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Just wondering... How does a digital multimeter work ? How can it convert a voltage, a current or a resistance to a numerical value ? I guess there is some programmable chip inside, but how does this chip give a specific value to a voltage ?

For example, my arduino is capable of giving a value between 0 and 1023 to a voltage applied to one of its analog inputs. How is this implemented ?

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  • \$\begingroup\$ en.wikipedia.org/wiki/Analog-to-digital_converter \$\endgroup\$ – Anindo Ghosh May 2 '13 at 8:55
  • \$\begingroup\$ Looking up multimeter at Wikipedia would lead to voltmeter which links to Analogue to Digital Converters (ADC). \$\endgroup\$ – RedGrittyBrick May 2 '13 at 9:11
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    \$\begingroup\$ There's a dedicated chip for that, which uses an ADC as others mentioned already. I once used the 7106 in a volt meter, for example. \$\endgroup\$ – Keelan May 2 '13 at 10:53
  • \$\begingroup\$ Do you know what a DAC is? This needs to be reasonably understood first to grasp how a lot of ADCs work. \$\endgroup\$ – Andy aka May 2 '13 at 14:00
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Converting a analog signal to a digital number is, oddly enough, done by something called a analog to digital converter, or often A/D for short.

There are many ways this conversion can be accomplished, like successive approximation, sigma-delta, tracking, flash, and probably a few more basic strategies. There are lots of variations and tradeoffs within the basic types too. Most microcontrollers have successive approximation A/Ds built in.

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