different voltage reading with multimeter

[JumperIQ]

Hello everyone.
I am new to powering and I am facing something I can't understand it, however, I bought a multimeter called DT-830B to measure the voltage of my components, the below measurements seems to be weird to me
1) 3.7v battery when measuring it the multimeter display 4.8V
2) AC-to-DC adapter output 12v when measuring it the multimeter display up to 15V

any help will be appreciated.

[jremington]

Both of those values are plausible.

Measure a brand new "1.5 V" alkaline battery. I usually get between 1.56 and 1.58V on several meters.

However, Wikipedia says:

The effective zero-load voltage of a non discharged alkaline battery, however, varies from 1.50 to 1.65 V, depending on the purity of the manganese dioxide used and the contents of zinc oxide in the electrolyte.

[JumperIQ]

Both of those values are plausible.

well, is that me it is ok?
I measured the Arduino +5v pin and it is giving me more than 5v!

[jremington]

I measured the Arduino +5v pin and it is giving me more than 5v!

No surprises there. Components have tolerance specifications, which are stated in the component data sheet.

The 5V regulator on the Arduino might typically produce anywhere between 4.75 to 5.25V (different for each chip), which is fine.

What do you get for a brand new alkaline battery, or several of them?

[slipstick]

It sounds like your meter is not accurate. If the 3.7V battery is a Lipo then it would probably have exploded before it actually got to 4.8V. You should never see more than 4.2V om a Lipo. As jremington says the best thing to test it with is a brand new 1.5V alkaline battery.

It would be worth checking the 9V battery in the meter. A bad battery will give all sorts of odd readings.

Steve

[Wawa]

+1
Some cheap DMMs give higher voltage readings when the internal battery is getting low.
One of my DMMs does.
Check if the "low batt" sign is also being displayed.
Leo..

[TheNoneP]

+1
Some cheap DMMs give high voltage readings

I would like to thank you all, Leo  your suggestion helped me.