Campbell SI-111, Product Manual, Page: 16 / 22

SI-111 and SI-111SS Precision Infrared Radiometers
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7.4.1 Sensor Body Temperature Measurements
7.4.1.1 Therm109() Instruction
CRBasic dataloggers measure the sensor body temperature (°C) using the
Therm109() instruction:
Therm109 ( Dest, Reps, SEChan, Mult, Offset )
Use the default values for Mult and Offset, which output the temperature in °C.
7.4.2 Thermopile Detector
7.4.2.1 VoltDiff() Instruction
CRBasic dataloggers measure the thermopile detector using the VoltDiff()
instruction:
VoltDiff ( Dest, Reps, Range, DiffChan, RevDiff, SettlingTime, Integ/Fnotch,
Mult, Offset )
The Range value should be mV200 (CR6, CR1000X), mV2_5 (CR800 series,
CR1000), mV34 (CR300 series), mV20 (CR3000, CR5000), or mV50
(CR9000(X)). The Integ/Fnotch parameter is often set to the 60 Hz option.
Use the default values for the RevDiff, SettlingTime, Mult , and Offset
parameters.
7.4.3 Target Temperature Calculations
These calculations are entered in CRBasic as expressions. Calculate the target
temperature using the following steps:
1. Calculate slope
2. Calculate intercept
3. Convert sensor body temperature (°C) to Kelvin.
4. Calculate target temperature (K)
5. If desired, convert target temperature (K) to degrees Celsius
Use Equation 1 to calculate slope:
m = mC2 • SBTempC^2 + mC1 • S mC0
(1)
Where,
m = slope
SBTempC = sensor body temperature in °C
mC2 = slope polynomial coefficient (C2) from the calibration sheet
mC1 = slope polynomial coefficient (C1) from the calibration sheet
mC0 = slope polynomial coefficient (C0) from the calibration sheet
Use Equation 2 to calculate intercept:
b = bC2 • SBTempC^2 + bC1 • S bC0 (2)