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Appendix C. CR3000/CR5000 Program that Controls the Heater

BeginProg

Scan (1,Sec,0,0)

'Control the net radiometer heater.

PWM (duty_cycle,4,250,mSec)

'Datalogger panel temperature.

PanelTemp (panel_temp,250)

'Measure battery voltage.

Battery (batt_volt)

'Measure the HMP45C temperature and relative humidity.

VoltDiff (t_hmp,1,mV1000C,5,TRUE,200,250,0.1,-40)

VoltDiff (rh_hmp,1,mV1000C,6,TRUE,200,250,0.1,0)

'Measure NR 01 Net Radiometer.

Resistance (t_nr01,1,mV200,10,Ix1,1,1675,TRUE,TRUE,200,250,1,0)

VoltDiff (Rs_downwell,1,mV20C,11,TRUE,200,250,NR01_SHORT_DW_CAL,0)

VoltDiff (Rs_upwell,1,mV20C,12,TRUE,200,250,NR01_SHORT_UW_CAL,0)

VoltDiff (Rl_down_meas,1,mV20C,13,TRUE,200,250,NR01_LONG_DW_CAL,0)

VoltDiff (Rl_up_meas,1,mV20C,14,TRUE,200,250,NR01_LONG_UW_CAL,0)

'Find the HMP45C vapor pressure and saturation vapor pressure (kPa).

VaporPressure (e_hmp,t_hmp,rh_hmp)

SatVP (e_sat_hmp,t_hmp)

'Compute net radiation, albedo, downwelling and upwelling longwave radiation.

t_nr01 = t_nr01/100

PRT (t_nr01,1,t_nr01,1,273.15)

Rn = Rs_downwell-Rs_upwell+Rl_down_meas-Rl_up_meas

albedo = Rs_upwell/Rs_downwell

Rl_downwell = Rl_down_meas+(5.67e-8*t_nr01*t_nr01*t_nr01*t_nr01)

Rl_upwell = Rl_up_meas+(5.67e-8*t_nr01*t_nr01*t_nr01*t_nr01)

CallTable (scratch)

If ( scratch.Output(1,1) ) Then

GetRecord (scratch_out(1),scratch,1)

rh_hmp_mean = 100*e_hmp_mean/e_sat_hmp_mean

DewPoint (t_dew_hmp_mean,t_hmp_mean,rh_hmp_mean)

'Control the NR 01 heater using 4 Hz pulse width modulation. Below the dew

' point temperature applies 100% power. Above the dew point, power is reduced

' linearly to 20% until the dew point plus DELTA_SET_POINT_1. After the dew

' point plus DELTA_SET_POINT_1 and until the dew point plus

' DELTA_SET_POINT_2 plus DELTA_SET_POINT_2, the power is reduced linearly to 0%.

If ( (t_nr01 <> NaN) AND (t_dew_hmp_mean <> NaN) AND (no_heat_flag <> TRUE) ) Then

set_point_temperature = t_dew_hmp_mean+273.15

Select Case t_nr01

Case Is < ( set_point_temperature )

duty_cycle = 1

Case Is < ( set_point_temperature+DELTA_SET_POINT_1 )

duty_cycle = MAX_DUTY_CYCLE_1+(t_nr01-(t_dew_hmp_mean+273.15))*SLOPE_1

Case Is < ( set_point_temperature+DELTA_SET_POINT_1+DELTA_SET_POINT_2 )

duty_cycle = MAX_DUTY_CYCLE_2+(t_nr01-

(t_dew_hmp_mean+273.15+DELTA_SET_POINT_1))*SLOPE_2

C-4

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Campbell CNR1 Especificaciones Pagina 36

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