Faulty Agilent 34410A multimeter - Page 1
Forum section: electronics / testgear

author: jgorsk
author_rank: Regular Contributor
timestamp: December 10, 2013, 02:01:43 pm
content: I have a problem with my 34410A multimeter. In some ranges it measures properly,in some with a little offset. I tried to calibrate it. It passed the ADC calibration but it failsthe DMM calibration. I get error 707 Calibration error: signal measurement out of rangein the first DMM calibration step which is zero adjustment.I ran a self-test and got error 623 ADC Mesure Zero Overload Test. That error is notmentioned in the service manual.I tried to repair it but it's difficult without a schematic and knowledge of the multimeteroperation. I checked all the components I could and they seemed to be fine.Does anyone have access to schematics for the Agilent 34410A/411A multimeter or have any cluewhat the problem with my multimeter might be?

author: tszaboo
author_rank: Super Contributor
timestamp: December 10, 2013, 04:00:24 pm
content: I know it is not the same, but you should check out the 34401A service manual. It has schematic and block diagram at the end. The 34410A did not come from outer space, a lot of things (I guess) should be more-less the same at least in principle.

author: jgorsk
author_rank: Regular Contributor
timestamp: December 10, 2013, 06:04:07 pm
content: Unfortunatelly 34401A has totally different circuitry than 34410A/411A.

author: jgorsk
author_rank: Regular Contributor
timestamp: December 13, 2013, 08:43:33 am
content: I got a schematic for the 34410Ahttp://www.home.agilent.com/owc_discussions/servlet/JiveServlet/download/123-36971-112352-6830/schematic.pdf

author: tszaboo
author_rank: Super Contributor
timestamp: December 13, 2013, 08:52:29 am
content: Did they just give it to you? Nice work!mod: first look: A 10 bit 20MSPS and a 8 bit 50MSPS ADC. the 8 bit is fed by a TL071. What is going on?Not to mention that strange construction again Q302-Q312. Anyone has any idea what that does?

author: jgorsk
author_rank: Regular Contributor
timestamp: December 13, 2013, 11:20:46 am
content: I just asked nicely at Agilent forum and I got the schematic.There is plenty of strange looking circuitry in Agilent meters, that's part of why they work so well.The TL071 does look curiously, doesn't it. It feeds ref input of the coarse ADC as well as both + and - inputs.Look at the feedback network around it. It's probably mainly used for AC measurements.Q302..Q312 and the other associated transistors must be overvoltage protection circuit in Ohm mode.

author: tszaboo
author_rank: Super Contributor
timestamp: December 13, 2013, 12:48:29 pm
content: Quote from: jgorsk on December 13, 2013, 11:20:46 amThat is nice from them. I know that most of their stuff comes from proven circuits, and sometimes they don't change something what works. I'm almost sure they only need 10 bit because they still use it with a dual slope architecture. And the Tl071 was working before, so why change it?Still, there are a lot of weirdness in this.Good luck with the repairs. If you find anything interesting let us know!

author: free_electron
author_rank: Super Contributor
timestamp: December 13, 2013, 11:00:08 pm
content: 34410 is a completely different beast than a 34401. fully new generation asics , new measuring technique. the only common part is the input range selection. the ADC is completely different.Fact that agilent disclosed the schematics proves once more that these guys are simply the best.There is not a single other company that does that. It's all hand-waving and other blabla.In terms of performance , price and customer support you can't beat Agilent.I flatly refuse to use any other brand of equipment. I have a few non agilent machines but as soon as i can get an agilent replacement they will go out the door.

author: echen1024
author_rank: Super Contributor
timestamp: December 14, 2013, 03:19:07 am
content: Quote from: free_electron on December 13, 2013, 11:00:08 pmI must agree. I own a 33120A and an E3610A and like them very much. High quality, good performance, no nonsense,

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 14, 2013, 12:21:42 pm
content: Would you please list the DCV ranges, where the zero or range error occurs?I assume you found errors in DCV already?!I would test that, by first shorting the inputs and then read the Zero reading foreachDCV range, afterwards the same with 100mV, 1V, 10V perhaps 100V inputs if available.Then you may localize the error either in the pre amplifier or in the ADC section.Frank

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 15, 2013, 11:07:04 pm
content: Quote from: free_electron on December 13, 2013, 11:00:08 pmI like Agilent and I almost exclusively use their test equipment, but I think they don't care about schematics because Agilent use custom-made ASICs in most of their designs. Those ASICs is where all interesting stuff happens.