatcharged by a solar panel or AC power source.The role of the lead acid battery is to supplypower when the charging source is absent, e.g.in case of power failures (AC charging), orduring times of zero charge with a solar panel.

21XL and CR7 lead acid batteries do not havethe required capacity for a typical RF station,they are only 2.5 Amp-hour batteries.Generally, we recommend a minimum of 5Amp-hour batteries for RF applications.

3.4.3.2 PSl2LA Lead Acid Power Supply

The PS12LA power supply includes a 12Y ,7 .OAmp-hour lead acid battery, AC transformer,and a temperature-compensated chargingcircuit with a charge indicating diode. An ACtransformer or solar panel should always beconnected to the PS12. The charging sourcetrickle charges the lead acid batteries whichpower the datalogger. The internal lead acidbattery continues to power the datalogger if thecharging source is interrupted. The PS12LAspecifications are given in Table 3-8.

The two leads from the charging source can beinserted into either of the CHG ports, polaritydoesn't matter. A tranzorb provides transientprotection to the charging circuit. A sustainedinput voltage in excess of 40V will cause thetranzorb to limit voltage.

Some solar panels are supplied with aconnector. This connector must be clipped offso the two wires can be inserted into the twoterrninalports.

3-9


The red charge light is on when AC power or asolar panel is connected to the PS12. lf theinput voltage is high enough, the battery willcharge even when the datalogger is on.

3.4.3.3 PS512M Voltage Regulator with NullModem Ports.

The PS512M 12 Volt Lead Acid Power Supplywith Charging Regulator and Null Modem Portsis used when 5 Volts is needed to powerexternal modems besides the capabilities of thePS12LA. The PS512M supplies 5 Volts to pin 1of the 9-pin null modem ports, otherwise thecapabilities and functions are identicalto thePS12LA. A common use for the PS512M is inradiotelemetry networks. The PS12LA cannotbe modified to the PS512M. The maximumcurrent drain on the 5 Volt supply of thePS512M is 150 mA.

3.5 RF232 BASE STATION3.5.1 RF232 INTRODUCTION

The RF232 Base Station provides a "single box"desktop base station with the following features:

. lnternal RF modem.o 25-pin RS232 port for connection to IBM

PC.

o 110 VACl12 VDC transformer and mountfor the base radio.

. Easy access to radio for antenna cableconnection.

The RF232 Base Station includes an RFModem with a carrier detect light. The RFModem sits directly behind the RF232 frontpanel. For a description of the Carrier DetectLight and the communication protocol, refer toSection 3.1. The RF Modem comes shippedfrom the factory with a Station lD number of254. Under most circumstances there is noneed to change this address.

The RF232's 25-pin female port connects to thecomputer's 25-pin RS232 port. The RF232's25-pin port is configured as Data Communi-cations Equipment (DCE) for direct cableconnection to Data Terminal Equipment (DTE),such as an IBM-PC serial port. Table 3-9shows the pin descriptign.

CAUTION: Switch the power to OFFbefore disconnecting or connecting thepower leads to the Wiring Panel. TheWiring Paneland PS12LA are at powerground. lf 12V is shorted to either of these,excessive current will be drawn until thethermalfuse opens.

The external port, labeled EXT, is not meant tobe used with the PS12LA. The primary powersource is the charging source, and thesecondary power source is the internal leadacid battery. Connecting a lead acid battery tothe external source is the same as connectingtwo lead acid batteries in parallel, causing onebattery to drop voltage and the other to raisevoltage. Alkaline batteries connected to theexternal port would be charged by the chargingsource, which can cause an explosion.

CAUTION: Do not use the external port,labeled EXT, with the PS12LA.

Monitor the power supply using dataloggerInstruction 10. Users are strongly advised toincorporate this instruction into their dataacquisition programs to keep track of the stateof the power supply. lf the system voltage levelconsistently decreases through time, someelement(s) of the charging system has failed.Instruction 10 measures the voltage of the leadacid battery. External power sources must bedisconnected from the CR10 and chargingcircuit in order to measure the actual lead acidbattery voltage.

TABLE 3-8. PSl2LA Battery and ACTransformer Specif ications

Lead Acid BatteryBattery typeFloat life @ 25"CCapacityShelf life, fullchargeCharge time, (AC Source)

AC TransformerInput:lsolated output:

Yuasa NA 7-125 years typical7.0 Amp-hourCheck twice yearly40 hr. fullcharge2Q hr.95"/o charge

120V AC, 60 Hz18V AC @ 880 mAmax.

3-10


3.5.2 220,230, AND 240VAC CONVERSION

The RF232 can be used with 22O,230, or 24OVAC if a smallwiring modification is done.

1. First, disconnect any AC Power!2. Lift the cover off the RF232 and locate the

power supply (P/N 4918) as shown inFigure 3-8.

3. Unscrew the four Phillips head screws ontop of the power supply and turn the powersupply upside down.

4. Clip the wire ties holding the power supplyleads to the base.

5. With the power supply on its back, locatepins 1 through 5. The power supply isshipped from the manufacturer configuredfor 120 VAC with pins 1 and 3 jumpered,pins 2 and 4 jumPered, and AC Powercoming onto pins 1 and 4. Theseconnections must be desoldered.

6. Resolder the pins as shown in Table 3-10for the Power Conversion you require.

TABLE 3-9. Pin Description for RF232's25-Pin Port

vo

..s

Pin

1

2342022

ioI

I

o

Descriotion

GroundTXRXRTSDTRRING

FIGURE 3-7. The RF232 Base Station

TABLE 3-1 0. RF232 Power Conversions

110 VAC120 VAC220VAC230 VAC240VAC

Pins Jumoered

1-3,2-41-3,2-42-32-32-3

Apply AC

1-41-41-51-41-4

3-11


R'232 TOP VIIW

RADIO

FIGURE 3-8. Top View of the RF232 Base Station

PCB P/N

POWTR SUPPLP/N 4e1B

R195

3-12

SECTION 4. OPERATION OF THE RADIOTELEMETRY NETWORK

Atl fietd stations can be accessed and monitored from the central base site. Regular visits to the fieldsites are required to ensure that allsensors are in place, enclosures are dry, solar panel is clean, andthat the tripod and antenna are secure. Frequency of visits to the field sites are variable depending onenvironmental conditions and the sensors utilized.

This section of the manuat includes a description of the PC208 Datalogger Support Software as itappties to RF applications, as well as a description of some special RF applications.

4.1 MONITORTNG AND COLLECTINGDATA. PC2O8 RF NOTESThe PC208 Datalogger Support Software is thekey to communicating with the field stations.Complete information on the PC208 Sottware isincluded in the PC208 Manual. This sectiongives a brief description of data collectionmethods, and provides specific RF applicationnotes.

4.1.1 COLLECTING DATA - TELCOM

TELCOM is the program for data collection.The user is required to complete a Station Filewhich stores information such as the frequencyof data collection, the datalogger type at thefield station, the communication baud rate, theCOM port, and the RF path.

Rather than collecting data from each fieldstation separately, it is most efficient to createone Script File (similar to a batch file) to retrievedata from severalstations. The next twosubsections describe the Station File and ScriptFile, respectively.

4.1.1.1 The Station File

A Station File must be created for each fieldstation. The following questions must beanswered in a Station File; options available arelisted in parentheses. Most options areobtained by pressing the spacebar, butunderlined options are obtained by pressing the"H" key.

Datalogger or Command Type: (CRIO, 21X,CR7, 300 Series, DOS Command, ExitTELCOM,2lX (2 PROM), CR7 w/700 CM,CR21, EB| None).Data Collection Method: (Since Last Call-Append File, Since Last Call-Create File, Most

Recent Arrays-Create, lvloslBecenll\rraE,Apoend).

FinalStorage Area: The CR10 Dataloggermay be programmed to have two final storageareas. You can select either final storage areaor a storage module when using a CR10datalogger.

Nbr of Arrays to Backup on First Call:Data File Format: (Comma Delineated ASC|l,Printable ASC|l, Same as Received FromDatalogger).

Fix Datalogger Clock Using PC Clock: (No,Check Only and Report When 30 seconds off,When 30 seconds off).

Primary Call lnterval (minutes):

Recovery Call Interval (minutes):

Repetitions of Recovery Interval #1:

Recovery Call Interval #2 (minutes):

Maximum Time Call Will Take (minutes):

Interface Devices: (COM Port, SC32A, HayesModem, RF Modem, MDg, RAD Modem, SC95Short Haul, Generic Modem).

Questions on any of these parameters areexplained in the PC208 Manual.

Two options under'lnterface Devices' will beutilized in a simple RF application. These arethe COM port and the RF modem. The COMport specification is needed to access theproper RS232 port of your computer. Thecommunication baud rate must be entered withthe'COM Port'option. The FIF95 in the RF232supports 9600 baud communication betweenthe computer and the RF95.

4-1


When the'RF Modem'option is chosen, aprompt for'Path'will appear. The RF path forany particular field station consists of theStation lDs which are in the link from the basestation to the field station, excluding the basestation lD number. lf no repeaters are used in alink, then the RF path will have only one numberwhich is the Station lD of the field station. l1there is one repeater, then two numbers arerequired with a space, or comma, separatingthe two. The numbers listed should be theStation lDs of the repeater and field station,respectively. The Station lDs must be in theorder of occurrence from the base station, andthe entire path cannot exceed 40 characters.

The letter F may be added to the end of thepath designation to speed communication.Example 4-1 shows an example of an RF pathdesignation to communicate to a field stationthrough 1 repeater. In this case, the repeaterhas a Station lD of 10 and the field station an lDof 95.

EXAMPLE 4-1. Sample RF Path Designation

Interface Device:COM1 Baud Rate:9600RF Modem Path:10 95FEnd

This example assumes use of communicationport 1, and the Station lDs shown. Refer to theTELCOM section of the PC208 Manualfor adescription of the other parameters.

Following the creation of the Station File, type"TELCOM name/C" to collect data from the fieldstation, where "name" is the name of the StationFile. For example, data can be collected usingStation File RFTEST by typing "TELCOMRFTEST/C." The data will be stored in a filecalled RFTEST.dat. The "/C" option afterRFTEST forces TELCOM to callthe stationNOW whether or not it is time to call accordingto the calling interval specified in the StationFile. Typing "TELCOM RFTEST" without the"/C" will call the field station only if the requiredtime between calls"has passed.

4.1.1.2 The Script File

The Script File contains a list of Station Fileswhich are called sequentially for data collectionwithout leaving TELCOM. The Script File ismore than a simple batch file. Within the ScriptFile, datalogger calls are optimized and

4-2

telecommunication control instructions areexecuted.

To edit a Script File, type "TELCOMname.SCF/E", where "name" is any Script Filename. The extension .SCR must be enteredwhen editing or TELCOM will assume the file isa Station File.

Attended operation allows data collection at anytime. Assume there are three field stations inthe network with names of H|LL1, MTN, andCRK; also assume the Script File is namedCALLALL. The Script File would be as follows.

EXAMPLE 4-2. Script File - Attended DataCollection

HILLl/CMTN/CcRl(c

All of the stations could then be called by simplytyping "TELCOM CALLALL." The data wouldbe collected and stored in files namedHlLLl.dat, MTN.dat, and CRK.dat according tothe Station File name of each site.

Unattended operation to allow data collection atspecific interuals is possible when the computeris left on. A Script File is used with the "/VV"wait option. The wait option is entered at theend of the Script File. Example 4-3 shows aScript File which willcallthe RF Station, andthen wait for the next time to call.

EXAMPLE 4-3. Script File - Unattended DataCollection

HILLlMTNCRKM

Further details of attended and unattended datacollection are explained in the PC208 Manual.

4.1.2 GENERAL COMMUNICATION _ GT

With the use of GT, a terminal emulatorprogram, it is possible to download programs tcthe datalogger and monitor the Input Locationsof the datalogger. GT has other capabilitieswhich are explained in the PC208 Manual, butthese two capabilities are commonly needed inan RF network.


4.1.2.1 Download Datalogger Programs

It is possible to create datalogger programs withEDLOG and then download the program to thedatalogger from the base station. This savesthe user from having to travel to the field stationto program the datalogger.

Collect all data from a datalogger before youdownload a new program. When GT loads aprogram into a datalogger, allfinal storagememory is erased.

EDLOG is a program within PC208 to createdatalogger programs. The use of EDLOG isexplained in the PC208 Datalogger SupportSoftware Manual. Once the dataloggerprogram has been created with EDLOG, it isready to be downloaded to the datalogger.

GT uses a Station File similar to GT; however,GT utilizes parameters from GT's Station File ifthe GT Station File has already been created.Type "GT name/E" to view the GT Station File,where "name" is the Station File name. Correctthe Station File, if needed, and then save thefile.

A list of options will appear on the screen.Download the program by selecting the "D"option. When prompted, type the name of theprogram to be downloaded, press [ENTER],and wait for the transfer to be completed.

4.1.2.2 View ReaFTime Measurements

The Monitor Mode of GT is used to view resultsof instantaneous measurements. Type "GTname/E" to view the GT Station File, where"name" is the name of the Station File. Correctthe Station File, if needed, and then save thefile.

A list of options will appear on the screen,choose "M" to monitor the Input Locations. TheInput Locations that are displayed can bechanged by using the'Locations Displayed'option at the bottom of the Monitor Modedisplay. While monitoring the locations, you canenter the graphics mode by pressing "G." Seethe PC208 manualfor more information.

The Monitor Mode updates the Input Locationsfrequently requiring a lot of transmission time'Due to the high current drain of the radiosduring transmission, it is not recommended touse this form of communication for long periodsof time when a solar panel is being utilized atthe field station.

4.2 DATALOGGER INITIATEDCOMMUNICATIONS

The datalogger can call the computer to initiatedata collection, sometimes termed "call back."Instruction 97, Initiate Telecommunications, isused for this purpose. Call back is commonlyused to initiate data collection under emergencysituations (e.9. water levelfalls below lowerlimit).

The computer must be left on and dedicated toRF communication to implement the call backoption. Call back instructions are explained inthe datalogger manual. The PC208 Manualexplains the use of call back in a telecom-munications network.

4-3

APPENDIX A. SETTING THE STATION ID

Each RF95, including the one in the RF base station, must have a unique Station lD. Each RF modemhas nine dip switches; the first eight must be set for a particular Station lD. Following is a list of allpossibte Station lDs with the corresponding sefting of the dip switches. Here, 1 represents open, 0 isclosed, and X is "don't care."

SWITCHESlD 1234 56789

SWITCHES1234 56789

"SWITCHES1234 56789

1 10002 01003 11004 00105 10106 01107 1110I 00019 1001

10 010111 110112 001113 101114 011115 111116 000017 100018 010019 110020 001021 101022 011023 111024 000125 100126 010127 110128 001129 101130 011131 111132 000033 100034 010035 110036 001037 101038 011039 111040 0001

0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x0000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x1000x0100x0100x0100x0100x0100x0100x0100x0100x0100x

0100x0100x0100x0100x0100x1100x1100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x1 100x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x0010x1010x1010x1010x1010x

1010x1010x1010x1010x1010x1010x1010x1010x1010x1010x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x01 10x1110X1110X1110X1110x1110x1110X1110X1110X1110X1110X1110X1110X1110X1110X1110X

ID

4344454647484950515253545556575859606162636465666768697071727374757677787980818283

1 101

001 1101 1

011111110000100001001 1000010101001 1011100001100101011 101001 1101 1011111110000100001001 1000010101001 1011100001100101011 101001 11011011111110000100001001 100

ID

8687888990919293949596979899

1001011021031041051061071081091101111121131141151161't7118119120121122123124125126

01 1011100001100101011 101001 1101 1011111110000100001001 100001 0101001 1011100001100101 011 101001 1101 1

011111110000100001001 1000010101001 101 1100001100101011 101001 1101 1

0111

A-1

APPENDIX A. SETTING THE STATION ID

SWITCHES1234 56789

SWITCHESf D 't234 56789 IDID

SWITCHES1234 56789

4',t 100142 0101

129 1000130 0100131 1100132 0010133 1010134 0110135 1110136 0001137 1001138 0101139 1101't40 0011141 1011142 0111143 1111144 0000145 1000146 0100147 1100148 0010149 1010150 0110151 1110152 0001153 1001154 0101155 1101156 0011157 1011158 0111159 1111160 0000161 1000162 0100163 1100164 0010165 1010166 0110167 1110168 0001169 1001170 0101171 1101

0100x0100x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x0001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x1001x0101x0101x0101x0101x0101x0101x0101x0101x0101x0101x0101x0101x

84 001085 1010

172 0011173 1011174 0111175 1111176 0000't77 1000178 0100't79 1100180 0010181 1010182 0110183 1110184 0001185 1001186 0101187 1101188 0011189 1011190 0111191 1111192 0000193 1000194 0100195 1100196 0010197 1010198 0110199 1110200 000120't 1001202 0101203 1101204 0011205 1011206 0111207 1111208 0000209 1000210 0100211 1100212 0010213 1010214 0110

1010x1010x0101x0101x0101x0101x1 101X1 101X1 101X1 101X1 101X1 101X1 101X1 101X1 101X1 101X1101X1 101X1 101X1 101X1 101X1 101X001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x001 1x101 1X1011X101 1X101 1X101 1X101 1X101 1X

127 1111128 0000215 1110216 0001217 1001218 0101219' 1101220 0011221 1011222 0111223 1111224 0000225 1000226 0100227 1100228 0010229 1010230 011023',t 1110232 0001233 1001234 0101235 1101236 0011237 1011238 0111239 1111240 0000241 1000242 0100243 1100244 0010245 1010246 0110247 1110248 0001249 1001250 0101251 1101252 0011253 1011254 0111255 1111

1110X0001x101 1X101 1X101 1X101 1X101 1X101 1X1011X101 1X1011X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X0111X1111X1111X1111X1111X1111X1111X1111X1111X1111X1111X1111X1111X1111X1111X111'tX1111X

A-2

APPENDIX B. AUTERNATE BASE STATION CONFIGURATIONS

The bash base station consr'sts of a computer and the RF232 Base Station. There are other options fora base station including a portable base station, a phone-to-RF base station, and a phone-to-RF basestation with measurement capability.

8.1 THE PORTABLE BASE STATIONThe portable base station is an aid in setting upa large radiotelemetry network, or in trouble-shooting RF network communication problems.A portable base station allows any ol the field orrepeater stations to act as a base station.Therefore, to try any particular RF link, it is notnecessary to travel to the fixed base station.

Figure B-1 is a block diagram of a portable basestation. The computer, with PC208 installed, isthe user interface to the RF network. Remem-ber that the "RF Path" designation will bechanged often to test various RF links. TheSC532 is the interface from the laptop computerto the RF95 Modem. The transformer on theSC532 should be cut off 6" up the cable. Thetwo leads on the SC532 should be stripped andtinned for connection to a battery. Most laptopshave a 9-pin RS232 port, so a 9- to 25-pinRS232 cable is needed to connect the com-puter to the SC532.

8.2 PHONE.TO-RF BASE STATIONWhen an RF network is a great distance fromthe desired place of data collection, a phonemodem can be used to callthe RF base station.A computer, with PC208 Datalogger SupportSoftware, and a Hayes phone modem can callaphone-to-RF base station. The configuration isshown in Figure B-2.

The Station File at the computer must includethe following interface devices: COM Port,Hayes Modem, and then RF Path. ThePSs12M Power Supply and Charging Regulatorsupplies 5 V to the RF95 and DC112, supplies12 V to the RF100 or RF200 Radio, and acts asa null modem between the DC112 and theRF95. The RF95 and DC112 are both con-nected to a separate 9-pin port on the PS512M.The RF95 Station lD at the phone-to-RF basestation must be 255 to allow more than onefield station to be called without terminating theinitialphone link. The RF95 in the RF95-MEState recognizes Station lD 255 as a commandto answer the phone and hold the ring line highwhich keeps the Modem Enable line high afterthe Ring from the Hayes has quit.

ANTENNA

FIGURE B-1. For'table Base Station

B-1

APPENDIX B. ALTERNATE BASE STATION CONFIGURATTONS

8.3 PHONE-TO.RF BASE STATIONWITH MEASUREMENT CAPABILITYWhen it is desired to have a datalogger at a phone-to-RF base station, the datalogger must be a CR10and the RF95 must be in the RF9S-SDC State.This configuration is used when the computer usesa phone modem to callthe RF base station which isalso being used as a field station (because mea-surements are being made at the station). Theconfiguration is shown in Figure B-3.

The Station File at the computer must include thefollowing intedace devices: COM Port, HayesModem, and then RF Path. The DC112 Phone

Modem and the RF95 are connected to theCR10, and powered by the CR10. The RF95Station lD at the phone-to-RF base station doesnot have to be 255 in this case. This isthe CR10 will automatically hold the ModemEnable line high, not being reliant on the RF95.

The datalogger at the base station should havesecurity set. See the CR10 manual for thedetails of security. With security set, a pass-word (number) is required before data can becollected. Withbut security, and with a CR10 atthe base, data can inadvertently be collectedfrom the base CR10 if an RF linkfails duringcommunication with another datalogger.

ANTENNA

PS512N/

SOLAR PANEL

OR

AC POWIR

RF1 OOOR

RF2OO

FIGURE B-2. Phone-To-RF Base Station

ANTTNNA

PS 1 2LA

SOLAR PANEL

OR

AC POWER

B-2

FIGURE B-3. Phone-To-RF Base Station With Measurement Capability

APPENDIX C. POWER CALCULATIONS

There must be enough transmission power in any RF link to complete communication. The sources ofpower are the radio and the antennas. Conversely, power is lost both through the cables (coax loss)and over the distance of communication (path loss). The power of the signal received (Signal Powefcan be calculated as stated below.

The signat power must be greater than -95 dBm (80 dBm @ 2.4K baud) to have a good radiotelemetrylink. Decibet mittiwatts (dBm) is a scale of power, 0 dBm represents one milliwatt of power. The lowerlimit of power for good data transmission is approximately 0.0000000000003 Wafts (3X10-13), whichrepresents -95 dBm.

Signal Power

SP

where, SPTPPL

AGand, CL

Path Loss

= TP+AG-PL-CL

= Signal Power (dBm) Power of the signal received,= Transmit Power (dBm) Rated output power of transmitting radio,= Path Loss (dB) Power lost over the distance of communication (calculated below),= Antenna Gain (dB) Total power gained by both the transmit and receive antennas,= Coax Loss (dB) Total power lost through both lengths of cable connecting the

transmit and receive radios to the antennas.

PL = 36.6+2O.Log(F)+2O"Log(D)

where, PL = Path Loss,F = Frequency (MHz),

and,D = Distance(miles).

CoaxialCable Loss

Typicalcoaxialcable losses are listed below.

Cable TvpeRG-8A/URG.58A/U

Transmit Power

5 Watt Radio4 Watt Radio

Power Gonversion

2O0MHzLoss/100 ft.

3.1 dB6.2 dB

400 MHz

5.0 dB9.s dB

36.99 dBm36.02 dBm

Conversion of Watts to dBm can be done with the following formula'

c-1

dBm = 1o. Log((Watts)/0.001)

APPENDTX D. FUNDAMENTALS OF RADIOTELEMETRY

D.l RADIO WAVESRadiotelemetry is the process of transferringinformation (data) in the form of radio waves.The data is transferred on a carrier wave whichnormally has a sinusoidalform. Therefore, thecarrier wave can be described entirely by thefrequency, amplitude, and phase with respect toa reference.

The commonly used term for radiotelemetry,RF, refers to radio frequency, which in actualityis the frequency of the carrier wave.

Radio waves can be divided into threecategories: 1) ground waves, 2) direct waves,and 3) sky waves. Allcommunication withCampbell Scientific's RF networks are done viadirect waves. Direct waves travel "line-of-sight"at a maximum distance ol approximately 25miles.

Low frequency radio waves (5-10 mHz) cantravel for thousands of miles using the groundwave portion of the radio wave. The groundwave is that portion of the radio wave whichtravels just above the surface of the ground.Conversely, the sky wave radiates to theionosphere where a certain percentage of theenergy is reflected back to earth. At the higherfrequencies used for data transmission theionosphere is penetrated by the radio wave andtoo small of a percentage is reflected back toearth. However, neither the ground wave or skywave is used in CampbellScientific's RF net-works.

Energy is lost from radio waves as they travelaway from the transmitting antenna. Onereason for this is the loss due to dispersion ofenergy over a larger area; analogous to waterwaves reducing in size (energy) as they getfarther from the source. Second, is that energyis absorbed by the earth over the distance oftravel. Eddy currents cut down signdl power,and intervening terrain and buildings canprevent a signalfrom being strongly received.

The higher the trequency, the stronger theradiation field. However, at higher frequenciesmore energy is absorlced by the surface. TheVHF and UHF frequencies can travel only ashort distance between radio stations. The

direct wave, where there is no obstaclesbetween stations, will transmit farther than anyindirect waves which have been transmittedthrough or reflected from obstacles.

The carrier wave can be thought,of as the radiowave which "carries" the data from one radio tothe next. The "data" consists of an electricalsignal which rides with the carrier wave. Theprocess of placing the signalon the carrierwave is called modulation. The signal is also inthe form of a wave, but usually the signal has amuch lower frequency. The carrier with themodulating signal is called the modulatedcarrier.

The signal wave isn't used as a carrier wavebecause radio transmission must be of a highfrequency to keep radio components small,antennas small, filtering efficient, and to isolatethe radio waves from the common lowfrequency man-made noise.

The main forms of modulation are amplitude,frequency, and pulse modulation. Frequencymodulation (FM) is used by Campbell Scientific.

D.2 ANTENNASAn antenna is a device which captures andradiates radio waves. The antenna at thetransmitting station is excited by the transmittingradio. The antenna converts energy from theradio to radiated energy. Electrons within theantenna oscillate at the frequency of the radiothereby producing radio waves. These radiowaves radiate out from the antenna at thespeed of light (299,800 km/s).

The transmitted radio wave willcause electronsin the receiving antenna to oscillate at thecarrier frequency. The AC current therebyproduced in the antenna is transferred to theradio for demodulation.

The antenna is constructed for a particularfrequency, operating radius, and gain. Length,diameter, number of elements, and elementspacing are among the items that can bechanged to alter antenna performance at thedesign stage.

D-1

APPENDIX D. FUNDAMENTALS OF RADIOTELEMETRY

Every antenna has a known horizontal andvertical pattern of radiation. The horizontalradiation pattern consists of any segment of a360 degree circle surrounding the antenna. Thehorizontal pattern is important to consider whena RF station is to communicate with more thanone other RF station. The vertical pattern is theradiating pattern in the upward and downwarddirections.

Any two communicating RF stations must havea minimum level of signal power. Power isnormally expressed in decibels (dB), or decibelmilliwatts (dBm). Power is lost throughtransmission cables (transmitting and receiving)and over the communicating distance. Power isgained through the transmitting radio, and thetwo antennas. Antenna gain is specified indecibels in reference to a dipole, and can varyfrom 0 to 10 dB in common antennas. A unitygain antenna has a 0 dB gain, therefore noadditional power is added by using theseantennas.

Antenna gain is accomplished by eitherconcentrating the radiating power in a smallsector, or using multiple radiating elements withadditive patterns.

D.3 RF95 MODEMThe RF95 Modem is the main communicationcontroldevice in a radiotelemetry network. TheRF Modem enables a central base site tocommunicate with up to 254 different RFstations.

The RF Modem is a microprocessor controlleddevice which codes all transmissions for aspecific communication path. Each has ahardware lD switch for identifying differentstations.

The purpose of the RF Modem is to controloperation of the radio and provide protection fordata integrity. The RF Modem controls thecommunication sequences, sets data to betransferred into.datablockg.creates signaturesof data blocks, modulates the radio's carrierwave, and stores information on communicationquality.

The user at the computer is responsible fornaming the desired communication path with asetup string. This setup string contains anyrepeater (MOL) modem lDs and the destination

D-2

(EOL) modem lD in sequence. After sendingthis information out through the RF system, allof the RF Modems in the specified link will setthemselves in the proper mode. The RFModem has different modes to distinguishresponsibilities at various localities within a link.These modes are described in Section 3.1.6.

Establishment of an RF link consists of gettingall of the RF Modems in the proper mode andreceiving a verification block from the EOLmodem.

D.4 TRANSCEIVERThe purpose of a transceiver (radio) is totransmit and receive the modulated carrierwave.

A radio is both a transmitter and receiver. Themain component in the transmitter is theoscillator of which the frequency of oscillation isprovided by a crystal. The crystal oscillates at adesired frequency, which is specific for thecarrier frequency. The oscillator converts DCpower to an AC signal. This signal is thenamplified, modulated with the signal, andtransmitted to the antenna system. Thereceiver consists of an amplifier, frequencyconverter to slow signal, limiter to give constantamplitude but same frequency, anddiscriminator or demodulator.

The radio has a known impedance, orresistance. Maximum power is transferred ifthe impedance of the radio matches theimpedance of the antenna and cable. Thisimpedance is generally 50 ohms. Mismatchingof impedance will cause a lesser transmit poweland result in a higher VSWR (Voltage StandingWave Ratio).

When the transmission cable and antenna doesnot match the impedance of the output circuit ofthe radio, not all of the energy fed down thecable will flow into the antenna. A percentageof the energy will be reflected back formingstanding waves on the cable. The ratio ofvoltage across the line at the high voltage pointsto that at the low voltage points is known as theVSWR. When the VSWR is 3.0:1 or greater,the percentage of errors per data value isgreater than 50o/o. The VSWR should be keptbelow 1.5:1 for error free radiotelemetry.

APPENDIX E.

The RF95 Modem operates in one of twoseparate states. The RF95 can be utilized ineither the RF95-ME (Modem Enable) State orthe RF95-SDC (Synchronous DeviceCommunication) State. The RF9S-ME State isnormally used for all RF networks. The RF95-SDC State must be used when there is aphone-to-RF base station with a CR10datalogger. A switch inside the RF95 needs tobe set according to the chosen state'

E.l RFgs.ME STATEThe RF9S-ME State is always used with 21Xand CR7 dataloggers, and normally with CR10dataloggers.

RF95-ME State DescriPtionThe RF95 rings the datalogger untilthedatalogger raises the ME line. The CR10 waitsapproximately 40 seconds to receive carriagereturns to establish the baud rate. After thebaud rate is set the CR10 transmits a carriagereturn, line feed, "*", and enters theTelecommunications Mode. lf the carriagereturns are not received within the 40 seconds,the CR10 hangs uP.

When the datalogger is in ihe Telecommuni-cations Mode, the ME line is high, and the RF95is subsequently in the Transparent Mode orEOL Mode depending on the relative location ofthe RF95.

E.2 RFgs-SDC STATE

The RF95-SDC State can be used to enable aCR10 to be recording measurements at aphone-to-RF base station. The SDC State isnever used with 21X or CR7 dataloggers.

RF95-SDC State DescriPtionThe RF95 obeys allSynchronous DeviceCommunication (SDC) protocolwhen set in theRF95-SDC State. The CR10 has the ability toaddress synchronous"devices' ' l he GR10 andthe RF95 use a combination of the Ring (pin 3)'Clock/Handshake (pin 7), and SynchronousDevice Enable (SDE, pin 6) lines to establishcommunication rather than just the ModemEnable line.

When the CR10 is connected to the RF95, a 1Ncommand is sent to the datalogger at setup.

RF95 STATES

The baud rate is set and the CR10 completesconnections with the RF95. The CR10 sets theRF95 in an addressing state by raising theCLK/HS followed by or simultaneously raisingthe SDE line. The RF95 drops the ring line andprepares for addressing.

The CR10 then synchronously clocks 8 bits (theaddress) onto TXD using CLI(HS as a clock.The least significant bit is transmitted first, eachbit is transmitted on the rising edge of CLI

-z oftf - campbell sci · 2016. 6. 28. · warranw and assistance the radiotelemetry network is...

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