Campbell Scientific HMP45C Temperature and RH Probe - Manual (Page 7)

Model HMP45C Temperature and Relative Humidity Probe
3. Installation
3.1 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 protected from thermal
radiation, and adequately ventilated.
Standard measurement heights:
1.5 m +/- 1.0 m (AASC)
1.25 – 2.0 m (WMO)
2.0 m (EPA)
2.0 m and 10.0 m temperature difference (EPA)
See Section 10 for a list of references that discuss temperature and relative
humidity sensors.
3.2 Assembly and Mounting
Tools Required:
• 1/2” open end wrench
• small screw driver provided with datalogger
• UV resistant cable ties
• small pair of diagonal-cutting pliers
The HMP45C must be housed inside a radiation shield when used in the field.
The 41003-5 Radiation shield has a U-bolt for attaching the shield to tripod
mast / tower leg (Figure 3-1), or CM200 series crossarm (Figure 3-2). The
radiation shield ships with the U-bolt configured for attaching the shield to a
vertical pipe. Move the U-bolt to the other set of holes to attach the shield it to
a crossarm.
Loosen the split-nut on the bottom plate of the 41003-5. Remove the yellow
protective cap on the HMP45C, and insert the sensor into the shield. Tighten
the split-nut to secure the sensor in the shield. Route the sensor cable to the
instrument enclosure. Secure the cable to the tripod/tower using cable ties.
The HMP45C must be housed inside a radiation shield when used in the field.
The 41003-5 Radiation Shield (Figure 3-1 and 3-2) mounts to a tripod mast,
tower leg, or CM200 series crossarm.
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