Campbell Scientific LI200X LI200X-L LI-COR Silicon Pyranometer - Page 14

LI200X Pyranometer CAUTION Handle the sensor carefully when cleaning. Be careful not to scratch the surface of the sensor. Recalibrate the LI200X every two years. Obtain an RMA number before returning the LI200X to Campbell Scientific, Inc. for recalibration. 6. Calibration LI200X pyranometers output a current that is proportional to the incoming solar radiation. Each LI200X has a unique calibration factor. A variable shunt resistor in the cable converts the current to the voltage measured by the datalogger. Campbell Scientific sets the shunt resistor so that the pyranometer outputs 5 mV kW-1 m2. The resistor value is found using Ohms law. The resistance is found by dividing the desired output voltage by the calibrated current output. For example, a pyranometer with a calibration of 92 μA kW-1 m2, will have the resistor set to: 54.35 Ω = 5 mV kW −1 m2 0.092 mA kW −1 m2. 7. Troubleshooting Symptom: -9999 or radiation values around 0 1. Check that the sensor is wired to the Differential channel specified by the measurement instruction. 2. Verify that the Range code is correct for the datalogger type. 3. Disconnect the sensor leads from the datalogger and use a DVM to check the voltage between the red (+) and the black (-) wires. The voltage should be 0 - 5 mV for 0 to 1000 Wm-2 radiation. No voltage indicates a problem with the photodiode, cable, or the variable shunt resistor. Symptom: Incorrect solar radiation 1. Make sure the top surface of the sensor head is clean, and that the sensor is properly leveled. 2. Verify that the Range code, multiplier and offset parameters are correct for the desired engineering units and datalogger type. 10