The insulation resistance may be measured between any number of windings. A dc voltage is applied across two groups of windings, with the windings in each group being shorted together. The voltage and current are measured; dividing the voltage by the current gives the insulation resistance.

On selecting ‘IR - Insulation Resistance’ from the available tests window, a form fillin dialogue box will be displayed:

To program the test :

Enter the test voltage.
Note that the Measure button cannot be used to determine the required Test Voltage.
Select (mouse click the button) the integration time you require.
'Medium' is the default setting. 'Long' will give more stable readings (for tighter limits) at the expense of an increased test time, and 'Short' will test at the maximum speed, but may give a slightly noisier reading.
Enter the terminal names for the High and Low Terminals.
Click with the mouse to select a terminal from the Available list; then click the ‘Add >‘ button to transfer it to the Used list.
(To correct a mistake, click with the mouse to select a terminal from the Used list; then click the ‘< Remove’ button to transfer it back to the Available list.)
Enter the minimum insulation resistance value in the bottom section.
Note: The combination of test voltage and minimum resistance must be equivalent to a test current less than 1 mA.
The Measure button may be used here as outlined in section 3.9.
Select OK. The test specification will then be displayed in the program window.

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