Voltech AT360, User Manual

Page: 322 / 470

T
ESTS AND
T
EST
C
ONDITIONS
P
AGE
7-24 V
OLTECH
AT
I
U
SER
M
ANUAL
This can be a problem when trying to compare measurements made on
commercially available impedance bridges, or component testers, with
measurements made using the ATi. The test signal in such bridges is usually
determined within the instrument, and is often at a fixed frequency and at a
voltage level that is not guaranteed to be constant for all value of inductance.
Usually, if the actual test conditions of the bridge can be determined, and the
tester is then programmed to deliver the same test conditions across the
inductance the results will then agree. (See also the comments below on
differences caused by the choice of equivalent circuit)
d) Equivalent Circuit
Inductance is always measured as part of a complex impedance, the result
being expressed in terms of either a series or parallel equivalent circuit.
Note that, for any given winding, the inductance values for the two circuits
are not necessarily the same. This should be born in mind when specifying
the test limits.
Choosing Test Limits
The test limits can be:
% A nominal value together with + and – percentage limits.
>< Minimum and maximum values
> A minimum value only
< A maximum value only
Use the PC Editor’s ‘Measure’ button (together with a sample part) if you are
unsure of the nominal value.
Remember to click on the units of limits (nH, mH etc.) when entering absolute
values as limits.