TDS 340A, TDS 360 & TDS 380 Technical Reference
3–7
Component-Level Overview
This section describes the electrical operation of the oscilloscope. Refer to the
schematics in the Diagrams section as necessary.
A11/A12/A13 Main Board
A signal enters the oscilloscope through a probe connected to a BNC on the A11
(TDS 340A), A12 (TDS 360), or A13 (TDS380) Main Board.
Attenuators. 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, three relays and a preamplifier. 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).
Probe Code Interface. The probe coding interface signals pass through the Main
Board to the A6 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. Figure 3–3 shows a block
diagram of the acquisition system.
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.
Daculator. 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.
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