slots provided in the cover plate.
The GND terminal at the rear of the
instrument should be connected to a low resistance ground point.
(5) The lamp power cable is connected to the 2-pin connector on the
left side of the Model 9461A Secondary Galvanometer.
b. Output connections. The amplifier has a very high output impedance
and the output current is independent of load resistance up to the point
where the output voltage exceeds approximately 150 mV, at which point the
amplifier overloads.
(1) When the amplifier is to be used in conjunction with a high input
impedance recorder or indicator it is necessary to reduce the input
impedance by shunting with an appropriate resistor. A chart of the input-
output characteristics versus load resistance is shown on Figure 2-10. From
this chart the shunt resistor most suitable for the application can be
determined.
(2) When the instrument is to be used as a voltage amplifier and is
to have the minimum loading effect upon the source, the amplifier gain
should
be
set
at
minimum where
the
input impedance is
highest
(approx. 4.7).
(3) Calibrating the indicator scale for a known input to the
amplifier can be achieved by using an adjustable shunt resistor instead of
adjusting the amplifier gain control.
(4) Since the amplifier has a common line between the input and
output circuits, the output recorder or indicator should have a high common
mode rejection ratio if applicable.
(Guildline Model 9461A has been
designed specifically as an indicating galvanometer for use with the Model
9460A Amplifier.)
4.
Operation.
a. Initial zero procedure.
One of the leads from the indicating
galvanometer is temporarily removed and the mechanical zero controls are
adjusted to zero the light spot. The inspection port on the left-hand side
of the amplifier is uncovered and the amplifier zero control is adjusted as
necessary to make the two illuminated vertical strips coincident with the
two vertical slits in the mask of the photo cell unit (fig 2-9). The final
adjustment should result in the light strips being slightly offset inwards.
The indicating galvanometer is recommended and the cover is replaced over
the inspection port.
(1) The
zero
control is
readjusted
so
that
the
indicating
galvanometer registers null deflection.
(2) The above procedure will be facilitated if the INCREASE GAIN control
is set near maximum feedback (approaching full anticlockwise rotation).
The
INCREASE GAIN control should be adjusted as necessary to obtain the
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