Campbell HMP45C Guide de l'utilisateur télécharger pdf (Page 24)

HMP45C Temperature and RH Probe

9. Troubleshooting

Symptom: -9999, NAN, -40 deg C, or 0% relative humidity

1. Check that the sensor is wired to the correct excitation and analogue input

channels as specified by the measurement instructions.

2. Verify the Range code is correct for the datalogger type.

3. Verify the red power wire is correctly wired to the 12V, Switched 12V, or

PSW12 module. The terminal the wire is connected to will depend on the

datalogger program.

Connect the red wire to a 12V terminal to constantly power the sensor for

troubleshooting purposes. With the red wire connected to 12V, a

voltmeter can be used to check the output voltage for temperature and

relative humidity on the yellow and blue wires respectively (temperature

°C = mV *0.1 – 40.0; relative humidity % = mV * 0.1).

Symptom: Incorrect temperature or relative humidity.

1. Verify the multiplier and offset parameters are correct for the desired units

(Table 5-1).

10. References

Goff, J. A. and S. Gratch, 1946: Low-pressure properties of water from -160° to

212°F, Trans. Amer. Soc. Heat. Vent. Eng., 51, 125-164.

Lowe, P. R., 1977: An approximating polynomial for the computation of

saturation vapour pressure, J. Appl. Meteor., 16, 100-103.

Weiss, A., 1977: Algorithms for the calculation of moist air properties on a

hand calculator, Amer. Soc. Ag. Eng., 20, 1133-1136.

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Campbell HMP45C Guide de l'utilisateur Page 24