Related Manuals for Campbell OBS-5+
Summary of Contents for Campbell OBS-5+
- Page 1 OBS-5+ System Revision: 11/13 C o p y r i g h t © 2 0 0 8 - 2 0 1 3 C a m p b e l l S c i e n t i f i c , I n c .
- Page 3 Campbell pricelist or product manual. Products not manufactured, but that are re-sold by Campbell, are warranted only to the limits extended by the original manufacturer. Batteries, fine-wire thermocouples, desiccant, and other consumables have no warranty.
- 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.
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Page 5: Table Of Contents
6. Operation ..............7 Instrument Setup ..................7 6.1.1 Mounting Suggestions..............7 6.1.2 Surveys..................7 6.1.3 Logging Data ................8 6.1.4 Battery Installation................8 OBS-5+Utility Software...............9 6.2.1 Software Installation ..............9 6.2.2 Running the OBS-5+ Utility ............10 6.2.3 Pull-Down Menus ...............11 6.2.4 Communication Settings .............11 6.2.5 Testing Sensors ................12 6.2.6 Monitoring Turbidity (NTU)............13... - Page 6 Table of Contents 7. Calibration ..............20 Sediment and NTU Calibration ............20 7.1.1 General Guidance............... 21 7.1.2 Equipment and Materials............24 7.1.3 Procedure for Sediment .............. 24 Turbidity (NTU) Calibration ............. 28 7.2.1 Equipment and Materials............28 7.2.2 Procedure for Turbidity .............. 28 8.
- Page 7 Table of Contents 8-1. Internal components ................31 10-1. Effects of sediment size ..............35 10-2. Near-infrared reflectivity of minerals..........36 10-3. Effects of disaggregation methods .............37 Tables 6-1. Working and Maximum Depths ............7 7-1. Schedule of Concentrations for Sediment Calibrations......23 7-2. SSC-Calculation Spreadsheet.............23 9-1.
- Page 8 Table of Contents...
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Page 9: Introduction
OBS-5+ System Introduction ® The manual describes the features of the OBS-5+ , as well as its use for surveys and battery-powered, internal-storage operations. Using backscatter from a 780 nm laser diode and a patented dual-detection system (U.S. Patent Number 5,796,481), a calibrated OBS-5+ measures suspended sediment –1 concentrations, suspended solids concentration (SSC), as large as 200 g L which is about 10 times higher than standard OBS technology. -
Page 10: Overview
OBS-5+ System Overview FIGURE 4-1 shows the dimensions of the OBS-5+, the sensors in the sensor endcap, and underwater connection. Detailed specifications are provided in Section 5, Specifications. The OBS-5+ can be operated in Survey or Cyclic Modes. In Survey Mode, the unit sends data via RS-232 or RS-485 to a PC at two hertz, and in Cyclic Mode, it logs as many as 200,000 scans of time, date, –1 depth, and g L... -
Page 11: Ssc-Measurement Principle
OBS-5+ System FIGURE 4-2. Schematic of optical system SSC-Measurement Principle In FIGURE 4-2, suspended particles scatter light from the NIR beam onto the near and far detectors, and suspended solids concentration (SSC) is estimated with signals counts from these detectors by a microcontroller, using a set of logic rules and lookup tables derived from calibration data. -
Page 12: Sample Calibration Curves (Fine And Bold Lines), Lookup Tables I, Ii, And Iii (Bold Curves), And Sediment Concentrations Pf Nd (Open Arrow) And Fd (Solid Arrow) Peaks
OBS-5+ System FIGURE 4-3. Sample calibration curves (fine and bold lines), lookup tables I, II, and III (bold curves), and sediment concentrations pf ND (open arrow) and FD (solid arrow) peaks. The concentrations associated with the ND and FD peaks depend on sediment characteristics as shown by the variety of response curves and the colored arrowheads on FIGURE 4-4. -
Page 13: Specifications
OBS-5+ System FIGURE 4-4. Calibration curves for four different sediments and SSC values for near-detector peaks (colored arrowheads). Specifications Features: • Connects directly to a PC—no datalogger needed • Operates up to six months on three C-cell batteries • Monitors high sediment concentrations (up to 200g/L) •... -
Page 14: Accuracy
OBS-5+ System Accuracy Mud: 2.0% of reading Sand: 4.0% of reading Pressure: 0.5% of full scale Turbidity: 1.5% of full scale OBS-5+ Sensor Laser wavelength: 780 nm Scattering angles (clean water): 105º to 165º Drift over time: <30 ppm per month Drift over temperature: <200 ppm per ºC Other Data... -
Page 15: Operation
OBS-5+ System Operation Instrument Setup 6.1.1 Mounting Suggestions CAUTION Maximum depth for the OBS-5+ is limited by the installed pressure sensor. If the maximum depths are exceeded, the pressure sensor will rupture and the housing will flood. The depth limits are listed in TABLE 6-1. TABLE 6-1. -
Page 16: Logging Data
OBS-5+ System 6 – 18 V d.c. (Red) Power GND (Black) (RS485) DB-9 4, 1, 5, 6, 9 (GND) DB-9 (RS232) (RD) (TD) (GND) FIGURE 6-1. Electrical connections 6.1.3 Logging Data In applications where a survey cable is impractical or when the OBS-5+ must be attached to an instrument frame, it can be powered by the internal batteries and the data can be logged by the data flash memory See instructions for... -
Page 17: Obs-5+Utility Software
(pn 21905) that allows lithium C-cell batteries to be used with the OBS-5+. Lithium C-cell batteries have a higher voltage than their alkaline counterparts, necessitating the spacer. Campbell Scientific does not sell lithium C-cell batteries. FIGURE 6-2. Battery installation: A) endcap removal, B) wiping,... -
Page 18: Running The Obs-5+ Utility
OBS-5+ System data with a PC or uploading data from the OBS-5+, 5) importing data into a spreadsheet, and 6) plotting data with OBS-5+ Utility. 6.2.2 Running the OBS-5+ Utility 1) Set PC to the time standard for your project. 2) Select the OBS-5+ program to start the OBS-5+ Utility and open the Data Window and Toolbar with the View pull-down menu. -
Page 19: Pull-Down Menus
OBS-5+ System 6.2.3 Pull-Down Menus The OBS-5+ Utility has four pull-down menus for File, OBS-5+, View, and Help. The File menu allows you to select the location and formatting for OBS-5+ files. Files can be opened as plots or ASCII text that can be brought into spreadsheet programs or text editors. -
Page 20: Testing Sensors
OBS-5+ System adjustment takes two seconds. If your PC is set to the wrong rate for some reason, use the check box to select ONLY change host computer port. Then click Apply and the OBS Settings button. If you get the OBS-5+ information box, the baud rate of the unit is synchronized with your PC. -
Page 21: Monitoring Turbidity (Ntu)
OBS-5+ System 2) Wave your hand in front of the OBS-5+ sensor; the turbidity and SSC levels on the top plot will fluctuate as data scrolls across the plot. 3) Blow into the pressure sensor or press your thumb on it to compress air on the diaphragm (FIGURE 4-1). -
Page 22: Sampling Modes And Terms
OBS-5+ System 1) Measures of central tendency, including the mean and median. 2) Measures of variation or spread in sample values, including the standard deviation (σ) and cumulative percentages, such as X and X (where X is the depth, SSC, or NTU values). The mean is the arithmetic average of the values (∑... -
Page 23: Surveying
OBS-5+ System recorded. Select the longest interval that will show the changes in turbidity and water depth that you wish to investigate. Rate sets measurement frequency. The quicker turbidity and depth change, the higher the sampling rate should be to get a stable average value for a sample. Finally, Duration sets how long sensor outputs will be averaged. - Page 24 OBS-5+ System 3) Click the lookup table icon and select a calibration table for your survey. The last active table will be used otherwise. 4) Click Survey to select: sensors, lines per minute, and depth units (Meters or Feet). Set temperature and salinity for the survey area. 5) Click Start Survey and check the data flow in the Data Window.
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Page 25: Cyclic Sampling
OBS-5+ System 6.2.11 Cyclic Sampling This mode is for logging data at regular intervals such as 1, 10, 15, 30, etc. minutes, for example. 1) Request Barometric Correction from the OBS-5+ menu. Be sure to do this while the OBS-5+ is at the surface (see Section 6.2.10, Surveying ). 2) Open the Data Window with the View pull-down menu. -
Page 26: Data Retrieval
OBS-5+ System 6.2.12 Data Retrieval 1) Remove dummy plug and connect OBS-5+ to PC with test cable (FIGURE 6-1). 2) Run OBS-5+ Utility. 3) Open the Data Window to verify that the instrument is transmitting data. 4) Click to end data collection and use Offload Data to save data in a file. -
Page 27: Excel Spreadsheets
OBS-5+ System 2) Click Open and select a file to view. Print will print a graph when Open As Plot is selected. To print a text file, select Open As Text, and use the Word Pad file print functions. For spreadsheet operations, see the next section. -
Page 28: Calibration
OBS-5+ System Calibration Sediment and NTU Calibration In addition to the concentration, the size, shape, and reflectivity of suspended sediment particles vary from one location to another and will influence OBS- 5+ measurements. When these sediment characteristics change, they will produce apparent changes in SSC by themselves unless sediment calibrations are performed. -
Page 29: General Guidance
OBS-5+ System FIGURE 7-1. Manual (left) and automatic (right) sediment suspenders 7.1.1 General Guidance The OBS-5+ uses response curves from the near and far detectors to create three lookup tables like those shown on FIGURE 4-3 and FIGURE 7-2. The objective of sediment calibration is to create lookup tables from the sediment you will monitor. -
Page 30: Lookup Tables And Table Limits (A, B, And C)
OBS-5+ System from the descending limb of the near detector curve. A calibration consists of a set of 15 to 30 calibration points that each includes an SSC value, a near detector count, and a far detector count. FIGURE 7-2. Lookup tables and table limits (a, b, and c) Six to ten calibration points are needed to define each table. -
Page 31: Schedule Of Concentrations For Sediment Calibrations
OBS-5+ System TABLE 7-1. Schedule of Concentrations for Sediment Calibrations MUD (D < 62 µm) Sand (D > 62 µm) Mid- High Mid- High range range (0-5 g/l) (5-20 g/l) (> 20 g/l) (0-10 g/l) (10-40 g/l) (> 49 g/l) 10.0 The operator can control the electronic gain of the detector circuits to optimize the instrument for his sediment. -
Page 32: Equipment And Materials
OBS-5+ System Sediment concentrations can also be calculated manually with the following equations: Sediment mass nitial volume (liters) ρ ⎡ ⎤ ediment density ⎢ ⎥ ρ (usually 2.65 g/l) ⎣ ⎦ 7.1.2 Equipment and Materials • Dry, completely disaggregated bottom sediment or suspended matter from the monitoring site •... -
Page 33: Obs-5+ In Big Black Tub Of Clean Water
OBS-5+ System 3) Click the button to view the list of lookup tables stored in the unit. Select an EMPTY Table number for the sediment calibration. 4) Start the calibration with the button and secure the unit in a big black tub filled with clean tap water (FIGURE 7-3). -
Page 34: Obs-5+ In Suspender Tub
OBS-5+ System 5) Enter 0.001 in the value box and click the Record button to log the clear- water data point. The unit will take 1,200 measurements in 60 seconds. When the process is complete, the data appear in the data table and the ND (red) and FD (green) points will be plotted on the calibration graph. - Page 35 OBS-5+ System 8) Withdraw about 10 ml of water from the suspender and add it to the tea cup containing the dry sediment. Stir the water-sediment mixture into a homogeneous slurry, breaking up clumps of sediment as you go. 9) Pour the sediment slurry into the suspender and rinse the cup with suspender water until it is clean.
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Page 36: Turbidity (Ntu) Calibration
OBS-5+ System the FD curve where it starts decay exponentially, also 10 on FIGURE 7-2 9. Points ‘b’ and ‘c’ will usually have the same numerical value. 15) Save the table in the EMPTY Table number selected at Step 3. Turbidity (NTU) Calibration 7.2.1 Equipment and Materials •... -
Page 37: Troubleshooting
OBS-5+ System FIGURE 7-5. OBS-5+ in 100 mm cup 6) Add enough 250-NTU standard to cover the sensor end (FIGURE 4-1) and swipe bubbles off the sapphire windows with your finger. Click the Record button. 7) Repeat Step 6 for the 500 and 1,000 NTU standards. 8) Review the data table and graph, and if they look satisfactory, click the Calculate Fit button. - Page 38 OBS-5+ System corroded surfaces of the contact and track with a scouring pad and reassemble unit. Unit does not communicate with PC. There are several possible causes for this symptom. 1) The batteries are dead. 2) The OBS-5+ will not wake up. 3) The test/umbilical cable is damaged or improperly connected 4) The OBS-5+ and PC are set to different baud rates or communication protocols (for example, RS-232 versus RS-485).
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Page 39: Internal Components
OBS-5+ System FIGURE 8-1. Internal components OBS-5+ or pressure sensor malfunction. • Open unit and inspect for: 1) broken sensor wires, and 2) loose pressure sensor connector (FIGURE 8-1). • Check sensor power by clicking Survey and selecting all sensors; the green LEDs should illuminate. -
Page 40: Maintenance
OBS-5+ System Bright sun near the surface (< 2 m) or black-colored sediments cause erroneous OBS readings. Do not survey in shallow water between 10:00 and 14:00 local time and avoid areas with suspended black mud; see Section 10.2, NIR Reflectivity. OBS-5+ indicates different NTU values in the field than other turbidimeters. -
Page 41: Batteries
Compound 55 and reassemble. User-Serviceable Parts Alkaline C cells and the components of the 21304 Accessory Kit can be purchased as replacement parts. Campbell Scientific manufacturing part numbers and product descriptions follow: pn 20993 End-cap O-ring, Parker 2-136 pn 20989 Optic Bushings O-ring, ARP5 7.5 X 1.2 mm OBN pn 21141 S.S. -
Page 42: Interfering Factors
OBS-5+ System pn 4576 Alkaline C-Cells Batteries pn 20806 OBS-5+ Test Cable, 2 m (6.5 ft) pn 21381 7-piece Allen Wrench Set, 5/64 to 3/16 Ball End pn 21139 SS Hex Socket Screw, #2-56 x .187 10. Interfering Factors Changes in sediment concentration (SSC) are the primary cause for OBS-5+ output fluctuations in the environment. -
Page 43: Nir Reflectivity
OBS-5+ System FIGURE 10-1. Effects of sediment size 10.2 NIR Reflectivity The output of an OBS-5+ will increase with the NIR reflectivity of suspended sediment independent of SSC. This can degrade accuracy when unknown reflectivity changes occur during a monitoring campaign. For instance, when a dredge cuts through a layer of oxidized, light-brown, reflective mud into an underlying layer of black anoxic mud, the OBS-5+ will indicate that SSC of mud stirred up by the cutter has dropped even when it has not. -
Page 44: Particle Shape, Flocculation, And Disaggregation
OBS-5+ System FIGURE 10-2. Near-infrared reflectivity of minerals 10.3 Particle Shape, Flocculation, and Disaggregation Particle shape can be an interfering factor. The sensitivity of an OBS-5+ sensor to plate-shaped particles is about ten times higher than it is to spherical particles. - Page 45 OBS-5+ System FIGURE 10-3. Effects of disaggregation methods Finally, flocculation of clay particles in estuaries can affect sensitivity by causing small particles to clump together into larger ones to which the OBS-5+ is less sensitive. For example, when a dredge works into a zone of saline water where flocculation occurs, an OBS-5+ can indicate less than the actual level of SSC.
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Page 46: References
OBS-5+ System 11. References Black, K.P., M.A. Rosenberg. 1994. Suspended Sand Measurements in a Turbulent Environment: Field Comparison of Optical and Pump Sampling. Coastal Engineering, 24, pp. 137-150. Conner, C.S. and A.M. De Visser. 1992. A Laboratory Investigation of Particle Size Effects on an Optical Backscatterance Sensor. -
Page 47: Turbidity Standards
Appendix A. Turbidity Standards AMCO Clear, supplied by GFS Chemicals (www.gfschemicals.com), is an approved calibration standard and is the one we use to certify our instruments. It is made from styrene divinylbenzene (SDVB) microspheres. SDVB spheres have a median size and standard deviation of 0.28μm (~1/5 that of formazin particles) and 0.10 μm respectively and a refractive index of 1.56. - Page 48 Appendix A. Turbidity Standards In the USA, formazin is a primary standard for the calibration of turbidimeters. The median particle size of formazin is 1.5 μm; the standard deviation of size is 0.6 μm (see size distribution graph); and as shown by the SEM images below, formazin particles have many different shapes.
- Page 49 Appendix A. Turbidity Standards We must emphasize that unlike SSC, which has physical units, turbidity values (NTUs, FTUs, etc.) do not. Therefore, if you measure water turbidity to be 100 NTU, you cannot directly infer any physical quantities from it. Turbidity values do not represent particular SSC values, indicate light levels at the bottom of a stream, or quantify biological process’.
- Page 50 Appendix A. Turbidity Standards...
- Page 52 Campbell Scientific Ltd. (CSL Germany) Fahrenheitstraße 13 28359 Bremen GERMANY www.campbellsci.de • info@campbellsci.de Campbell Scientific Spain, S. L. (CSL Spain) Avda. Pompeu Fabra 7-9, local 1 08024 Barcelona SPAIN www.campbellsci.es • info@campbellsci.es Please visit www.campbellsci.com to obtain contact information for your local US or international representative.