Standalone and Computer-Based Instruments
The output of most transducers is an electrical signal. Transmitting modulated electrical voltages
down conducting wires is a robust and inexpensive way to communicate sensor information, and it is
often simple to construct secondary electrical circuits, if necessary, that process the information,
making it directly observable, or recordable by the experimenter. 20 years ago, the array of recording
devices included ingenious mechanical-electrical devices such as chart recorders and gauges. Today,
almost all signals are eventually processed by computer, which has now become the host for
, where the traditional role of the transducer/recorder is combined and moved
the control box.
Indeed, 10 years ago it looked as though all special-purpose equipment (and their manufacturers)
would be replaced by this digital revolution. Instead, something interesting happened. Realizing the
engineering and economic advantages of having a digital platform, the manufacturers of instruments
such as oscilloscopes and function generators redesigned their entire product line so that they were
also digital based, but with such speed and resolution as to make them act like their analog
predecessors, only faster, better and cheaper.
In the 341 lab, we have introduced a full range of computer-based instrumentation and
devices. In Fall02 this lab was named “Analog and digital instrumentation”. Now there is no such
thing (almost) as analog instrumentation, and we compare instead two different design philosophies of
Since the devices you will learn to use this afternoon are genuinely serious-caliber instruments, we
can conclude with a realistic exercise that could be used directly in your future engineering career.
The homework will be to conduct and report an evaluation of the comparative performance and
economic advantages of the two different types of hardware (computer based, and standalone), using
data from the lab and data dragged out from the internet soup.
2. The lab in general
The lab itself is one of learning by doing. Superficially, the controls are rather easy to learn and since
a combination of instruments is available, the effect of pushing one button can be verified quite easily
by its effect on the other boxes. As we progress into the lab, we will discover that sometimes there are
hidden subtleties and traps that must be detected, and we will understand that the correct use of these
instruments cannot be done without care and attention.
Still, the basic buttons are fast and easy. As a guide to the perplexed, here is a list of buttons and
controls whose position and function needs to be learned for each instrument.