New Uni-Trend UT513 and UT61E do not mix  - Page 1
Forum section: electronics / testgear

author: Lightages
author_rank: Unknown
timestamp: March 29, 2013, 11:28:33 pm
content: I just picked up a Unit-Trend UT513 insulation tester for some specific uses but wondered about the leads on my multimeters and how my mulitmeters would stand up to high voltage. Do they stand up to 1000V? Well yes all survive this test. I can say that the UT61E does not like 2500V though!.I get nice arcing across the selector dial traces on the UT33C and it works to spec afterwards. Not so on the UT61E. Nice buzzing sound, and then when restarted, not so happy anymore. What did I expect? Well I expected problems as the Unit-Ts have no MOVs or spark gaps on the inputs and it shows.The UT61E now displays the ohms symbol on the voltage range, mF on the mV range, displaying random numbers, megohms on the miliamp and microamp ranges with overload. I am not blaming the meter as I did something clearly outside of its specifications but this does show you that perhaps he exclusion of MOVs or spark gaps is a cost cutting decision that will come to haunt the owner of the meter. A cheap little MOV would have prevented this damage, and it is damage that could occur by static discharge from a carpet.I might see if there is some little passive that has failed on the input but I will not be too diligent. Maybe I will order another from Frankie.

author: Monkeh
author_rank: Super Contributor
timestamp: March 30, 2013, 12:56:17 am
content: I put some spark gaps in mine. Still wouldn't try 2.5kV across it on purpose!No point checking passives, you've done the main IC in.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 30, 2013, 01:22:32 am
content: Yes, you probably fried the IC. I would still check the current limiting resistor and the PTC for damage, just in case.How many amps does that UT513 deliver with a 2500V short? Probably a lot more than your Persian carpet.My 71B has also got a spark gap now.

author: Lightages
author_rank: Unknown
timestamp: March 30, 2013, 01:30:34 am
content: The UT513 says it is limited to less than 2ma. AT 2500V that is still a lot of energy for the chip to dissipate. I knew I was going to blow something up and I wanted to see what it would take to make the UT61E go silly. Yeah, I am sure the main chip is fried internally too. Too bad I didn't put some MOVs in first to test it and then without so we could see if they make a difference in this case. The UT513 will do 5000V at 1ma at least BTW.Any meter I review from now on will be tested at 500V or 1000V depending on its claimed ratings.

author: Spawn
author_rank: Frequent Contributor
timestamp: March 30, 2013, 01:54:57 am
content: Here a cheaper device to blow up your meters if the protection is bad, with 1000V 1Hz pulses at <2mA and 0.5 joulehttp://www.produktinfo.conrad.com/datenblaetter/100000-124999/114448-an-01-ml-Mini_Generator_de_en_fr_nl_es.pdfWytnucls, a real Persian carpet is made with wool so it is less static than those nylon mixed factory made ones

author: Lightages
author_rank: Unknown
timestamp: March 30, 2013, 04:37:09 am
content: Oh I could generate some really dangerous voltages and amperages like photoninduction does, but I don't have the time to do it safely. The UT513 was purchased for other purposes but it will serve nicely and safely for testing the ratings of meters too. Well at least that they survive their rated voltages and don't die. Actually I have tried the 2500V on the UT33C, the UT61E, and the UT71E. Only the UT61E was damaged. the other two are still working as before.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 30, 2013, 07:41:32 am
content: Did you test the meters on just the volt range or did you also put 2500V on the mV, Ohm, Cap and Temp ranges?If you have spare glass fuses, you could test the amp ranges on the 71E for arcing, with a steady 2000V and blown fuses in place, like the EN 61010 regulations require. Although, at your altitude, the air dielectric properties would be quite different and may invalidate the test.

author: Lightages
author_rank: Unknown
timestamp: March 30, 2013, 08:05:30 am
content: I tested only on the voltage ranges, yes. The arcing occurs across the range selection switch contacts, quite spectacularly! Testing on the other ranges would provide no other result. The UT513 can only provide 500, 1000, 2500, and 5000V outputs. I don't have any spare fuses yet. Remember that the CAT tests do not require that the meter continue to work after the test, just that the operator would not be injured at any time. I don't feel like risking any more meters for this test.

author: dimlow
author_rank: Frequent Contributor
timestamp: March 30, 2013, 09:21:59 am
content: Quote from: Lightages on March 30, 2013, 08:05:30 amWould have been nice to see this test done on video.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 30, 2013, 10:44:34 am
content: Quote from: Lightages on March 30, 2013, 08:05:30 amOn the Volt/Ohm ranges, yes.AFAIK, on the amps ranges, the check is really to make sure that there is no residual arcing across the ruptured fuses, fuse clip holders and the traces. Even if the damage is contained, any arcing would mean a failed test, otherwise fuses would serve no purpose in a DMM.So, after a successful test and with new fuses in place, the meter should work normally on the amps ranges.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 31, 2013, 07:12:47 am
content: Quote from: Spawn on March 30, 2013, 01:54:57 amI'm not so sure about that...can you do a teardown video, please?

author: SeanB
author_rank: Super Contributor
timestamp: March 31, 2013, 12:03:01 pm
content: Checked, and a real Iranian carpet is wool, not polyester. It does not generate a static charge at all, nor does the Axminster carpet. The Nova does though.

author: Spawn
author_rank: Frequent Contributor
timestamp: March 31, 2013, 01:40:53 pm
content: Lightages, I think purpose of those CAT rating tests are for the safety so they check with much higher energy in joules to see if it blows up in your hands and arks reach to the person measuring, not if the meter would survive.But your tests are also nice to see if they at least survive the Voltage range they claim to measure with little bit current. You are at least brave to do that, I wouldn’t do with my meters since they cost enoughKeep up the nice tests, can you capture those arks in the range switches, or is it hard to get with a camera?Quote from: Wytnucls on March 31, 2013, 07:12:47 amLOL, I don’t have one at home, my roots come from a neighbor country but still don’t have a fancy carpet

author: Lightages
author_rank: Unknown
timestamp: March 31, 2013, 05:04:05 pm
content: Yes I know that CAT ratings are for safety and not for function guarantee. Although I went much higher than the input spec I was still surprised at the total failure of the UT61E. This really does illustrate the need for better input protection. I would have expected a better margin of safety, but then it is a Uni-T. I suppose this is why its ratings were lowered considerably with the GS revision. I bet under the right conditions, it would arc over at closer to 1000V. My conditions here are very dry and the meter was extremely clean.