Campbell Scientific HMP35C Temperature and RH Sensor - Manual (Page 7)

HMP35C TEMPERATURE AND RH PROBE
5
;Pause 150 milliseconds, before making the measurement, so the
;probe can stabilize on the true relative humidity.
;
03: Excitation with Delay (P22)
1: 1 Ex Channel
2: 0 Delay W/Ex (units = 0.01 sec)
3: 15 Delay After Ex (units = 0.01 sec)
4: 0 mV Excitation
;Measure the HMP35C relative humidity.
;
04: Volt (SE) (P1)
1: 1 Reps
2: 5 2500 mV Slow Range ;CR500 (2500 mV); CR23X (1000 mV); 21X, CR7 (5000 mV)
3: 4 SE Channel ;Green wire (SE 4), Purple wire (AG)
4: 2 Loc [ RH_pct ]
5: 0.1 Mult ;See Table 5 for alternate multipliers
6: 0 Offset
;Turn the HMP35C off.
;
05: Do (P86)
1: 51 Set Port 1 Low ;Yellow wire (C1)
6. LONG LEAD LENGTHS
When long lead lengths are required, the
measurement settling time for the temperature
measurement must be increased. For
HMP35Cs with lead lengths greater than 300
feet, use the DC Half Bridge instruction
(Instruction 4) with a 20 millisecond delay to
measure the thermistor (Example 2).
Long lead lengths cause errors in the measured
relative humidity. The approximate error in
relative humidity is 0.6% RH per 100 feet of
cable length. When long lead lengths are
required and the above errors in relative
humidity are unacceptable, use the HMP45C
temperature and humidity probe.
TABLE 7. Wiring for Example 2
Description Color CR10(X)
Temperature Orange SE 3 (2H)
Relative Humidity Green SE 4 (2L)
Temperature Signal Reference White AG
Temperature Excitation Black E1
Power Control Yellow C1
Power Red 12 V
RH Signal, Power, & Control Reference Purple AG
Shield Clear G