Campbell OBS-3+ Instruction Manual
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Campbell OBS-3+ Instruction Manual

Suspended solids and turbidity monitors
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OBS-3+ and OBS300
Suspended Solids and
Turbidity Monitors
Revision: 9/14
C o p y r i g h t
©
2 0 0 8 - 2 0 1 4
C a m p b e l l
S c i e n t i f i c ,
I n c .

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Summary of Contents for Campbell OBS-3+

  • Page 1 OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Revision: 9/14 C o p y r i g h t © 2 0 0 8 - 2 0 1 4 C a m p b e l l S c i e n t i f i c , I n c .
  • Page 3 Limited Warranty “Products manufactured by CSI are warranted by CSI to be free from defects in materials and workmanship under normal use and service for twelve months from the date of shipment unless otherwise specified in the corresponding product manual. (Product manuals are available for review online at www.campbellsci.com.) Products not manufactured by CSI, but that are resold by CSI, are warranted only to the limits extended by the original manufacturer.
  • Page 4 SCIENTIFIC, INC., phone (435) 227-9000. After an application engineer determines the nature of the problem, an RMA number will be issued. Please write this number clearly on the outside of the shipping container. Campbell Scientific’s shipping address is: CAMPBELL SCIENTIFIC, INC.
  • Page 5 • Periodically (at least yearly) check electrical ground connections. WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL SCIENTIFIC PRODUCTS, THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER INSTALLATION, USE, OR MAINTENANCE OF TRIPODS, TOWERS, OR ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC.

  • Page 7: Table Of Contents

    Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. Introduction ..............1 2. Cautionary Statements ..........1 3. Initial Inspection ............1 4.
  • Page 8 Table of Contents 10. Maintenance .............. 22 11. Factors that Affect Turbidity and Suspended- Sediment Measurements ........23 11.1 Particle Size ..................23 11.2 Suspensions with Mud and Sand ............24 11.3 Particle-Shape Effects ............... 24 11.4 High Sediment Concentrations ............25 11.5 IR Reflectivity—Sediment Color ............
  • Page 9 D-1. Wiring diagram for connecting an OBS sensor to an external relay and a datalogger ..............D-1 Tables 7-1. Connection to Campbell Scientific Dataloggers ........ 11 8-1. SDVB NTU values for turbidity calibrations in standard low ranges....................15 8-2.
  • Page 10 Table of Contents...

  • Page 11: Introduction

    • Damages caused by freezing conditions will not be covered by our warranty. • Campbell Scientific recommends removing the sensor from the water for the time period that the water is likely to freeze. Initial Inspection • Upon receipt of the OBS-3+ or OBS300, inspect the packaging and contents for damage.

  • Page 12: Quickstart

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Quickstart Preparation for Use 1. Bench test the sensor to ensure that it functions properly prior to making field installations (see Section 7.1, Pre-Deployment Tests). Calibrate the sensor using suspended solids from the waters that will be monitored (see Section 8, Calibration 3.
  • Page 13 OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 3. When Short Cut opens, select New Program. 4. Select Datalogger Model and Scan Interval (default of 5 seconds is OK for most applications). Click Next.
  • Page 14 OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 5. Under the Available Sensors and Devices list, select the Sensors | Water | Quality folder. Select OBS3+/OBS300 Turbidity Sensor. Click to move the selection to the Selected device window. Select your sensor’s Low and High NTU Range and Maximum Voltage Output.

  • Page 15: Overview

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 8. If LoggerNet, PC400, or PC200W is running on your PC, and the PC to datalogger connection is active, you can click Finish in Short Cut and you will be prompted to send the program just created to the datalogger. 9.

  • Page 16: Design Details

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Turbidity is caused by suspended and dissolved matter such as sediment, plankton, bacteria, viruses, and organic and inorganic dyes. In general, as the concentration of suspended matter in water increases, so will its turbidity, and as the concentration of dissolved light-absorbing matter increases, turbidity will decrease.

  • Page 17: Measurement Details

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors FIGURE 5-1. Components of the OBS-3+ (left) and orientation source beam and detector acceptance cone of the OBS-3+ (top right) and OBS300 (bottom right) The beam divergence angle of the VCSEL source is 42 (95% of the beam power is contained within a 42 cone).

  • Page 18: Specifications

    Fitted with MCBH-5-FS, wet-pluggable connector—multiple mating cable length options available Accurate and rugged • Compatible with Campbell Scientific CRBasic dataloggers: • CR200(X) series, CR800 series, CR1000, CR3000, CR5000, and CR9000(X). Also compatible with Edlog dataloggers: CR500, CR510, CR10(X), CR23X, 21X, and CR7 Operating Temperature: 0°...

  • Page 19: Installation

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 141 mm 131 mm (5.56 in) (5.15 in) 25 mm 25 mm (0.98 in) (0.98 in) Installation If you are programming your datalogger with Short Cut, skip Section 7.3, Wiring to Datalogger, and Section 7.4, Datalogger Programming. Short Cut does this work for you.

  • Page 20: Mounting Considerations

    Wiring to Datalogger TABLE 7-1 and FIGURE 7-1 show the recommended wiring configuration for connecting the OBS sensor to a Campbell Scientific datalogger; wiring to dataloggers manufactured by other companies is similar. In this configuration, single-ended analog inputs are used to measure the OBS sensors’ voltage signal.

  • Page 21: Obs-3+ Connected To A Cr1000 Datalogger (Obs300 Has The Same Wiring)

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors TABLE 7-1. Connection to Campbell Scientific Dataloggers CR800, CR850 CR1000, CR3000 Color Description CR5000, CR23X CR10X White High Range Signal Single-ended Input Single-ended Input Blue Low Range Signal Single-ended Input Single-ended Input...

  • Page 22: Datalogger Programming

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Datalogger Programming CRBasic and Edlog are included in our PC400 and LoggerNet Datalogger Support Software Packages. CRBasic supports our newer dataloggers (for example, CR200(X), CR800, CR1000, CR3000). Edlog supports our CR7 and most of our retired dataloggers (for example, CR510, CR10(X), CR23X).

  • Page 23: Calibration Certificate Showing Millivolt Coefficients

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Polynomial for Curve Type Converting to Polynomial for Converting to FIGURE 7-2. Calibration certificate showing millivolt coefficients...

  • Page 24: Calibration

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors Polynomial for Curve Type Converting to Polynomial for Converting to FIGURE 7-3. Calibration certificate showing volts coefficients Calibration Turbidity The normalized response of an OBS sensor to styrene divinylbenzene beads (SDVB) turbidity over the range from 0 to 4000 NTU is shown on FIGURE 8-1.

  • Page 25: Normalized Response Of Obs-3+ To Amco Clear ® Turbidity. The Inset Shows The Response Function Of An Obs Sensor To High Sediment Concentrations

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors NTU value with a 2 -order polynomial. This section explains how to do a turbidity calibration. 4000 3000 2000 1000 20000 40000 60000 SSC (mg/l) 1000 2000 3000 4000 Tur bidity (TU) FIGURE 8-1.

  • Page 26: Materials And Equipment

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors The NTU values of the standards will remain the same as long as the ratio of particle mass (number of particles) to water mass (volume) does not change. Evaporation causes this ratio to increase and dust, bacteria growth, and dirty glassware can also cause it to increase.

  • Page 27: Setup

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 8.1.2 Setup 1. Plug the test cable into the OBS sensor; connect the red and black leads to the battery and clip the DMM or datalogger test leads across the blue (+) and green (–) leads.

  • Page 28: Sediment

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 8. Perform 2nd-order polynomial regressions on the calibration data to get the coefficients for converting OBS signals to NTU values. FIGURE 8-3. OBS-3+ (left) and OBS300 (right) in 500-NTU AMCO Clear ® turbidity standard in 100-mm black polyethylene calibration Sediment There are three basic ways to calibrate an OBS sensor with sediment.

  • Page 29: In Situ Calibration

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors suspender after each addition of sediment for the determination of SSC by filtration and gravimetric analyses. 8.2.3 In situ Calibration In situ calibration is performed with water samples taken from the immediate vicinity of an OBS sensor in the field over sufficient time to sample the full range of SSC values to which a sensor will be exposed.

  • Page 30: Procedure

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors see FIGURE 8-4. For the OBS300, mount the sensor so that the laser diode is submerged just below the water surface to maximize the distance from the detector and the bottom of the container. FIGURE 8-4.

  • Page 31: Troubleshooting

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 8. Add enough additional sediment to get one full increment of sediment, Wi ± 5%. Repeat steps 4, 5, and 6. 9. Repeat step 8 until five full increments of sediment have been added or until the OBS signals exceed the output range.

  • Page 32: Maintenance

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors TABLE 9-1. Troubleshooting Chart Fault Cause of Fault Remedy Fails finger wave test No power, dead battery Replace battery and reconnect wires MCIL-5 plug not fully seated Disconnect and reinsert plug. Sensor broken Visually inspect for cracks.

  • Page 33: Factors That Affect Turbidity And Suspended-Sediment Measurements

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 11. Factors that Affect Turbidity and Suspended- Sediment Measurements This section summarizes some of the factors that affect OBS measurements and shows how ignoring them can lead to erroneous data. If you are certain that the characteristics of suspended matter will not change during your survey and that your OBS was factory calibrated with sediment from your survey site, you only need to skim this section to confirm that no problems have been over...

  • Page 34: Suspensions With Mud And Sand

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors FIGURE 11-2. The apparent change in turbidity resulting from disaggregation methods 11.2 Suspensions with Mud and Sand As mentioned in Section 11.1, Particle Size, backscattering from particles is inversely related to particle size on a mass concentration basis. This can lead to serious difficulties in flow regimes where particle size varies with time.

  • Page 35: High Sediment Concentrations

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors OBS-3+ Plates Cubes Spheres 0.01 Scattering Angle FIGURE 11-3. Relative scattering intensities of grain shapes 11.4 High Sediment Concentrations At high sediment concentrations, particularly in suspensions of clay and silt, the infrared radiation from the emitter can be so strongly attenuated along the path connecting the emitter, the particle, and the detector, that backscatter decreases exponentially with increasing sediment concentration.

  • Page 36: Ir Reflectivity-Sediment Color

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors FIGURE 11-4. Response of an OBS sensor to a wide range of SSC 11.5 IR Reflectivity—Sediment Color Infrared reflectivity, indicated by sediment color, has a major effect on OBS sensitivity because with other factors remaining constant, it changes the intensity of light scattering.

  • Page 37: Water Color

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors FIGURE 11-5. Infrared reflectivity of minerals as a function of 10-Munzell value 11.6 Water Color Some OBS users have been concerned that color from dissolved substances in water samples, not colored particles discussed in Section 11.5, IR Reflectivity— Sediment Color, produces erroneously low turbidity measurements.

  • Page 38: Biological And Chemical Fouling

    OBS sensors is required more often during the summer because warm water and bright sunlight increase biological and chemical activity. Campbell Scientific sells two wipers from a third-party manufacturer: the Hydro-Wiper C with its own controller, or the Hydro-Wiper D that is controlled by a datalogger.

  • Page 39: Terminology

    OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 13. Terminology 110 Rule: 100 ppm of 100-μm suspended sand will scatter light with the same intensity as 10 ppm of 10-μm suspended silt, other factors, such as size, shape and color, remaining constant. Backscatter/forward scatter: The interaction of light with suspended particles, water molecules, and variations in refractive index that alters the direction of light transport through a sample without changing the wavelength.
  • Page 40 OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors sediment, plankton, bacteria and viruses, organic acids, and dyes. In general, as the concentration of suspended matter increases, so will water turbidity, and as the concentration of dissolved light-absorbing matter increases, turbidity will decrease.

  • Page 41: Importing Short Cut Code

    Appendix A. Importing Short Cut Code This tutorial shows: How to import a Short Cut program into a program editor for • additional refinement. How to import a wiring diagram from Short Cut into the comments of • a custom program. A.1 Importing Short Cut Code into a Program Editor Short Cut creates files that can be imported into either CRBasic Editor or Edlog program editor.

  • Page 42: Edlog

    Appendix A. Importing Short Cut Code 5. The program can now be edited, saved, and sent to the datalogger. 6. Import wiring information to the program by opening the associated .DEF file. Copy and paste the section beginning with heading “-Wiring for CRXXX–”...

  • Page 43: Example Programs

    Appendix B. Example Programs B.1 CRBasic Examples B.1.1 CR1000 Example Program Below is an example CR1000 program. The calibration values used in this program are from the calibration certificate shown in FIGURE 7-3. The example program uses the voltage curve’s coefficients.

  • Page 44: Cr200(X) Example Program

    Appendix B. Example Programs 'the true NTU. Big particles can cause errors that would skew an average NTU = NTUX(11) 'Use the low range channel to get a more accurate measurement. If NTU < 250 Then 'The value of 250 was chosen because it is the nominal low range value of 'this OBS sensor.

  • Page 45: Edlog Example

    Appendix B. Example Programs For i = 1 To n 'n=10 in this case so ten measurements will be made for both the high and low 'input ranges. A multiplier of 0.001 is used because the coefficients are 'from the voltage calibration sheet VoltSe (NTUarray(i),1,2,0.001,0) NTUarray(i) = A(2) * NTUarray(i)^2 + B(2) * NTUarray(i) + C(2) Next i...
  • Page 46 Appendix B. Example Programs ;activate SW12V for turbidity probe, delay 3 seconds, then measure Do (P86) Set Port 8 High Excitation with Delay (P22) Ex Channel Delay W/Ex (0.01 sec units) Delay After Ex (0.01 sec units) mV Excitation Beginning of Loop (P87) Delay Loop Count Volt (SE) (P1)
  • Page 47 Appendix B. Example Programs NTU = -0.20709 + (401.11*NTU_Volts) + (35.310*NTU_Volts^2) End (P95) End Program...
  • Page 48 Appendix B. Example Programs...

  • Page 49: Electrical Connections Details

    Appendix C. Electrical Connections Details FIGURE C-1 shows the contact numbers for the MCIL/MCBH-5 connectors and TABLE C-1 lists the electrical functions and wire colors. The user need only be concerned with the wire colors for the 8425 cable as the MCBH wires are not accessible.

  • Page 50: Pin Numbers, Electrical Functions And Wire Color Codes For Obs Sensor Bulkhead Connectors

    Appendix C. Electrical Connections Details TABLE C-1. Pin numbers, electrical functions and wire color codes for OBS sensor bulkhead connectors. MCBH-5-FS/MCIL-5-MP Electrical Wire Color Wire Color Contact Number Function (MCBH) (8425) Power (5 – 15V) Power Ground Black Black Signal Common Green Green High Range Signal (4X)

  • Page 51: Datalogger Connection To A Relay

    The assignment of channel number (for example, SE Channel 1 or C1) may vary depending on the application. You may use a relay such as Campbell Scientific pn 7321 instead of the switched 12 V connection on the CR10(X), CR1000, and CR23X wiring panel. Since the CR510 wiring panels do not have switched 12 V, you will need an external relay if you need to conserve battery power.
  • Page 52 Appendix D. Datalogger Connection to a Relay...
  • Page 54 • info@campbellsci.com.cn • info@campbellsci.de www.campbellsci.com www.campbellsci.de Campbell Scientific do Brasil Ltda. (CSB) Campbell Scientific Spain, S. L. (CSL Spain) Rua Apinagés, nbr. 2018 ─ Perdizes Avda. Pompeu Fabra 7-9, local 1 CEP: 01258-00 ─ São Paulo ─ SP 08024 Barcelona...

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