Campbell Scientific CNR1 Net Radiometer - Manual (Page 33)

Appendix C. CR3000/CR5000 Program
that Controls the Heater
This program applies power to the CNR1 heater using the SW12V relay
controller and the pulse width modulation instruction (PWM ()).
The program below uses the dew point value. The datalogger calculates dew
point using the relative humidity (RH) measurements provided by the
HMP45C Temperature/Relative Humidity probe. Enter 0 degrees C as the set
point for the heater when a temperature/RH probe is not used.
The algorithm turns the heater on/off at 4 Hz. The duty cycle of the pulse is
changed depending on how close the radiometer body temperature is to the
dew point temperature. At or below the dew point, the duty cycle is 100%. It
drops off linearly to 20% until the body temperature is 5 degrees C above the
dew point. For body temperatures greater than 5 degrees C above the dew
point, the duty cycle continue to drop linearly, but with a different slope, until
0% at 33 degrees C above the dew point. If necessary, the user can change the
two duty-cycle slope transitions.
'CR3000 or CR5000 Series Datalogger
'CR3000 Series Datalogger
'Copyright (c) 2009 Campbell Scientific, Inc. All rights reserved.
'11 March 09
'version 0.0
'*** Wiring ***
'ANALOG INPUT
'5H
HMP45C temperature signal (yellow)
'5L HMP45C signal reference (white)
'gnd HMP45C shield (clear)
'6H
HMP45C relative humidity signal (blue)
'6L short jumper wire to 5L
'10H
CNR1 Pt100 signal (red)
'10L CNR1 Pt100 signal reference (blue)
'gnd CNR1 Pt100 shield (silver)
'11H
CNR1 downwelling shortwave radiation signal (red)
'11L CNR1 downwelling shortwave radiation signal reference (blue)
'gnd CNR1 shield (silver)
'12H
CNR1 upwelling shortwave radiation signal (white)
'12L CNR1 upwelling shortwave radiation signal reference (green)
'13H
CNR1 downwelling longwave radiation signal (brown)
'13L CNR1 downwelling longwave radiation signal reference (yellow)
C-1