Avtech 14260, Инструкция по эксплуатации

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BASIC MEASUREMENT THEORY
The basic procedure for measuring the forward recovery voltage and time is described
in method 4026.3 of MIL-STD-750E. The user should familiarize themselves with this
method before using this instrument.
The basic parameters are shown in Figure 4026-1 of MIL-STD-750E, reproduced in part
here:
“Waveform B” in this figure is the voltage across the DUT, V
DUT
. This is related to the
OUT signal on the test jig by:
V
OUT
= V
DUT
/ 10.
“Waveform A” in this figure is the current through the DUT, I
F
. This is related to the OUT
and MON signals on the test jig by:
I
F
≈ (V
IN
- V
DUT
) / 50Ω
I
F
≈ (10 × V
MON
- 10 × V
OUT
) / 50Ω
The above figure shows t
fr
as the time between 0.1 I
F
and V
fr
.
Unfortunately, the text also says t
fr
is “measured from the time forward voltage becomes
positive to the time that forward voltage recovers to a specified vfr”, which is slightly
different. The “time forward voltage becomes positive” is before the time where 0.1 I
F
is
reached.
In practice, it is impossible to measure the “time forward voltage becomes positive”
repeatably. 0.1 I
F
is a much easier time to identify and measure in an automated
system.
In the test results included in later sections, the approximation that 0.1 I
F
occurs at 0.1
V
IN
(or 0.1 V
MON
) is used to simplify measurements. This provides conservative results,
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