Multimeter Question -solved-

[Luciano2572]

Hey guys,
Been watching Dave vids for some time, and finally decided to order a better multimeter , a ET-997 (ordered on dx.com - this one: http://dx.com/p/3-0-lcd-handheld-digital-multimeter-voltage-current-resistance-temperature-1-6f22-42269 ) to replace my old crappy 15$ one.
But when checking just the basic DC, it gave me way different voltages than my old meter, see pics
http://i58.tinypic.com/25q7rip.jpg
http://i60.tinypic.com/2ep5a52.jpg
http://i60.tinypic.com/14vqtle.jpg -> from a lm7805 (also from china), with a ~9.5V input, no load

I saw a pic from a user in the forums here, here: https://www.eevblog.com/forum/testgear/minipa-et-997-$50-multimeter-review/15/
where he compared the results with a fluke 89 and they were pretty similar (Didn't post there to avoid reviving the thread - almost 2 yrs)

The ET-997 has a 0.5% on DC, while the old ET-1002 has  0.8%, which should only be 0.025 vs 0.04 off

I don't have a precision voltage source (Wish I had one in times like this...)

Which one should I trust? =/


Thanks in advance!

[Excavatoree]

I don't know if anyone will concur with me, but I'd say until you get some type of known reference to use, you can't be sure which one is more correct. 

If you know someone with a calibrated meter that you can borrow, you could use that to compare, but comparing one unknown instrument to another won't tell you anything.

[Luciano2572]

Was thinking about that, too - and hoping the lm7805 would be of any help to the case
Seems like I'll have to spend some more and buy a voltage reference, since everyone I know has either a 10$ dmm or none

[Excavatoree]

Perhaps someone with more experience about 78xx regulators can explain further, but the first data sheet I looked at specified that the Vout could be anywhere from 4.75 min to 5.25 max. 

[Wytnucls]

Like Excavatoree said.
If you have a fresh Duracell AA size battery, it should measure close to 1.6V. The meter which is not in the ballpark is probably the one out of specs.

[Luciano2572]

Thanks for the replies!

Tested on a new duracell battery,
1.663 on the et-997 (new)
1.60 on the et-1002 (old)

[Wytnucls]

1.663V sounds a bit excessive. So the new meter could be slightly out. Try to compare it to your friends cheap meters. They should be accurate enough for such a discrepancy.

[Luciano2572]

1.663V sounds a bit excessive. So the new meter could be slightly out. Try to compare it to your friends cheap meters. They should be accurate enough for such a discrepancy.

It's now reading 1.725 while the old one is still at 1.60, only a few mins after the original result. Its really out, mailing it back to china isn't a option so I'll try with ininipa directly.

Thanks for all the help Wytnucls & Excavatoree! Really appreciate it

[Wytnucls]

Good luck with Minipa. Have they still got an office or factory in Brasil?

[Luciano2572]

Good luck with Minipa. Have they still got an office or factory in Brasil?

Yea, they have an office here & I believe a factory too, since they offer lots of products for a good  price and they are pretty popular here

[rsjsouza]

Good luck with Minipa. Have they still got an office or factory in Brasil?

They do have an office in Brazil. They moved manufacturing to China about twenty years ago, though.

[retiredcaps]

Try a new fresh battery in the Minipa.  Some meters I find give high incorrect readings when the battery is weak even though the low battery indicator is not on.

[Luciano2572]

Try a new fresh battery in the Minipa.  Some meters I find give high incorrect readings when the battery is weak even though the low battery indicator is not on.

It was already on a new one, forgot to mention that

[IanB]

Another helpful reference for ball park voltage measurements is a brand new super heavy duty (zinc chloride) 9 V battery. This should read very close to 10 V. (An alkaline battery will read closer to 9.6 V)