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If the 108 probe is to be used with long cable lengths or in electrically noisy environments,
consider employing the measurement programming techniques outlined in
environments
(p. 11) and
Details of 108 probe measurement and linearization of the thermistor output are provided in
Measurement and output linearization
7.2.1 Therm108() instruction
Therm108()
The
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
output linearization
follows:
Therm108(Dest, Reps, SEChan, VxChan, SettlingTime, Integ/f
Variations:
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
l
noisy environments
Compensate for long cable lengths — Set SettlingTime to 20000 (see
l
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
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 30 m (EPA) from large paved
areas. Sensors should be protected from thermal radiation, and adequately ventilated.
Standard air temperature measurement heights:
1.25 to 2.0 m (WMO;
l
2.0 m (EPA;
Attributions and references
l
2.0 m and 10.0 m for temperature difference (EPA)
l
Long cable lengths
(p. 10).
(p. 10) for more information.
(p. 11))
(p. 13)) in diameter. The surface should be covered by short grass or
Attributions and references
(p. 11).
Therm108()
instruction and parameters are as
to the 60 Hz or 50 Hz option (see
N1
(p. 13))
(p. 13))
Electrically noisy
Measurement and
, Mult, Offset)
N1
Electrically
Long cable
108 Temperature Probe 7
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