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SECTION III
- DESCRIPTION
The Model 701 Electronic
Relay consists of a three stage
vacuum tube amplifier
following
a
60
cycle mechanical chopper.
The output of the amplifier
is synchronously clemodulatcd end
filtered
to provide a D. C. al.gnel at the grid of & thyratron.
The thyratron
operates a relay.
Positive
feedback from the
thyratron
grid to the input of the amplifier
prevents relay
chatter.
The voltage reference consists of a mercury battery
across
which is placed an accurate divider
and a l$ linear
potentio-
meter.
The chopper compares the input voltage to the divider
voltage.
If the input voltage is less than the divider
volt-
age the D. C. voltage to the thyratron
grid keeps the thyratron
on, if the input voltage exceeds the reference voltage the
thyratron
extinguishes.
If circuit
failure
occurs) the signal
to the demodulator, which keeps the thyratron
on, is removed
and the relay opens to indicate
the alarm position.
The basic sensitivity
of the instrument
is 10 millivolts,
however, provision
is made for mounting internal
dividers
if reduced sensitivity
is desired,.
Also, with an input
impedance of one megohm currents down to 10-e amperes may
be measured by means of shunt resistors.
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