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The
;21PL
position of the Voltmeter Function switch establishes the circuit shown
in Figure Sb where the output of the selected amplifier provides the input to the
volt=eter
o
The Voltmeter Range switch is used to select a convenient full-scale
range for the voltmeter.
Note that the wiper of the AMPL SEL switch is connected
to the AMPL OUT jack so that amplifier outputs can be monitored with external
equipment-.
The VM position of the Voltmeter Function switch connects the
VM
jack to the
Voltmeter Range switch (Figure Sc).
Voltages patched into the
VM
jack are read
on the voltmeter.
The NULL position of Sl provides a means of accurately measuring unknown voltages
with respect.to the computer reference voltage.
The circuit arrangement is shown
in Figure Sd.
The voltage to be measured is patched to the
VM
jack and connected
to one side of the meter.
The wiper of the NULL POT is connected to the other
side of the meter.
The Reference Selector switch S3 is switched to the position
that supplies reference voltage with the same polarity as the voltage to be
measured. .The
NULL
POT is varied until the meter reads zero.
The position of
the turns-counting dial on the NULL POT indicates the magnitude of the unknown
voltage; the position of S3 indicates the polarity of the unknown voltage.
This
null comparison method of voltage measurement is accurate to within ±p.l% of full
scale.
An
important feature of the method is that no current is drawn from the
source being measured once a balance is attained.
Thus the resistance of the
source has no effect in the measurement.
A large source resistance, however, will
decrease the- sensitivity of the meter to unbalanced conditions.
The POT BUS position of Sl is used when setting attenuators (Figure Se).
The
readout circuit is connected to measure the voltage on the pot bus by the null
comparison method.
When the pushbutton switch associated with an attenuator is
depressed, +10 volts is connected to the top of the attenuator, and the wiper is
connected to the pot bus.
The Reference Selector switch, S3 must be in the +10
position.
The
NULL
POT is set to the desired attenuator coefficient.
The atten-
uator is adjusted until the meter reads zero.
The attenuator is then set to the
same coefficient as the NULL POT.
b.
Manual Mode Control
The Mode Control switch
(8S)
on the Control Panel provides a means of starting
and stopping computer solutions and of establishing initial conditions.
The
switch controls the operation of a circuit which actuates the reset and operate
relays of the integrators.
The switch positions are RESET, HOLD, and OPER (operate).
All computing components except the integrators are operational in all three modes.
The integrators are controlled as follows:
IS
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