Problem with Agilent U1232A - Page 1
Forum section: electronics / general

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 02, 2012, 06:08:55 am
content: I bought a couple of Agilent U1232A DMMs and discovered a problem with them.I had a D.C. motor connected to my power supply and I took one of the U1232A to measure the voltage across it's terminals, the measurements on the unit were moving between 13 and 14 volts, the voltage on the internal voltmeter on the power supply was stable at 12 volts.Then I took my Fluke 87V and the measurement was stable at 12 volts, same with my ~20 years old BK Precision DMM. I tried a second power supply just to get the same results.Then I connected my Agilent scope I saw that the signal was very noisy, set the voltage measurement on the scope and it was also stable at around 12 volts.I was able to reproduce the problem using my signal generator by setting a dc component with a noise level, the Agilent multimeters start to fluctuate when setting the noise level greater than 15 volts, my Fluke and my old BK Precision no problem. Unfortunately I was not able to get the value where the Fluke or the BK precision start to fluctuate due limitations on my Sig Gen, the max noise level I can set is 18 volts.I contacted Agilent explaining the problem and they asked me to replace the two units with new ones thinking they were defective, but the new multimeters have the same problem. The Agilent engineer told me it will be a difficult fix, if they are going to fix it, probably one customer complaining will not make any noise inside the company. I'm thinking if I will return the multimeters, the only reason I bought these cheap units was for the IR-USB connection to the computer.I'm glad I have some other multimeters for comparison, imagine a person having just one of these, how can you rely on them !

author: retiredcaps
author_rank: Super Contributor
timestamp: March 02, 2012, 07:29:52 am
content: Quote from: DavidDLC on March 02, 2012, 06:08:55 amI can't help with your problem, but I'm curious regarding Agilent's exchange program. Did you take it back to the dealer or have to send/mail it to Agilent directly? If the latter, did you pay for postage out of your own pocket?

author: saturation
author_rank: Super Contributor
timestamp: March 02, 2012, 11:58:11 am
content: Thanks. It reads like its picking up the noise and averaging with it, like a DC+AC value, and is too sensitive.Try using the MinMaxAvg function and read the avg value out in real time.The low Z function might suppress it too, if the transients do not have enough energy to appear across a low impedance.Please let us know what you find.

author: FenderBender
author_rank: Super Contributor
timestamp: March 04, 2012, 05:02:45 am
content: I was actually looking at getting one of those for the same reason- USB. Shucks. Agilent seems to have some issues with firmware as of the late. It seems something like this might be firmware.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 05, 2012, 03:10:23 am
content: Quote from: retiredcaps on March 02, 2012, 07:29:52 amI sent the units back to the dealer, they gave me their account number to return them, so I didn't pay to ship them back.

author: Drirr
author_rank: Regular Contributor
timestamp: March 05, 2012, 07:18:22 pm
content: I have tried similar measurement with my U1231A, which is similar to U1232A. Without problem.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 05, 2012, 09:41:15 pm
content: Can you capture the screen on the Rigol and post it here ?Thanks.David.

author: Drirr
author_rank: Regular Contributor
timestamp: March 06, 2012, 05:29:38 am
content: Here it is,..

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 06, 2012, 05:33:40 am
content: Thank you Drirr,The problem on the meters is with noise signals greater than 15 volts, under this value the measurements are stable, I did a similar test with the next signal and they didn't present the problem.

author: Drirr
author_rank: Regular Contributor
timestamp: March 06, 2012, 06:05:58 am
content: I will try it

author: Drirr
author_rank: Regular Contributor
timestamp: March 06, 2012, 07:44:03 pm
content: new measurement