Campbell Scientific 108-L Temperature Probe - Manual (Page 18)

Model 108 Temperature Probe
C2 = –40.66
C3 = 16.573
C4 = –3.455
C5 = 0.301
1 CRBasic dataloggers are CR800, CR1000, CR3000, and CR5000.
2 Coefficients provided by the thermistor manufacturer.
3 Edlog dataloggers are CR10(X), CR510, CR500, CR23X, 21X, and CR7.
8.3 Electrically Noisy Environments
EMF noise emanating from the ac mains power grid can be a significant source
of measurement error. 60 Hz noise is common in the United States. 50 Hz
noise is common in Europe and other regions. Depending on the datalogger
model, this noise can usually be filtered out.
The following code examples filter 60 Hz noise. The key parameters are in
bold type.
CRBasic
Therm108 (T108_C,1,1,Vx1,0,_60Hz,1.0,0.0)
Edlog
1: AC Half Bridge (P5)
1: 1
Reps
2: 23 25 mV 60 Hz Rejection Range ;CR23X:50 mV; 21X,CR7:50 mV slow range
3: 1 SE Channel
4: 1 Excite all reps w/Exchan 1
5: 1000 mV Excitation ;CR23X,21X,CR7: 2000 mV
6: 1 Loc [ T108_C ]
7: 200 Multiplier
8: 0 Offset
8.4 Long Cable Lengths
Long cable lengths may require longer than normal analog measurement
settling times. Settling times are increased by adding a measurement delay to
the datalogger program.
CRBasic
For CRBasic loggers, the 60 Hz and 50 Hz integration options include a 3 ms
settling time; longer settling times also can be entered into the Settling Time
parameter. The following example uses a 20000 µs settling time:
Therm108 (T108_C,1,1,1,20000,_60Hz,1.0,0.0)
Edlog
If the 108 probe has cable lengths of more than 300 feet, use the Excite-Delay
(SE) (P4) instruction with a 20 ms delay to measure the temperature, as shown
in the following Edlog code.
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