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205 Keith Valley Road Horsham, PA 19044US Sales 1-800-553-909224 Hour Service 1-800-527-6297International + 215-674-1234Fax + 215-674-2731E-mail drexelbrook.info@ametek.comWeb www.drexelbrook.comAn ISO 9001 Certified Company

DREXELBROOK

408-8200-LMEDO# 1-14-126Issue# 6

Table of Contents

Table of Contents (cont.)

408-8200-LM/p. 1

SECTION 1- INTRODUCTION

The instructions in this manual are for theDrexelbrook 508-4X-XX Series Universal IIsystem for level measurement in liquids,slurries, interfaces and granulars.

1.1 System Description

Each Drexelbrook 508-4X-X Universal IIsystem Consists of a 408-8200 Series two-wire, 4-20 mA electronic unit and a 700series sensing element (probe). Most 508-4X-XX Universal II systems are available ineither integral or remote applications. A380 series connecting cable is also suppliedfor remote systems.

The system model numbers indicate theapplication where they most often will beused:

508-0045-XXX: For conducting liquids508-0046-XXX: For liquid/liquid interfaces508-0047-XXX: For insulating liquids508-0049-XXX: For granular solids

The final digits in the system model numberrefer to the type of 700 Series sensingelement used.

The 508-004X-XXX is an admittance-to-currenttransducer. A change in level produces a change in admittance which results in a change in current. It is termed a two-wire transmitter because the same two wires used to power the unit also indicate thechange in level (4-20mA). See Figure 1-1.

INTRODUCTION

Figure 1-1Universal II Block Diagram

408-8200-LM/p. 2

1.2 Models Available

1.2.1 Electronic Chassis

The following is a partial list of the various408-82X2 Series chassis models available:

408-8202-001 — Basic electronic unitintended for use with insulatingmaterials, interfaces, and semi-conducting granulars.

408-8232-001 — Basic electronic unit(408-8200) internally connected foruse with conductive materials andcertain insulating granulars.

408-82X2-001 — Time delay optionincluded.

1.2.2 Housings

The 408-8200 Series electronic units areavailable in a NEMA 4 or explosionproofhousing. A “1” in the last position of theelectronic unit number indicates chassisonly, no housing. Example, 408-82XX-0X1means chassis only. The standard housingmeets the following NEMA classifications:

NEMA 1 General Purpose 2 Drip Tight 3 Weather Resistant 4 Waterproof 4X Waterproof/Corrosion Resistant 7 Explosionproof 9 Dust/Ignitionproof 12 Industrial use: oil and dust-tight

1.2.3 Sensing Elements

For identification, the last digits of the sensingelement model number are stamped into themounting gland or flange. Certain sensingelements are identified with a tag. If you haveadditional questions about sensing elements,contact the factory or your local representa-tive.

1.2.4 Connecting Cables

When necessary to avoid excessivetemperatures and vibration, the electronicunit and sensing element can be connectedby a three-terminal coaxial cable.Drexelbrook cables are available in:

General Purpose: 380-0XXX-012High Temperature: 380-0XXX-011Composite: 380-0XXX-018 (first 10 feet high temperature)

The XXX in the model number indicates thelength of the cable in feet. 25 feet is stan-dard (e.g. 380-025-12), but longer andshorter lengths are available. Cable canalso be purchased in bulk lengths with ter-mination kits. Consult factory for maximumrecommended lengths per specific applica-tions

INTRODUCTION

408-8200-LM/p. 3

1.3 Technical Specifications

1.3.1 Electronic Unit (typical)A. Power requirement: 11.5 to 50 Vdc

B. Input range: 408-8202: 3.75 to40,000pF; 408-8232: 6 to 40,000pFwith 5 ft. of cable.

C. Output range: 4-20 mA

D. Linearity: ±0.25%.

E. Load resistance:Vs-11.5* (i.e. max 625 @ 24Vdc).

.02*Where Vs = power supply voltage.

F. Temperature effect: ±0.25% of fullscale per 30oF or ±0.1 pF whicheveris larger.

G. Supply voltage effect: 0.2% max.from 11.5 to 50 Vdc.

H. Effect of load resistance: 0.2% orless for full resistance range at 24Vdc supply.

I. Response to Step Change: 0.5-30seconds standard (to 90% of final value)

J. Fail-Safe: Field adjustable. Low-Level Fail-Safe (LLFS) is default. Alsocalled direct acting because currentincreases as the level increases.High-Level Fail-Safe (HLFS). Alsocalled reverse acting because cur-rent decreases as level increases.

NOTE: There are no devices that are abso-lutely “fail-safe”. “Fail-safe”means that in theevent of the most probable failures, the instru-ments will fail safely. Examples of “mostprobable failures” are loss of power and mosttransistor and component failures. If yourapplication needs absolute fail-safe, abackup instrument should be installed.

K. Ambient temperature: -40o to+150oF (-40o to 65oC) at 24 Vdc.

L. Calibration Adjustments: StepZero, Fine Zero, Step Span, FineSpan, Time Delay.

M. Lowest permitted resistance(bare sensing element to ground)causing 5% error in each model:

600Ω - 8202 100KΩ - 8232

All transmitters are KEMA approved:EEx ia IIC T4. All sensing elements are certi-fied EEX ia II C T6--T3. 5-inch housings areIP 65.

NOTEWiring drawings for KEMA-approved

units are provided inthe appendix of this manual.

SPECIFICATIONS

408-8200-LM/p. 4

N. Cable Length: 150 feet maxi-mum.

O. Independence of zero and span:±1% maximum.

P. RFI Protection: Inherent with unitagainst standard walkie-talkie inter-ference; 5 ft. standard distance withproper installation.

1.3.2 Three-Terminal Cable

A. General Purpose:380-0XXX-012: .51" OD at largestpoint, 160oF temperature limit.

B. Composite Cable (first 10 feethigh temperature):380-0XXX-018: .62" OD at largestpoint, 450oF temperature limit for first10 ft. 160oF temp limit for remainder.

C. High Temp. Cable 380-0XXX-011:.51" OD at largest point. 450oFtemperature limit.

SPECIFICATIONS

408-8200-LM/p. 5

SECTION 2 - INSTALLATION

2.1 Unpacking

Carefully remove the contents of the cartonand check each item against the packinglist before destroying any packing material.If there is any shortage or damage, report itimmediately to the factory.

2.2 Mounting the Electronics

The 408-8200 Series system was designedfor field mounting, but it should be mountedin a location as free as possible from vibra-tion, corrosive atmospheres, and any possi-bility of mechanical damage. For conve-nience at start-up, mount the instrument ina reasonably accessible location. Ambienttemperatures should be between -40oF and140oF. (-40o and 60oC). See Figure 2-1.

Figure 2-1ATypical Mounting Dimensions

(Integral Unit)

Figure 2-1BTypical Mounting Dimensions

(Remote Unit)

INSTALLATION

408-8200-LM/p. 6

2.4 Wiring the Electronic Unit

The signal connections are made to thethree terminal block on the front of chassis.Due to the low power consumption of theinstrument, the wiring need only be lightgauge (e.g. 20 AWG). See Figure 2-2 forproper connections. Twisted shielded paircables are recommended for lengths over200 feet.

The cable from the sensing element isconnected to the black, four terminal stripon the back of the instrument chassis. SeeFigure 2-3. The cable connections arecenter wire (CW), ground (gnd), and shield(SH).

Only coaxial cables supplied byDrexelbrook Engineering Company shouldbe used to connect the transmitter to thesensing element. Use of other cables canresult in unstable calibration.

NoteFor wiring in Explosion Hazard Areas,

refer to Appendix for wiring diagrams.

2.3 Mounting the Sensing Element

The mounting location for the sensingelement (probe) is often determined by theplacement of nozzles or openings in thevessel. The sensing element should not beplaced in a fill stream. When there is nosuitable location inside a vessel, an exter-nal side arm or stilling well can be consid-ered.The following sensing element mountingand installation instructions should befollowed so that the equipment will operateproperly and accurately:

A. In applications requiring an insulatedsensing element, use particular care duringinstallation. There is always the danger ofpuncturing the insulating sheath, especiallywith the thin-walled, high capacitanceprobes.B. Sensing elements should be mounted insuch a manner that they are not in the directstream of a filling nozzle or chute. If this isnot possible, a deflecting baffle should beinstalled between the probe and the fill.

C. Do not take a sensing element apart orloosen the packing glands.

D. Tighten the sensing element with thewrench flats nearest the mounting threads.

CAUTIONAvoid using single-part RTV (silicone rubber)sealant in the probe or instrument housing.The single-part sealants frequently containacetic acid and cause corrosion of circuitcomponents. Special two-part sealants (non-corrosive) are available. Consult factory fortypes of recommended two-part sealants.

INSTALLATION

408-8200-LM/p. 7

Figure 2-2Power/Signal Connections

2.4.1 Ground Wiring

The 408-8200 series transmit-ters have Radio FrequencyInterference (RFI) filtering builtinto the unit. In order to beeffective, The electronic unitcondulet (housing ) must begrounded to low impedanceearth (ground) rod in the vicin-ity of the transmitter. Thevessel wall also needs to begrounded to reduce interfer-ence through the sensor. Ifusing a non-metallic vessel,consider concentrically-shielded sensors or externalRFI filtering. Further, improve-ment is generally obtained byplacing the sensor cable in agrounded metal conduit andshortening any excess cable.In particularly troublesome RFIsituations, additional RFIfiltering may be required.Contact the factory for moreinformation.

2.4.2 Ground Wiring in FiberglassHousings

When the transmitter is mounted in a fiber-glass housing, be sure that an earth ground iscarried through the fiberglass housing andput in contact with the "sprayed in" metalliccoating on the inside of the housing. Thiscoating provides additional RFI filtering.Additionally, the ground wire should beconnected to the transmitter ground terminal.See Figure 2-2.

CAUTIONBefore using Intrinsic Safety Barriers, readthe manufacturers instructions for barrieroperation.

The 408-8200 has a built-in current limiterwhich holds the signal current to a maxi-mum of 28 mA. Make sure that the voltageapplied to the barrier will not exceed thebarrier voltage rating, if barriers are used.

INSTALLATION

408-8200-LM/p. 8

Figure 2-3Cable Connections to the Transmtter

INSTALLATION

408-8200-LM/p. 9

2.5 Sensing Element Connections(Remote System)

The cable connections to the sensing ele-ment are shown in Figures 2-5A and 2-5B.Do not connect the cable to the sensingelement until after the sensor has beeninstalled in the vessel and the condulethousing has been screwed on securely. Ifyour probe does not have a shield connec-tion, be sure to clip and/or tape the shieldwire at the probe end of the cable.

Figure 2-5AThree-Terminal Cable Connections to

Two-Terminal Sensing Element

Figure 2-5BThree-Terminal Cable Connections to

Three-Terminal Sensing Element

If spark protection is supplied (for specialapplications, consult factory), use the fol-lowing instructions for installing the sparkprotector in the sensing element condulet:(See Figure 2-6.)

A. Attach the mounting link on thespark protector to the probe centerconnection screw.

B. Connect the green wire from thespark protector to the ground screw.

C. Feed the cable into the condulet.

D. Connect the cable center wire(CW) to the spark protector and theground wire (gnd) to the groundscrew as shown.

E. Connect the shield wire to theCote-Shield terminal (SH).*

Figure 2-6Typical Spark Protection

(Remote System)

*For sensing elements that Do not haveShield connections, clip the shield wire asshown in Figure 2-6.

377-0001-019

INSTALLATION

408-8200-LM/p. 10

2.6 Sensing Element Connections(Integral System)

In an integral system, there is no cable.Therefore, the connections to sensingelement are made directly to the electronicunit. Refer to Figures 2-7A and 2-7B.

Figure 2-7AIntegral-Mount Sensing

Element Connection

Figure 2-7BIntegral-Mount Sensing Element

Connection with Spark Protection

2.7 Intrinsic Safety Barriers -Installation with DrexelbrookContinuous Instruments

A typical installation of a single intrinsicsafety barrier is shown in Figure 2-8. Asingle barrier installation is usually rated foroperation at 24-26V with a maximum of 80mA. The barrier will typically start limitingthe current at 26 mA. Drexelbrook recom-mends that a current-limiting, rather than atrip type barrier be used in the installation.The reason for this approach is that a trip-type barrier must be reset by breaking theloop power to reset the barrier. The inad-vertent tripping often occurs during calibra-tion. This condition does not occur with acurrent-limiting style barrier.

Single-Barrier Installations (Figure 2-8)

When using barriers, an important consider-ation is the overall loop resistance. Using astandard 24 Vdc power supply, the maximumloop resistance is 1200 ohms. Each 50ohms in a loop uses 1 Vdc. A typicalDrexelbrook transmitter requires a minimumof 11.5 Vdc, leaving 12.5 volts for the loopand a maximum load in the loop of 625 ohms.All of the loop resistance must be totaled todetermine the remaining resistance thatcan be used by a barrier. Usually a “positive”barrier in a loop has a resistance of between200 and 250 ohms, leaving approximately400 ohms for other items in the loop.

2-Barrier Installations (Figure 2-9)

In certain instances, it is desirable that twobarriers be used in an installation, such aswhen the signal is being fed to a micropro-cessor input card. A two-barrier installationallows the loop to float relative to ground.When this condition exists, it is very importantthat the loop resistance is checked to be surethat sufficient voltage is available for correcttransmitter operation. As shown in Figure 2-9, if two barriers are used, each having an

INSTALLATION

408-8200-LM/p. 11

internal resistance of 250 ohms, there wouldbe only 125 ohms available for all otherdevices. To gain additional resistance,change the return (negative leg) barrier to alower voltage type, e.g. rating of +6V. Nor-mally the barriers have a resistance of ap-proximately 12.5 ohms + 2V. By lowering thevoltage type, the overall effective resistancewould be 312.5 ohms, which allows an addi-tional 312.5 ohms in the loop.

Figure 2-8 Single Barrier Installation

Figure 2-9Two-Barrier Installation

2.8 Surge Voltage (Lightning)Protection

Optional surge protection is sometimessupplied with transmitters that are expectedto be exposed to surges or lightning on thetwo-wire loop. A Drexelbrook Model377-4-12 Surge Voltage Protection affords agreat deal of protection to the transmitter butis not absolute in its protection against a veryclose lightning strike.

INSTALLATION

2.9 RFI (Radio FrequencyInterference) Filters

When installing the Universal II transmitter,follow these recommendations to avoidproblems with Radio Frequency Interference.

•Mount the electronic unit at least 6 feet (2M) from a walkway where personnel using walkie talkies may pass.

•If the vessel is non-metallic, select a shielded (concentric) sensor.

•For remotely-mounted electronic units connect the sensor to the electronic unit by placing the coaxial cable in grounded metal conduit. Integrally mounted electronic unit sensor connections are already shielded.

•Use Twisted Shielded Pair wiring for all loop wiring connections. Loop connection wiring should also be in grounded metallic conduit.

•Where possible, use of cast aluminum housings without windowed openings for the electronic unit is recommended. If local close-coupled indicators are used, install a loop filter between the indicator and the electronic unit.

Ground the electronic unit and housing with aminimum of 14 gauge wire to a good earthground. Make sure that conduits entering andleaving the housing have a good electricalground connection to the housing

If the recommendations listed above arefollowed it is usually not necessary to addRFI filtering to protect against signalstrengths of 10 Volts/ Meter or less. Thisdegree of protection is usually sufficient toprotect against walkie talkies that are used 3feet (1M) or more from a typical electronicunit. If greater protection is required, or filtershave already been provided, install RFI filters.Consult factory.

408-8200-LM/p. 12

The Step Span and Fine Span controls alsowork together to provide continuous adjust-ment of the change in capacitance requiredto produce full scale current. Each StepSpan position advances the range in inchesor feet to approximately five times the previ-ous setting. The Fine Span provides con-tinuous adjustment between the Step Spanpositions.

3.1.2 Time Delay Control and LoopCurrent Testpoints

Time delay is standard on this transmitter.See Figure 3-2. It is an RC time constantcircuit that is variable over a range of 0.5 to30 seconds. For most applications requir-ing damping, five or ten seconds is usuallysufficient. Calibration of the transmitter isdone with the time delay turned off (fullCCW).

Figure 3-2Time Delay Unit

SECTION 3 - CALIBRATION

3.1 Controls and Adjustments

3.1.1 Zero and Span Controls

There are two main controls on the chassisfront panel. They are the Step Zero, andStep Span controls. The Fine Zero and FineSpan controls are located on the top of thechassis. See Figure 3-1.

The Step Zero and Fine Zero controls worktogether to provide continuous adjustmentof the minimum current point. Each StepZero position advances the minimum cur-rent point approximately 25 pF, while theFine Zero provides continuous adjustmentbetween each step.

NOTEUnder normal circumstances, the inter-action between zero and span should beless than 1%. If this interaction becomesgreater than 1%, consult factory for assis-tance.

Figure 3-1Zero and Span Controls

CALIBRATION

408-8200-LM/p. 13

After calibration is complete, a time delaycan be added, without affecting the calibra-tion, by turning the control knob clockwise.Occasionally, when the time delay is firstturned on, there is a temporary upset in thetransmitter output until the circuit settles out.Two testpoints are provided so that loopcurrent can be monitored without breakingthe loop with a standard analog or digitalmultimeter set to measure 0 to 20 mA.

3.1.3 Below-Chassis Adjustments

There are two adjustments in the chas-sis that are set by the factory and normallydo not need to be changed. However, ifnecessary, they may be reset by field per-sonnel. They are the fail-safe selector anda modification procedure for changing the408-8202 to a 408-8232.

A. Fail-Safe Selector

The fail-safe selector determines whetherincreasing or decreasing level will cause theoutput current to increase. It is a movablelink located on a printed circuit board on theinside of the chassis. See Figure 3-3.

The instrument is supplied with the morecommon low-level fail-safe unless otherwisespecified. Low Level Fail Safe (LLFS)provides increasing current signal with in-creasing level. (See description in subse-quent paragraph.) The fail-safe can bechanged in the field, after which the unitmust be recalibrated.

To change the fail-safe of the instrument,take the chassis out of the condulet byturning the two captive chassis mountingscrews CCW and lifting unit up. See Figure3-4. Note position of step zero and step span switches for proper re-assembly.

Figure 3-3Fail-Safe Link

using an allen wrench, then remove the twoscrews on the top of the unit to remove unitcover. Change the 3-terminal jumper that isclosest to the bottom of the PC board asshown in Figure 3-3. When link has beenchanged, re-assemble unit cover and knobsand install unit in condulet.

Low-Level Fail-Safe is also called DIRECT-ACTING. This is the most commonly usedfail-safe position FOR CONTINUOUS IN-STRUMENTS. Output CURRENT IN-CREASES as the LEVEL INCREASES.(Exception being inverted interface, seeSection 3.3.3). In the event of most prob-able failures, the output current will dropand indicate LOW LEVEL.

High-Level Fail-Safe is called REVERSEACTING. Output CURRENT INCREASESas the LEVEL DECREASES. In the event ofmost probable failures, output current willdrop indicating HIGH LEVEL.Remove the two knobs

CALIBRATION

408-8200-LM/p. 14

Figure 3-5Modification Procedure for 408-8230

3.2 Start-Up

Before applying power to the instrument, besure that the input power will be from 11.5 to50 VDC. Check all wiring connections,observing polarity of the output loop. (Unitwill not function if polarity is reversed.

Caution: Explosionproof Units in Hazardous Areas: Before the explosionproofcondulet cover is removed to calibrate theinstrument, the area must be checked andknown to be nonhazardous if barriers arenot used. When calibration is complete,replace the condulet cover. Each lead fromthe explosionproof case must be equippedwith an approved seal fitting.

Avertissement: Risque D'Explosion: Avantde deconnector l'equipment, couper lecourant ou s'assurer que l'emplacement estdesigne non dangereux.

Figure 3-4Electronic Unit in Typical Housing

B. 408-8230-XX ModificationProcedure

The following procedure can be used tomodify a basic 408-8200 electronic unit to a408-8230 electronic unit. See Figure 3-5. Itshould only be used when the applicationmakes it necessary. Consult Factory.

Take the chassis out of the condulet byturning the two chassis mounting screwsCCW and lifting unit up. See Figure 3-4.

remove theNote the position of step zero and step spanswitches for proper reassembly,two knobs using an allen wrench, thenremove the two screws on the top of the unitto remove unit cover. The phasing linkis the 3-terminal jumper nearest the middleof the PC board as shown in Figure 3-5.When the phasing link has been changed,re-assemble unit cover and knobs, andinstall unit in condulet. To convert a 408-8230 unit to a 408-8200 unit, follow thepreceding instructions in reverse. Aftermodification, recalibration (paragraph 3.4.2)should be performed.

CALIBRATION

408-8200-LM/p. 15

3.3 Calibration Procedures

NOTE: If the transmitter has beenprecalibrated at the factory, do not recalibrate.

The calibration instructions for the 408-8200Series transmitter are divided into threemajor application categories with differentmethods in each category. The three calibra-tion categories are immersion applications,proximity applications, and interface applica-tions.

3.3.1 Immersion Applications (SeeFigure 3-6)

A. Immersion - Direct Acting (LLFS)(Output rises as material rises.)Calibrating the instrument in an immersionapplication for low-level fail-safe is the mostcommonly used method.

1) With fail-safe link in "DIR" position,(factory pre-set unless unit is ordered highlevel, see Section 3.1.3), set Fine Zero andFine Span to extreme counterclockwiseposition. See Figure 3-7.

2) Set Step Span and Step Zero to Posi-tion #1.

Figure 3-6Immersion Application

Figure 3-7Zero and Span Controls

3) With the vessel empty (or probe uncov-ered), adjust the Step Zero control clock-wise, if necessary, until the output is lessthan 4 mA.

4) Turn Fine Zero control clockwise untiloutput is exactly 4 mA.

5) Fill the vessel (or raise the level as muchas possible). Output current will typicallyexceed full scale current.

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifcurrent did not exceed full scale in Step 5),then leave Step Span in Position #1.)

7) Turn the Fine Span control clockwiseuntil the output is full scale (20 mA) orreading actual level.

Calibration is now complete. Record thecapacitance values that produce 4 mA and20 mA outputs. Refer to paragraph 3.4.1 touse a capacitance calibration standard.

CALIBRATION

408-8200-LM/p. 16

3.3.2 Proximity Applications

In applications where the product beingmeasured is an insulator, it may be neces-sary to install a ground plate just below theproduct lower level. This ground plateshould be at least 25% larger than thesensing plate and electrically connected toground. The ground plate need not be asolid plate. It could be a series of rods,spaced apart, enclosing the same areas asa plate. Consult factory.

There are two different methods for calibrat-ing your instrument for a proximity applica-tion. See Figure 3-8. Set the instrument foreither low-level or high-level fail-safe.

Figure 3-8Proximity Application

A. Proximity - Direct Acting (LLFS)(Output rises as material rises.)

1) Be sure fail-safe link is in "DIR" position.See Section 3.1.3.

2) Set Fine Span and Fine Zero controls toextreme counterclockwise position. Do notforce. See Figure 3-7.

B. Immersion - Reverse Acting (HLFS)(Output falls as material rises.)

1) Set the Fail-Safe link in the "REV" posi-tion See Section 3.1.3.

2) Set Fine Span and Fine Zero controls toextreme counterclockwise position. SeeFigure 3-7.

3) Set Step Span and Step Zero toPosition #1.

4) With the material at the upper operatinglevel, adjust the Step and Fine Zero controlsuntil the output is 4 mA. For this calibrationprocedure, a compensation capacitor isusually required to obtain the minimum 4mAoutput. It will be added by the factory whenthe application is known. If needed and notsupplied, add-in 100 pF steps: an NPOcapacitor across Terminals PAD and CWuntil the minimum output can be obtained.See Figure 3-10 or call factory service forvalue.

5) Lower the material to the minimumoperating level. Output current will typicallyexceed full scale.

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifcurrent did not exceed full scale in Step 5),leave Step Span in Position #1).*

7) Turn the Fine Span control clockwiseuntil the level is full scale (20 mA) or actuallevel.*Calibration is now complete.

*If output is less than full scale, a highersensitivity instrument may be required.Consult factory.

CALIBRATION

408-8200-LM/p. 17

3) Set Step Span and Step Zero toPosition #1.

4) With the material at the lower operatinglevel, adjust the Step and Fine Zero controlsuntil output is minimum (4mA).

5) Raise the material to the upper operatinglevel, but not touching the probe plate.Output current will typically exceed full scalecurrent.

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifcurrent did not exceed full scale in Step 5,leave Step Span in Position #1).*

7) Turn the Fine Span control clockwiseuntil the output is full scale (20 mA) oractual level.*

Calibration is now complete. (Note thatproximity applications are non-linear.)

*If output is less than full scale, a highersensitivity instrument may be required.Consult factory.

B. Proximity - Reverse Acting (HLFS)(Output falls as material rises.)

1) Be sure Fail-Safe link is in "REV" posi-tion. See Section 3.1.3.

2) Set Fine Span and Fine Zero controls toextreme counterclockwise position. Do notforce. See Figure 3-7.

3) Set Step Span to Position #1.

4) With the material at the upper operatinglevel (but lower than the probe plate), adjustthe Step and Fine Zero controls until theoutput is minimum (4 mA).

5) Lower the material to the lower operatinglevel. Output current will typically exceed full scale.

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifcurrent did not exceed full scale in Step 5),leave Step Span in Position #1).*

7) Turn the Fine Span control clockwiseuntil the level is full scale (20 mA) or actuallevel.*

Calibration is now complete.

*If output is less than full scale, a highersensitivity instrument may be required.Consult factory.

3.3.3 Interface Applications

All level control applications are actuallyinterface measurements. The most com-mon being the interface of air and product.The term interface generally refers to theinterface of two immiscible liquids (liquidsthat don’t mix).

For the purpose of level control, two typesof interface are considered. The first andmore common is called normal interface.An interface is considered “normal” whenthe lower product has the higher conducti-vity (i.e. oil and water). The other type ofinterface is called inverted interface. In aninverted interface, the upper-phase producthas the higher conductivity, indicating theinsulating phase is heavier than water.

There are four separate methods for cali-bration in interface applications. (SeeFigure 3-9.) They are normal interface ineither high- or low-level fail-safe, andinverted interface in high- and low-level fail-safe.

CALIBRATION

408-8200-LM/p. 18

Figure 3-9Interface Application

A. Normal Interface-Direct Acting (LLFS)

1) Set fail-safe link to "DIR" position (seeSection 3.1.3) and set Fine Span to ex-treme counterclockwise position. Do notforce. See Figure 3-7.

2) Set Step Span to Position #1.

3) Lower the interface level until the probe(or its lowest level) is covered with only theupper phase, insulating material. Set theStep and Fine Zero controls until the outputis minimum (4 mA).

4) For this calibration procedure, a com-pensation capacitor may be required toobtain the minimum 4 mA output. It will beadded by the factory when the application isknown. If needed and not supplied, add - in100 pF steps - an NPO capacitor acrossTerminals PAD and CW until the minimumoutput can be obtained. See Figure 3-10 orcall factory service for value.

5) Raise the interface until most of thelower, waterlike phase of material is cover-ing the probe (or its highest level). Outputcurrent will typically exceed full scale.

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (If

current did not exceed full scale in Step 5,then leave Step Span in Position #1).

7) Turn the Fine Span control clockwiseuntil the output is equal to the actual inter-face level on the probe.

Calibration is now complete.

B. Normal Interface - Reverse Acting(HLFS)

1) Set the fail-safe link to the "REV" posi-tion (see Section 3.1.3) and set the FineSpan control to the extreme counterclock-wise position. See Figure 3-7.

2) Set the Step Span to Position #1.

3) Raise the level until the lower phase,conducting material is covering the probe(or its highest level). Adjust the Step andFine Zero controls until the output is mini-mum (4 mA).

4) If 4 mA cannot be obtained, add a pad-ding capacitor equal to or less than 1/4 thefull scale capacitance of the probe in theupper phase. This capacitor will be addedacross Terminals PAD and CW by thefactory when the application is known. SeeFigure 3-10.

Figure 3-10NPO Capacitor Connections

5) Lower the interface until only the upperphase, insulating material is covering theprobe (or its lowest level). Output currentwill typically exceed full scale.

CALIBRATION

408-8200-LM/p. 19

6) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifcurrent did not exceed full scale in Step 5,then leave Step Span in Position #1).

7) Turn the Fine Span control clockwiseuntil the output reads the correct interfacelevel.

Calibration is now complete.

C. Inverted Interface-Direct Acting(LLFS)

1) Move fail-safe link to "REV" position, not"DIR". See Section 3.1.3.

2) Set the Step Span control to Position #1and Fine Span in the full counterclockwiseposition. See Figure 3-7.

3) Lower the level until the probe (or itslowest level) is covered with only the conducting, upper phase material.

4) Set the Step and Fine Zero controls untiloutput is minimum (4 mA).

5) If 4 mA cannot be obtained, add a pad-ding capacitor equal to or less than 1/4 thefull scale capacitance of the probe in theupper phase. This capacitor will be addedacross Terminals PAD and CW by thefactory when the application is known. SeeFigure 3-10.

6) Raise the interface until most of thelower insulating phase of the material iscovering the probe (or its highest level).Output current will typically exceed fullscale current.

7) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifoutput current did not exceed full scale inStep 6), then leave Step Span in Position#1).

8) Turn the Fine Span control clockwiseuntil the output is equal to level of lowerphase material covering the probe.

Calibration is now complete.

D. Inverted Interface-Reverse Acting (HLFS)

1) Set fail-safe link to Low-Level Fail-Safeposition, not High Level. See Section 3.1.3.

2) Set the Step Span control to Position#1, and the Fine Span in the full counterclockwise position. See Figure 3-7.

3) Raise the interface to the desiredupper level.

4) Adjust the Step and Fine Zero con-trols until the current output is minimum(4 mA).

5) If 4 mA cannot be obtained, add apadding capacitor equal to or less than1/4 the full scale capacity of the probe inthe lower phase. This capacitor will beadded across Terminals Pad and CW bythe factory when the application isknown. See Figure 3-10.

6) Lower the interface to the desiredlower level. Output current will typically exceed full scale.

7) Turn the Step Span control clockwiseuntil the output is less than full scale. (Ifoutput current did not exceed full scale inStep 6), then leave Step Span in Position#1).

8) Turn the Fine Span control clockwiseuntil the output is full scale (20 mA) oractual level.

Calibration is now complete.

CALIBRATION

408-8200-LM/p. 20

3.4 Secondary Calibration Standard

In some applications, it is difficult or evenimpossible to completely fill or empty avessel. In such a case, it is desirable tohave a secondary calibration standardsuch as the Drexelbrook Model 401-6-8,which can be used to simulate the capa-citance of an empty or full vessel. Thefollowing procedure permits recalibrationof an instrument without the necessity ofemptying the vessel. Figure 3-11 shows atypical calibration standard. Refer to thecalibration standard manual (401-6-8) forproper connection and operation.

3.4.1 Recording Calibration Data

After initial calibration, do the following:(Also, see instruction manual for calibrationstandard.)

A. Disconnect the probe wire.

B. Connect the calibration standard to theinstrument. See Figure 3-11.

C. Adjust the calibration standard until theinstrument indicates minimum current (4mA).

D. Record the value read on the calibrationstandard and its serial number for later use.

E. Adjust the calibration standard until theinstrument indicates maximum current (20mA).

F. Record the capacitance value as inStep D.

G. Disconnect the calibration standardfrom the instrument terminals and recon-nect the probe.

3.4.2 Recalibration

Whenever it is subsequently desired tocheck or reset the calibration, or replacethe instrument, the calibration capacitor setto the value recorded above may be substi-tuted for the probe. Proceed as follows:

A. Disconnect the probe wire.

B. Connect the calibration standard to theinstrument. See Figure 3-11.

C. Set the calibration standard to the re-corded values.

D. If necessary, adjust the zero control forthe minimum current calibration and thespan control for the maximum current cali-bration.

E. Disconnect the calibration standard andreconnect the probe wire to probe.

Unit is again ready for operation.

When replacing a malfunctioning electronicunit, the replacement chassis can be cali-brated on the bench by the precedingmethod and then installed in the field.

Figure 3-11Calibration Standard

CALIBRATION

408-8200-LM/p. 21

408-8200-LM/p. 22

408-8200-LM/p. 23

SECTION 5 - TROUBLESHOOTING

5.1 Introduction

The 408-8200 Series instruments are de-signed to give years of unattended service.No periodic or scheduled maintenance isrequired.

A spare chassis is recommended for every10 units so that, in case of a failed unit, acritical application will not be held up whilethe unit is returned to the factory for repair.

If a difficulty occurs when operating yourmeasurement system, mentally divide thesystem into its component parts and testeach part individually for proper operation.

These troubleshooting procedures shouldbe followed in checking out your system. Ifattempts to locate the difficulty fail, notifyyour local factory representative or call thefactory direct and ask for the servicedepartment.

5.2 Testing the 408-8200 SeriesElectronic Unit

5.2.1 Operation Check

A. Remove the sensing element and signalwires from the transmitter.

B. Be sure Fail-Safe link is in low-level fail-safe position. See Figure 3-3.

C. With pencil, mark the positions of allcontrols on the faceplate in order to returnto them.

D. Put the Step Span in Position #1 andthe Fine Span in the full clockwise position.Put the Step Zero in Position #1 (mostsensitive position). See Figure 3-1.

E. Observing polarities, connect a DCmilliammeter and DC power supply (11.5 to50 volts) in series, and complete the loop byconnecting Terminals (-) and (+). SeeFigure 5-1.

F. Adjust the Fine Zero until the meterreads 0% (4 mA).

G. Turn the Fine Zero one clockwise turnfurther. The output should read approxi-mately between 33% and 100% (9-20 mA).

If so, the instrument is probably workingcorrectly. Each turn of the Fine Spanchanges the input a known amount. Thischecks the operation and gain of the trans-mitter.

H. If the difficulty has not been located atthis point, proceed to the output checkoutprocedure in paragraph 5.3.

Figure 5-1Power/Signal Wiring

TROUBLESHOOTING

408-8200-LM/p. 24

Table 5-1Minimum Allowable Resistance

MAXIMUM LOOP V(SUPPLY) RESISTANCE (VOLTS) (OHMS)

50 192540 142530 92524 62520 42518 32512 2511.5 0

5.3 Checking the Sensing Element

A. With an analog ohmmeter*, check theresistance of the probe-to-ground with levelbelow the probe. See Figure 5-2.

*A digital ohmmeter may produce erroneousreadings.

Figure 5-2Testing the Sensing Element with Level

Below the Probe

Resistance should be infinite. Resistanceless than 1 megohm indicates leakage,probably due to product or condensation inthe condulet, around the gland/packing nutarea. Resistance of less than 100K ohmscan cause errors in the reading. Consultfactory service.

TROUBLESHOOTING

0.02 amps

5.2.2 Drift Check

If the output of a transmitter seems to bedrifting, it is important to determine whetherthe drift is in the transmitter or in the probe.(A properly connected cable/probe neverdrifts.)

A. Remove the sensing element cable fromthe transmitter.

B. Without disturbing the dial settings,connect a capacitance standard or an NPOcapacitor* across the probe to ground input.Adjust the capacitance standard or select acapacitor value that will bring the unit onscale (preferably around 50%).

*NPO capacitor remains stable withchanges in temperature.

C. Record meter reading.

D. Observe the reading over a 24-hourperiod to see if it is stable.

E. If the reading is stable, the sensingelement or the application must be thesource of the drift. If the reading drifted,return the instrument for repair. Be sure tomark on the tag that the problem is drift.(List the capacitor size and mA deviation.)

F. Measure the resistance between the twowires that were just removed from (+) and(-) terminals of the electronic unit. Use thefollowing table to determine if the resistanceis too large.

Rmax Ω = Vsupply - 11.5 volts

408-8200-LM/p. 25

B. Check the resistance of the probe-to-ground with level above the probe. SeeFigure 5-3. Resistance readings less than100K ohms indicate either defects in theprobe insulation or, if a bare probe, that thematerial is conductive and an insulatedprobe may be required. (Consult factory.)

Figure 5-3Testing the Sensing Element with Level

Above the Probe

TROUBLESHOOTING

C. Coating error is characterized by highoutput with failing level, and a sharp drop to0% when the material goes below the tip ofthe probe. To verify a coating problem, wipethe coating off the probe and recheck instru-ment operation. If the instrument readscorrectly after cleaning, consult the factoryfor the best solution to the problem.

D. If a three-terminal sensing element isused, check resistance between centerwire/shield and shield/ground. If readingsare below 100K ohms, consult factory ser-vice.

5.4 Checking the Sensing ElementCable

Use Figure 5-4 10 check the cable.

Figure 5-4Testing the Cable

408-8200-LM/p. 26

5.5 Checking the Two-Wire SystemLoop

A. See Figure 5-5. Disconnect the powerfrom (+) and (-) terminals and measure theopen circuit voltage from the power supply.Voltage should be equivalent to sourcevoltage.

*SeeTable 5-1 for minimum allowablevoltage.

B. Connect the signal wires to (+) and (-)terminals . Turn the Step Span and StepZero to Position #1. Put Fine Span controlcompletely clockwise and adjust the FineZero until 20 mA flows.

Figure 5-5Loop Check

TROUBLESHOOTING

C. Measure the voltage between (+) and (-)terminals. Voltage should be between 11.5and 50 VDC. If there is less than the mini-mum 11.5 volts required, the loop has toomuch resistance or not enough powersupply voltage.

D. If, in Step C above, the voltage is lessthan 11.5 VDC, disconnect the power supplyand signal wires to the unit. Short the wiresthat were removed from the power supply(+) and (-) terminals.

Note: If there are active devices in the loop,the resistance can be very high.

408-8200-LM/p. 27

5.6 List of Some Possible Problems and Causes

Problem Possible Cause Checkout1. Transmitter reads 20 mA or greater a. Transmitter malfunction a. Sec. 5.2.1 even when vessel is not full. b. Water in probe condulet b. Sec. 5.4

c. Short in cable c. Sec. 5.4d. Cut in probe insulation d. Sec. 5.4e. Calibration is wrong e. Sec. 3.3

2. Transmitter never reaches 20 mA even a. Load resistance too high a. Sec. 5.2.2 though the vessel is full, or the output b. Calibration is wrong b. Sec. 3.3 reading is nonlinear at the upper end of c. Transmitter malfunction c. Sec. 5.2.1 the scale.

3. Transmitter is drifting. a. Moisture in probe gland a. Sec. 5.3b. Water in probe condulet b. Sec. 5.4c. Transmitter malfunction c. Sec. 5.2.2d. Water in cable d. Sec. 5.4e. Cut in probe insulation e. Sec. 5.4f. Calibration is wrong f. Sec. 3.3g. Material properties are changing g. Consult factory

4. Transmitter is erratic. Output reading a. Radio frequency interference a. Need RFI filters. jumps anywhere from 0% to 100%. b. Cut in probe insulation b. Sec. 5.4

c. Waves in the liquid c. Sec. 3.1.2

5. Transmitter was shipped precalibrated a. Wrong precalibration information a. Verify precal but is not reading correct level. supplied to factory information

b. Nozzle or pipe around probe is not b. Need to include specified on precalibration sheet info. on nozzle

for precal c. Accuracy being checked by c. Note: The zero point

measuring outage as a % of full tank is at end of probe;not bottom of tank

6. Probe installed in stilling well, and a. Probe touching stilling well a. Adjust mountingreadings are incorrect. b. Reading lower than actual level: Air b. Put holes in stilling

trapped in stilling well well to allow air toescape.

c. Calibration is wrong c. Sec. 3.3d. Material in stilling well may be d. Consult factory interfacinge. If plastic, may cause non-saturation e. Consult factory of probe

7. As level increases, output reading a. Fail-safe in HLFS position a. Sec. 3.1.3decreases. b. Transmitter malfunction b. Sec. 5.2.1

8. Transmitter reading 5% to 10% or a. Conductive buildup on probe a. Sec. 5.4 Consultgreater in error. Factory

b. Calibration is wrong b. Sec. 3.3

9. Erratic or incorrect readings. a. Ungrounded conducting liquid in a a. Instrument may need fiberglass vessel a ground. Consult

factory.

10. Output current reading less than a. Wiring short from shield-to-ground, a. Sec. 2.53.5 mA probably in probe head

b. Probe not connected to transmitter b. See 3.5 or 3.6

TROUBLESHOOTING

408-8200-LM/p. 28

5.7 Factory and Field ServiceAssistance

5.7.1 Telephone Assistance

If you are having difficulty with yourDrexelbrook equipment, and attempts tolocate the problem have failed, notify yourlocal Drexelbrook representative, or call toll-free for the service department; 1-800-527-6297. The Fax number is 1-215-674-2731.Drexelbrook Engineering Company is lo-cated at 205 Keith Valley Road, Horsham,Pa. 19044. To help us solve your problemquickly, please have as much of the follow-ing information as possible when you call:

Instrument Model #408-8200

Probe Model #

P.O. #Date of P.O.

Cable LengthApplication

Material being measured

TemperaturePressureAgitationBrief description of the problem

Checkout procedures that failed

Do not return equipment without first contacting the factory for a return authorizationnumber. Any equipment being returnedmust include the following information:

Reason for return

Return Authorization #

Original P.O. #Drexelbrook order #

Your company contact

“Ship To” address

To keep the paperwork in order, pleaseinclude a purchase order with returnedequipment even though it may be comingback for warranty repair. You will not becharged if covered under warranty. Pleasereturn your equipment with freight chargesprepaid. We regret that we cannot acceptcollect shipments.

Drexelbrook usually has a stock of recondi-tioned exchange units available for fasterturnaround of a repair order. If you preferyour own unit repaired rather than exchanged,please mark clearly on the return unit, “DONOT EXCHANGE”.

Spare instruments are generally in factorystock. If the application is critical, a sparechassis should be kept on hand.

5.7.2 Field Service

Trained field service personnel are avail-able on a time-plus-expense basis to assistin start-ups, diagnosing difficult applicationproblems, or in-plant training of personnel.

Periodically, Drexelbrook instrument trainingseminars for customers are held at thefactory. Contact the service department forfurther details on any of the above.

TROUBLESHOOTING

Section 6

WIRING AND CONTROL DRAWINGSFOR

CENELEC-APPROVED TRANSMITTERS

APPROVALS

408-8200-LM/p. 37

APPROVALS

408-8200-LM/p. 38

APPROVALS

205 Keith Valley Road Horsham, PA 19044US Sales 1-800-553-909224 Hour Service 1-800-527-6297International + 215-674-1234Fax + 215-674-2731E-mail drexelbrook.info@ametek.comWeb www.drexelbrook.comAn ISO 9001 Certified Company

DREXELBROOK