AT3600 User Manual

3.4.15 GBAL - General Longitudinal Balance

The general longitudinal balance test is intended to measure what is effectively the Common Mode Rejection Ratio of a transformer designed to connect to a balanced line. Two measurements are performed each by applying a voltage to the transformer and measuring the resulting voltage to calculate the CMRR. To overcome the differences of three standard methods of measuring the CMRR the GBAL dialogue box has a separate group of terminals X and Y for the first and second measurements respectively. The preferred method of measurement is the LBAL test for which Voltech provide a separate test specifically for this measurement.

This test is suitable for audio & telecommunication transformers and checks the effective common mode rejection ratio of the transformer.

On selecting "GBAL General Longitudinal Balance" from the available tests window, a dialogue box will be displayed:

To program the test:

1. Enter the voltage and frequency parameters of the test signal.
   (If in doubt, refer to Chapter 7 - ‘Test Conditions’, which lists recommended test conditions).
   Note also that the Measure button may be used here as outlined in section 3.9.
2. Select 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.
3. Enter the names for the energised and measured terminals for the X measurement.
4. Similarly configure Y terminals.
5. When required the "Optional 2nd Energised Hi" allows an additional terminal connection to the energised high node.
6. Set (X/Y) limits.

   +/-	Enter a nominal value and then the limits as negative and positive values.
   ><	Enter minimum and maximum values.
   >	Enter just a minimum value.

7. Since components on the test fixture may scale measured readings the "Compensate for Test Fixture Scaling" allows the test to account for this.
8. Select OK. The test specification will then be displayed in the program window.