DM3068 - False reading of 10M resistor - Page 1
Forum section: electronics / testgear

author: PSR B1257
author_rank: Frequent Contributor
timestamp: September 14, 2014, 07:07:31 pm
content: Hey Guys,I'd just discovered, that my Rigol DM3068 reads a 10M resistor (verified at four different other meters) as 7.somethingMOhm (2 or 4 wire, 10M or 100M rage - it makes no difference)It reads 1M resistors also too low: 957k (the Keithley 2000 reads 999k75)The reading of 1k resistors is spot on...Has anybody noticed a similar problem?

author: Wytnucls
author_rank: Super Contributor
timestamp: September 14, 2014, 07:21:19 pm
content: Perhaps not relevant, but my DM3058E has no problem measuring 1M and 8M resistors. That is true for both ranges, 10M and 100M.

author: SeanB
author_rank: Super Contributor
timestamp: September 14, 2014, 07:51:56 pm
content: I would guess surface leakage across the PCB on the input side, likely from either a no clean flux residue or from poor cleaning during manufacture.

author: TooOldForThis
author_rank: Regular Contributor
timestamp: September 15, 2014, 02:25:46 am
content: I just measured a "10M" resister on my DM3068 and got 10.752MOhm.The same resister on an Agilent 34461A read 10.750MOhm.The resister I used had crummy thermal specs, if i touch it with my finger it drops 300K.PSR B1257, Do you get a better reading with a 4-wire connection?

author: PSR B1257
author_rank: Frequent Contributor
timestamp: September 15, 2014, 07:44:43 am
content: Quote from: SeanB on September 14, 2014, 07:51:56 pmI doubt it would pass the QC after manufacturing if this would be the case...but you never know until you know...I did a couple more measurements:DUT is once again the 1M resistor. But this time I looped the µcurrent in between, to check the measuring current against the datasheet.1M rage: 1.93µA (supposed to be 2µA)10M range: 196.7nA (supposed to be 200nA)100M range: 178.97nA (supposed to be 200nA||10MOhm, due to currentdivider: 196.7nA*10M/(10M+1M+10k)=178.65nA)If I put in the 10M resistor (cleant with isopropanol after fixing it - just in case) everything changes:10M range (readout 8.8M this time): 176nA100M range (readout 8.9M this time): 93.3nAPretty poor for a 840$ "precision" meter - go figure...I'm afraid I have to contact the customer service.

author: Owen
author_rank: Contributor
timestamp: September 15, 2014, 11:36:10 am
content: Is your >10G input option activated?

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 15, 2014, 12:36:49 pm
content: There is definitely an issue with it. I have several 6.5 digit multimeters and 10 Mohms should never be a problem to measure accurately. Was this meter purchased brand new by you? If so hopefully its under warranty so Rigol can repair it with no cost to you. On the other hand if it was bought used, I can't count the number of meters I have repaired that had damage to them from previous owner morons putting excessive power in to them while in resistance ranges. Good designed meters can tolerate accidental input power in ohms to a point, but they will give in beyond that point where something will blow. Then either resistance functions don't work at all, or the readings are way off.-Mark-

author: PSR B1257
author_rank: Frequent Contributor
timestamp: September 15, 2014, 01:41:11 pm
content: Quote from: Owen on September 15, 2014, 11:36:10 amWell, this topic is about resistance measurementQuote from: MarkPalmer on September 15, 2014, 12:36:49 pmYes, fortunately. I already contacted the distributor...

author: PSR B1257
author_rank: Frequent Contributor
timestamp: September 19, 2014, 08:24:33 am
content: Unfortunately I dont get a free repair (not even inspection) of my unit, since it isolderthen 6 monthI did another ordinary test with open jacks: 20oddMOhm (initially, slowly rising, after 1/2h about 70M)Hmm, could it be just leakage current, as SeanB assumed...Update: After 1.5h or so, its finaly managed to read "OVER LOAD" at open input jacks - that dosent sounds like leakage current.

author: Orange
author_rank: Frequent Contributor
timestamp: September 19, 2014, 10:54:51 am
content: Quote from: PSR B1257 on September 19, 2014, 08:24:33 amWell how long do you have it then ?,Batronix claims 3 years warranty

author: PSR B1257
author_rank: Frequent Contributor
timestamp: September 19, 2014, 05:37:44 pm
content: Quote from: Orange on September 19, 2014, 10:54:51 amAbout 15 month.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: January 17, 2015, 08:21:30 pm
content: Late UpdateI finally got a new unit from Rigol since there were not able to calibrate or fix it.