HP E1411A, Service Manual

Page: 68 / 78

Measurement
Uncertainty
Calculations
Measurement uncertainties for the Datron 4708 source are calculated using
the 90-day accuracy specifications in the Datron 4708 User’s Handbook:
Measurement Uncertainty = Datron Ac Calibration Uncertainty,
where Datron Accuracy (ppm) = Accuracy Relative to Calibration
Standards =
±
(ppm ppm FS)
and FS = 2 x range for all ranges except 1000V
FS = 1100 for the 1000V range
The assumed test conditions are:
•
Temperature of 23
o
C
±
1
o
C
•
90 days since calibration
•
4-wire sense function for ohms measurements
Calculate DCV
Measurement
Uncertainty
From Section 6 - Specifications of the Datron 4708 User’s Handbook, DC
Voltage (Option 10) Accuracy (90 days since calibration and 23
o
C
±
1
o
C)
follows, where Datron Accuracy =
±
(ppm ppm FS).
Datron
OUTPUT
(DCV)
Datron
Range
(Volts)
Datron
Accuracy
(ppm)
Calibration
Uncertainty
(ppm)
0.1
0.9
7.0
58.0
300.0 1.0000000V
1.0000000V
10.000000V
100.00000V
1000.0000V 2 + 0.4
2 + 0.4
1 + 0.15
2 + 0.25
3 + 0.25 2
2
1.5
2
2
Example: Calculate DC Voltage Measurement Uncertainty
Since Measurement Uncertainty = Datron Ac Calibration
Uncertainty, for a 7.0 DCV OUTPUT and the Datron 4708 range set to
10.000000 V, Measurement Uncertainty (
µ
V)=
±
[(1.0 x 7.0) + (2 x 0.15 x
10)] + (1.5 x 7.0)] =
±
20.5
µ
V =
±
0.000021 V.
Or, with a 300 DCV OUTPUT and the 1000.0000V range, Measurement
Uncertainty (
µ
V) =
±
[(3.0 x 300) + (0.25 x 1100)
+ (2.0 x 300)] =
±
1775
µ
V =
±
0.001775 V.
68 Calculating Multimeter Accuracy Appendix A