Short #35 - Resolution, Precision & Accuracy

What is the difference between accuracy, precision, and resolution? In today's short podcast, Jim Bergmann explains the differences and why they matter.

People commonly confuse accuracy and precision. Accuracy refers to how close a measurement is to the correct value, but precision refers to the consistency of values. For example, you can get several infrared thermometers to measure the difference between circuit breakers, and the thermometer readings all come out close to the same value. They aren't necessarily accurate, but they are precise.

In cases where we use a voltmeter to measure for the presence of voltage, we don't need a high degree of accuracy. However, when we want to measure exact voltage values, we want to make sure our tools are accurate. Sometimes, voltage that is too low can cause issues with the circuit boards.

Resolution refers to the smallest possible amount of change you can detect. For example, one voltmeter may measure to the nearest whole volt, and another may measure to the nearest tenth of a volt. The resolution is higher on the latter voltmeter, as it detects a smaller change than the first voltmeter. Some tools measure with a high resolution, but the increased resolution may compromise the accuracy. For example, if a manometer reads into the Pascals range, it may only have a tolerance of +/- 5 Pascals, which leaves room for inaccuracy.

However, again, accuracy is not always the most important value. Sometimes, resolution and precision are more important than accuracy. After all, in the words of Jim Bergmann, it's pretty difficult to measure feet with your car odometer. One common example where precision and resolution are more important than accuracy is when techs try to measure microns with analog gauges. The accuracy means nothing when the precision and resolution are poor.

 

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