Technical data

Calibration Procedures 3

34980A Service Guide 65

–10 Vdc Adjustment Procedure (Optional)

The –10 Vdc calibration electronically enhances the Internal DMM’s a- to- d

converter linearity characteristic. This adjustment should ONLY be

performed after servicing the A- to- D converter or replacement of the

calibration RAM.

You will need an input test connector as described in “Input

Connections" on page 52.

1 If a zero calibration has not been performed recently, perform one

before beginning this procedure (see page 60).

2 Configure the instrument as follows:

DC VOLTS 

10 V range

[SENSe:]VOLTage[:DC]:RANGe 10

6½ digits 

INTEG 100 PLC

[SENSe:]VOLTage[:DC]:NPLC 100

INPUT R > 10 G [SENSe:]VOLTage[:DC]:IMP:AUTO ON

Measure and note the voltage offset present at the end of the

measurement cable by shorting the ends of the cable. Be sure to use a

copper wire and allow enough time for the residual thermal offset to

stabilize (usually about 1 minute).

4 Connect the input cable to the calibrator output and set the calibrator

to output +10V. Allow enough settling time for any thermal offset

voltages to stabilize (usually about 1 minute).

5 Perform a +10V dc gain calibration.

6 Send an adjustment to the instrument. The adjustment value is the sum

of the calibrator output and the measured offset (from step 3). For

example, if the calibrator output is 10.001 volts and the measured offset

is 10 µV, send the value +10.001010 volts. When the adjustment finishes,

verify that new readings fall within ±20 µV of the calibrator output plus

the offset.

7 Reverse the cable connections to the calibrator to create a –10 Vdc

voltage standard. You must physically reverse the cables. DO NOT

switch the output polarity of the calibrator.

8 Perform a –10V DC gain calibration. Be sure to allow time for thermal

offsets to stabilize (usually about 1 minute).

9 Send an adjustment to the instrument. The adjustment value is the sum

of the calibrator output and the measured offset (from step 3). Using

the previous example values, enter 10 µV minus 10.001 volts or

–10.000990 volts.

10 When the adjustment finishes, verify that new readings fall 

within ± 30 µV of the calibrator output minus the offset.