Model HC2S3 Temperature and Relative Humidity Probe
9. Troubleshooting
Symptom: -9999, NAN, -40°C, or 0 % relative humidity
1. Check that the sensor is wired to the correct analog input channels as
specified by the measurement instructions.
2. Verify the voltage range code for the single-ended or differential
measurement instruction is correct for the datalogger type.
3. Verify the green power wire is connected to the 12V, SW12V, or 5V
terminal. When SW12V is used with a CR10X datalogger, verify the
SW 12V CTRL is jumpered to the Control Port specified in the program.
Cables longer than 3 m (10 ft) should be powered by the 12V, rather than
the 5V terminal.
A voltmeter can be used to check the output voltage for temperature and
relative humidity on the brown and white 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 7-3) and temperature range.
2. Default settings are listed in Appendix A, which include the setting “Limit
humidity output to 100%”. This setting is “disabled” for probes
purchased through Campbell Scientific. Accuracy of the humidity
measurement over temperature is shown in the graph in Section 6.2. For
example, at -20°C the accuracy is ±2.3%, so a reading of 102.3% at 100%
humidity is within the accuracy specification. Programs created by Short
Cut set humidity values greater than 100% and less than 103% to 100%.
Humidity values greater than 103% are left unchanged to indicate a
problem with the probe or measurement.
10. References
AASC, 1985: The State Climatologist (1985) Publication of the American
Association of State Climatologists:
Heights and Exposure Standards for
Sensors on Automated Weather Stations
, v. 9, No. 4 October, 1985.
(www.stateclimate.org/publications/state-climatologist/NOAA-NCY-
SCBOOKS-SC77097/00000029.pdf)
EPA, 2000:
Meteorological Monitoring Guidance for Regulatory Modeling
Applications
, EPA-454/R-99-005. Office of Air Quality Planning and
Standards, Research Triangle Park, North Carolina 27711.
EPA, 2008:
Quality Assurance Handbook for Air Pollution Measurement
Systems
, Vol. IV, Meteorological Measurements, Ver. 2.0, EPA-454/B-08-
002 (revised 2008). Office of Air Quality Planning and Standards,
Research Triangle Park, NC 27711.
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.
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