balance to return the trace to the graticule centerline. When the step attenuator
balance is properly adjusted, the trace does not shift when the volts/division
switch is changed from 20mV to 5mV.
15.
The vertical positioning control, which is located to the right of
the
volts/division switch (fig 2-8a), controls the vertical position of the trace.
16.
The AC-GND-DC switch (fig 2-8a) is located below the volts/division control.
It is used to select the method of coupling the input signal to the grid of the
input amplifier. When DC position is selected, all components of the input signal
are passed to the input amplifier. DC coupling can be used for most applications.
However, with the DC component, it is better to select the AC position.
a. In the AC position the DC component of the input signal is blocked by a
capacitor in the input circuit.
The low frequency limit in the AC position is
about 1.6 Hz. Although you can use the AC position for frequencies between 1.6 Hz
and 16 Hz, use the DC position for signals below 16 Hz because they are attenuated
by AC coupling.
Also, you can expect some low frequency distortion at these low
frequencies in the AC position.
b. When you select the GND position, a DC ground reference is established at
the input circuit.
The grid of the input tube is at ground potential.
However,
the input signal is not grounded. You may obtain a reference without removing the
applied signal from the input connector (fig 2-8b).
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