3 electrically noisy environments, 4 long cable lengths, Electrically noisy environments – Campbell Scientific 107-L Temperature Probe User Manual
Page 18: Long cable lengths
Model 107 Temperature Probe
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
Therm107
(T107_C,1,1,Vx1,0,_60Hz,1.0,0.0)
Edlog (except CR10, 21X, and CR7)
x: Temp (107) (P11)
1:
1
Reps
2:
1
SE Channel
3:
21
Excite all reps w/E1, 60Hz, 10ms delay
4:
1
Loc [ Air_Temp ]
5:
1.0
Multiplier
6:
0.0
Offset
Edlog (CR10, 21X, and CR7)
CR10, 21X, and CR7 dataloggers do not have
60Hz or 50Hz integration
options for the excitation channel. When using these dataloggers in electrically
noisy environments, use the
AC Half Bridge (P5) instruction, which
incorporates ac noise rejection in input voltage range options. After the
measurement, convert the result to temperature using
Polynomial (P55). The
following example shows the use of the
P5 and P55 instructions:
x: AC Half Bridge (P5)
1:
1
Reps
2:
22
7.5 mV 60 Hz Rejection Range ;21X,CR7: 50 mV slow range
3:
1
SE Channel
4:
1
Excite all reps w/Exchan 1
5:
2000
mV Excitation ;21X,CR7: 4000 mV
6:
1
Loc [ Air_Temp ]
7:
800
Mult
8:
0
Offset
x: Polynomial (P55)
1:
1
Reps
2:
1
X Loc [ Air_Temp ]
3:
1
F(X) Loc [ Air_Temp ]
4:
-53.46
C0
5:
90.807
C1
6:
-83.257
C2
7:
52.283
C3
8:
-16.723
C4
9:
2.211
C5
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.
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