Voltech AT5600, Руководство пользователя

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C H A P T E R 7 – T E S T S A N D T E S T C O N D I T I O N S
AT5600 User Manual 98-119 issue 14
Page 126
7.19. GBAL – General Longitudinal Balance
Where Used
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.
Measurement Conditions and Types
Unfortunately, there are several published specifications for measuring
longitudinal balance. These are all different, and potentially give different results
for the same transformer.
To allow each user the freedom to test to his preferred method, the GBAL test
has been configured with the greatest flexibility. It therefore consists of two
separate measurements which the user can program, and the result is the ratio
between the two expressed in dB.
Operation
For the reasons outlined above, the test consists of two separate user
programmed measurements, each with its own ‘ energized ’ and ‘measured’
terminals. This approach is illustrated below with reference to three standard
methods: