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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

'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

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Campbell CNR1 Spezifikationen Seite 33