P
AGE
11
TABLE 2
Temperature Error in
°
F per 1000 feet of Leadwire
AWG
Thermocouple Type:
No.
J
K
T
R
S
E
B
N
C
10
.61
1.54
.69
1.84
1.91
1.04
12.60
2.65
2.27
12
.97
2.41
1.09
2.97
2.96
1.64
19.80
4.21
3.66
14
1.57
3.86
1.75
4.81
4.76
2.63
31.50
6.69
5.74
16
2.47
6.09
2.77
7.47
7.52
4.14
49.95
10.64
9.10
18
4.00
9.90
4.50
12.17
12.28
6.72
79.95
10.64
9.10
20
6.43
15.51
7.06
19.43
19.59
10.61
126.90
26.89
23.24
24
15.80
39.44
17.83
48.89
49.13
26.70
320.85
68.03
58.75
Example:
An MIC is to be located in a control room 660 feet away from the process. Using 16 AWG,
type J thermocouple, how much error is induced?
Terr = TLe * L
TLe = 2.47 (
°
F/1000 ft) from Table 2
Terr = 2.47 (
°
F/1000 ft) * 660 ft
Terr = 1.6
°
F
RTD LEAD RESISTANCE
Rtd lead length can affect instrument accuracy, since the size (gauge) and length of the wire
affect lead resistance.
To determine the temperatire error resulting from the lead length resistance, use the following
equation:
Terr = TLe * L
where; TLe = value from Table 3 if 3 wire RTD or Table 4 if 2 wire RTD
L = length of lead wire in thousands of feet.
TABLE 3
3 Wire RTD
AWG No.
Error
°
C
Error
°
F
10
+/-0.04
+/-0.07
12
+/-0.07
+/-0.11
14
+/-0.10
+/-0.18
16
+/-0.16
+/-0.29
18
+/-0.26
+/-0.46
20
+/-0.41
+/-0.73
24
+/-0.65
+/-1.17
TABLE 4
2 Wire RTD
AWG No.
Error
°
C
Error
°
F
10
+/-5.32
+/-9.31
12
+/-9.31
+/-14.6
14
+/-13.3
+/-23.9
16
+/-21.3
+/-38.6
18
+/-34.6
+/-61.2
20
+/-54.5
+/-97.1
24
+/-86.5
+/-155.6
(Continued on next page)
