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5790A
Service Manual
Always ensure that the proper range has been selected before
applying the voltage to the 792A input. Inputs that exceed the
protection level shown on its rear panel label disrupt the state
of calibration and can cause instrument damage.
While a calibration step is in progress, inaccurate values may appear on
the Measurement Display. This is normal. When the 5790A is finished with
the step, the display will read accurately.
3-24
e. Set the 5700A to the nominal test voltage, DC positive (Do not use a
characterized setting as the 5790A is now used as the DC reference, thus
allowing for any resistive drop caused by the 792A loading). Wait for the
5700A "U" annunciator to go out.
f.
Wait for 30 seconds for the DMM reading to stabilize. Record the DMM
reading under the 792A column in the worksheet for +DC. Record the
reading on the 5790A Output Display under the 5790A column for +DC.
g. Press [ ][ENTER] on the 5700A to toggle output polarity.
h. Again, allow the DMM reading to stabilize. Record the DMM reading
under the 792A column in the worksheet for -DC. Record the reading on
the 5790A Output Display under the 5790A column for -DC. Ignore
polarity for the 5790A reading (Record the absolute value).
i.
Apply the frequency required for the calibration step. Wait for the "U"
annunciator on the 5700A to go out.
j.
Allow the DMM reading to stabilize. Record the DMM reading under the
792A column in the worksheet for AC. Do not record a reading for the
5790A.
k. Now do a computation to get the measured AC using the formulas shown
in the worksheet:
1) Compute the average of the DC readings for the 5790A and the
792A as shown.
2) Compute "AC MEAS" using the formula shown. Be sure to
include the 792A correction as indicated in the formula.
l.
Observe the default "EXACT VALUE" on the display. It shows the
allowed number of decimal places for you to enter. Enter your
computation of "AC MEAS" in the 5790A using the keypad, and press
the [ENTER] key. After you press [ENTER], the Control Display shows
the progress of the internal process of the calibration step.
m. When the step has completed, set the 5700A to standby.
7. For an AC calibration point in the 60 mV through 600 mV group, you will need
to adjust the 5700A in accordance with the error displays that you recorded in
Table 3-3. Proceed as follows:
a. Obtain a copy of Figure 3-7, the worksheet for this group. Fill in the
voltage, frequency, 5700A error displays (positive and negative) from
Table 3-3, and the associated 792A correction.
b. Press the "DO Step" softkey. This automatically selects the appropriate
5790A range.
W Caution
Note
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