AMPLITUDE CONTROL
The amplitude may be controlled directly from the front panel, or by computer
command.
When operating near maximum duty cycle (between 0.05% and 0.1%), the amplitude
should not be increased in large steps, or the internal high voltage power supplies may
become overloaded while charging up the internal capacitor banks. This will result in a
reduced actual output amplitude and degraded fall times. This is not dangerous to the
instrument, but it may cause unexpected results. To avoid this, increase the amplitude
slowly when operating at high duty cycles.
LOAD IMPEDANCE
The AVRF-7A-B is designed to drive 50 Ohm loads. It should not be used with other
load impedances.
If your load impedance is higher than 50 Ohms, add a resistance in parallel with the
load to reduce the total effective resistance to 50 Ohms.
If your load impedance is lower than 50 Ohms, add a resistance in series with the load
to increase the total effective resistance to 50 Ohms.
A 50 Ohm load impedance is required. Open circuits, short circuits, and other non-
50Ω loads may damage the instrument.
PREVENTING OUTPUT STAGE FAILURE
The output stage is protected against some 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 5 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 PW to a minimum.
•
Never apply an externally generated voltage to the output port.
•
Reduce the amplitude below 100 Volts before changing the output polarity. Note
that internal protection circuits will prevent the polarity from switching when the
amplitude is set higher than ±100V, until the internal power supplies have
discharged the voltage on the internal energy-storage capacitors to below ±100V.
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Summary of Contents for AVRF-7A-B
Page 47: ...PERFORMANCE CHECK SHEET 47...