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c. Set the 792A INPUT RANGE knob to the appropriate position. Always
use the lowest range that will accept the input.
Always ensure that the proper range has been selected before
applying 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.
d. Set the 5700A to nominal positive and then turn the knob to obtain the
error display reading you recorded in Table 3-3. Wait for the 5700A "U"
annunciator to go out.
e. Wait for 60 seconds for the DMM reading to stabilize. Record the DMM
reading under the 792A column in the worksheet for +DC. Do not record
a reading for the 5790A.
f.
Set the 5700A to nominal negative, and then turn the knob to obtain the
error display reading you recorded in Table 3-3. Wait for the 5700A "U"
annunciator to go out.
g. Again, allow the DMM reading to stabilize. Record the DMM reading
under the 792A column in the worksheet for -DC. Do not record a
reading for the 5790A.
h. Apply the nominal voltage at the frequency required for the calibration
step. Wait for the "U" annunciator on the 5700A to go out.
i.
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.
j.
Now do a computation to get measured AC using the formulas shown in
the worksheet:
1) Compute the average of the 792A DC readings as shown.
2) Compute "AC MEAS" using the formula shown. Be sure to
include the 792A correction as indicated in the formula. Use
nominal DC in the formula.
k. 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.
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.
l.
When the step has completed, set the 5700A to standby.
8. For an AC calibration point in the 2 mV through 20 mV group, you use a
bootstrapping technique. This procedure assumes the you have calibrated the
60 mV points. Each range is bootstrapped from the next higher range as shown in
Figure 3-9.
W Caution
Note
Calibration and Verification
Periodic Calibration
3
3-25
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