Resistance And Dc Current Adjustment - Agilent Technologies 3458A Calibration Manual

Resistance and DC
Current Adjustment
26 Chapter 3 Adjustment Procedures
This adjustment calculates gain corrections for the resistance and DC current
ranges. The DC Gain Adjustment must be performed prior to this adjustment
because this adjustment relies on the values calculated by the DC Gain
Adjustment.
Note
When offset compensated ohms is enabled (OCOMP ON command), the
default delay time used by the multimeter for this adjustment is 50ms
(50ms is the settling time used after the current source is switched on or
off). For most resistance standards and cabling, this provides adequate
settling time for the measurements made during the adjustment. If,
however, the resistance standard and/or cabling has slow transient response
or high dielectric absorption you should specify a longer delay. You can
determine this experimentally prior to performing the following adjustment
by measuring the resistance standard using a 50ms delay and then
measuring it using a much longer delay (e.g., 1 second). If the two
measurements are significantly different, you should use a longer delay in
the adjustment procedure. You must specify the longer delay using the
DELAY command prior to executing the CAL command (step 5). For
example, to specify a 200ms delay execute: DELAY 200E-3. The
multimeter will then use the specified delay in the adjustment. If a value of
less than 50ms is specified, the multimeter will automatically use a delay of
50ms. Do not specify a delay longer than 60 seconds; a delay >60 seconds
will adversely affect the adjustment.
Equipment required: A 10kW resistance standard (the resultant accuracy
of the multimeter depends on the accuracy of the resistance standard used).
Note
Resistance standards from 1kW to 12kW can be used for the procedure.
However, using a resistance standard <10kW will degrade the multimeter's
accuracy specifications.
1. Select the 4-wire ohms measurement function (use the shifted OHM
key).
2. Execute the OCOMP ON command (use the front panel Offset Comp
W key).
Note
You can perform this adjustment with offset compensation disabled
(OCOMP OFF command). This eliminates the settling time requirement
(DELAY command) when dealing with high dielectric absorption in the
adjustment setup (see note as the beginning of this adjustment). However,
with offset compensation disabled, any offset voltages present will affect
the adjustment. For most applications, we recommend enabling offset
compensation for this adjustment.