Some alternate information displays for an electrical signal.
Types of instruments
Although all instruments share the same basic role, there is a large variety of instruments. As
mentioned previously, some instruments are used for measurements, while others are
designed to provide stimulus. Figure 1.3 illustrates three primary elements of instruments that
can be used to describe variations among instruments.
1. The interface to the DUT depends on the nature of the physical property to be measured (e.g.,
temperature, pressure, voltage, mass, time) and the type of connection to the instrument. Different
instruments are used to measure different things.
2. The operator interface is determined by the kind of information desired about the physical property,
and the means by which the information is communicated. For example, the user of an instrument that
detects electrical voltage may desire different information about the electrical signal (e.g., rms voltage,
peak voltage, waveform shape, frequency, etc.), depending upon the application. The interface to the
instrument may be a colorful graphic display for a human, or it may be an interface to a computer. Figure
1.5illustrates several possible information displays for the same electrical signal.
3. The fidelity of the transformation that takes place within the instrument itself—the extent to which the
actual instrument behaves like an ideal instrument—is the third element that differentiates instruments.
The same limitations of human perception described in the introduction apply to the behavior of
instruments. The degree to which the instrument overcomes these limitations (for example, the accuracy,
sensitivity, and sample rate) is the primary differentiator between instruments of similar function.
Electronic instruments have several advantages over purely mechanical ones, including:
Electronic instruments are a natural choice when measuring electrical devices.
The sophistication of electronics allows for improved signal and information processing
within the instrument. Electronic instruments can make sophisticated measurements,
incorporate calibration routines within the instrument, and present the information to the user
in a variety of formats.
Electronic instruments enable the use of computers as controllers of the instruments for fully
automated measurement systems.