How can I increase the measurement accuracy using automated measurements vs cursors?
While Cursors are quick and easy at approximating measurements, using the automated measurements can give you a much better and accurate measurement results. Here are some techniques to be successful in making accurate measurements.
Always use automated measurements over cursors for accurate results. If you had three people make a cursor rise time measurement, most likely you'll get three different results. Automated measurements reduces these discrepancies and helps you analyze your signal with consistency and accuracy.
Always make sure your signal is not undersampled. This is important because undersampling leads to more guessing in reconstructing the waveform and sometimes this causes inaccuracies for what the waveform is really doing.
Always make sure you're maximizing the signal on screen. The Analog-to-Digital Convertor (ADC) represents the full vertical range on screen, so on an 8-bit ADC this is 256 digitizing levels. Every time you half the signal on screen you lose a bit of resolution. For example, a signal peak to peak taking up 1/4 of the screen is like using a 6-bit ADC. A good technique for making quality measurements is to maximize the signal entering the ADC by using 80% to 100% of the vertical screen. If your signal goes outside the screen the data will be clipped and lost. This is not recommended because it stresses the ADC requiring a recovery time for accurate measurements.
Filter unwanted noise. You can do this many ways, but first understanding the frequency content of your signal is important. If your signal frequency ends in the Hz to MHz, you don't need GHz of Bandwidth, this adds noise. Turning on a Bandwidth Filter (e.g. 20MHz or 250MHz) reduces the noise. Some active probes have BW filters so be sure to take advantage of them when possible.
Maximize your oscilloscopes sampling modes. By default your scope is in Sampling Mode. Another solution is Hi-Resolution mode, since the ADC is always running at max speed. When you tell it to acquire a slower sampling rate the scope throws out data points. We can take advantage of these extra data points by boxcar averaging them into the displayed points for single acquisitions. For repeatable signals use Averaging mode. These options can increase the Vertical Resolution up to 12-bits which help filter noise and improve measurements accuracy.
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