Service manual

Test Accuracy
Ratio (TAR)
Definition
Test Accuracy Ratio (TAR) is the ratio of multimeter accuracy to
measurement uncertainty. For the E1411 multimeter performance tests, test
accuracy ratio = (High Limit value - Test Input value)/Measurement
Uncertainty value. This value is shown in the "Test Accuracy Ratio (TAR)"
column of Table 4-1.
NOTE
Test accuracy ratio does not apply to the DC Voltage (Zero Volts Input)
test, since no measurement uncertainty value applies.
Multimeter
Accuracy
Calculations
For the E1411 multimeter performance verification tests, multimeter
accuracy is defined for DC Voltage, AC Voltage, and 4-Wire Resistance
measurements using the 90-day specifications in Appendix A -
Specifications of the E1326A/E1411A User’s Manual or the
E1326B/E1411B User’s Manual. The assumed test conditions are:
• 90 days since calibration
• Temperature within ± 5
o
C of calibration temperature
• Module calibration temperature 18
o
C to 28
o
C
• One hour warmup
• 4-wire ohms resistance measurements
• Aperture = 16.7 msec (60 Hz) or 20 msec (50 Hz)
• Autozero ON
DC Voltage
Accuracy
Equations
From Appendix A - Specifications of the E1326A/E1411A User’s Manual or
the E1326B/E1411B User’s Manual, DC voltage 90-day accuracy =
±(% of
reading + volts). The accuracy equations for the ranges and apertures used
in the performance verification tests are:
Range
Accuracy [
±(% of reading + Volts)]
125 mV
1 V
8 V
64 V
300 V
0.023 + 5.0
µV
0.013 + 15.0
µV
0.010 + 50.0
µV
0.015 + 1.0 mV
0.015 + 5.0 mV
Example: Calculate DC Voltage Accuracy
For a 7.0 DCV input to the multimeter, using the 8 V range and 16.7/20
msec aperture, multimeter accuracy (90-days) =
±(.010% reading + 50.0
µV) = ±(.0001 x 7.0 + 50 x 10
-6
) = ±0.00075 Volts. Thus, for a 7.0 DCV
input the High Limit in Table 4-1 = 7.00075 Volts and the Low Limit =
6.99925 Volts.
64 Calculating Multimeter Accuracy Agilent E1411A/E1411B Service Manual