Keysight U1461A insulation meter teardown - Page 1
Forum section: electronics / testgear

author: blueskull
author_rank: Unknown
timestamp: June 18, 2016, 06:10:33 pm
content: ********************Go to reply 11 for the bug********************The U1461A is fine, see below.My U1461A arrived a couple of weeks ago, and I finally got my hands on it days ago. Besides its rich feature, complete accessory kit and amazing working temperature (yeah, the same temperature range of U1273AX), I'm also curious about its building quality. Let's find out, shall we?First of all, fuse compartment. The fuse is awesome, properly rated HRC fuse, but the thing I didn't get it is the water seal. It does not match the groove beneath it, and hence, can not fit tightly in the groove. I am not sure if the pressure of the plastic lid can push it hard enough to be waterproof, but I doubt it will.

author: TheSteve
author_rank: Unknown
timestamp: June 19, 2016, 02:16:07 am
content: Silly Fluke - it really had you going for a bit there!

author: Electro Detective
author_rank: Super Contributor
timestamp: May 30, 2017, 12:03:12 am
content: Fwiw my 289 reads the same as OP at 1000v insulation test too,but ok from 50 to 500v

author: noidea
author_rank: Unknown
timestamp: May 30, 2017, 06:10:26 am
content: Hi BlueskullDo you have any low resistances that you can test and do you have something with 4 wire resistance measurement that you can make some comparisons with?I need to be able to measure the windings of three phase brushless DC motors with resistance specs at 20 degrees from 0.188\$\Omega\$, 0.293\$\Omega\$ up to 1.703where the allowable imbalance is 5%. I currently have a small 4 wire resistance measurement adapter that I use with my DMM for this. At the same time I need to be able to do insulation resistance tests at 500VDCI am searching for the holy grail of meters that can do the above as well as be a half decent multimeter that also beeps on diode check function and wondering if this could be the one.

author: noidea
author_rank: Unknown
timestamp: May 30, 2017, 03:50:33 pm
content: Quote from: blueskull on May 30, 2017, 06:25:05 amIt's not so bad at all. I just measured an Ohmite 2mR shunt with 2-wire mode of U1461, in earth bond measurement mode. Without DUT it reads 59mR, and with DUT it reads 61mR, bang on!Cool, I had a look through the manual later today what do you get if you null the test leads?

author: Electro Detective
author_rank: Super Contributor
timestamp: May 31, 2017, 05:29:50 am
content: Quote from: blueskull on May 30, 2017, 12:12:26 amHad some meters handy today and got curious, as I'd done these tests ages ago and remembered something seemed amiss but consistent at the same time,so re-tested again to get some cheap closureTest results:BOTH Fluke 289 and the 189 display anywhere from 8.3 to 8.4 Megohms when fed with direct 1000* volts from both a Fluke 1507 and 1520 insulation testers,and a couple of others on hand, including the analogue meter type.*Fluke insulation zappers actually put out about 1052v to 1070v, so taking into account the extra, I'd speculate it's close to or on the money to what the Keysight U1461 reads out.Any voltage applied from 500 volts to 50v displays the expected 10 megsThe same test on Fluke 87V, 114 and other meters display 10meg on the insulation testers when fed same 1000 volts, even if it's beyond the DUT multimeter rated display rangeThere must be a reason for itor it's just one of things to make a note of so you don't get caught outHope this helps anyone else scratching their heads too

author: noidea
author_rank: Unknown
timestamp: May 31, 2017, 05:59:58 am
content: Is it not just a case of the 1000v approaching the point on the MOV's curve where it starts to conduct and that point being slightly below 1000V?What does the current voltage curve of the varistor actually look like?

author: Electro Detective
author_rank: Super Contributor
timestamp: May 31, 2017, 09:33:02 am
content: Quote from: noidea on May 31, 2017, 05:59:58 amI have absolutely no clue, it only does it with these 2 meters when applying 1000v, and I thought it may be normal on some meters perhaps?You would think the Fluke 87V and other Flukes might do it as the input business might be similar, but they don'tPerhaps the feature bloated meters with logging and wireless stuff need 'earlier' protection from HV?I'll leave it to the EEVblog Jedi Meter Masters to rock up here and have a go at explaining itI wonder how the $$$ bells and whistles Keysight, Brymen, Extech, Gossen meters fare in the Megohm dept. with a 1000 volt insulation testWARNING:DO NOT ATTEMPT THIS WITH YOUR METERunless you are 100% sure of what you are doing,or you may find yourself 100% out of pocket!