A Guide to Digital & Analogue Multimeters by Poole Ian

Author:Poole, Ian [Poole, Ian]
Language: eng
Format: azw3
Publisher: Adrio Communications Ltd
Published: 2015-06-07T16:00:00+00:00

How a DMM works

The operation of a digital multimeter is relatively straightforward, although there are obviously differences between the actual implementation from different manufacturers.

A typical DMM

The key process that occurs within a digital multimeter for any measurement that takes place is that of voltage measurement. All other measurements are derived from this basic measurement.

Accordingly the key to understanding how a digital multimeter works is in understanding this process.

There are many forms of analogue to digital converter, ADC. However the one that is most widely used in DMMs is known as the successive approximation register or SAR. Some SAR ADCs may only have resolution levels of 12 bits, but those used in test equipment including DMMs generally have 16 bits or possibly more dependent upon the application. Typically resolution levels of 16 bits are used, with speeds of 100k samples per second. These levels of speed are more than adequate for most DMM applications, where high levels of speed are not normally required.

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