How can you fool a multimeter?

[MikeW]

I'm bored cos I'm on holiday, so I'm just sitting around with no trousers on thinking about shit.

How could we fool a multimeter?

For example, continuity, I'm guessing a multimeter checks for continuity by looking for equality in current levels in and out. Much like a circuit breaker.

Is it possible you could somehow feed in the current from a totally different circuit and make that equality?

So, can I push electrons out of one end of the (multimeter) battery and feed them in to the other end without them having done a loop? Does the battery care that the electrons it is receiving are not the same as it is giving out?

This isn't so much about multimeters anymore than a theoretical electronics question about loops but never mind.

[Stonent]

Well you need a starting point and an ending point for the current to flow.

Though I suppose if you charge yourself up and send a spark of static electricity to one of the leads, it may interpret it as continuity.

[Augustus]

Put it in the microwave and see what happens.

[jwm_]

Try it with a AA battery and see what happens.

A large capacitor can fool a continutity tester, it can appear to be connected while it charges up.

diodes may or may not show continutiy, depending on the meter and the diode.

A large AC component when measuring DC voltage or vice versa can confuse some meters. (I love dual display meters that separate out the components.)

Your fingers holding the leads when measuring resistance can skew the results, especially if sweaty, stressed, or have a high thetan level.

AC that is not a sine wave will give incorrect results on meters that don't do RMS properly.

capacitance measurement with long leads is a crapshoot.

You can heat up one lead and freeze the other and get odd thermal effects.

You too can use these effects and more to create a video supposedly showing free energy, putting up an indigogo campaign and retiring off the proceeds from the gullible.

[Galenbo]

How could we fool a multimeter?

Put a batteriser over a flat battery and put it into a device.
The voltmeter will still show a flat battery, but in reality there is 800% more capacity.

[Tomorokoshi]

During radiated immunity EMC testing Fluke multimeters that were exposed to the RF would beep and show strange things on the display. This happened even if they were turned off.

[RickBrant]

For example, continuity, I'm guessing a multimeter checks for continuity by looking for equality in current levels in and out. Much like a circuit breaker.

No. There's always equality between current in and out. Think about it. (If there wasn't, where would the "extra" electrons be going, or coming from?)

"Continuity" is basically just a resistance measurement. It beeps if the R is below some low threshold.