Avtech 14260, Инструкция по эксплуатации

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The SYNC output of the mainframe should be used to trigger the oscilloscope.
A 50 Ohm resistance (R
C
in the diagram above) must be connected to ground on
the output. This can be a discrete resistor, a feed-through terminator, or the input
impedance of an oscilloscope (the latter method is shown in the diagram). If a high-
speed sampling oscilloscope is used, the input should be protected by adding
attenuator on the input.
The 450 Ohm resistance in series with the test jig output and the 50 Ohm input
impedance of the oscilloscope form a 10:1 voltage, so the measured voltage is:
VOUT = VDUT / 10
The monitor output is similarly divided by a factor of 10, so that:
VMON = VIN / 10
The monitor output is provided so that the user may determine the starting point of the
transient.
SETTING THE AMPLITUDE LEVELS
The amplitude pulse may be set from the front panel of the instrument, or by computer
command. This amplitude is expressed in terms of the voltage present on the test jig
input.
The amplitude is related to the forward diode current by:
I
F
≈ (V
IN
- V
DUT
) / 50Ω
where V
DUT
is the forward voltage drop of the diode (typically 0.7V for the classic silicon
PN junction diode, and usually somewhat lower for a Schottky diode).
For instance, if the desired forward current amplitude is 500 mA, the amplitude should
be set at 25.7V, so that (25.7V – 0.7V) / 50Ω = 500 mA. It may be necessary to adjust
the amplitude iteratively to obtain the desired I
F
, since V
DUT
may not be known in
advance.
AMPLITUDE ACCURACY
Due to the variations in V
F
as a function of operating conditions, the amplitude
settings should not be relied upon for any degree of accuracy . Instead the voltage at
the OUT terminal on the test jig should be monitored with a calibrated oscilloscope.
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