5700A/5720A Series II Calibrator
Service Manual
1-32
Current Derating Factors
Value of Derating Factor K for Over or Under Current
Nominal Value
(Ω)
Two-Wire Comp
I < I
L
[1]
Four-Wire
I < I
L
[1]
Four-Wire
I
U
< I < I
MAX
[2]
SHORT
1
1.9
10
19
100
190
1 k
1.9 k
10 k
19 k
100 k
190 k
1 M
1.9 M
10 M
19 M
100 M
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
5000
5000
0.3
300
160
30
16
3.5
2.5
0.4
0.4
50
50
7.5
4.0
1.0
0.53
0.2
0.53
0.1
4 x10
-5
1.5 x 10
-4
1.6 x 10
-3
3 x 10
-3
1 x 10
-2
1.9 x 10
-2
0.1
0.19
2.0
3.8
2 x 10
-5
3.8 x 10
-5
1.5 x 10
-4
2.9 x 10
-4
1 x 10
-3
1.9 x 10
-3
Notes:
1. For I < I
L
, errors occur due to thermally generated voltages within the 5720A. Use the following equation to determine the error,
and add this error to the corresponding uncertainty or stability specification.
Error = K(I
L
- I)/( I
L
x I)
Where: Error is in mΩ for all two-wire comp values and four-wire short, and in ppm for the remaining four-wire values.
K is the constant from the above table;
I and I
L
are expressed in mA for short to 1.9 kΩ;
I and I
L
are expressed inµA for 10 kΩ to 100 MΩ
2. For I
U
< I < I
MAX
errors occur due to self-heating of the resistors in the calibrator. Use the following equation to determine the
error in ppm and add this error to the corresponding uncertainty or stability specification.
Error in ppm = K(I
2
-I
U
2
)
Where: K is the constant from the above table;
I and I
U
are expressed in mA for short to 19 kΩ;
I and I
U
are expressed in µA for 100 kΩ to 100 MΩ
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