Fluke 5720A service manual Resistance Verification Test

Calibration and Verification 3

Full Verification

3-16. Resistance Verification Test

The following test requires testing at the high, low and intermediate values only. This is because the 5700A/5720A Series II creates the other values of resistance from these values. Use Tables 3-16 (5720A) and 3-17 (5700A) for test records. For the convenience of anyone wishing to test the intermediate values, the tolerance limits are included. Testing these values could be done using a Hamon-type ratio device and a very stable, high-resolution bridge or DMM, or a combination of the two. Table 3-3 lists equipment required for this test. See Table 3-15, Minimum Use Requirements, for substitution information.

Equipment

Resistance

Standards

Current Source

DMM

Table 3-3. Equipment Required for Resistance Testing

Decsription

Fluke 742A Series in the following values: 1Ω, 1.9Ω, 10Ω, 10 kΩ, 19 kΩ, 10 MΩ, and 19 MΩ

Fluke 5500A or 5520A

Wavetek 1281 or HP 3458A

1.Connect the equipment as shown in Figure 3-8.

2.Set the Calibrator output to 1Ω with external sensing (EX SENS indicator lit) and set the dc DMM to read dc V. Record the 1Ω resistance standard value on the test record as the 1Ω STD RES VALUE.

3.Multiply the certified value of the 1Ω resistance standard by 0.1 and record the result on the test record as the 1Ω STD VOLTAGE.

4.Connect the DMM across the sense terminals of the 1Ω resistance standard.

5.Set the direct current source for a nominal 100 mA output. Vary the source until the DMM reading is as close as possible to the 1Ω Standard Voltage recorded in the

previous step. Record the DMM voltage reading on the test record as the

MEASURED 1Ω STD VOLTAGE.

Note

If the current source used has the resolution to achieve a voltage reading to within ±5 ppm of the value in step 3, it is not necessary to calculate the cal current in take next step. In this case, when you come to step 9 you will simply multiply the voltage reading from step 9 by a factor of 10, which is the same as dividing by 100 mA (0.1A).

6.Calculate the exact current by dividing the MEASURED 1Ω STD VOLTAGE by the 1Ω STD RES VALUE; record the result on the test record as the CAL CURRENT.

7.Enter the Calibrator displayed 1Ω value on the test record as the UUT 1Ω

DISPLAYED VALUE.

8.Transfer the dc DMM leads to the Calibrator sense terminals.

9.Enter the DMM voltage reading on the test record as the UUT 1Ω VOLTAGE.

10.Calculate the UUT true 1Ω resistance by dividing the UUT 1Ω VOLTAGE by the

CAL CURRENT.

11.Adjust the output adjustment knob for a UUT Control Display reading equal to the true 1Ω resistance value calculated in the previous step. The error from the displayed value is also shown on the Control Display. Enter the value of the error on the test record as the UUT DEVIATION FROM DISPLAYED VALUE.

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