If the 107 probe is to be used with long cable lengths or in electrically noisy environments,
consider employing the measurement programming techniques outlined in Electrically noisy
environments (p. 11) and Long cable lengths (p. 11).
Details of 107 probe measurement and linearization of the thermistor output are provided in
Measurement and output linearization (p. 10).
7.2.1 Therm107() instruction
The Therm107() measurement instruction programs CRBasic data loggers to measure this
sensor. It applies a precise excitation voltage, makes a half-bridge resistance measurement, and
converts the result to temperature using the Steinhart-Hart equation. See Measurement and
output linearization (p. 10) for more information. Therm107() instruction and parameters are as
follows:
Therm107(Dest, Reps, SEChan, VxChan, SettlingTime, Integ/f
N1
, Mult, Offset)
Variations:
l Temperature reported as °C — set Mult to 1 and Offset to 0
l Temperature reported as °F — set Mult to 1.8 and Offset to 32
l AC mains noise filtering — set Integ/f
N1
to the 60 Hz or 50 Hz option (see Electrically
noisy environments (p. 11))
l Compensate for long cable lengths — Set SettlingTime to 20000 (see Long cable
lengths (p. 11))
7.3 Air temperature installation
For air temperature measurements, locate probes over an open, level area at least 9 m (EPA;
Attributions and references (p. 13)) in diameter. The surface should be covered by short grass or
the natural earth surface where grass does not grow. Probes should be located at a distance of at
least four times the height of any nearby obstruction, and at least 30m (EPA) from large paved
areas. Sensors should be protected from thermal radiation, and adequately ventilated.
Standard air temperature measurement heights:
l 1.25 to 2.0 m (WMO; Attributions and references (p. 13))
l 2.0 m (EPA; Attributions and references (p. 13))
l 2.0 m and 10.0 m for temperature difference (EPA)
107 Temperature Probe7
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