5790B
Operators Manual
4-24
Establish a Reference
To establish a reference, apply an external dc reference to INPUT 1 or INPUT 2.
For highest resolution and most stable measurement, set the Digital Filter to
SLOW. (Setup Menu>Instrument Setup.) Under Digital Filter Setup select
Mode>Slow (32). Adjust the digital filter speed and/or restart threshold if the
settled reading (Filter Fill indicator above the measured reading) is too long.
To set a reference:
1. Connect an accurate dc voltage source to INPUT 1 or INPUT 2 and select the
input from the front panel.
2. Apply a positive dc voltage and wait for the measurement to stabilize. Make
sure the magnitude of the dc voltage is the same as the ac voltage to be
measured.
3. Select the Set Reference softkey on the main menu. This will store the
positive dc voltage for the reference.
4. Apply a negative dc voltage by reversing the polarity of the input. Make sure
the negative value is the same as the positive dc voltage applied in step 2.
5. Select the Average Reference softkey on the menu. This stores the negative
dc measurement and completes the reference process. Now AC voltage
measurements can be made. The error is shown on the screen, and at any
time the reference calculation can be viewed on the screen by selecting the
View Reference softkey. The delta units can be changed as described in the
subsequent sections.
6. Repeat this sequence for subsequent measurements.
View Reference Softkey
If a reference is set, push Reference Menu>View Reference (if you are not
already in the Reference Menu) to show the measured value of the active
reference.
If you previously pushed the Average Reference softkey, you will see both input
values that were used to compute the averaged reference.
Push Hide Reference or Back to return to normal operation.
Choose Delta Units
During transfers, the display shows the difference between an applied input and
the stored reference or average of references. The difference can be shown in
units of V (or mV), ppm, percent, or ratio. Once a reference has been
established, push Reference Menu>Select Formula to cycle through the
choices. From the Select Formula menu, you can select which formula you would
like for the difference calculation. After choosing which calculation to use, the
display shows the difference calculation at the bottom of the screen.
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