The maximum amplitude error within the first year is:
0.04 % of set value + 0.01 % of range + 0.001 %/°C of set value
Now, the maximum error can be calculated:
I
err max
= I
set
× (0.04 % + 0.001 % × ΔT) + 0.01 % I
range
For ΔT = 40 °C – 28 °C = 12 °C, the resulting maximum error is:
I
err max
= 1 A × (0.04 % + 0.012 %) + 0.01 % × 1.25 A = 0.52 μA + 0.125 μA = 0.645 μA
For comparison: The permissible error for a temperature range of 23 °C ± 5 °C is 0.525 μA.
3.18.2.2 Higher ambient temperature (DC)
When operating the CMC 430 at ambient temperatures beyond 23 °C ± 5 °C, the temperature
coefficient has to be taken into account.
Set value: I
set
= 1 A
Range: I
range
= 1.25 A
Ambient temperature: T
ambient
= 40 °C
The maximum amplitude error within the first year is:
0.04 % of set value + 0.01 % of range + 0.001 %/°C of set value + 0.005 %/°C of range
Now, the maximum error can be calculated:
I
err max
= I
set
× (0.04 % + 0.001 % × ΔT) + (0.01 % + 0.005 % × ΔT) × I
range
For ΔT = 40 °C – 28 °C = 12 °C, the resulting maximum error is:
I
err max
= 1 A × (0.04 % + 0.012 %) + (0.01 % + 0.06 %) × 1.25 A = 0.52 μA + 0.875 μA = 1.395 μA
For comparison: The permissible error for a temperature range of 23 °C ± 5 °C is 0.525 μA.
3.18.2.3
Accuracy of combined AC + DC RMS values
If the test object evaluates AC and DC components in the RMS value, the offset has to be considered.
The offset is calculated from the range part of the DC specification:
V
offset
= 150 V × 0.015 % = 22.5 mV
For a set value of V
set
= 1 V, the maximum AC error is:
V
error
= 0.04 % × 1 V + 0.01 % × 150 V = 0.4 mV + 15 mV = 15.4 mV
The resulting RMS value uses the quadratic mean of the AC voltage and the DC offset:
sqrt(V
offset
2
+ (V
set
+ V
error
)
2
) = 1.01565 V
The resulting relative error is 1.56 %. The relative error without the offset is 1.54 %.
The maximum relative error can therefore be calculated as follows:
Relative error < sqrt(V
offset
2
+ (V
set
+ V
error
)
2
) / V
set
– 1
CMC 430 User Manual
44
OMICRON
To Next Page
Loading...
