Avtech AVRF-7B-B, Instructions Manual

Page: 23 / 39

OPERATIONAL CHECK
This section describes a sequence to confirm the basic operation of the instrument. It
should be performed after receiving the instrument. It is a useful learning exercise as
well.
Before proceeding with this procedure, finish read this instruction manual thoroughly.
Then read the “Local Control” section of the “Programming Manual for -B Instruments”
thoroughly. The “Local Control” section describes the front panel controls used in this
operational check - in particular, the MOVE, CHANGE, and ADJUST controls.
1. Connect a cable from the SYNC OUT connector to the TRIG input of an
oscilloscope. Connect a 50Ω (or higher) load to the OUT connector and place the
scope probe across this load. The load resistor must have a voltage rating of at
least 750V. The power dissipated in the resistor is given by
P = (V 2 / R) × (PW / T) = (V 2 / R) × PW × f
where “V” is the output voltage, “R” is the load resistance, “PW” is the pulse width,
and “T” is the pulse period (1/frequency), and “f” is the frequency. If a 50Ω resistor
is used, the worst-case average power dissipation is 11 Watts. Factory tests are
conducted using twenty 10Ω, 2W resistors connected in a series-parallel
combination to make a 50Ω, 40W composite load. Fan cooling the resistors allows
for slightly higher power dissipation. (Ohmite “OY” ceramic composition resistors -
http://www.ohmite.com - are recommended for such applications. These resistors
are readily available from http://www.digi-key.com/ and other distributors.)
2. Set the oscilloscope to trigger externally with the vertical setting at 100 Volts/div
and the horizontal setting at 1 us/div. Be sure that your oscilloscope and probe
setup can handle the maximum amplitude of 750V. (The Tektronix P5100 probe is
23
AVTECH
PULSER
MAIN OUTPUT
CONNECTOR
SYNC
OUTPUT
AC
POWER
ALL CABLES: 50 OHM COAXIAL
REAL-TIME
OSCILLOSCOPE
CHANNEL A
TRIG
INPUT
SCOPE
PROBE
TEST
LOAD,
50Ω