Avtech AVR-G1-B-P-EMRA-R5-RP-IM, Instructions Manual

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OUTPUT IMPEDANCE
The AVR-G1-B-P-EMRA-R5-RP-IM has an output impedance (i.e., an internal
resistance in series with the output) of 50 Ohms, to provide transmission line back-
matching and short-circuit protection.
If the load is capacitive, the RC time constant of the output impedance and the
capacitive load will tend to degrade the rise and fall times.
CURRENT MONITOR
This instrument includes a current monitor, for measuring output currents of up to 250 mA.
The monitor circuit samples the output current at the end of the pulse, and reports it on the
front panel LCD. The value may also be queried remotely using the “meas:ampl?”
command.
The current monitor circuit also provides a rear-panel “M” BNC connector. The voltage
waveform on this connector is proportional to the output current (V
M
= I
OUT
x 2V / 100 mA),
for currents of up to 250 mA. The voltage waveform is pulsed, similar to the main output. It
is not a DC output. This output is intended to drive high impedance (> 10 kΩ) loads, such
as an oscilloscope probe. It can drive 50Ω loads, but the output voltage will be reduced by
a factor of two, approximately. The DC component of the waveform varies as a function of
duty cycle and other parameters, and should be ignored. The pulse amplitude (peak-to-
peak) should be measured instead.
PREVENTING OUTPUT STAGE FAILURE
The output stage is protected against overload conditions by an overload circuit and
fuses on the main frame back panel. However, the output switching elements may fail if
the unit is triggered at a PRF exceeding 10 kHz or at duty cycles resulting in an
average output power in excess of 11 Watts. Heating and subsequent possible failure
of the output stage is reduced if the following action is taken where possible:

PRF is kept to a minimum, i.e. operate in a low PRF range when possible rather
than in a high PRF range.

Keep the output pulse width to a minimum.

Never apply an externally generated voltage to the output port.
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