Rigol DM3058E strange behavior - Page 1
Forum section: electronics / testgear

author: BUkitoo
author_rank: Contributor
timestamp: February 05, 2014, 05:28:43 am
content: Hi, I recently bougth a DM3058E DMM from Rigol.I was witnessing a strange behavior, and maybe you may could know what is happening.The thing is that I was trying to caracterize the RDS of a mosfet. So I have just varied the GS voltage while measuring resistance with the DMM (setted in autorange) step by step . All was good until I reached the Kohms range. The internal relay go crazy and the DMM never decide which range to choose, and of course, the display show me nothing. Even the small ring that the dmm has that shows the sampling frequency, stoped. Then I remove the autorange setting, and set it manually in the kohm range but the display still doesn't show me any value. Of course I get my handheld DMM and the measurments went perfect in every range.After that, I have tried to vary a potetiometer from Mohms down to ohms, and the rigol worked perfectly.Do you KNOW what is happening !?well... maybe dave could try this and see what happens. He has more advance intrumentation that I.anyway, thanks in advance!Franco

author: Spikee
author_rank: Frequent Contributor
timestamp: February 05, 2014, 08:49:50 am
content: Put it in manual range , you can also try a firmware update to fix it.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: February 05, 2014, 09:01:34 am
content: You should add a constant voltage and measure the current instead.Changing drain-source voltage can/will change the current hence changing range can change the resistance. (probably the reason it's stuck in a loop)

author: BUkitoo
author_rank: Contributor
timestamp: February 05, 2014, 11:55:00 am
content: Hi!Thanks for the both of you.I tried in a manual range, but the thing is still there. Anyway, where can I download Rigol FW updates? I couldn´t find anything at the website.I will measure the voltage that the DMM is applying when getting stuck, and then I will tell you the results.Many thanks, again.Franco

author: mcinque
author_rank: Unknown
timestamp: February 05, 2014, 12:09:41 pm
content: write to rigol on rigol.com and request a firmware update specifying your version (I know that sounds stupid that you must ask for update files, they should put them on the website...). Ask always if after the update the instrument will require recalibration or not.

author: BUkitoo
author_rank: Contributor
timestamp: February 05, 2014, 12:24:56 pm
content: OK, that why I couldn´t find anything at the website.I´ll do write them! (by the way, I wrote them asking for this behavior, and I just received an automatic email and that´s all.... lets wait)Thanks!Franco

author: BUkitoo
author_rank: Contributor
timestamp: February 07, 2014, 12:41:08 pm
content: Yeah, I measured the voltage applied by the DMM and in the range where the issue appear, the voltage is a square wave....well I guess the DMM should detect those kindda conditions...thanks!I still wainting the reply from Rigol about the firmware.Franco

author: larry42
author_rank: Regular Contributor
timestamp: February 07, 2014, 12:46:23 pm
content: Quote from: BUkitoo on February 07, 2014, 12:41:08 pmMultimeters that can detect that - those things are called oscilloscopesPS I wouldn't measure MOSFET resistance like that - measure voltage across a resistance instead with a known/fixed V_DS