Fluke 5790B, Руководство по обслуживанию

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5790B
Service Manual
3-24
d. Set the 5730A to nominal positive and then turn the knob to obtain
the error display reading you recorded in Table 3-2. Wait for the
5730A “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 5790B.
f. Set the 5730A to nominal negative, and then turn the knob to
obtain the error display reading you recorded in Table 3-2. Wait
for the 5730A “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 5790B.
h. Apply the nominal voltage at the frequency required for the
calibration step. Wait for the “U” annunciator on the 5730A 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 5790B.
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 Product using the keypad, and
push the [ENTER] key. After you push [ENTER], the Control
Display shows the progress of the internal process of the
calibration step.
Note
While a calibration step is in progress, inaccurate values may appear
on the Measurement Display. This is normal. When the Product is
finished with the step, the display will read accurately.
l. When the step has completed, set the 5730A to standby.
7. 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. The bootstrap method relies on the
linearity of the ranges starting from 70 mV and below. To minimize error
due to DUT linearity, the linearity of each range used in this process has
to be measured and corrected for. Build a 100:1 resistive divider with low
power coefficient. This divider has to be linear - its ratio should not
change with input voltage from 6 V to 0.2 V. It is not required to know the
divider division ratio. Connect the Fluke 5730A, Fluke 792A, and the DUT
as shown in Figure 3-10. Measure the linearity error of each range at
1 kHz only. The 1 kHz error is applicable to all frequencies within a range.