Product manual

Model HC2S3 Temperature and Relative Humidity Probe
CM200 Series Crossarm
FIGURE 3-2. HC2S3 and 41003-5 Radiation Shield on a CM200
Series Crossarm
4. Wiring
Connections to Campbell Scientific dataloggers for measuring humidity and
temperature using two single-ended or two differential analog inputs are given
in Tables 4-1 and 4-3. 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 6
for a discussion on errors caused by long cable lengths.
The HC2S3 draws approximately 2 mA powered from 12V. The HC2S3 can
be continuously powered from the 12V terminal, or power can be switched
with the SW12V terminal to conserve battery life. When power is switched, a
3-second warm-up time is required. Using the SW12V terminal on the CR10X
datalogger requires a user-supplied jumper wire connected between the SW
12V CTRL terminal and a Control Port (C1..C8).
When measuring the HC2S3 with single-ended
measurements, the yellow and gray leads must both be
connected to AG on the CR10(X) and CR500/CR510 or to
on the CR1000, CR5000, and CR23X. Doing otherwise
will connect the datalogger’s analog and power ground
planes to each other, which in some cases can cause
offsets on low-level analog measurements. To avoid 2 mA
flowing into analog ground, switch power on/off for its
measurement.
CAUTION
6