Verifying Absolute Ac Error For Region Ii (2.2 V Through 1000 V Range) - Fluke 5790B Service Manual

Verifying Absolute AC Error for Region II (2.2 V through 1000 V Range)

Because of the loading of 792A in its 700 mV to 1000 V ranges, the dc voltage at
the reference point of the calibration (center of the tee) is not the same as the dc
voltage at the output terminals of the source unless sense terminals are provided
for the source to the tee. If sense terminals are provided for dc, the absolute ac
error may be determined as for region II; however, the sense connections should
be removed when the ac measurements are being made.
Alternatively, you can determine dc errors and ac-dc errors independently, then
combine them. This is the procedure presented here.
In this case, you take the measurements and make calculations in the same way
as Regions I and III to obtain the ac-dc errors (You may have already calculated
these errors if you are verifying both the ac-dc and the absolute ac performance
of the instrument). You then take dc measurements and calculate dc errors.
Combine the errors to obtain absolute ac error.
Proceed as follows to use the error combination method:
1. To determine the dc errors, connect the test equipment as shown in
Figure 3-5.
2. Use characterized 5730A dc settings as follows: Set the 5730A to
nominal, then use the knob to adjust for the error display you recorded in
Table 3-2. Take dual polarity dc readings and record them in Figure 3-18.
3. Calculate the dc error as shown in Figure 3-17.
4. Combine the dc errors and the ac-dc errors using the following equation
to obtain the absolute ac reading error and enter the result in Table 3-14.
AC READING ERROR = DC ERROR - (AC - DC ERROR).
Calibration Adjustment and Verification
Calibration Verification
3
3-49