Help buying my first digital multimeter

[Electro Detective]

The battery tester on the Samwa puts a 30ohm resistor in parallel with the DMM input[/b], therefore simulating a scenario where the battery is in an active circuit. This helps evaluate if the internal resistance is high (the voltage reading is much lower) and if the battery has not much charge left (the voltage read decreases at a fast rate). Despite not being extremely accurate, as these factors depend of the size of the battery, this serves as a quick check.

30 ohm resistor?  or 3k ohm that some meters have for Low-Z/ghost voltage nuking?

[rsjsouza]

Zlow is a different beast. I have never seen a battery checker have such high resistance, given this would yield only 500uA in a fresh battery.

At any rate, that is what is shown in the Sanwa manual.

[P90]

yup, lo-z is low input impedance, and the battery test function is just a small load to take off the surface charge of a battery under test.

[Electro Detective]

Thanks for the clarification gents,

I use the Low Z mode to occasionally test batteries (and test trip RCD/GFIs)

It's not as good as my battery tester, but if I see a significant difference between Low Z and standard Volts DC readings, the battery gets swapped out.

[SeanB]

Thanks for the clarification gents,

I use the Low Z mode to occasionally test batteries (and test trip RCD/GFIs)

It's not as good as my battery tester, but if I see a significant difference between Low Z and standard Volts DC readings, the battery gets swapped out.

I have a somewhat well used Tadiran 3V primary lithium cell that expired around 2 decades ago, but which has not leaked, and which still has an open circuit ( into 10M) voltage over 3V. However, loading it with 1M will drop the voltage to under 2V.

I was using it in a chime mechanism for around 5 years, simply by having 100 000uF of capacitor ( 2 47000uF 16V electrolytics) across the cell, but eventually the cell was taking over an hour to recharge the capacitor after the hour had been played, and it was warbling. Put in some white mystery AA cells after ( glade air freshener batteries that come in the pack, I had been buying the starter packs instead of the refills, because the starter pack came with 2 refills and the dispenser, at the price of a single refill can) that, and yesterday changed them out again, after probably a year of use after they no longer would run the dispenser motor.  Now have some Duracell AA cells in there, hopefully good till 2026.