Campbell CMP11, Инструкция по эксплуатации

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CMP6, CMP11, and CMP21 Pyranometers
TABLE 7-5. Multipliers Required for Flux Density and Total Fluxes
Units Multiplier Output Processing
W • m –2 M Average
MJ • m –2 M * t * 0.000001 Totalize
kJ • m –2
M *
t
* 0.001
Totalize
cal • cm –2 M * t * 0.0239 * 0.001 Totalize
cal • cm –2 • min –1 M * 1.434 * 0.001 Average
W • hr • m –2 t / 3600 Totalize
M = calibration factor with units of W • m –2 / mV
t = datalogger program execution interval in seconds
7.3.1.3 Offset
The offset will normally be fixed at zero as the sensor should output no
significant signal in dark conditions. In practice, because of the nature of
thermopile detector sensors, there will be some offset in dark conditions;
sometimes this offset can give negative light readings. This offset varies with
several factors (e.g., rate of change of sensor temperature), so it cannot be
removed with a fixed offset. Some users may wish to remove small negative
readings by including code after the measurement instructions that sets
negative readings to zero.
7.3.1.4 Output Format Considerations
Over-ranging may be an issue if the measurement values are totalized. Over-
ranging can be prevented when using CRBasic by storing the data in the IEEE4
format.
7.3.2 CMP21 Internal Thermistor Measurement
The thermistor is measured using the BrHalf CRBasic instruction. The value
provided by the half bridge instruction needs to be converted to resistance and
then converted to temperature.
The following equation is used to convert to resistance:






−
=
x
x
V 1
V
1000 Res.
Where,
Vx = the value provided by the half bridge instruction
In CRBasic, the conversion to resistance is entered as a mathematical
expression.
The Steinhart-Hart equation is used to convert resistance to temperature. The
Steinhart-Hart equation for converting resistance to degree Celsius is as
follows:
Temperature = 1/[A + B*LN(resistance) + C*(LN(resistance))^3] - 273.15
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