Campbell Scientific NR01 Net Radiometer - Manual (Page 39)

Appendix A. CR3000 Program that
Controls the Heater
This program applies power to the NR01 heater using the SW12V relay
controller and the pulse width modulation instruction (PWM ()).
Rather than using 0 degrees C as a set point for the heater, 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 Series Datalogger
'*** 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
NR01 Pt100 signal (white)
'10L NR01 Pt100 signal reference (green)
'gnd NR 01 Pt100 shield (silver)
'11H
NR01 downwelling shortwave radiation signal (red)
'11L NR01 downwelling shortwave radiation signal reference (blue)
'gnd NR01 shield (silver)
'12H
NR01 upwelling shortwave radiation signal (white)
'12L NR01 upwelling shortwave radiation signal reference (green)
'13H
NR01 downwelling longwave radiation signal (brown)
'13L NR01 downwelling longwave radiation signal reference (yellow)
'14H
NR01 upwelling longwave radiation signal (purple or pink)
'14L NR01 upwelling longwave radiation signal reference (gray)
A-1