Multimeter Question -solved- - Page 1
Forum section: electronics / beginners

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 03:39:18 pm
content: 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 picshttp://i58.tinypic.com/25q7rip.jpghttp://i60.tinypic.com/2ep5a52.jpghttp://i60.tinypic.com/14vqtle.jpg-> from a lm7805 (also from china), with a ~9.5V input, no loadI 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 offI don't have a precision voltage source (Wish I had one in times like this...)Which one should I trust? =/Thanks in advance!

author: Excavatoree
author_rank: Frequent Contributor
timestamp: February 06, 2014, 03:42:55 pm
content: 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.

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 03:50:02 pm
content: Was thinking about that, too - and hoping the lm7805 would be of any help to the caseSeems like I'll have to spend some more and buy a voltage reference, since everyone I know has either a 10$ dmm or none

author: Excavatoree
author_rank: Frequent Contributor
timestamp: February 06, 2014, 03:57:53 pm
content: 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.

author: Wytnucls
author_rank: Super Contributor
timestamp: February 06, 2014, 04:08:32 pm
content: 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.

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 04:28:08 pm
content: Thanks for the replies!Tested on a new duracell battery,1.663 on the et-997 (new)1.60 on the et-1002 (old)

author: Wytnucls
author_rank: Super Contributor
timestamp: February 06, 2014, 04:34:00 pm
content: 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.

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 04:49:28 pm
content: Quote from: Wytnucls on February 06, 2014, 04:34:00 pmIt'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

author: Wytnucls
author_rank: Super Contributor
timestamp: February 06, 2014, 05:04:31 pm
content: Good luck with Minipa. Have they still got an office or factory in Brasil?

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 05:12:41 pm
content: Quote from: Wytnucls on February 06, 2014, 05:04:31 pmYea, 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

author: rsjsouza
author_rank: Super Contributor
timestamp: February 06, 2014, 05:14:14 pm
content: Quote from: Wytnucls on February 06, 2014, 05:04:31 pmThey do have an office in Brazil. They moved manufacturing to China about twenty years ago, though.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 06, 2014, 05:15:39 pm
content: 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.

author: Luciano2572
author_rank: Contributor
timestamp: February 06, 2014, 07:42:34 pm
content: Quote from: retiredcaps on February 06, 2014, 05:15:39 pmIt was already on a new one, forgot to mention that

author: IanB
author_rank: Super Contributor
timestamp: February 06, 2014, 08:20:13 pm
content: 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)