Campbell Scientific CS500-L Temperature and Relative Humidity Probe - Manual (Page 15)

CS500 Temperature and Relative Humidity Probe
11
;Compute the vapor pressure in kPa.
;Relative humidity must be a fraction.
;
07: Z=X*Y (P36)
1: 3 X Loc [ e_sat ]
2: 2 Y Loc [ RH_frac ]
3: 4 Z Loc [ e ]
8. Maintenance
The CS500 Probe requires minimal maintenance. Check monthly to make sure
the radiation shield is free from debris. The white screen at the tip of the probe
should also be checked for contaminants.
When installed in close proximity to the ocean or other bodies of salt water
(e.g., Great Salt Lake), a coating of salt (mostly NaCl) may build up on the
radiation shield, sensor, filter and even the chip. NaCl has an affinity for water.
The humidity over a saturated NaCl solution is 75%. A buildup of salt on the
filter or chip will delay or destroy the response to atmospheric humidity.
The filter can be rinsed gently in distilled water. If necessary, the chip can be
removed and rinsed as well. Do not scratch the chip while cleaning.
The offset and gain on the CS500 electronics can not be adjusted as part of a
recalibration. Replace the RH chip as needed.
9. 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 vapor 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.