BENEFITS OF PC-BASED USB OSCILLOSCOPES

PC-based USB oscilloscopes, which display signal voltage as two-dimensional graphs and indicate amplitude distortions related to events and frequency, are used by hobbyists and professionals alike for testing hardware and research. Conventional oscilloscopes are typically stand-alone pieces of testing equipment that aren’t readily portable. PC-based oscilloscopes connect directly to your computer’s USB port and enable you to power the device, acquire and store data, and supply record evaluation; these features have given users more options and new techniques when using an oscilloscope.

PC-based oscilloscopes utilize your computer’s hardware — specifically its processor(s) — to display data on the computer’s screen and record that data on the computer’s hard drive or other storage devices. There are myriad modifications that can be done with PC-based oscilloscopes that aren’t practical for stand-alone oscilloscopes.

There are a wide variety of uses for PC-based oscilloscopes. Technicians use PC-based oscilloscopes as diagnostic tools for computer problems and maintenance work on all sorts of electrical equipment. PC-based oscilloscopes are also useful for everything from conducting electrocardiograms (medical professionals) to diagnosing issues with cars (automotive repair).

Modern computer processors are faster than they’ve ever been and their prices are dropping all the time — it’s no wonder that PC-based oscilloscopes are being used more often. In addition PC-based oscilloscopes can do everything that stand-alone units can but cost less and work with just about any computer. Old PCs are often significantly faster and more powerful than many stand-alone oscilloscopes that cost hundreds or even thousands of dollars, meaning that you can pull that ten-year-old computer out of storage, dust it off, and bring it back to life with an oscilloscope.

Furthermore data collected with a PC-based oscilloscope can be quickly and easily stored, shared, or exported as a result of a computer’s word processing and spreadsheet software, storage capacity, and networking capabilities. On top of that PC-based oscilloscopes offer better screen resolution and portability. It’s not hard to see why PC-based USB oscilloscopes have increased in popularity in recent years. Stand-alone oscilloscopes may soon be a thing of the past.

USING THE RIGHT OSCILLOSCOPE PROBE

A piece of test equipment’s performance is always limited by its peripheral equipment, and the same holds true for digital storage oscilloscopes. Most people tend to focus on an oscilloscope’s specifications — especially considering that specifications generally determine price — but an oscilloscope probe’s performance is every bit as important. A substandard oscilloscope probe will impair the performance of even the very best oscilloscope.

You want your oscilloscope probe to provide a simple means of presenting the signal on a circuit board or whatever is being tested to the oscilloscope’s input. A standard oscilloscope probe will consists of a probe tip, length of shielded wire, and a compensation network.

Passive probes are the most common kind of oscilloscope probe and there are two noteworthy types of passive probes: X1 and X10. X1 probes present a signal as it exists to your oscilloscope. Ordinarily an oscilloscope’s input impedance is one megohm, but this impedance can load the device you’re testing and distort the waveform. Moreover, an X1’s tip capacitance can be as high as one hundred picofarads. To avoid these limitations and lessen the load on the circuit you’re testing an X10 probe can be used instead. Because an X10 probe has an input impedance of ten megohms and a tip capacitance of around ten picofarads, this type of probe will distort the waveform far less than an X1.

Active oscilloscope probes are another option when you need even greater levels of performance. These probes have very low levels of capacitance and significantly higher input impedances as a result of having an active element quite close to the oscilloscope probe’s tip.

Calibration

It’s very easy to simply plug your oscilloscope probe in and start taking measurements with your oscilloscope; however, your oscilloscope probe needs to be calibrated before you use it to make sure that its response is flat. Almost every oscilloscope has a built-in calibrator for this reason. The calibrator provides a square wave output, and the oscilloscope probe has a small preset adjustor. You connect the probe to the calibrator’s output and manipulate the present adjustor until the shape of the displayed waveform is perfectly square. When the oscilloscope probe’s high frequency response is down the edges of the square wave on the display will be rounded and, if the high frequency response is up, the probe’s wave will overshoot the edges.

This simple adjustment is imperative for ensuring that the oscilloscope probe performs perfectly.

Differences Between Digital and Analog Oscilloscopes

The oscilloscope has been a commonly used piece of testing equipment for over fifty years now and is used by TV technicians and aerospace engineers alike. Oscilloscopes are one of the most frequently used instruments in the field of electronics circuit design, testing, and troubleshooting because they have the ability to graphically depict the waveform, magnitude, and time base of electrical signals on its screen.

In addition it can be calibrated so that the magnitude and frequency can be observed with a great deal of accuracy. Most models also have more than one input, allowing for two or more signals to be observed at once. For these reasons oscilloscopes are invaluable to those seeking to observe the function and operation of electronic circuits in real time. Because electronic circuits operate in a decidedly non-visually way, an oscilloscope acts as a window into its operation.

Early oscilloscope designs were based on analog amplifier circuits which brought the signal’s amplitude to a level sufficient to drive the oscilloscope’s cathode ray tube’s deflection plates. An analog oscilloscope’s built-in sawtooth waveform moved the CRT’s beam from one side to the other and rapidly returned it for a consecutive scan, but these days it needs to be able to trigger at the exact moment of a digital event and it needs to be capable of showing what happens in other parts of the circuit when a digital event occurs (it may or may not be repetitive).

For this reason triggering systems capable of causing the oscilloscope to sweep exclusively at the instruction of the incoming pulse were developed. It was also commonly necessary to synch the horizontal sweep to the digital system’s clock frequency in order to show the digital switching events because timing was and is a high priority for those debugging a logic module.

It’s no wonder that digital oscilloscopes developed into a collection of of electronic circuits when you take into account all the functionality digital devices demanded. Digital oscilloscopes have quickly become very complex instruments that require some of the brightest minds in the digital electronics field for their design and to fine tune their performance characteristics as digital equipment — especially computers — become faster and more sophisticated.

Types of Oscilloscope Waveforms

Most waveforms on digital storage oscilloscopes are easy to identify: there are sine, square, rectangular, triangle, sawtooth, step-, and pulse-shaped waves.

Good Ol’ Sine Waves

Sine waves are the fundamental waveform because of their prevalence and their harmonious mathematical properties. (It’s the same sine wave you had to learn in high school math class.) The voltage from your wall’s outlet makes a sine wave. Test signals from a signal generator’s oscillator circuit make sine waves. AC power sources make sine waves. You get the picture.

Then there’s the damped sine wave. You’re likely to see this in a circuit that oscillates while winding down over time. Whereas an ordinary sine wave rolls up and down with regularity, a damped sine wave rolls up and down while getting decreasing in amplitude — the wave gets closer to zero the longer it goes on.

Square and Rectangular Waves

Square waves are almost as common as sine waves. A square wave is, in essence, a voltage that turns on and off — or abruptly alternates between high and low — at recurring intervals. Television, radio, and computer circuitry frequently uses square waves for timing signals.

Rectangular waves are similar to square waves, save for the fact that the high and low intervals aren’t equal lengths.

Sawtooth and Triangle Waves

Linearly controlled voltages result in sawtooth and triangle waves on the digital storage oscilloscope. The voltage levels of these types of waves transition at a constant rate, and these transitions are called “ramps”.

Step- and Pulse-Shaped Waves

Signals like steps or pulses that occur just once are called single-shot or transient signals. A step represents a sudden change in voltage — it’s what you’d see if you flipped a power switch. If you flipped that power switch on and then off, then you’d get a pulse.

Computer components communicate with one another using pulses. Pulses are common in x-ray and communications equipment as well.