What can an oscilloscope measure?

 

measuring current from voltage drop across a shunt resistor

Most, if not all, consumer products have electronic circuits or components – whether they’re simple or complex – and oscilloscopes are required throughout the design, verification, and debugging process. Understanding oscilloscope basics is critical to almost all product design. But this begs the question – what can an oscilloscope measure?

Put simply, an oscilloscope is a sophisticated diagnostic instrument that draws a graph of an electrical signal. This graph can tell you many things about a signal, such as:

  • The time and voltage values of a signal.
  • The frequency of an oscillating signal.
  • The "moving parts" of a circuit represented by the signal.
  • The frequency with which a particular portion of the signal occurs relative to other portions.
  • Whether or not a malfunctioning component is distorting the signal.
  • How much of a signal is direct current (DC) or alternating current (AC).
  • How much of the signal is noise and whether the noise is changing with time.

At a very basic level, the graph displayed on an oscilloscope shows the signal changes over time.

signal change over time

The intensity or brightness of the signal on the scope’s display is sometimes called the Z-axis. On Digital Phospher Oscilloscopes (DPO), the Z-axis can be represented by colour grading of the display.

Digital Phospher Oscilloscopes (DPO) Z-axis

For more information about reconstructing signals, signal integrity, and waveform measurements, visit our XYZ of Oscilloscopes page.

This provides and in-depth breakdown of the basics of waveforms and waveform measurements, helping you to understand each element before choosing a scope that’s appropriate for your application.

What else can an oscilloscope measure?

Whilst oscilloscopes are primarily designed to measure volts, they can detect and measure a variety of other signals:

Current

There are a couple of ways to measure current using a scope; one would be to measure the voltage dropped across a shunt resistor, and the other by simply using a current probe.

Sound

It is possible to measure sound through an oscilloscope. You would need a transducer (to ‘convert’ the audio signal to a voltage), which you then connect to a channel on the scope, you’ll then display the signal as a corresponding voltage vs time

Resistance

Oscilloscopes are not the ideal tool to measure resistance, an Ohmmeter or even better, a digital multimeter should be utilised instead

Capacitance

While an oscilloscope won’t give a direct measure of capacitance, it can be used to measure a time constant in order to find the actual capacitance of an electrical system or component with the added use of an Arbitrary Function Generator 

DC Voltage

Most modern oscilloscopes provide the option to measure DC voltage automatically, however you can measure it manually by ‘counting’ the vertical reticules and multiplying by the volts per division

Frequency

Most modern oscilloscopes will measure frequency automatically, giving you an accurate reading. However, it is possible to calculate the frequency manually by calculating the period of the signal (using cursors or the horizontal reticules) and dividing 1 by the period giving you the frequency 

Inductance

If you don’t have an LCR meter, you can measure inductance with an oscilloscope and a function generator. This will be a simple measurement with a 3%-5% uncertainty value.

How to choose the right oscilloscope?

Not all oscilloscopes are created equal. So, before deciding which machine to invest in, it’s important to have an understanding of what’s required for your project and the type of oscilloscope you might need to get the most efficient, accurate measurement.

There are a number of things to consider when deciding which oscilloscope to buy, including bandwidth, rise time, sample rate, channel density and compatible probes. Read our breakdown of things to consider in order to make the right decision for you! 

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