Campbell Scientific HMP155A Temperature and Relative Humidity Probe - Manual (Page 31)

Appendix B. Example Programs
B.2 Differential Measurement Examples
These examples use the differential voltage instruction to measure the sensor
and use the datalogger’s SW12V terminal to power the sensor only when it is
being measured. The differential instruction is recommended for long lead
lengths. TABLE B-2 shows the wiring used for these examples.
TABLE B-2. Wiring for
Differential Measurement Examples
Color Description CR1000 CR10(X)
Yellow Temperature 2H 2H
Jumper to 1L 2L 2L
Blue Relative Humidity 1H 1H
White Signal Reference 1L 1L
Jumper from SW12V Control C1
Red Power SW12 V SW12 V
Black Power Ground G G
Clear Shield G
B.2.1 CRBasic Differential Measurement Program
Below is an example CR1000 program. Other CRBasic dataloggers are
programmed similarly.
'CR1000 program to measure HMP155A with differential measurements
Public AirTC
Public RH
DataTable(Temp_RH,True,-1)
DataInterval(0,60,Min,0)
Average(1,AirTC,IEEE4,0)
Sample(1,RH,IEEE4)
EndTable
BeginProg
Scan(5,Sec,1,0)
'HMP155A Temperature & Relative Humidity Sensor measurements AirTC and RH:
PortSet (9,1)
Delay(0,2,Sec)
VoltDiff (AirTC,1,mV2500,2,True,0,_60Hz,.14,-80)
VoltDiff (RH,1,mV2500,1,True,0,_60Hz,0.1,0)
PortSet (9,0)
If RH>100 And RH<108 Then RH=100
CallTable(Temp_RH)
NextScan
EndProg
B-3