Agilent U1241A also affected by the "going crazy" bug? - Page 1
Forum section: electronics / general

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2012, 10:38:13 am
content: Can't find an actual name for the problem - but I'm sitting here with an Agilent U1241A multimeter measuring about 1200V with the probes disconnected.It has done it a few times since I flicked it on volts DC using the range switch.Seems to be incorrectly autoranging from noise on the low ranges.My whole uni lab is full of these things and I bet most of them have the problem as I tried another one and was able to get it to do the same thing.Any news if it affected more than the U1272A?

author: Achilles
author_rank: Regular Contributor
timestamp: October 10, 2012, 05:51:25 pm
content: Well, I just have a U1272A but never had a problem like that. I think it had been a software bug which got fixed in a firmware update.If you have a similar problem on a U1241A, I would suggest to write Agilent an email about it. Sometimes it seems the firmware just gets basicly tested and released.I could imagine that they grab some code from an older model for the firmware of a newer model and therefore transfer problems.For example in the U1253B:-If I use the Temperature mode and setup a secondary display with primary °C and secondary °F, both displayed reading are the same. I would consider that a quite obvious bug.-If I drain the battery and the meter is shutting off automatically, I need to recharge the battery to bring it back. If I am in the field and change the empty battery against an Alkaline....nada....it shows me OL (or some crazy reading as far as I remember) all the time won't come back until I recharge it.-If I enter the Setup Menu and disable the sound it is quiet, but when I hold the shift button to exit the Setup it is still beeping (4800Hz always)-In logging mode (as well as with the U1272A) it is not possible to change the Display brightness (or switch on/off the Background light at the U1272A)... That is the Bug/Feature that is annoying me most of the times

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2012, 07:05:53 pm
content: Well, it's not my job to contact Agilent about it as it's university equipment. We have about 100 in the lab. (The lab was sponsored by Agilent Technologies though - it has their name tattooed everywhere. I wonder what discount the university got for that. There are also some very, very nice network analysers (30kHz - 3GHz IIRC) and nice new scopes, PSU, DDS x 2 on each bench.)Anyway it looks to me like it measures normally but is 10 - 10,000x bigger than it should be. So when it's in the going crazy mode, I can attach it to a PSU and read the value correctly but the order of magnitude is completely wrong. 99% of the time flicking the range switch back and forth will fix it. Almost makes me thing of contact corrosion but it looks more like a very sensitive autoranger.

author: nanofrog
author_rank: Super Contributor
timestamp: October 10, 2012, 09:20:55 pm
content: Why not turn off Auto Ranging in such cases?

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2012, 09:34:39 pm
content: Why should I? It goes crazy maybe 1 in 5 times under normal use.

author: EEVblog
author_rank: Unknown
timestamp: October 10, 2012, 10:14:20 pm
content: Can you get some video of this and post it somewhere?Preferably trying to reproduce it step by step. Others can then try to replicate and confirm.Also, if there is a way to find the firmware version, that could be very important.Dave.

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2012, 10:34:23 pm
content: Quote from: EEVblog on October 10, 2012, 10:14:20 pmI will see if I can get some lab time out of lessons, but I think that's only available after the mandatory safety course.After all, 6V and 20V DC lab supplies can cause a serious shock. And you could burn yourself on the soldering iron.

author: EEVblog
author_rank: Unknown
timestamp: October 10, 2012, 10:49:11 pm
content: Quote from: tom66 on October 10, 2012, 10:34:23 pmNot to mention all those power points, they can KILL!Can't have anyone unsupervised and uncertified in a room with such dangerous outletsDave.

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2012, 11:29:09 pm
content: Well, allegedly, the labs are now supervised 8am-6pm because a student DID manage the formidable task of extinguishing one's life.I know we do have a power electronics division, kind of 3rd yr stuff involving IGBTs and MOSFETs (the kind of stuff I like) and they do have a very nice motor controller built up by a PhD student with some big caps (I looked: 1500µF 400V, times two, on each board, 8 boards in total.) But still... I mean it's tattooed in high voltage warnings, in a sealed box, under lock and key...

author: tom66
author_rank: Super Contributor
timestamp: October 11, 2012, 06:47:28 pm
content: Well, I tried it on another meter, and I was able to replicate it... but only once out of maybe 50 tries. This makes me think that it's more related to the range switch as it only occurred when I switched from diode test to volts DC. So 2/3 have the problem maybe 20-30% of the time, and 1/3 has the problem ~2% of the time.Also, we had two DSO6014A's die today. One that makes a continuous ticking sound (at a few Hz) when powered up but nothing further (no LEDs etc.) The other, well, I pressed the button to turn it on, and it made a crackling sound inside then wouldn't turn on anymore.(It was working 5 minutes previously and I simply went to turn it on to use it again.) So I'm not sure about the reliability of Agilent equipment any more! Both will be repaired under warranty though, according to the tech there.

author: Baliszoft
author_rank: Frequent Contributor
timestamp: October 11, 2012, 07:17:28 pm
content: Quote from: tom66 on October 11, 2012, 06:47:28 pmMy first MSO-X2k had a faulty (noisy) psu for the LCD. The replacement has a bad pixel on it. I guess no more agilent for me.

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: October 12, 2012, 07:51:28 pm
content: Quote from: Achilles on October 10, 2012, 05:51:25 pmMy 1253B also does this and my 1252B won't display both Celsius and Fahrenheit no matter what. It allows me to choose the proper mode in the setup but no matter what, both primary and secondary display show either c or f...I don't have a 1241A to check but neither of the above have this bug.

author: Achilles
author_rank: Regular Contributor
timestamp: October 12, 2012, 09:21:46 pm
content: Quote from: StubbornGreek on October 12, 2012, 07:51:28 pmIt's the same on the U1272A. You can setup °C-°F or °F-°C, but it is only showing you °C or °F for the Thermocouple and internal Sensor. So, that would fit to my idea that Agilent uses his code crossed over all models.

author: nanofrog
author_rank: Super Contributor
timestamp: October 12, 2012, 11:11:13 pm
content: Chalk up another confirmation of this with the U1252B. And given the different models sharing the same issue, I'm withAchilleson the recycled code theory.

author: tom66
author_rank: Super Contributor
timestamp: October 13, 2012, 01:08:16 am
content: Add to this: more bad equipment. We have some power supplies (30V/2A(x2)+5V/2A) on each desk, in the embedded systems lab (sponsored by Farnell.) 1 in 20 times, if you are lucky, you will blow the mains fuse in the power supply when you turn it on. Display will light up then fade out. Found 3 in a row that wouldn't work, almost had connect4. They aren't Agilent equipment though - I think they are "BST" or some vague brand.

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: October 13, 2012, 09:11:22 am
content: Quote from: EEVblog on October 10, 2012, 10:14:20 pmOh God ,I did buy a Agilent 1241AN Off ebay in usa for sales in india .Will check the same and post results once it reaches me .Damn Dave any idea whats the N at the back as we all talk of A mostly .This was a brand new one i nailed for USD 127 IMHO

author: djsb
author_rank: Super Contributor
timestamp: October 13, 2012, 03:27:30 pm
content: Does anyone actually check the equipment in this lab for electrical safety? I have to do annual PAT testing in the design electronics lab that I'm responsible for. When this is done any faulty/non functioning equipment is replaced immediately. It seems someone is not doing there job properly.David.

author: tom66
author_rank: Super Contributor
timestamp: October 13, 2012, 03:37:22 pm
content: Quote from: djsb on October 13, 2012, 03:27:30 pmSure everything is safety tested (all has green PAT stickers), but there's a difference between working and safe.The PSUs are failing due to insufficient fuses, they need to be bigger but I suspect they were too small from the factory and by law maybe they're not allowed to put a larger value in or a different type such as antisurge.The scopes... no idea myself.

author: djsb
author_rank: Super Contributor
timestamp: October 13, 2012, 03:53:26 pm
content: Sounds to me like some incident has damaged the equipment in the lab. Fuses should not blow when a power supply is turned on without a load connected (or at all for that matter). There is generally a fuse at the cable entry point to the equipment as well as the actual mains plug.Also there should be one or more mains isolation switches and contact breakers on the mains distribution side.I'd refuse to do any work in this lab as it doesnt sound very safe to me.David.

author: tom66
author_rank: Super Contributor
timestamp: October 13, 2012, 03:57:09 pm
content: Quote from: djsb on October 13, 2012, 03:53:26 pmThese are linear lab PSUs (dual 30V, 2A plus 5V, 2A) so have big input capacitors. The fuses are almost certainly blowing due to inrush. You can turn it on and it will die quickly (flash from the display.) It never fails once it's started.The Agilent scopes, no idea. The ticking to me reminds me of a shorted PSU. The other one may have died due to some other failure on the power supply as it simply made a crackling sound inside then was dead. But it could have been the mains switch (which can make a noise when depressed) or completely unrelated.There is an isolation switch in each lab which cuts all power.

author: djsb
author_rank: Super Contributor
timestamp: October 13, 2012, 04:34:20 pm
content: Sounds like the contact breakers in the mains distribution panel dont have the correct time constant. Are there any PC's present in the lab as well? If so they generally cause the circuit breakers to trip due to the inrush current at startup. In last university I worked in the breakers in one lab regularly tripped out due to the computer power supplies. Doesnt happen where I work now.DavidPS Sorry for diverting you from the original subject.

author: Monkeh
author_rank: Super Contributor
timestamp: October 13, 2012, 04:38:30 pm
content: Quote from: djsb on October 13, 2012, 04:34:20 pmI'm pretty sure he's talking about equipment fuses, not distribution circuit breakers.

author: tom66
author_rank: Super Contributor
timestamp: October 13, 2012, 04:51:36 pm
content: Quote from: Monkeh on October 13, 2012, 04:38:30 pmYes, it is a fuse in the rear of the equipment. Sorry if this wasn't clear.

author: tom66
author_rank: Super Contributor
timestamp: October 16, 2012, 05:10:13 pm
content: Played around with another meter, and it will do the problem too, BUT, only when the range switch is flicked from diode to VDC. The other way never seems to do it. So I'm now very certain it's some kind of range switch problem.I was lucky enough to sit down at the bench of the replacement for the tick of death scope. I think they stole it from the Microwaves/Photonics department, it's a 500MHz 4GSa/s MSO6054A. It is optioned out on EVERYTHING. It has a battery pack in it, I went to turn it off at the wall at the end of the lab session and I was thinking huh? It's still running, but then it pops up with a message warning about grounds and such and the battery LED lights up on the side of it.Also quality of Agilent tech - went to turn on one of the spec analysers there. Screen lit up and you could see an image, but it was like it had lost horizontal sync. You could see an image but it was really jittery. What are the students doing to this equipment that causes this?!

author: Achilles
author_rank: Regular Contributor
timestamp: October 17, 2012, 10:02:09 am
content: Quote from: tom66 on October 16, 2012, 05:10:13 pm+1. It's a common problem. A lot of student's are not really fit enough or understand what to do. Blown fuses and so own are normal I would guess, due to wrong operation. They will need some time to learn what causes the problem.In school we had these nice old Metrix analog meters with a fuse-wire you had to repair yourself when you blew it up. That helps to remember and learn a lot about the technical stuff compared to just replacing the meter to another one....So in Schools or Universities there is a much higher abuse and misuse of equipment that could cause failures. Here I don't even think about these fellows playing around with stuff because it makes nice sounds or so.....

author: tom66
author_rank: Super Contributor
timestamp: October 18, 2012, 08:06:04 pm
content: OK, this does it... another meter I've found with the problem. Lab tech finally told me - it's a common problem. However, interestingly, this one does it on ohms too! It's the first one I've seen that does it - it started reading hundred ohm measurements with the probes disconnected...

author: Monkeh
author_rank: Super Contributor
timestamp: October 18, 2012, 08:07:36 pm
content: Have you checked for damage or contamination on the range switch?

author: tom66
author_rank: Super Contributor
timestamp: October 18, 2012, 08:52:02 pm
content: Quote from: Monkeh on October 18, 2012, 08:07:36 pmThey're not mine to take apart.The tech said they'd wish they had got Fluke meters or other meters - but that Agilent gave them a very hefty discount on the equipment order (something close to £400k of equipment) but it has to be plastered in "Agilent Technologies" per the agreement.