Electrically noisy environments, Long lead lengths temperature – Campbell Scientific 247-L Conductivity and Temperature User Manual
Page 14
247 CONDUCTIVITY AND TEMPERATURE PROBES
10
11. ELECTRICALLY NOISY
ENVIRONMENTS
AC power lines can be the source of electrical
noise. If the datalogger is in an electronically
noisy environment, the 107/107B temperature
measurement should be measured with the AC
half bridge (Instruction 5) with the 60 Hz rejection
integration option on the CR10(X) and slow
integration on the 21X and CR7 (see Section 13
of the datalogger manual for more information
on noise). Instruction 11's fast integration will
not reject 60 Hz noise.
Example 2. Sample CR10(X) Instructions
Using AC Half Bridge
01:
P5
AC Half Bridge
01:
1
Rep
02:
22**
7.5 mV 60 Hz rejection Range
03:
9*
IN Chan
04:
3*
Excite all reps w/EXchan 3
05: 2000**
mV Excitation
06:
11*
Loc [:Air_Temp ]
07:
800
Mult
08:
0
Offset
02:
P55
Polynomial
01:
1
Rep
02:
11*
X Loc Air_Temp
03:
11*
F(X) Loc [:Air_Temp ]
04:
-53.46
C0
05:
90.807
C1
06:
-83.257
C2
07:
52.283
C3
08:
-16.723
C4
09:
2.211
C5
*
Proper entries will vary with program and
datalogger channel and input location
assignments.
**
On the 21X and CR7 use the 15 mV input
range and 4000 mV excitation.
12. LONG LEAD LENGTHS
TEMPERATURE
If the 247-L/247W-L has lead lengths of more
than 300 feet, use the DC Half Bridge
instruction (Instruction 4) with a 2 millisecond
delay to measure temperature. The delay
provides a longer settling time before the
measurement is made. Do not use the
247-L/247W-L with long lead lengths in an
electrically noisy environment.
Example 3. Sample Program CR10 Using DC
Half Bridge with Delay
01:
P4
Excite, Delay,Volt(SE)
01:
1
Rep
02:
2**
7.5 mV slow range
03:
9*
IN Chan
04:
3*
Excite all reps w/EXchan 3
05:
2
Delay (units .01sec)
06: 2000**
mV Excitation
07:
11*
Loc [:Temp_C ]
08:
.4***
Mult
09:
0
Offset
02:
P55
Polynomial
01:
1
Rep
02:
11*
X Loc Temp_C
03:
11*
F(X) Loc [:Temp_C ]
04:
-53.46
C0
05:
90.807
C1
06:
-83.257
C2
07:
52.283
C3
08:
-16.723
C4
09:
2.211
C5
*
Proper entries will vary with program and
datalogger channel and input location
assignments.
**
On the 21X and CR7 use the 15 mV input
range and 4000 mV excitation.
*** Use a multiplier of 0.2 with a 21X and CR7.