188.8.131.52 MAGX Test (External Source)
The accuracy for measuring magnetising current using an external source is:
AT = AR + AC + AI + AOFF + AESI + ASRCE
AT is the total accuracy (%)
AR is the basic relative accuracy (%)
AC is the calibration accuracy (%)
AI is the correction for the current level (%)
AOFF is the error in the compensation measurement (%)
AESI is the error in the current measurement from the source interface (%)
ASRCE is the correction for the external source type (%)
The value of AR is given in the table in section 1.1 of this chapter
AC = 0.03% + (0.001 * FM)
AI = 0.03% + (0.0001 / IM) + (2 * IM)
AOFF = (0.76% + (0.001 * FM) ) * (0.3 / IM)
AESI = 0.5%
ASRCE = 0.5% for manual / line supply
= 0.0% for analogue / amplifier and AT output transformer
FM is the test frequency (Hz)
IM is the measured current (A)
During a MAGX test, the AT3600 automatically applies the test voltage to the part under test and checks that the voltage has stabilised before recording measurements. The time that the voltage takes to stabilise will vary with the source type used and the nature of the part under test.
In general (and especially for source types 'Programmable' and 'AT Output Transformer'), the AT3600 will record a measurement very quickly, (typically in less than 0.5 seconds) which is desirable in a production test environment.
If the measurement were to be recorded after a longer period of time under power, slightly different readings may be obtained due to self-heating effects in the part under test. This effect may be noticed when comparing results taken using different source types or with slower measurement systems.