Cheapish tweezer SMD testers:  Uni-T UT116A and Mastech MS-8911 - Page 1
Forum section: electronics / testgear

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 03:46:00 am
content: Today, I attempted to use these two tweezers to determine the values of the resistors and capacitors on the small PCB in the picture.The performance difference between the two in this use case is pretty amazing... the Mastech returned plausible looking readings on all of the passive components, while the Uni-T failed to get a reading at all on some capacitors, and got very implausible looking numbers on others.Both work well when the components are out of circuit, but there is no comparison when it comes to testing in circuit... the Mastech is in a different league.

author: Algoma
author_rank: Frequent Contributor
timestamp: February 19, 2021, 03:56:25 am
content: Looking at the spec sheets, that Mastech offers both more resolution and accuracy for the same 6000 counts.Smallest Capacitance supported:Mastech 0.1pf ±(2.0%+10)vsUT116A has only 1pf resolution and much lower accuracy ±(3.0%+50)UT116C isn't any better..But the Mastech doesn't measure voltage and test LEDs and Diodes, like the UT116A/C can.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 03:59:17 am
content: Smallest cap is 100nF from what I am able to glean.

author: Algoma
author_rank: Frequent Contributor
timestamp: February 19, 2021, 04:07:38 am
content: Those tiny caps, at that frequency.. those could only be a few picofarads at best. 100nf = 100000pF A vastly larger SMD. Perhaps the meter is picking up something else.

author: Algoma
author_rank: Frequent Contributor
timestamp: February 19, 2021, 04:10:22 am
content: apologies, 100nf does come that size. I can only imagine the density of the layers inside.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 04:32:34 am
content: I was pretty surprised by how much capacitance they pack into such a tiny space... Welcome to 2021, I guess?100nF is well within the range of both meters, so there must be something else (resistance in parallel?) that confuses the Uni-T.

author: tautech
author_rank: Super Contributor
timestamp: February 19, 2021, 06:48:37 am
content: Quote from: SilverSolder on February 19, 2021, 04:32:34 am10 yr old SMD caps from my small stash..... 10uF 0805 still in the tape and 330uF in the even older ST3 SMD tweezers.

author: indman
author_rank: Super Contributor
timestamp: February 19, 2021, 07:19:18 am
content: Quote from: SilverSolder on February 19, 2021, 03:46:00 amQuite right, since these tweezers have completely different circuitry!MS8911 is a bridge LCR meter principle with low voltage selection at test contacts.UT116A (C) - Based on a standard DMM processor for testing components outside the circuit.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 02:10:36 pm
content: Quote from: tautech on February 19, 2021, 06:48:37 amThe caps on this board measure as 0603, so not the smallest possible format....The largest capacitor I was able to quickly find, in the 0603 size, was10uF!!!That's pretty amazing...

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 02:43:48 pm
content: Quote from: indman on February 19, 2021, 07:19:18 amOn this board, it works fine in 1V mode. So, that part of the test was fair! It seems the Mastech measurement algorithm is better.

author: Kosmic
author_rank: Super Contributor
timestamp: February 19, 2021, 03:19:34 pm
content: Quote from: SilverSolder on February 19, 2021, 02:43:48 pmIt's not just an algorithm. The technique they use to measure components is completely different. Like indman said, the UT116A is more like a DMM and the MS8911 a LCR meter.Check the output of both device. You will find a nice sinewave on the MS8911 and probably some kind of slow ramp on the UT116A.Iet labs as a nice document on LCR measurementhttp://www.ietlabs.com/pdf/application_notes/030122%20IET%20LCR%20PRIMER%201st%20Edition.pdf

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 05:52:36 pm
content: Quote from: Kosmic on February 19, 2021, 03:19:34 pmI can confirm that my "regular" handheld meters can't get a reading on the small caps on the board either.I guess the conclusion is - use an LCR type tweezer if you want to probe PCBs with it...Would be interesting to see how the Mastech compares with other LCR tweezers. So far, I'm pretty impressed, but I'm starting from a low level of expectation!

author: bc888
author_rank: Regular Contributor
timestamp: February 19, 2021, 09:44:39 pm
content: Thanks for the review. Anyone compare the Mas8911 to the "DT71 Mini Digital Tweezers SMD Tester" that Dave recently did a video review on?

author: tautech
author_rank: Super Contributor
timestamp: February 19, 2021, 09:50:41 pm
content: My money is on the Mastech being better although one of their earlier ones was not much chop vs my ST3 so I gave the thing to a mate that didn't have any SMD tweezers.

author: Bud
author_rank: Super Contributor
timestamp: February 19, 2021, 10:32:57 pm
content: Quote from: SilverSolder on February 19, 2021, 02:10:36 pmSmall physical size capacitors lose more capacitance at nominal voltage then their bigger physical size brothers. This is in addition to capacitance loss due to the type of dielectric.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 11:14:35 pm
content: Quote from: Bud on February 19, 2021, 10:32:57 pmSo it is only 10uF when not installed in a circuit?

author: Kosmic
author_rank: Super Contributor
timestamp: February 20, 2021, 03:25:50 pm
content: Quote from: bc888 on February 19, 2021, 09:44:39 pmThe DT71 is another of those "DMM in a tweezer form factor". I would expect the MS8911 to do a lot better.

author: tszaboo
author_rank: Super Contributor
timestamp: February 20, 2021, 10:39:51 pm
content: QuoteIs it really that hard to get a product right?

author: Bud
author_rank: Super Contributor
timestamp: February 20, 2021, 11:07:44 pm
content: Quote from: SilverSolder on February 19, 2021, 11:14:35 pmThis may be a shock to you, the answer is pretty much yes

author: SilverSolder
author_rank: Super Contributor
timestamp: February 20, 2021, 11:46:33 pm
content: Quote from: NANDBlog on February 20, 2021, 10:39:51 pmI am not a big fan of that decision either. That said, (1) battery life has not been an issue so far, (2) what are the alternatives at this price point?