How do cheap Ammeters work?

Hey guys, I wanted to buy a cheap analog ammeter (50µA) to check on my low power arduino products. Does this type of ammeter work (check attachment)? and I can’t see any place to plug the wires, except for 2 bolts on the back. Do I need crocodile clips to use it, like a car battery?? And what voltage does it use? Thanks!

here’s a link to here to buy one

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Yes those posts are the terminals that connect to whatever you’re measuring.

Current or voltage range will be in the specs for the meter.

Do you really want to use those? Surely a basic DMM would be easier, much more flexible, no less accurate and the same price as two of those panel meters.

e.g. https://m.ebay.com/itm/New-Digital-DT-9205A-Multimeter-LCD-AC-DC-Ammeter-Resistance-Capacitance-Tester/172548700011

It’s a bit naughty describing it as

50uA-30A-DC-Ammeter

.
It’s really just a 50uA ammeter.
You can drive it from a PWM output with just a 100k series resistor (5v / 50x10-6)- it may not be quite linear, and you may need to play around with the resistor.

All about analog meters

DMM would be easier, much more flexible, no less accurate and the same price as two of those panel meters.

jpskippy has point. I didnt know DMMs could be that cheap, I thought it was 100$ + if I wanted it to reach microamps precision. I'll go with that!

Thanks a lot peeps!

Google AN8008 multimeters. Excellent accuracy for $20. Just don’t use them on AC mains even though they’re rated for it.

Analog meters are superior for many uses, any real time monitoring of fluctuating loads an analog
meter is way more useful than madly flickering digits that never stabilize enough to read! A bench supply
without analog meters is a poor choice (its nice to have digital meter too for accurate measuring of constant
loads, but for a changing load they are inferior, a twitching needle says so much about what’s happening).

For instance think about a VU meter - a numeric display would be hopeless - hence bargraph LEDs are
chosen as a pseudo-analog option.

Having said that you need to put protection circuitry on most analog meters if you want them to last(!), and
they are not good for measuring high impedance circuits due to the very low impedance of the meter (20k ohms per volt is common), and they are not very accurate (unless expensive and regularly calibrated).

avr_fred:
Google AN8008 multimeters. Excellent accuracy for $20. Just don’t use them on AC mains even though they’re rated for it.

Wow! 1uV and 1uA resolution. Not bad. Not bad at all.

Why do you say not to use on AC mains?

There are a lot of cheap meters with maximum AC ranges of 250V. That may look like it would be safe to use on a 240V circuit.

However that is NOT SAFE. The probes and wires do not have sufficient insulation in the case of minor voltage variations. If a large motor is started in the house next door, you may get lethal voltages arcing from your multimeter leads to your body.

There is a complex set of categories which define what meters can be used on what types of circuits. Probing a power outlet in your livingroom requires at least a CAT III meter. Testing a distribution board in a factory requires CAT IV or higher.

JCSB:
jpskippy has point. I didnt know DMMs could be that cheap, I thought it was 100$ + if I wanted it to reach microamps precision. I'll go with that!

Thanks a lot peeps!

Measuring microamps is trivial, a few k ohms of shunt resistor and a voltmeter is all you need,
so all general purpose multimeters tend to have microamp ranges - frankly its not hard to get
nanoamp measurements either, as CMOS opamps have input currents well below that.