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UNDERWATERData Logging

A GUIDE FOR SELECTING AND DEPLOYING UNDERWATER SENSORS AND DATA LOGGING SYSTEMS

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Located in the Lower Great Lakes and Ohio River Valley region, Fondriest Environmental sells and services environmental monitoring products from industry leading suppliers such as YSI, Hach, Thermo Scientifi c, In-Situ, Turner Designs, SonTek, Vaisala, RM Young, NexSens, and many more...

The applications engineers and scientists at Fondriest Environmental specialize in designing and implementing real-time monitoring systems with data transmission via cellular, radio, landline phone, and satellite telemetry, as well as sharing data via the internet.

It is the company’s goal to supply equipment that provides high-quality data and years of service. Unlike many suppliers who carry every brand with every option, Fondriest seeks out vendors and products that meet stringent performance and quality standards. The company searches for advanced technologies that extend deployments and provide new methods of detection. The application engineers and scientists deploy many of the same products that they offer their customers.

Over the years, Fondriest Environmental has greatly expanded its product offering to provide environmental professionals with not only the fi nest measurement instrumentation, but also with a wide variety of equipment and accessories used extensively in day-to-day fi eld work.

Fondriest’s commitment to customers and their projects ensure continued product support, resulting in long-lasting, value-added business relationships.

Conducting real-time water sampling has never been easier. The highly portable NexSens MB-100 data buoy and versatile SDL submersible data logger complement each other well to achieve a powerful, easy-to-use, and cost effective water monitoring solution.

The NexSens SDL supports nearly every environmental sensor interface and can transmit data wirelessly in real-time. It can withstand even the harshest conditions, run for months on alkaline batteries, and be fully submersed in water. And with radio, cellular, and satellite telemetry options, it’s able to transmit data from even the remotest locations on Earth.

The lightweight MB-100 data buoy provides fl otation for the SDL in both surface and sub-surface applications. To the passerby, the system appears to be a simple marker buoy. Safely hidden beneath the buoy’s hood, though, are all the electronics needed to record and transmit data.

This guide is intended to provide the information needed to conceptualize, design, and build underwater data logging systems using the NexSens SDL and MB-100.

INTRODUCTION

WHAT’S INSIDE

Surface and Sub-Surface Buoys

MB-100 Data Buoy

Submersible Data Loggers

Sensor Interface

Measurement Parameters

Common Deployments

Telemetry

Managing Data

Short-Term Projects

Application

System Confi guration Tool

3

5

7

11

13

27

31

33

33

35

37

Fondriest Environmental, Inc.

1415 Research Park Drive

Beavercreek, OH 45432

when your

demandsresearchquality data

Underwater Data Logging | 2

SURFACE BUOY

TEMPERATURESTRING

TEMPERATURESTRING

MULTI-PARAMETERSONDE

MULTI-PARAMETERSONDE

MB-100

MB-100

ANCHOR & CHAIN

ANCHOR

SUB-SURFACE BUOY

Underwater Data Logging | 43 | Underwater Data Logging

The MB-100 data buoy securely houses the NexSens SDL data logger. A wireless transmitter and antenna can be positioned above the water but hidden under the buoy hood. All sensor connections are below the surface with ruggedized and double-sealed waterproof connectors. The data buoy’s sturdy construction includes an inner core of cross-linked polyethylene foam, heavy polymer skin, and an unbreakable stainless steel instrument cage.

A fully loaded system (with data logger and batteries) weighs just over 30 lbs. and is easily deployed by one person from any size vessel. Simply attach a single-point mooring assembly and throw it overboard. The buoy will “right” itself and begin logging data immediately. It can then transmit this data via radio-to-shore, cellular, or Iridium satellite telemetry.

Designed for years of service and robust enough for the roughest of seas, the MB-100 is an ideal platform for almost any water monitoring project.

Buoyancy (surface buoy with hood)

Buoyancy (sub-surface buoy)

Weight (no payload)

Weight (with SDL500 and batteries)

Deployment Depth (minimum)

Mooring

100 lbs

60 lbs

20 lbs

33 lbs

12 inches

Single Point

MB-100 Data Buoy

MB-100 Specifications


Remove buoy hood for sub-surface deployments

Remove buoy hood Remove buoy hood for sub-surface for sub-surface deploymentsdeployments

18” 12” 32”

9”BUOY HOOD

FLOTATION

SDL500

INSTRUMENT CAGE

MOORING EYE

The NexSens SDL Submersible Data Logger is a rugged, self-powered remote data logging system that integrates seamlessly with an MB-100 data buoy. It consists of the data logger and communication module housed in a fully-submersible, fi ve-inch-diameter round enclosure. The SDL can be outfi tted with radio, cellular, or satellite telemetry.

SDL data loggers can connect to virtually any sensor via analog and digital interfaces. The system is confi gured with fi ve sensor ports for connection to industry-standard communication protocols. It is the fi rst in a line of smart environmental data logging equipment with sensorBUS Technology, allowing multiple protocols to be transmitted along a single eight-wire bus. sensorBUS supports SDI-12, RS-485, and 1-wire. Other sensor connections compatible with the SDL include 0-2.5 VDC, pulse count, and digital I/O. Each sensor port offers a UW receptacle with double O-ring seal for a reliable waterproof connection.

Common sensor connections include multi-parameter sondes, water quality sensors, temperature strings, Doppler velocity meters, and water depth sensors. User-supplied sensor cable assemblies can also be connectorized and tested at the factory for SDL integration. With this sensor interface versatility, the measurement possibilities are endless.

When it comes to fi eld ruggedness, the NexSens SDL is in a class of its own. The housing is constructed of impact-resistant PVC and includes two elastomer bumpers for long-term deployment in close-fi tting pipes and buoy ports. Internal circuit boards and communication modules are shock mounted, and all access ports incorporate redundant sealing. The SDL withstands extreme wave action, drops, fl oods, periodic and long-term deployment underwater, and more. When fi tted for wireless remote communication, the antennas are also waterproof.

The SDL can be powered autonomously by eight D-cell alkaline batteries. When used with NexSens buoys larger than the MB-100, optional solar power kits can provide long-term continuous operation and solar charging.

Submersible Data Logger SDL500 KEY FEATURES

ANTENNA

HOUSING

BATTERY PACK

SENSOR CONNECTION

High gain radio, cellular & satellite antennas are designed for brief periods of submersion.

Gray PVC construction with redundant O-ring seal allows the data logger to be submerged up to 200 feet.

White Delrin top with O-ring seal allows quick access to (8) D-cell batteries without the need for tools.

Five sensor ports with digital and analog interfaces for multi-parameter water quality & hydrology measurements.


Analog Inputs

Analog Outputs

Power Outputs

Pulse Counters

Digital I/O Ports

SDI-12 Interface

RS-232 Interface

RS-485 Interface

NMEA 0183 Interface

Modbus RTU Interface

Internal Memory

Power Requirements

Typical Current Draw

Battery

Maximum Depth

Temperature Range

Dimensions

Weight

(2) differential or (4) single-ended, 0-2.5V auto range, 12-bit resolution

(1) 12-bit channel, 0-2.5V

(1) 12V 100 mA switch; (1) 5V 100 mA switch; (1) 12V output, fused from battery

(1) tipping bucket counter, max rate: 12 Hz

(1) standard generic I/O port

(1) SDI-12 port (10 sensors), v1.3, can be confi gured as master or slave

(2) RS-232 ports

(2) RS-485 ports, host and sensor interface

(2) RS-232 ports

RS-232 or RS-485, can be confi gured as master or slave

2 MB Flash memory, over 500,000 data points minimum

Voltage: 10.7 to 16 VDC

5 mA sleep, 10 mA processing, 36 mA analog measurement

(8) D-cell alkaline batteries, internal; optional 12VDC power

200 ft.

0 to +60°C

18.25” length x 5.5” diameter

11.0 lbs without batteries; 13.8 lbs with batteries

SDL500 Specifications

Sensor Bulkhead Sensor Bulkhead Port

PORT P0

Pin Signal Direction

1

2

3

4

5

6

7

8

Sensor RS-485A

Sensor RS-485B

SDI-12 Data

Battery

Switch 5 V, 100 mA

P0.Rx

Ground

P0.Tx

Input/Output

Input/Output

Input/Output

Input/Output

Output

Input

Output

PORT D


1

2

3

4

5

6

7

8

Sensor RS-485A

Sensor RS-485B

SDI-12 Data

Battery

Switch 5 V, 100 mA

Rain

Ground

DIO0

Input/Output

Input/Output

Input/Output

Input/Output

Output

Input

Input/Output

PORT P1


1

2

3

4

5

6

7

8

Sensor RS-485A

Sensor RS-485B

SDI-12 Data

Switch 12 V, 100 mA

Switch 5 V, 100 mA

P1.Rx

Ground

P1.Tx

Input/Output

Input/Output

Input/Output

Output

Output

Input

Output

PORT A


1

2

3

4

5

6

7

8

AD12

AD13

AD14

Switch 12 V, 100 mA

DA1

AD15

Ground

Analog Ground

Input

Input

Input

Output

Output

Input

PORT T


1

2

3

4

5

6

7

8

Sensor RS-485A

Sensor RS-485B

SDI-12 Data

Switch 12 V, 100 mA

Switch 5 V, 100 mA

1-Wire

Ground

P2.Rx

Input/Output

Input/Output

Input/Output

Output

Output

Input/Output

Input

PIN 8 PIN 1

SDL500 Pin Description

T

P1 P0 A

D


sensorBUS technology is an integration of several popular sensor interface types into a single, eight-wire cable bus. The technology was developed to simplify deployments of numerous sensors on fl oating platforms. This has historically required cable assemblies for each sensor, causing issues with sensor wiring, cable tangling, and excessive cable weight. However, by connecting all sensors along a single cable bus, the sensor string becomes easier to work with and more versatile.

Using a single cable assembly, sensorBUS users can connect SDI-12, RS-485 multi-drop, and 1-wire temperature string sensors. Additionally, sensorBUS can provide both 12VDC and 5VDC power to connected probes. Each sensor is identifi ed by a unique address or serial number, and parameter data is logged.

SENSOR INTERFACEsensorBUS Connections

The Plug-and-Play power of NexSens sensorBUS

SDI-12 is a serial data interface capable of supporting as many as 10 sensors. The three-wire system was developed specifi cally for environmental monitoring applications. The motivation to develop SDI-12 began in the 1980s, when a group of environmental monitoring specialists were frustrated with the complexity of interfacing analog sensors with the data loggers of the time. These low-power sensors were also extremely unreliable.

The Serial Digital Interface at 1200 baud Protocol (SDI-12) was the solution to the environmental monitoring specialist’s frustrations. SDI-12 governs exactly how a sensor must communicate with a data logger. Any sensor claiming to be SDI-12 compatible must accept a standard set of commands and conform to specifi c electrical and power standards. SDI-12 sensors are smart sensors. They contain specialized circuitry and programming to enable users to confi gure and calibrate the sensor completely independent of a data logger.

RS-485 is a multi-point communications network capable of supporting hundreds of nodes (sensors) over a few thousand feet. It offers superior performance when communicating at high data rates or over long distances. The balanced 2-wire system is constructed with a twisted pair of conductors surrounded by a shield.

Differential signal transmission allows for high immunity to signal noise, making the RS-485’s long cable distances possible. The RS-485 specifi cation allows for a truly multi-point communications network, accommodating as many as 32 drivers and 32 receivers. RS-485 communication is between a master (data logger) and slaves (smart sensors) communicating at 1,200 to 57,600 baud.

Some sensors output analog voltage within a specifi c range, which is proportional to a parameter concentration and can be interpreted by a data logger. For example, 0-2.5 VDC temperature sensor will output 0 volts at 0 degrees Celsius and 2.5 volts at 50 degrees Celsius. This relationship is linear, and actual translation to a temperature value is handled within the data logger.

Some sensors output frequency (pulses), which is proportional to parameter concentration and can be interpreted by a data logger. An electronic pulse counter within a NexSens data logger can record the frequency of pulses that are transmitted from a sensor. A common example is a tipping bucket rain gauge, which records rainfall. Every time a specifi c amount of rain falls into the sensor, a small “bucket” tips, triggering a switch that sends an electronic signal. The data logger determines total rainfall based on the number of electrical pulses received. Some fl ow sensors output frequency (pulses per second), and the data logger translates the frequency into fl ow (CFS).

SDI-12

RS-485 multi-drop

Voltage Output: 0-2.5 VDC

Pulse Count

Other Supported Connections

1-wire temp string is a multi-point communications network capable of supporting 128 temperature measurement nodes (sensors) across distances as far as 200 meters. The underlying protocol, called 1-Wire, is a communications bus system designed by Dallas Semiconductor Corp. It allows for low-speed data, signaling, and power over a single signal. Since all functions are communicated via a single-contact serial interface, it requires only one wire. 1-wire temp string communication is between a master (data logger) and slaves (smart sensors) communicating at 9,600 baud.

In addition to the three sensorBUS options, the SDL is capable of supporting analog and digital interfaces. This includes sensors with voltage and frequency outputs.

1-Wire Temperature String


MEASUREMENT PARAMETERSand Sensors Temperature

Temperature is one of water’s most basic properties, and many other parameters depend on temperature for sensor compensation and parameter calculation. Furthermore, water’s temperature has many important effects on the biological, chemical, and physical aspects of aquatic environments. It affects the growth, reproduction, and migration of living organisms. Warmer water also decreases the solubility of oxygen, thus limiting oxygen supply.

Temperature data is one of the most commonly reported water quality parameters. Not only is it extremely important in a number of aquatic processes, but it is relatively inexpensive and easy to measure.

In-situ monitoring systems commonly measure water temperature with a thermistor, which is a device that undergoes a predictable change in resistance in response to temperature changes. This resistance is measured and converted to a temperature reading in Celsius or Fahrenheit.

A vast selection of in-situ sensors and monitoring options exists, allowing the measurement of numerous water quality and hydrology parameters. The following measurement parameters are commonly integrated on MB-100 buoys with submersible data logging systems. The NexSens SDL’s powerful interface allows for integration with virtually any sensor, and a Fondriest applications engineer can confi rm sensor compatibility if it is not listed.

T-Node connectorized water temperature sensorT-Node connectorized water T-Node connectorized water temperature sensortemperature sensor

Sensor Application

NexSens T-Node

In-Situ Rugged TROLL 200

YSI 6-Series Sonde

Temperature strings

Temperature & depth

Temperature, combined with the most common water quality parameters


Dissolved OxygenSalinity / Conductivity

Dissolved oxygen, or how much oxygen is dissolved within the water, is vital for underwater life. It is what aquatic creatures need to breathe. The DO concentration is often expressed in milligrams of oxygen per liter (mg/L) of water, parts per million (ppm), or percent air saturation (% air sat).

Dr. Leland Clark offered the fi rst practical in-situ measurements with his patented membrane-covered, electrochemical sensor. Over the years, the technology has evolved into three common electrochemical sensor technologies: galvanic, polarographic, and pulsed polarographic.

Galvanic and polarographic DO sensors both use a thin semi-permeable membrane that wraps over an electrolyte solution and two metal electrodes. Oxygen in the water diffuses through the membrane at a rate proportional to its partial pressure. These probes measure the current as oxygen is reduced at the cathode and more oxygen diffuses through the membrane. Membrane-based DO sensors, however, are not ideal for extended deployments. The membrane is fragile and must be replaced often. Moreover, these sensors require frequent calibration and stirring or fl owing water.

Newly developed dissolved oxygen sensors based on optical sensing technology offer improved performance for unattended deployments. These units have more durable sensing elements than membrane-based DO sensors. They utilize a fl uorescent element that reacts to different levels of oxygen in the water, which is measurable by the color of light that refl ects off the fl uorescent element and into a light detector inside the sensor. This technology has changed DO sensors from having the shortest deployment endurance to one of the longest and is far more feasible for long-term monitoring applications.

Aquatic animals and plants are adapted for a certain range of salinity. Spikes outside of this range may indicate a pollution event, negatively affecting and possibly killing aquatic life. Industries may release chemicals that alter the salinity in a particular body of water.

The most comprehensive method to determine salinity is to perform a chemical analysis of the concentrations of different ions in water, such as calcium, sodium, chloride, and carbonate. However, since this method is time-consuming, tedious, expensive, and infeasible for real-time monitoring, salinity is estimated from conductivity.

Salts in water conduct current, thus conductivity is proportional to the salt concentration. The equation used to derive salt concentration from conductivity levels also accounts for the temperature dependence of conductivity.

Conductivity is reported using a unit called a siemen, often reported in millisiemens per centimeter (mS/cm) or microsiemens per centimeter (uS/cm). Since conductivity increases as water temperature increases, a temperature-independent reading called specifi c conductance is often used. Specifi c conductance adjusts readings to what conductivity would be if the water were 25 degrees Celsius. This allows the conductivity of water at different temperatures to be compared.

Conductivity is measured by a sensor that determines how easily an electrical current fl ows between two electrodes. The electrical current has a direct relationship with the conductivity of the solution.


Sensor ApplicationSensor Application

In-Situ RDO PRO

YSI 600OMS V2 Sonde

YSI 6-Series Sonde

In-Situ Aqua TROLL 100

In-Situ Aqua TROLL 200

YSI 6-Series Sonde

Optical dissolved oxygen & temperature

Optical dissolved oxygen, conductivity, salinity & temperature

Optical dissolved oxygen, combined with the most common water quality parameters

Conductivity, salinity & temperature

Conductivity, salinity, temperature & depth

Conductivity, combined with the most common water quality parameters

In-Situ Aqua TROLL 100 conductivity, salinity & temperature sensor

In-Situ RDO PRO optical dissolved oxygen & temperature sensorIn-Situ RDO PRO optical dissolved In-Situ RDO PRO optical dissolved

In-Situ Aqua TROLL 100 In-Situ Aqua TROLL 100

TurbiditypH

Suspended sediments in water, such as clay, silt, and algae, can have many negative effects on aquatic life. Suspended materials reduce water clarity and can block light to aquatic plants, smother aquatic organisms, and carry contaminants and pathogens, such as lead, mercury, and bacteria. Suspended sediments are introduced by runoff from construction, agriculture, and logging sites; runoff from urban areas with paved and impermeable surfaces; dredging activities; eroding stream banks; bottom-dwelling fi sh and burrowing animals; excessive algae growth; high-velocity water, including storm water; and windy conditions in shallow-water areas.

While measuring total suspended solids (TSS) directly is the ideal method to evaluate sediment suspension, it is not feasible for real-time applications. TSS can presently only be evaluated by collecting water samples and performing laboratory tests, which involve separating the sediment from the water and weighing it. Thus, turbidity, a measurement of water cloudiness, is typically used to provide real-time data that represents approximate levels of suspension.

Turbidity is commonly reported in nephelometric turbidity units (NTU). An instrument called a nephelometer, also named a turbidimeter, is the most common device used present-day to measure turbidity. It does so by shining a light beam through the water and then measuring how much light is scattered to the side at a 90-degree angle. Particle density in the water is thus a function of how much light is scattered.

Water’s pH level can indicate the presence of pollution from accidental spills, agricultural runoff, sewer overfl ows, and both point and non-point sources. While young fi sh and insect larvae are highly sensitive to low pH values, extreme values at either end of the scale can be lethal to most organisms.

Electronic pH sensors typically use a specially-prepared electrode with an ion-selective barrier that measures the hydrogen ion concentration in the water. A measurable potential is generated between this electrode and a reference electrode, which is surrounded with a neutral pH buffer. The voltage generated is directly proportional to the water’s pH level.

YSI’s sonde-based pH sensors utilize this technique and contain a “long-life” sealed gel reference, eliminating the need to refi ll. These pH sensors have been carefully designed to perform under all ionic strength conditions, from seawater with a conductivity of 53,000 uS/cm, to “average” freshwater lakes and rivers with conductivities of 200 to 1500 uS/cm, and even pure mountain streams with conductivities as low as 15 uS/cm, which has historically been the most diffi cult medium with respect to accuracy, quick response to pH changes, and minimal fl ow dependence.


Sensor Application

YSI 6-Series Sonde pH, combined with the most common water quality parameters

Sensor Application

Turner Cyclops-7

YSI 600OMS V2 Sonde

YSI 6-Series Sonde

Turner C3

Turner C6

Turbidity

Turbidity, conductivity, salinity & temperature

Turbidity, combined with the most common water quality parameters

Turbidity, combined with two additional optical sensors

Turbidity, combined with fi ve additional optical sensors

YSI 600OMS V2 sonde with self-wiping turbidity sensor

53,000 uS/cm, to “average” freshwater lakes and rivers with conductivities of 200 to 53,000 uS/cm, to “average” freshwater lakes and rivers with conductivities of 200 to 1500 uS/cm, and even pure mountain streams with conductivities as low as 15 uS/cm, 1500 uS/cm, and even pure mountain streams with conductivities as low as 15 uS/cm, which has historically been the most diffi cult medium with respect to accuracy, quick which has historically been the most diffi cult medium with respect to accuracy, quick response to pH changes, and minimal fl ow dependence.response to pH changes, and minimal fl ow dependence.

Sensor ApplicationSensor Application

YSI 6920 V2-2 sonde outfi tted with full sensor suite

YSI 600OMS V2 sonde with self-wiping YSI 600OMS V2 sonde with self-wiping

Cyanobacteria (Blue-Green Algae)Chlorophyll

Cyanobacteria, also known as blue-green algae, are a group of bacteria that obtain their energy through photosynthesis, similar to plants. Besides chlorophyll, cyanobacteria also have other pigments that can be detected by fl uorescence. Cyanobacteria are known for their important role in highly visible and noxious surface scums, called harmful algal blooms, that form on the surfaces of lakes and ponds around the world. Cyanobacteria can produce toxins harmful to other aquatic organisms and humans.

Cyanobacteria often contain pigments of phycocyanin or phycoerythrin. Fluorescence sensors can measure the concentration of phycocyanin or phycoerythrin in water. Phycocyanin, found in freshwater systems, absorbs red and orange light at about 620 nm, and it fl uoresces at about 650 nm. Found in saltwater, phycoerythrin absorbs light in 495 and 545-566 nm wavelengths and fl uoresces at 575 nm.

There are sensors specifi c to measuring either phycocyanin or phycoerythrin. Examples are the YSI models 6131 (phycocyanin) and 6132 (phycoerythrin). Measuring in units of cells per milliliter, these sensors are insensitive to other parameters, like chlorophyll and dissolved oxygen, in the water. Using in-situ fl uorometry, these sensors provide real-time data on the biomass of algae without the need to retrieve water samples and take them back to the laboratory for analysis.

Chlorophyll is the key biochemical component in photosynthesis. In its many forms, it is present within all photosynthetic organisms, such as phytoplankton and cyanobacteria (blue-green algae). Chlorophyll levels can serve as a measurement of the concentration of phytoplankton, which is an indicator of the general biological “health” of a river. The data is also useful for predicting detrimental algal blooms and, indirectly, determining nutrient loading.

Chlorophyll fl uoresces when irradiated with light of a particular wavelength (435-470 nm), emitting light of a higher wavelength. In-situ fl uorometers shine a beam of light of the proper wavelength into the water and then measure the higher wavelength light which is emitted. Since these sensors only scan a narrow range of possible wavelengths, ambient light within the water does not drastically interfere with readings. These real-time chlorophyll measurements can complement extractive lab analysis.


Sensor Application Sensor Application

Turner Cyclops-7

YSI 600OMS V2 Sonde

YSI 6-Series Sonde

Turner C3

Turner C6

Turner Cyclops-7

YSI 600OMS V2 Sonde

YSI 6-Series Sonde

Turner C3

Turner C6

Chlorophyll

Chlorophyll, conductivity, salinity & temperature

Chlorophyll, combined with the most common water quality parameters

Chlorophyll, combined with two additional optical sensors

Chlorophyll, combined with fi ve additional optical sensors

Blue-green algae

Blue-green algae, conductivity, salinity & temperature

Blue-green algae, combined with the most common water quality parameters

Blue-green algae, combined with two additional optical sensors

Blue-green algae, combined with fi ve additional optical sensors

Turner C3 submersible fl uorometer with self-cleaning wiper Turner C6 multi-sensor platform

for up to six optical sensors

Underwater LightDissolved Organic Matter (CDOM)

Light and water transparency are two of the most fundamental properties of aquatic ecosystems. The amount of light exposure can regulate the heating and cooling of a given water body. Transparency regulates a number of in-water processes, including the maximum depth of photosynthesis and oxygen production as well as changes in temperature throughout the water column.

Underwater light sensors can be used to measure transparency. Typically, two light sensors are placed below water at different depths. These sensors provide data on changes in light with depth thereby providing an estimate of transparency. Underwater light sensors are typically located on an arm away from the monitoring platform to reduce or eliminate potential shading effects.

Many different light sensors exist depending on the wavelength(s) of interest. Sensors exist to measure visible light (400 – 750 nm), PAR (photosynthetically active radiation, 400 – 700 nm), ultraviolet light UVA and UVB (280-400 nm), infrared (700-3000 nm), total shortwave radiation, total long wave radiation, and total global radiation. PAR sensors are generally the most common light sensors because PAR wavelengths are important in aquatic ecosystems as they are used by photosynthesizing algae.

Colored (or chromophoric) dissolved organic matter (CDOM) often gives water a brownish or yellowish hue. CDOM naturally forms from trees and other vegetation in the landscape around water bodies but is also concentrated in water from agriculture and improper land use. CDOM is analogous to what happens when tea leaves soak in a cup of hot water. It often regulates transparency to both visible light and damaging ultraviolet radiation in lakes, and it is a food source for the basis of aquatic food webs, providing nutrients for algae and energy for bacteria.

Typically, CDOM is measured in the water with a fl uorometer. A lamp inside the sensor emits ultraviolet light onto a water sample containing CDOM. CDOM fl uoresces in the same manner a black light shining on clothing produces different color light. The fl uorescence is registered by a photodiode inside the sensor and outputs a measurable voltage. The voltage is proportional to the concentration of CDOM.


Turner Cyclops-7 CDOM sensor

LI-COR LI-193SA spherical PAR sensor

400 – 700 nm), ultraviolet light UVA and UVB (280-400 nm), infrared (700-3000 nm), 400 – 700 nm), ultraviolet light UVA and UVB (280-400 nm), infrared (700-3000 nm), total shortwave radiation, total long wave radiation, and total global radiation. PAR total shortwave radiation, total long wave radiation, and total global radiation. PAR sensors are generally the most common light sensors because PAR wavelengths are sensors are generally the most common light sensors because PAR wavelengths are important in aquatic ecosystems as they are used by photosynthesizing algae.important in aquatic ecosystems as they are used by photosynthesizing algae.

Sensor Application

Turner Cyclops-7

Turner C3

Turner C6

CDOM

CDOM, combined with two additional optical sensors

CDOM, combined with fi ve additional optical sensors

Turner Cyclops-7 Turner Cyclops-7 CDOM sensorCDOM sensor

Sensor Application

LI-COR LI-192SA

LI-COR LI-193SA

Biospherical QCP-2200

Biospherical QSP-2200

Biospherical QSR-2200

Photosyntheically Active Radiation (PAR)

Photosynthetic Photon Flux Fluence Rate (PPFFR)

Downwelling cosine irradiance over PAR

Downwelling scalar irradiance over PAR

Sky irradiance over PAR

Distance to BottomDepth

Currents and other forces can cause sea-bottom sediment to shift, resulting in changes in the shape of the sea fl oor. Sonar altimeters are typically utilized to provide an accurate distance to the sea fl oor from a fi xed position.

The altimeter transmits a narrow beam acoustic signal and then measures the round trip time for the sound pulse to travel from the transducer through the water, refl ect off a surface, and return to the transducer. Since the nominal speed of sound through water is known (1,500 meters per second), the pulse’s travel time can be used to calculate the total distance from the altimeter to the bottom of a water body.

Modern sonar altimeters use digital technology and output an RS-232 signal for interfacing with NexSens submersible data loggers. The sensor cable can be factory-connectorized with NexSens underwater connectors for integration to an SDL sensor port.

It is often important to know water depth, which is defi ned as distance below the surface. Depth is most commonly measured by a non-vented strain gauge, also called an absolute pressure sensor.

A differential strain gauge transducer measures pressure with one side of the transducer exposed to the water and the other side exposed to a vacuum. The resulting measurement includes the combined pressure exerted on the sensor by the atmosphere and the head of water above it. Calibrating, or zeroing, the offset in air prior to deployment removes the atmospheric pressure contribution. The sensor is fi xed along a mooring line beneath the buoy with a cable that runs up to the buoy and connects to the submersible data logger. Depth sensors are often integrated with other sensors, or a fi xed depth sensor can be attached on a mooring line with another sensor to track its position in the water column.

In order to determine only the water’s pressure, absolute sensors must be regularly calibrated with an atmospheric pressure reading as the atmospheric pressure fl uctuates. If the depth sensor will be left underwater for long periods of time and accurate depth is required, then barometric compensation will be required. A barometric pressure sensor can be placed on shore in proximity to the monitoring buoy to provide compensation data.

Sensor Application

Benthos PSA-916 Distance-to-bottom

In-Situ Rugged TROLL 200 depth & temperature sensor

Benthos PSA-916 sonar altimeter

Sensor Application

In-Situ Rugged TROLL 200

NexSens Absolute Accustage

Depth & temperature

Depth & temperature



Sensor Application

NexSens Absolute Accustage Wave height & period

Currents are the vertical or horizontal movement of water. Among other factors, they can signifi cantly affect the circulation of sediments and nutrients, degree of temperature stratifi cation, oxygen distribution, and level of turbidity.

Acoustic Doppler current meters use sonar for precise water velocity measurements in rivers, streams, channels, harbors, or lakes. They are often anchored to the sea fl oor and can directly measure water velocity in two or three dimensions.

A current meter emits ultrasonic signals of known frequency into the water and then measures the reverberation frequency. The difference in frequencies, called the Doppler shift, is proportional to the speed of the water traveling in the area. Doppler current meters are available in several confi gurations, making them suitable for a wide range of applications. Many also support the use of one of their measurement cells for recording changes in water level.

SonTek Argonaut-XR 3D current meter

Current

Waves transmit immense amounts of energy through the world’s water bodies. They are often the primary factor that determines the geometry of beaches, transportation of sediments in the nearshore region, and stresses on coastal structures. Larger waves can also pose a threat to ships and people in the water.

Fast sampling depth sensors are capable of monitoring data about wave frequency and height. Wave direction measurements are also possible but require more sophisticated monitoring equipment.

To measure wave information, a pressure-based depth sensor can be mounted at a fi xed location underwater and calculate the height of the water column above it. As a wave crest passes by, water column height increases; when troughs approach, it decreases. The resulting record of sea surface elevations can be used to calculate wave energy data.

Wave

NexSens AccuStage water level sensor

Sensor Application

SonTek Argonaut-SL

SonTek Argonaut-XR

2-Dimensional velocity

3-Dimensional velocity

COMMON DEPLOYMENTSTemperature String Multi-Parameter

Water Quality

Part # Description Quantity Part # Description Quantity

MB-100 MB-100

SS187-10 UW-6091

A49-SDL A49-SDL

SSPA625i-BOW SS187-10

UW-1 6565

DOR70 SSPA625i-BOW

DOR70

SDL500C SDL500C

SSPA500i-BOW MC6920

T-Node 6920V2-01

HGPC500i SSPA500i-BOW

HGPC500i

T-Clamp 6150

Monitoring buoy, polmymer-coated foam hull,100 lb. buoyancy


Custom built 3/16” vinyl coated SS mooring line, 10’ Underwater cable adapter for YSI 6-series sondes, 25 ft.

High gain cellular antenna for SLD500 data logger High gain cellular antenna for SLD500 data logger

Stainless steel bow shackle, 5/8” Custom built 3/16” vinyl coated stainless steel mooring line, 10”

Underwater cable assembly, 1m pH/ORP sensor

Pyramid anchor, 70 lbs. Stainless steel bow shackle, 5/8”

Pyramid anchor, 70 lbs.

SDL500 submersible data logger with cellular modem telemetry


Stainless steel bow shackle, 1/2” Mooring clamp for YSI 6920 series sondes

T-Node connectorized water temperature sensor YSI 6920 V2-2 Sonde with combinationtemperature/conductivity sensor

Galvanized chain, 1/2”, priced per foot Stainless steel bow shackle, 1/2”

Galvanized chain, 1/2”, priced per foot

Mooring clamp for NexSens temperature strings ROX optical dissolved oxygen sensor with self-cleaning wiper

1 1

1 1

1 1

1 1

3 1

1 1

1

1 1

2 1

3 1

6 2

6

3 1

Email [email protected] for pricing on this and other confi gurations.



Turbidity Monitoring Oxygen Profiling

Part # Description Quantity

MB-100

SS187-10

A49-SDL

SSPA625i-BOW

6136

DOR70

SDL500C

SSPA500i-BOW

600-01

HGPC500i

MC600


Custom built 3/16” vinyl coated SS mooring line, 10’

High gain cellular antenna for SLD500 data logger

Stainless steel bow shackle, 5/8”

Turbidity sensor with self-cleaning wiper




600OMS V2 Sonde with temperature/conductivity sensor


Mooring clamp for YSI 600 series sondes

1

1

1

1

1

1

1

2

1

6

1

Part # Description Quantity

MB-100

SS187-10

A49-SDL

SSPA625i-BOW

UW-TL8

DOR70

SDL500C

SSPA500i-BOW

0089760

HGPC500i

MC600


Custom built 3/16” vinyl coated SS mooring line, 10’

High gain cellular antenna for SLD500 data logger


Underwater cable adapter for In-Situ sensors




In-Situ RDO PRO optical dissolved oxygen sensor, Twist-Lock connector


Mooring clamp for RDO PRO optical dissolved oxygen sensor

1

1

1

1

3

1

1

2

3

6

3

Email [email protected] for pricing on this and other confi gurations.

NexSens SDL data loggers can transmit from almost anywhere on Earth. Options are available for radio, cellular, and satellite telemetry. Two factors help determine the best and most cost-effective telemetry method — site conditions and distance to the project computer.

When the project computer can be located within a few miles (line-of-sight) or few hundred feet (non-line-of-sight), license-free, spread-spectrum radio telemetry is often the best choice. A radio telemetry data logger is able to communicate with a NexSens radio base station, which serves as a central hub for one or more remote data loggers and can connect directly to a base computer or relay data to a remote computer.

Cellular telemetry requires the additional cost of a cellular data plan, but it offers greater geographic fl exibility. With this method, data transmissions from almost anywhere in the U.S. are possible. A cellular data logger does not need to be in proximity to a base station; instead, its data is accessible, with appropriate credentials, over the Internet. NexSens SDL data loggers can use cellular data plans from many U.S. providers, such as AT&T, Verizon, or Sprint Nextel.

For the remotest applications — where cellular telemetry is unfeasible — satellite telemetry may be required. Data loggers with this option communicate with Iridium satellites, allowing them to transmit data from even the most remote locations.

TELEMETRY

Radio

Cellular

Satellite

BASE STATION COMPUTER


An underwater data logging system will record sensor readings at a user-defi ned interval. The user also sets the rate at which data is transmitted to a base station. The data logging and transmission intervals depend on a number of factors, including the system’s power source, energy required by sensors, and number of sensors. Fondriest engineers will help devise a power budget to ensure realistic sampling intervals.

MANAGING DATA

The computer at the receiving end of data logger transmissions requires software to acquire, process, analyze, and possibly publish water quality data. NexSens iChart software is a user-friendly package that can fulfi ll these needs, serving as the centralized interface and database for all incoming data. All data and sensor confi guration settings are stored in a single iChart database. The software is designed with an open architecture and offers a straightforward interface, making it easy for individuals at any level of technical expertise to confi gure and customize a monitoring and data collection project.

The software offers a unique historical report creation tool that can generate customized reports with data from all sensors in an iChart database. When creating a report, users can include specifi c information about the monitoring site, location, sensors, and project. After creation, reports can be converted to PDF, exported to Microsoft Excel or CSV fi les, sent to interested parties via email, uploaded to a web server, and more. The report template can also be saved and automatically generated, further automating the reporting process.

iChart software can immediately transmit automated alarm notifi cations when certain pre-defi ned parameter limits are exceeded.

Software alarms can notify persons via SMS text messaging or email. If a voice message alarm is preferable, the NexSens system can be confi gured with an auto-dialer to call a designated individual (or list of individuals) with a pre-recorded message.

Additionally, NexSens data loggers can temporarily change their functionality as a response to exceeded parameter limits. For example, the data logger can change sample and log intervals based on a particular sensor reading. Data logger control outputs are also available to control external devices via 5 V DIO or 12 V switches.

iChart can export data directly into WQData, a secure web datacenter providing an online interface for viewing environmental data. It offers 24/7 instant access to project data using any web browser.

Project datacenter sites can be password-protected or publicly accessible. Using WQData, visitors can view dynamic project area maps overlaid with the most recent data, historical data, time series graphs, statistical summaries, and project-specifi c information.

An administrator login provides an intuitive interface for setting up the project, modifying data views, and adding relevant project information. Administrators can select from a library of predefi ned themes, enter site descriptions, set up data fi lters, and graph scales and other data attributes. Also included with WQData is the NexSens embeddable Web-Data Applet. This HTML code can be added to any web page to present visitors with a quick snapshot of project data that also links back to the complete project datacenter.

Data Acquisiton Software

Alarm Notifications

Real-Time Online Datacenter

Automatic alerts can be transmitted via email or SMS text message

iChart softwareWQData Software

SHORT-TERM PROJECTSRental vs. Purchase

While it often makes sense to purchase monitoring equipment outright, many short-term applications make it cost-prohibitive. Fondriest offers underwater data logging systems with weekly and monthly rental rates to meet project requirements. Fondriest leases a wide array of monitoring technology as well as necessary fi eld supplies.

Application engineers are available to assist in confi guring an ideal solution for project needs. They can also help with training and technical support. To reach them, please call (888) 426.2151 or email [email protected].

Fondriest offers both extensive fi eld experience and a wide array of deployment hardware to facilitate seamless implementation of monitoring systems. Moreover, if existing solution options are not suitable for a new project, Fondriest engineers can design custom platforms, sensors, and adaptations to suit a growing list of unique applications.

Fondriest Environmental, Inc.

1415 Research Park Drive

Beavercreek, OH 45432


The release of overly warm surface water, or oxygen-depleted bottom water, at selective withdrawal dams could devastate downstream fish populations. At a number of reservoirs across Pennsylvania, the US Army Corps of Engineers Pittsburgh District obtains real-time temperature stratification data using NexSens T-Node temperature strings.

The T-Nodes are suspended below data buoys and record temperature at various points throughout the water column. Every hour, temperature profile measurements are collected by a data logger on the buoy platform and then transmitted via radio telemetry to a host computer, which automatically posts the data to an online, password-protected website.

With the easy, on-line access provided by the NexSens system, dam operators and reservoir managers are able to release water selectively from different depths in order to maintain acceptable water quality conditions downstream of the reservoirs. Additionally, tracking stratification conditions throughout the year provides long-term data sets that aid in research efforts and the development of best management practices.

Among the more common concerns is the depletion of oxygen in the deeper layers of stratified lakes during the summer months. Below the thermocline, dissolved oxygen is insufficient to support most aquatic life.

In the fall, the temperature and density gradient weakens as surface waters cool and sink. Mixing by wind and the sinking of cooler waters will eventually destroy the gradient, a process known as fall turnover. The resulting isothermal conditions restore water circulation and oxygen to the deeper layers of the lake.

Monitoring the yearly evolution of temperature stratification is a critical component in many lake management and research programs due to its pronounced effects on aquatic chemistry and biology. Fisheries management, hydroelectric plants, selective withdrawal dams, and numerous areas of aquatic and sediment research often depend on obtaining temperature profile data for a water body.

Lake stratification develops seasonally as increasing solar radiation in the spring and summer heats up surface waters. Heat quickly dissipates in the upper layers of water, and deeper water remains cool. Because warmer water is significantly less dense than colder water, temperature-dependent density differences develop that prevent mixing and result in the formation of isolated layers of water. Due to the absence of water circulation between the layers, each strata of water develops its own distinct chemistry.

Selective Withdrawal Dams

Overview

APPLICATIONLake Stratification Monitoring

Prepping a mooring line and anchor for deployment.


SYSTEM CONFIGURATION TOOL

Contact Information

Name:

Organization:

Telephone:

Email:

Site Location

Desired Water Quality Parameters

Telemetry

Desired Hydrology Measurement

Data Management

Project Length (Rental vs. Purchase)

Site Conditions

Fondriest Environmental application engineers will assist with configuration and equipment selection on a site-by-site basis to ensure reliability, safety, and proper data management. However, the questionnaire below can help you get started. Once completed, this form can be faxed to (937) 426.1125 or, if completed digitally, emailed to [email protected].

The location of a monitoring system can affect what buoy configuration best suits the conditions. Please select in what type of water body the system will reside.

NexSens submersible data loggers can connect to almost any water quality sensor, making it possible to measure a wide array of parameters. Please select all necessary parameters.

License-free spread-spectrum radio telemetry allows communication with a shore-side NexSens radio base station as far as five miles line-of-sight from the monitoring site. Cellular telemetry allows greater geographic flexibility and is able to transmit from almost anywhere in the U.S., but it includes the cost of a cellular data plan.

NexSens monitoring buoys can measure depth, distance to bottom, current, and wave energy. Depth is measurable with a differential strain gauge transducer that monitors pressure. A sonar altimeter is capable of measuring distance to the sea bottom from a fixed point. A SonTek Argonaut acoustic Doppler system can record current. Finally, rapidly-sampled water depth information allows for the calculation of wave energy. Please select any desired hydrology measurements.

While turbidity monitoring systems can function with iChart software alone, WQData is a seamless extension and enhancement of the software. It is a secure web datacenter providing an online interface for viewing environmental data. It offers 24/7 instant access to project data using any web browser.

Although it often makes sense to purchase systems outright, many short-term dredging projects make it cost-prohibitive. NexSens Technology offers real-time turbidity monitoring systems with weekly and monthly rental rates to accommodate these operations. An application engineer can make recommendations on what choice is most cost-effective.

Describe the site conditions in a paragraph or two. Please include details regarding the levels of wind, waves, and boat traffic experienced in the area.

Lake River Coastal Other

Temperature Conductivity Dissolved Oxygen pH

Turbidity Chlorophyll Cyanobacteria (Blue-Green Algae)

Dissolved Organize Matter (CDOM) Underwater Light Other ____________________

Cellular Radio Satellite None (direct connect only)

Depth Distance to Bottom Current Wave

iChart iChart & WQData

1-3 Months 3-6 Months 6-12 Months 1 year


underwater - fondriest environmental, inc. · underwater data logging a guide for selecting and...

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