Campbell Scientific HMP45C Temperature and RH Probe - Manual (Page 11)

Model HMP45C Temperature and Relative Humidity Probe
The temperature and relative humidity signals from the HMP45C can be
measured using a single-ended analog measurement or a differential analog
measurement.
Use a single-ended analog measurement when the HMP45C signal lead length
is less than 6.1 m (20 ft.) or if the probe will be turned on and off under
datalogger control between measurements. For lead lengths greater than 6.1 m
(20 ft.) or when the probe will be continuously powered, use a differential
analog measurement. For a discussion on errors caused by long lead lengths
see Section 6.
The HMP45C output scale is 0 to 1000 millivolts for the temperature range of
-40
°C to +60°C and for the relative humidity range of 0 to 100%. Tables 5-1
and 5-2 provide calibration information for temperature and relative humidity.
TABLE 5-1. Calibration for Temperature
Units
Multiplier
(degrees mV -1 )
Offset
(degrees)
Celsius 0.1 -40
Fahrenheit 0.18 -40
TABLE 5-2. Calibration for Relative Humidity
Units
Multiplier
(% mV -1 )
Offset
(%)
Percent 0.1 0
Fraction 0.001 0
TABLE 5-3. Wiring for Single-ended
Measurement Examples
Color Description CR1000 CR10(X)
Yellow Temperature SE 2 (1L) SE 3 (2H)
Blue Relative Humidity SE 1 (1H) SE 4 (2L)
White Signal Reference AG
Jumper from
SW12V Control
C1
Red Power SW12V SW12 V
Black Power Ground AG
Clear Shield G
7