Specifications

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intensity control adjusts the magnitude of the electron beam current -- the more current, the brighter the
spot the beam makes on the screen. The accelerating potential on plate B is not adjustable by the user.
The voltages on the plates C and D are the responsibility of the horizontal and vertical deflection
circuitry as shown in the following block diagram of a scope:
Figure 7
The display circuitry is responsible for generating and adjusting the voltages on the deflection plates.
Vertical circuits
A block diagram of the vertical circuitry is:
Figure 8
The input coupling choices are ground, AC, and DC. Grounded coupling is used to determine where 0
volts is on the screen. AC coupling is used to couple only the AC component of the signal to the vertical
amplifier; it is often done with a coupling capacitor that blocks the DC. This is useful when a small AC
signal is riding on a large DC component, such as in a biased transistor circuit. DC coupling allows you
to see both the DC and AC components of a signal.
The attenuator is used to reduce the input signal's amplitude with range of the vertical amplifier's
capabilities. Typical oscilloscopes offer a wide range of signal gains. The B&K 2125A has vertical
amplifier ranges of 5 V/div to 1 mV/div. With a 1X/10X probe, you can measure signals from hundreds
of volts to a few millivolts -- roughly 5 orders of magnitude. The attenuators must have flat responses
for signals with frequencies from DC to approximately the scope's bandwidth.
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