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I have read discussions on NOT to use external power, say an ac adapter, instead of the 9V battery. But what if I mostly do is to test for continuity, would it be acceptable in such case? What other alteratives are possible, such as the 6 x1.5V cells battery case or most recently, use Li rechargeable battery (for phone use) (2 x5V or what? ) for this purpose?

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  • \$\begingroup\$ Why are you against using a 9V battery? \$\endgroup\$ – Hearth Oct 12 '18 at 16:10
  • \$\begingroup\$ It's also worth mentioning that a 9V battery is a 6x 1.5V battery pack, or at least the usual alkaline ones are. \$\endgroup\$ – Hearth Oct 12 '18 at 16:11
  • \$\begingroup\$ test for continuity .... use a power adapter, a lightbulb and two probes all connected in series .... touch probes together and the lightbulb will light \$\endgroup\$ – jsotola Oct 12 '18 at 16:26
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    \$\begingroup\$ If you want to be tied to the mains for power, then buy a bench multimeter that is line powered. To compromise the isolation provided by a battery powered multimeter with an unknown and probably uncertified power supply seems a poor decision. \$\endgroup\$ – Jack Creasey Oct 12 '18 at 16:34
  • \$\begingroup\$ Why are you against using a 9V battery? 9V battery is not a reuseable form of energy. Given more and more rechargeable Li battery available on the market, it is reasonable to replace them in future. \$\endgroup\$ – DriveCarefully Oct 16 '18 at 7:17
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I have read discussions on NOT to use external power, say an ac adapter, instead of the 9V battery. But what if I mostly do is to test for continuity, would it be acceptable in such case?

If you are only using the multimeter on circuits that are safe to touch it should be no problem to run it off a power brick (assuming the power brick meets normal safety standards) or a 6xAA battery box.

The problem comes if you are using the meter on circuits that are not safe to touch. The electronics of the multimeter are connected to the input terminals and therefore during work on circuits containing dangerous voltages the internals of the multimeter including the battery will become dangerous to touch.

That is ok if you are using the multimeter as intended, the enclosure of the multimeter protects against contact with live parts* but if you compromise the electrical isolation of that enclosure (for example by running a cable through it to a power brick or an external battery holder) then the meter will no longer meet it's safety standards.

* This BTW is why modern multimeters always require a tool to change the battery.

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