Avtech AVR-AHF-1-B series, Инструкция по эксплуатации

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ELECTRONIC AMPLITUDE CONTROL, "-EA" OPTION
The output amplitude can be set to track the voltage on this input. Zero Volts in
corresponds to zero amplitude output, and +10V in corresponds to maximum amplitude
out. This mode is activated by selecting "Ext Control" on the front-panel amplitude menu,
or with the "source:voltage external" command. The polarity remains at its last setting.
OUTPUT IMPEDANCE
The AVR-AHF-1-B features an output impedance of the order of several Ohms (rather
than 50 Ohms). The following consequences of this feature should be noted:

When used to switch some semiconductor devices (eg. bipolar and VMOS power
transistors), the AVR unit will yield much faster switching times than those provided
by 50 Ohm pulse generators.

The AVR unit will safely operate in to load impedances in the range of 50 Ohms to
an open circuit. However, severe ringing may occur on the output waveform if a
high-impedance load is used, due to transmission line impedance mismatching.
When driving high impedance loads, it may be beneficial to add a 50 Ohm
impedance
in parallel with the high impedance load (as close to the load as
possible), in order to provide a proper termination for any transmission lines used.
Alternatively, a 50 Ohm resistance may be added
in series with the AVR output (as
close to instrument output connector as possible) to provide transmission line "back-
matching".

The AVR unit may be effectively converted to a 50 Ohm output impedance
generator by placing a 50 Ohm carbon composition resistor in series with the output
of the unit and the load. The maximum available load voltage will then decrease to
125 Volts (from 250 Volts).
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 100 kHz or at duty cycles resulting in an
average output power in excess of 50 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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