Operational Verification Tests 2
Keysight 3458A Calibration Manual 33
11 Execute Trig SGL and read the value as measured with the 3458A under test
and record this value in the “Unit under test reading” column of the DC voltage
operational test record.
12 Connect the DC voltage source to the transfer standard DMM.
13 Repeat steps 8 through 11 for a –10 V DC voltage source output.
14 Calculate, and record in the column provided, the difference (absolute value)
between the transfer standard DMM reading and the unit under test reading.
15 If the difference calculated is greater than the specified limits, refer to
Chapter 3, "Adjustment Procedures" to make adjustments.
DC voltage function offset test
This procedure tests the DCV offset voltage specification on the 10 V range. This
reading and the 10 V and –10 V readings from the previous DCV gain test are used
to do a turnover check of the A-D converter and verify its linearity.
1 Connect a low thermal short across the front panel HI and LO input terminals
of the DMM under test (see Figure 3-1 on page 39).
2 Set the range of the 3458A under test to 10 V.
3 Let the instrument sit for five minutes before taking a reading to allow the
short and relays to thermally stabilize.
4 Execute Trig and record the offset reading on the Test Card.
Turnover check
The turnover check is a calculation using the unit under test readings from tests 4,
5, and 6 on the Test Card. This check verifies the linearity of the A-to-D converter
which is fundamental to the 3458A's calibration technique. Calculate the
following:
(UUT Reading #4) - (UUT Reading #6) = A
(UUT Reading #5) - (UUT Reading #6) = B
If the A-to-D converter is linear. the difference in the absolute values of
A and B will be less than or equal to 4 µV.
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