Campbell Scientific HC2S3 Temperature and Relative Humidity Probe - Manual (Page 17)

Model HC2S3 Temperature and Relative Humidity Probe
7. Installation
7.1 Siting
Sensors should be located over an open level area at least 9 m (EPA) in
diameter. The surface should be covered by short grass, or where grass does
not grow, the natural earth surface. Sensors should be located at a distance of
at least four times the height of any nearby obstruction, and at least 30 m
(EPA) from large paved areas. Sensors should be housed in a suitable radiation
shield.
Standard measurement heights:
1.5 m (AASC)
1.25 to 2.0 m (WMO)
2.0 m (EPA)
See Section 10, References for a list of references that discuss temperature and
relative humidity sensors.
7.2 Assembly and Mounting
Tools Required:
• 1/2 in. open end wrench
• small screw driver provided with datalogger
• UV resistant cable ties
• small pair of diagonal-cutting pliers
The HC2S3 probe and its calibration card are shipped in a small box, with the
box and PN 27731 Hex Plug attached to the cable. PN 27731 is used to mount
the probe inside the 41003-5 Radiation Shield as described in Section 4,
Quickstart.
Attach the probe to the cable by aligning the keyed connectors, pushing the
connectors together and tightening the knurled ring.
When exposed to solar radiation the probe must be housed in a radiation shield
such as the 41003-5 naturally aspirated shield, or the 43502 motor aspiration
shield (please refer to the 43502 product manual for details). The 41003-5
Radiation Shield has a U-bolt for attaching the shield to a tripod mast/tower leg
or CM200 series crossarm (shown in FIGURE 4-1 and FIGURE 4-2 in the
Quickstart section).
7.3 Wiring
Connections to Campbell Scientific dataloggers for measuring humidity and
temperature using two single-ended or two differential analog inputs are given
in TABLE 7-1 and TABLE 7-2. Use a single-ended analog measurement when
the cable length is less than 6.1 m (20 ft), or if power is switched off between
measurements. For cable lengths longer than 6.1 m or when the probe is
continuously powered, use a differential analog measurement. See Section 7.5
for a discussion on errors caused by long cable lengths.
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