68 34980A Service Guide
3 Calibration Procedures
34951A 4-Ch Isolated DAC Module
Each isolated DAC output channel can be measured and adjusted using the internal
DMM. The Internal DMM is recommended because it compensates for ambient
temperature.
The 34951A features “auto-calibration”. Upon receipt of the calibration command, all
channels on the DAC are adjusted using the internal DMM. Additionally you may adjust
ALL 34951A modules installed in the instrument with one command. The adjustments
require approximately
one minute per module.
There are two ways to adjust the DACs, depending upon the state of calibration security
(see “Calibration Security" on page 49).
• If the instrument is secured for calibration when the adjustment is begun, the
adjustments are considered volatile. All adjustments are discarded when power is
cycled. This provides an easy means to make immediate temperature-compensated
adjustments to the DAC outputs without overwriting stored calibration constants.
When this type of adjustment is made, the calibration count
(see page 50) is not advanced.
• If the instrument is unsecured for calibration, the adjustments are written to
non-volatile calibration memory. The calibration count
(see page 50) is advanced.
The 34951A 4-Ch Isolated DAC is intended to be adjusted frequently to
compensate for changes in the module’s environment (changes in
ambient temperature, changing the mainframe slot used, adding or
removing modules to a system). These adjustments can be made either
volatile or non-volatile as described below. The adjustment procedure is
given beginning on page 72.
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