Oscilloscope Measurement Techniques

There are various ways of taking measurements using the oscilloscope. One of the most basic oscilloscope measurement techniques is voltage measurement. Voltage refers to the sum of electrical potential found between two points within a circuit. One of these two points is usually ground (zero volts). It can be measured from peak-to-peak, starting from the signal’s maximum point to the signal’s minimum point.

Since the oscilloscope is basically a voltage-measuring device, once users have made the necessary voltage measurements, other quantities are just a matter of simple calculation. Although calculations are complicated for AC signals, the point is that knowing the voltage measurement is the first step to determining the other quantities.

Counting the divisions a waveform covers on the vertical scale of the oscilloscope is the simplest and easiest way of taking voltage measurements. For best voltage measurements, users must adjust the signal to cover most of the oscilloscope’s screen vertically. Utilizing more screen area will enable users to read more accurately from the screen.

Most oscilloscopes feature on-screen line cursors that allow users to automatically take waveform measurements on-screen, without counting graticule marks. Users can move two horizontal cursor lines up and down to bracket the amplitude of a waveform for voltage measurements, while two vertical lines can be moved left and right for time measurements. Meanwhile, the readout indicates the time or voltage at their positions.

Time measurement can be made using the oscilloscope’s horizontal scale. It includes measuring the pulse width and period of pulses. Since frequency is merely the reciprocal of the period, knowing the period will enable users to easily determine the frequency. Time measurements, just like voltage measurements, are more accurate when the signal to be measured is adjusted to cover a large part of the screen.

The details of a pulse’s shape are vital for most applications. Pulses can be distorted, causing a digital circuit to malfunction, while the pulse’s timing in a pulse train is usually significant.

Pulse rise time and pulse width are standard pulse measurements. Measured from 10 percent to 90 percent of the pulse’s full voltage, rise time is the total amount of time a pulse spends to go from low voltage to high voltage. On the other hand, pulse width refers to the amount of time the pulse spends to go from low to high, then back to low again. It is usually measured at 50 percent of the pulse’s full voltage.

Users will have to fine tune the oscilloscope’s triggering when taking pulse measurements. To be an expert at capturing pulses, users should also learn to set the digital oscilloscope and use its trigger holdoff. The oscilloscope’s horizontal magnification feature is also useful for measuring pulses, since it enables users to view fine details of a fast pulse.

Meanwhile, the XY mode can be utilized to determine the phase shift measurement — which is the difference in timing of two identical periodic signals. This can be achieved by inputting one signal into the horizontal system and another in the vertical system. The resulting waveform from this method is known as the Lissaious pattern. The shape of the pattern indicates the phase difference of the two signals as well as the frequency ratio.