Specifications 2
34980A Service Guide 39
To Calculate Total DMM Measurement Error
Each specification includes correction factors which account for errors present due to
operational limitations of the optional internal DMM.
This section explains these errors and shows how to apply them to your measurements.
Refer to “Interpreting Internal DMM Specifications" on page 41, to get a better
understanding of the terminology used and to help you interpret the internal DMM’s
specifications.
The internal DMM’s accuracy specifications are expressed in the form:
(% of reading + % of range).
In addition to the reading error and range error, you may need to add additional errors for
certain operating conditions. Check the list below
to make sure you include all measurement errors for a given function. Also, make sure
you apply the conditions as described in the footnotes
on the specification pages.
• If you are operating the internal DMM outside the 23 °C ± 5 °C temperature range
specified, apply an additional temperature
coefficient error.
• For dc voltage, dc current, and resistance measurements, you may need to apply an
additional reading speed error.
• For ac voltage and ac current measurements, you may need to apply an additional low
frequency error or crest factor error.
Understanding the “% of reading“ Error The reading error compensates for
inaccuracies that result from the function and range you select, as well as the input signal
level. The reading error varies according to the input level on the selected range. This
error is expressed in percent of reading.
The following table shows the reading error applied to the internal DMM’s 24-hour dc
voltage specification.
Range Input Level Reading Error
(% of reading)
Reading Error
Voltage
10 Vdc
10 Vdc
10 Vdc
10 Vdc
1 Vdc
0.1 Vdc
0.0015
0.0015
0.0015
150 V
15V
1.5 V
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