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When we measure an electrical quantity on Digital multimeter (DMM) like current, if we dont get readings of small range scale we switch the range utill we get our reading, same goes for voltage. But what is the quantity for which we do not change the scale on DMM and why?

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... if we dont get readings of small range scale we switch the range utill we get our reading ...

No, you should start on a high range and work down to more sensitive range. If you do it the other way you risk damaging your meter if the voltage or current is higher than expected.

But what is the quantity for which we do not change the scale on DMM and why?

This part of your question is not clear. It depends what you are measuring

  • If I am checking to see if 12 V or 24 V is present then sometimes I switch to a high range so that the meter display 12 or 24 rather than 11.93 or 24.12 which can be a bit distracting.
  • If I need to know the voltage with some precision then I select the lowest (most sensitive) range that will display the voltage without the "over-range" indication turning on (usually 1--- in the display).
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  • \$\begingroup\$ Yes i get this. The next part of my question is that 'my instructor asked ne today that for current we change the range, but there is quantity we do not the range for it we measure it on single range' , i am cinfused as well \$\endgroup\$ – Feroza Noor Nov 26 '19 at 12:30
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    \$\begingroup\$ It could be frequency, continuity or diode forward voltage? They normally only have one range. \$\endgroup\$ – Jakob Halskov Nov 26 '19 at 12:33
  • \$\begingroup\$ You don't need to change scale, if there is a text "auto" on the display ;) \$\endgroup\$ – Adriano Nov 26 '19 at 16:19
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Yes i get this. The next part of my question is that 'my instructor asked ne today that for current we change the range, but there is quantity we do not the range for it we measure it on single range' , i am cinfused as well

Sounds like it could be a continuity test. It allows you to test for a connection between two points and if this connection exists the DMM gives a beep.

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  • \$\begingroup\$ yes i am aware of this but i don't think she asked for this. can think of any other quantity? \$\endgroup\$ – Feroza Noor Nov 26 '19 at 16:09

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