18.104.22.168 VOCX Test (External Source)
The accuracy for measuring open circuit voltage is given as:
AT = AR + AC + AV + ASRCE
AT is the total accuracy (%)
AR is the basic relative accuracy (%)
AC is the calibration accuracy (%)
AV is the correction for voltage level (%)
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
The values of the other factors are given below.
AC = 0.03% + (0.001% x FM )
AV = 0.03% + (0.001% / VM )
ASRCE = 0.5% for manual / line supply
= 0.0% for analogue / amplifier and AT output transformer
FM is the measurement frequency (Hz)
VM is the measured voltage (V)
During a VOCX 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.