Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 156
Table 23., Calibration Report for Salinity Sensor, KnownSalt, CalMode, 37.48, 37.23
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Section 7. Installation Scan(100,mSec,0,0) 'Simulate measurement by exciting channel VX1/EX1 ExciteV(Vx1,mV,0) 'Make the calibrated measurement VoltSE(RH,1,mV2500,6,1,0,250,Multiplier,Offset) 'Perform a calibration if CalMode = 1 FieldCal(0,RH,1,Multiplier,Offset,CalMode,KnownRH,1,30) 'If there was a calibration, store it into a data table CallTable(CalHist) NextScan EndProg 7.8.1.5.2 Offset (Option 1) Case: A sensor measures the salinity of water. Multiplier is known to be stable, but sensor offset drifts and requires regular offset correction using a standard solution. The following procedure offsets the measurement to obtain the calibration report shown. Table 23. Calibration Report for Salinity Sensor Parameter Parameter at Deployment Parameter at 7-Day Service mV output 1350 mV 1345 mV KnownSalt (standard 30 mg/l solution) 30 mg/l Multiplier 0.05 mg/l/mV 0.05 mg/l/mV Offset -37.50 mg/l -37.23 mg/l RH reading 30 mg/l 30 mg/l 1. Send the program in CRBasic example FieldCal Offset Demo Program (p. 156) to the CR800. An excitation channel has been programmed to simulate a sensor output. 2. To simulate the salinity sensor in deployment-calibration conditions (30 mg/l standard solution), place a jumper wire between channels VX1/EX1 and SE6 (3L). Set variable mV to 1350. Set variable KnownSalt to 30. 3. To simulate the deployment calibration, change the value in variable CalMode to 1 to start calibration. When CalMode increments to 6, offset calibration is complete. Calibrated offset will equal -37.48 mg/l at this stage of the example. 4. To continue this example and simulate an offset-drift condition, change variable mV to 1345. 5. To simulate 7-day, service-calibration conditions (30 mg/l standard solution), set variable KnownSalt to 30.0. Change the value in variable CalMode to 1 to start calibration. When CalMode increments to 6, 7-day, service-offset calibration is complete. Calibrated offset will equal -37.23 mg/l. 156