Oscilloscope Required for Serious Digital Electronics Work
By Stephen Bucaro
Hantek DSO5102P USB Storage Oscilloscope
2 Channels 100MHz 1GSa/s
Although the signals in a digital circuits are voltages, in most cases they are changing too fast
for a voltmeter to be able to acquire any useful information. The oscilloscope is an instrument
that displays digital signals on a line graph with time on the horizontal axis and voltage on
the vertical axis. I often refer to an oscilloscope as the electronics technicians or engineers
eyes. It will be difficult to do digital logic design without the use of an oscilloscope.
Oscilloscopes come in analog and digital versions. An analog oscilloscope uses analog circuitry
to display the screen. This was the most common type of oscilloscope back when they used cathode
ray tubes for displays. Today, oscilloscopes use LCD or LED screens. The fact that the signal is
converted to digital data for display presents the ability for the oscilloscope to store the
signal digitally, for that reason today's oscilloscopes are usually digital storage oscilloscopes.
One of the main features of an oscilloscope is the number of input channels. Each channel requires
a probe to connect to a signal point. Each probe also has a ground clip. The signals displayed
on the oscilloscope screen are voltages relative to the circuit ground. You usually need a minimum
of two input channels because you are studying the relationship between two signals. Oscilloscopes
come with one to four channels. An instrument with more than four input channels is usually called
a logic analyzer.
It would be nice if digital signals were always perfectly square, but in the real world there are
certain parasitic properties that tend to distort the shape of electronic signals. Three properties
that affect signals are resistance, inductance and capacitance. Together they create a property
called impedance. You can't totally avoid these parasitic properties in an electronic circuit.
On the other hand, you don't want to hang an oscilloscope probe on the circuit that makes matters
worse. The higher the impedance, the less the signal is distorted, therefore oscilloscope inputs
and probes are made high impedance.
One specification that is related to oscilloscope input impedance, and to the quality of the
circuitry of which the oscilloscope circuitry is constructed is bandwidth. The bandwidth of a
circuit is the frequency at which the signal is half-attenuated (sometimes called the 3 dB
(decibel) point. Without going into a long explanation, you want an oscilloscope with a high
bandwidth, otherwise it will not be able to accurately display high-speed signals or fast rise
and fall times.
Oscilloscope bandwidths range between 30 MHz and several hundred MHz. High bandwidth capability
adds considerable cost to an oscilloscope, so it's best to determine what bandwidth you'll need
for your work, or what bandwidth you're willing to pay for.
If signal storage is important to you, you should pay attention to the instruments maximum
sampling rate. sampling rates range from 1 GS/s (Giga Samples per second) to 60 GS/s per
channel. Also consider the length of signals it can store, usually stated as Kpts (thousands
of data points per second), which relates to how much memory there is in the oscilloscope.
Tektronix TDS2024C 200 MHz
4 Channel, Oscilloscope, 2 GS/s Sampling,
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