INSTRUCTION MANUAL 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 .
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.
Assistance Products may not be returned without prior authorization. The following contact information is for US and international customers residing in countries served by Campbell Scientific, Inc. directly. Affiliate companies handle repairs for customers within their territories. Please visit www.campbellsci.com to determine which Campbell Scientific company serves your country. To obtain a Returned Materials Authorization (RMA), contact CAMPBELL SCIENTIFIC, INC., phone (435) 227-9000.
Precautions DANGER — MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON OR AROUND TRIPODS, TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC. FAILURE TO PROPERLY AND COMPLETELY ASSEMBLE, INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS, TOWERS, AND ATTACHMENTS, AND FAILURE TO HEED WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS INJURY, PROPERTY DAMAGE, AND PRODUCT FAILURE.
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. Quickstart .................................................................... 2 4.1 4.
Table of Contents 10. Maintenance ..............................................................22 11. Factors that Affect Turbidity and SuspendedSediment Measurements........................................23 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 Particle Size ....................................................................................... 23 Suspensions with Mud and Sand ....................................................... 24 Particle-Shape Effects ...........................................
Table of Contents 8-3. 8-4. 11-1. 11-2. 11-3. 11-4. 11-5. C-1. D-1. OBS-3+ (left) and OBS300 (right) in 500-NTU AMCO Clear® turbidity standard in 100-mm black polyethylene calibration cup .................................................................................................. 18 Portable sediment suspender (left) and OBS beam orientation in suspender tub (right) ....................................................................... 20 Normalized OBS sensitivity as a function of grain diameter ..
Table of Contents iv
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 1. Introduction The OBS-3+ and OBS300 are submersible, turbidity sensors that use OBS® technology to measure suspended solids and turbidity for applications ranging from water quality in freshwater rivers and streams to sediment transport and dredge monitoring. The OBS-3+ and OBS300 are identical except for the orientation of their optics.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 4. Quickstart 4.1 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). 2. Calibrate the sensor using suspended solids from the waters that will be monitored (see Section 8, Calibration). 3. 4.2 Refer to Section 7.2, Mounting Considerations, for siting and mounting options.
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.
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. You can use the default value (V) for the Coefficients based on signal voltage in units of.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 5. 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. If the sensor is connected to the datalogger, as shown in the wiring diagram in step 6, check the output of the sensor in the datalogger support software data display to make sure it is making reasonable measurements.
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.
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 42o (95% of the beam power is contained within a 42o cone). The sensor can see to a distance of approximately 50 cm (20 in) in very clean water. 5.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 6.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 141 mm (5.56 in) 7. 131 mm (5.15 in) 25 mm (0.98 in) Installation 25 mm (0.98 in) 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. See Section 4, Quickstart, for a Short Cut tutorial. 7.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 7.2 Mounting Considerations Schemes for mounting the OBS-3+ and OBS300 will vary with applications; however, the same basic precautions should be followed to ensure the unit is able to make a good measurement and that it is not lost or damaged. 7.2.1 Siting The most important general precaution is to orient the unit so that the sensor looks into clear water without reflective surfaces.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors TABLE 7-1. Connection to Campbell Scientific Dataloggers Color Description CR800, CR850 CR1000, CR3000 CR5000, CR23X White High Range Signal Single-ended Input Single-ended Input Blue Low Range Signal Single-ended Input Single-ended Input Green Signal Ground Black Power Ground G G Red Power SW12V SW12V Clear Shield G G CR10X AG FIGURE 7-1.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 7.4 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).
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors CSL Curve Type Polynomial for Converting to NTU Polynomial for Converting to NTU FIGURE 7-2.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors CSL Curve Type Polynomial for Converting to NTU Polynomial for Converting to NTU FIGURE 7-3. Calibration certificate showing volts coefficients 8. Calibration 8.1 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.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors NTU value with a 2nd-order polynomial. This section explains how to do a turbidity calibration. 0.8 0.6 0.4 4000 3000 0.2 Turbidity (NTU) Normalized OBS-3+ Response (OPV330 VCSEL) 1.0 A B C 2000 1000 0 0.0 0 20000 40000 60000 SSC (mg/l) 0 1000 2000 Tur bidity (TU) 3000 4000 FIGURE 8-1. Normalized response of OBS-3+ to AMCO Clear® turbidity.
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. Therefore: 1. Always use clean glassware and calibration containers. 2. Don’t leave standards on the bench in open containers or leave the standard bottles uncapped.
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. 2. Swab sensor with an alcohol-soaked towel to sterilize it. 1. In a large black tub of fresh tap water, aim the OBS sensor so that it’s the maximum distance from the sensor optics to the far corner of the tub (see FIGURE 8-2).
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 cup 8.2 Sediment There are three basic ways to calibrate an OBS sensor with sediment.
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.
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. Portable sediment suspender (left) and OBS beam orientation in suspender tub (right) SSC = Wts [Vw + Wts/ρs]–1; where: Wts = total sediment weight in tub, in mg; Vw = volume of water in liters; ρ = density of water (ρ = 1.
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. 10. Perform third-order polynomial regressions on the data to get the coefficients for converting OBS output to SSC. 9. Troubleshooting WARNING Do not use a sensor with a stainless steel housing in seawater.
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. Return the sensor to manufacturer if cracks are found. Electronic failure. Units draws less than 11 mA or more than 40 mA. Return the sensor to manufacturer.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors 11. Factors that Affect Turbidity and SuspendedSediment Measurements This section summarizes some of the factors that affect OBS measurements and shows how ignoring them can lead to erroneous data.
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.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors OBS-3+ 1 Relative Scattering Intensity Plates Cubes 0.1 Spheres 0.01 0 20 40 60 80 100 120 140 160 180 Scattering Angle FIGURE 11-3. Relative scattering intensities of grain shapes 11.
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. Although OBS sensors are color blind, tests have shown that “whiteness”, color, and IR reflectivity are correlated.
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.
OBS-3+ and OBS300 Suspended Solids and Turbidity Monitors organic matter and interference from these materials can therefore be ignored most of the time. One notable exception is where biological productivity is high and sediment production from rivers and re-suspension is low. In such an environment, OBS signals can come predominately from plankton. 11.8 Biological and Chemical Fouling Sensor cleaning is essential during extended deployments.
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.
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.
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. These files normally reside in the C:\campbellsci\SCWin folder and have the following extensions: • • • • • • • • .
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–” into the CRBasic program, usually at the head of the file. After pasting, edit the information such that a ' character (single quotation mark) begins each line.
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. Since the coefficients of the voltage curve are used, the multiplier for VoltSE() needs to be 0.001. Make sure you use the correct units. NOTE The calibration values are different for each probe.
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. For i = 1 To n VoltSe (NTUX(i),1,mV5000,2,1,0,_60Hz,0.
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 AvgSpa (NTU,10,NTUarray()) StdDevSpa (NTU_SD,10,NTUarray()) If NTU < 250 Then For i = 1 To n VoltSe (NTUarray(i),1,1,0.
Appendix B. Example Programs ;activate SW12V for turbidity probe, delay 3 seconds, then measure 1: Do (P86) 1: 48 Set Port 8 High 2: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay W/Ex (0.01 sec units) 3: 300 Delay After Ex (0.01 sec units) 4: 0 mV Excitation 3: Beginning of Loop (P87) 1: 0 Delay 2: 10 Loop Count 4: 5: Volt (SE) (P1) 1: 1 Reps 2: 25 2500 mV 60 Hz Rejection Range 3: 1 SE Channel 4: 3 -- Loc [ NTU_V_1 ] 5: 0.001 Mult 6: 0.
Appendix B. Example Programs NTU = -0.20709 + (401.11*NTU_Volts) + (35.
Appendix B.
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. When a custom cable assembly is purchased from a thirdparty vendor to connect the OBS sensor to a current meter or CTD, the user will not have access to any of the wires listed in TABLE C-1.
Appendix C. Electrical Connections Details TABLE C-1. Pin numbers, electrical functions and wire color codes for OBS sensor bulkhead connectors.
Appendix D. Datalogger Connection to a Relay The CR10, CR7, CR510, and 21X dataloggers do not have a switched 12 V channel. Either the sensor can remain on or a relay may be used to switch the power on and off. FIGURE D-1 shows the relay connections. 12V C1 Black White Blue Green G G SE1 SE2 AG FIGURE D-1. Wiring diagram for connecting an OBS sensor to an external relay and a datalogger NOTE 1. The assignment of channel number (for example, SE Channel 1 or C1) may vary depending on the application.
Appendix D.
Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com • info@campbellsci.com Campbell Scientific Centro Caribe S.A. (CSCC) 300 N Cementerio, Edificio Breller Santo Domingo, Heredia 40305 COSTA RICA www.campbellsci.cc • info@campbellsci.cc Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za • cleroux@csafrica.co.za Campbell Scientific Ltd.
