NF ZM2371 - Page 70

3.5 Basic Operations
3-40 ZM2371/ZM2372
 Trigger delay time: Trigger delay setting menu
The trigger delay time is the time from trigger up to signal acquisition start. The signal
settling time varies depending on the nature of DUT or required accuracy. For the trigger
delay time, set long time to the extent that the measured value does not vary even if the
trigger delay time is changed a little.
Press the _ SHIFT _ + [TRIG MODE] keys to display the trigger setting menu, and select
Delay with a numeric key and the trigger delay setting menu (see below) will be
displayed.
Trigger Delay : 0.456s Current setting
0.000 to 999.999s Range of settable values
Input a numeric value to set the trigger delay time. The setting resolution is 1ms.
If a setting is made or the EXIT operation is performed, one-previous menu comes back.
For high permittivity type capacitors having hysteresis characteristics or inductors having a
core, it is recommended to acquire the signal after at least one period of signal elapsed (1ms
at 1kHz, or 8ms at 120Hz) since the measurement signal was applied to the DUT. It may
take long time for settling if dielectric absorption of DUT is large.
When the DUT does not have hysteresis or dielectric absorption, the settling time of signal
is determined by the following two factors:
1) Time constant determined by ZM2371 / ZM2372 output impedance or maximum drive
current and capacitance of DUT
2) ZM2371 / ZM2372 internal settling time
The ZM2371 / ZM2372 output impedance and maximum drive current depend on the
measurement range.
For details  “3.5.6.3 Measurement Range”
If the DUT is pure capacitance C or inductor L, the signal settles at the time constant CRd
or L/Rd where the ZM2371 / ZM2372 output impedance is Rd. Make allowance for the
settling time of 5 to 7 times the time constant. The settling time will vary if the current is
limited.
The measurement will be incorrect if the trigger delay time is set to zero when the triggered
drive is enabled. When the triggered drive is enabled, it will take time for the drive signal to
settle in the ZM2371 / ZM2372. Also, the settling time is required when the frequency or
signal level is changed.
Approximate settling time in the measurement of large capacitance can be obtained from the
measurement frequency, DUT capacitance C (F), and output impedance Rd ().
Measurement frequency 120Hz Settling time = 4ms + 6  Rd  C
Measurement frequency 1kHz Settling time = 1ms + 6  Rd  C
Setting example of trigger delay time (in both cases, Rd=100)
Measurement frequency 120Hz, DUT 220F Trigger delay time 142ms (about 17
periods of signal)
Measurement frequency 1kHz, DUT 10F Trigger delay time 7ms
The settling time by CR time constant can be reduced if the output impedance Rd = 5.