Campbell Scientific SI-111 (IRR-P) Precision Infrared Radiometer - Manual (Page 11)

SI-111 Precision Infrared Radiometer
'Instruction to measure mV output of thermopile detector (red wire to 2H, black wire to 2L,
clear ‘wire to ground)
VoltDiff (TargmV,1,mV2_5,2,True ,0,_60Hz,1.0,0)
'Calculation of m (slope) and b (intercept) coefficients for target temperature calculation
m = mC2 * SBTempC^2 + mC1 * SBTempC + mC0
b = bC2 * SBTempC^2 + bC1 * SBTempC + bC0
'Calculation of target temperature
SBTempK = SBTempC + 273.15
TargTempK = ((SBTempK^4) + m * TargmV + b)^0.25
TargTempC = TargTempK - 273.15
'Call output tables
CallTable IRR
NextScan
EndProg
5.2 CR10X Example Program
This example CR10X program measures the sensor once a second and outputs
the average values once an hour. The actual measurement rate and output
intervals need to be adjusted for the actual installation and application.
Explanation of Labels Used in the Program
mV_thrm = mV output of the thermistor
1_mV_thrm = first step in converting the mV output of the thermistor to resistance
2_mV_thrm = second step in converting the mV output of the thermistor to resistance
R_thrm = resistance of the thermistor
InR_thrm = natural log of the resistance of the thermistor
Scaled_R = intermediate step in converting the natural log of the resistance to temperature
SH_Coeff = application of the Steinhart and Hart coefficients to convert the scaled resistance to the
reciprocal of temperature
SB_Temp_K = sensor body temperature in Kelvin
SB_Temp_C = sensor body temperature in degrees Celsius
mV_tpile = mV output of the thermopile (dependent on the temperature difference between the
target and the sensor body)
m_slope = slope of the equation relating target and sensor body temperature to mV output of the
thermopile
b_inter = y-intercept of the equation relating target and sensor body temperature to mV output of the
thermopile
Exponent1 = exponent used to raise the sensor body temperature to the 4th power
Exponent2 = exponent used to calculate the 4th root of the sum of the terms used to calculate the
target temperature
1_SB_4Pow = first calculation step; sensor body temperature (Kelvin) raised to the fourth power
2_mVxm = second calculation step; mV output of the thermopile multiplied by m (slope)
3_Sum1 = third calculation step; sum of calculation steps one and two
4_Sum2 = fourth calculation step; the sum of calculation step 3 and b (intercept)
T_Temp_K = target temperature in Kelvin; calculated by adding the temperature difference between
the target and sensor body to the sensor body temperature
T_Temp_C = target temperature in degrees C
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