Physics and Engineering of Radiation Detection

A.2. Oscilloscope 745

Attenuator

Measurement

Lead

Display

Processor

Vertical

Amplifier

Time Base Generator

Horizontal Trace System

Trigger System

Analog−to−Digital Converter

Memory

Vertical Trace System

Figure A.2.2: Main components of a typical digital oscilloscope.

using a digital to analog converter (DAC) so that it could be displayed on the
fluorescent screen in much the same way as in an analog oscilloscope.
The bandwidth of a digital oscilloscope is limited by its sampling speed. Any
signal frequency above the sampling frequency is ignored by the oscilloscope. This
is a serious limitation of such oscilloscopes as compared to their analog counterparts,
which can be built with very high bandwidths.
A good feature of digital oscilloscopes is that their operations, such as triggering,
can be controlled by external logic units. Similarly the digital data can also be
retrieved and transported through data bus to the processing and analysis units.

A.2.C SignalProbes...........................

A signal probe is used to carry the input signal to be measured to one of the os-
cilloscope inputs. There are different kinds of probes suitable for different kinds of
input signals. But broadly speaking we can divide them into two categories: passive
and active. In the following we will look at some commonly used probes belonging
to both of these categories.

C.1 PassiveProbes

A passive probe consists of passive electronic components and a cable to carry the
signal to the oscilloscope.