Programming instructions
Chapter 4 Performance Verification Tests 39
DC Voltage Function
Offset Test
The following procedure tests the offset voltage specification with the input
terminals shorted. A low-thermal short must be used to minimize thermally
induced errors. Also, you must allow five minutes before making the first
measurement to allow for thermal stabilization of the range relays.
1. Connect a low thermal short across the front panel HI and LO input
terminals of the DMM under test (see Figure 1 on page 23).
2. Set the range of the 3458A under test as specified in Table 1.
3. Let the instrument sit for five minutes before taking the first reading to
allow the range relay and short to thermally stabilize. NOTE: The
thermal stabilization achieved for the 100 mV range is present for the
1V and 10V ranges since these ranges use the same relays. The range
relays are opened for the 100V and 1000V ranges and therefore, have
no thermal impact on the measurement.
4. Execute Trig and record the offset reading (absolute value) for each
range listed in Table 1 and on the DC VOLTAGE TESTS Test Card
provided at the end of this chapter.
5. If any of the offset readings are greater than the limits specified on the
DC VOLTAGE TESTS Test Card, the instrument should be adjusted.
Refer to Chapter 3. "Adjustment Procedures", to make adjustments.
6. Remove the short from the front panel terminals.
DC Voltage Function
Gain Test
The following is a step-by-step procedure for all test points that verify gain
of the DC voltage function. The procedure requires alternately connecting
the transfer standard DMM and then the 3458A under test to the DC voltage
source as described in the general test description.
1. Set the output of the DC voltage source to standby/off and short the HI
and LO output terminals of the source using a shorting strap.
2. Connect the leads of a shielded low-thermal EMF cable from the
source output terminals to the Input HI and LO terminals of the
transfer standard DMM.
3. Connect the Guard terminal of the voltage source to the guard terminal
Table 1. Offset Performance Tests
Offset Test Number DMM Range
1 100 mV
21 V
3 10 V
4 100 V
5 1000 V