User manual

User Manual
19
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 9-1) 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 CSI. Accuracy of the humidity measurement over temperature is
shown in the graph in Section 2.2. 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 >100%
and <103% to 100%. Humidity values >103% are left unchanged to
indicate a problem with the probe or measurement.
13. 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 Modelling
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.
Lowe, P. R., 1977: An approximating polynomial for the computation of
saturation vapour pressure, J. Appl. Meteor., 16, 100-103.
Meyer, S. J. and K. G. Hubbard, 1992: Nonfederal Automated Weather Stations
and Networks in the United States and Canada: A Preliminary Survey,
Bulletin Am. Meteor. Soc., 73, No. 4, 449-457.
Weiss, A., 1977: Algorithms for the calculation of moist air properties on a
hand calculator, Amer. Soc. Ag. Eng., 20, 1133-1136.
WMO, 2008. Guide to Meteorological Instruments and Methods of Observation.
World Meteorological Organization No. 8, 7
th
edition, Geneva, Switzerland.