Theory of Operation
Theory of Operation
3Ć4
A signal enters the oscilloscope through a probe connected to a BNC on the
A1 Main Board.
Attenuators A1Ă
2
Circuitry in the attenuator selects the input coupling and attenuation factor.
The processor system controls the attenuators with a serial interface as well
as through voltage changes with the daculator.
The Main Board assembly contains two attenuator hybrids, six relay drivers,
and two probe connectors. Each attenuator hybrid contains resistive
dividers, an AC coupling capacitor, relays and a preamplifier.
Probe Coding Interface
The probe coding interface signals pass through the Main Board to the A4
Front Panel, which converts the probe code voltage to a digital value.
Acquisition System
The acquisition system amplifies the input signals, samples them, converts
them to digital signals, and controls the acquisition process under direction
of the processor system. The acquisition system includes the trigger,
acquisition timing, and acquisition control circuitry.
The sampler driver (U204) amplifies and acquires the analog signal supplied
by the attenuators. The acquisition system converts the signal to digital and
stores it in acquisition memory. The time base controller controls the
acquisition process. The CPU monitors and controls the overall system, and
transfers the acquired waveform to the display system. Figure 3Ć3 provides
an overview of the acquisition system.
Attenuator A1Ă
2
Ċ Each attenuator hybrid has 3 relays. The AC/DC
coupling relay couples the output of the BNC to the other relays in the
attenuator hybrid. For AC signals, the AC/DC coupling relay inserts a
coupling capacitor into the input signal path. The second relay generates a
calibration or ground signal. The third relay selects the attenuation factor
(X1, X10, or X100).
Daculator A1Ă
2
Ċ The daculator system provides DC voltage signals that
set the offsets and variable gain control voltages for the attenuator hybrids
and trigger levels. The CPU controls the daculator serially.
A1 Main Board
