need help understanding how this multimeter works - Page 1
Forum section: electronics / testgear

author: castironman
author_rank: Contributor
timestamp: November 14, 2017, 12:34:48 am
content: Hello. I have a multimeter that is doing something new to me. It has a slow auto range and it displays all zero's as it goes through the ranges. It works like this: lets say you are measuring 9vdc, and because it is a 6000 counts, it has to move to the nearest scale to 9v volts, so it will display 0.000 then 0.00 then it will display the readings without shooting high or low. I never saw this on other meters that I own. So if anyone can explain it to me I thank you very much. It's a new meter, replaced batteries and checked with different voltages DC with same results. Thank you for your help.Joe

author: retiredcaps
author_rank: Super Contributor
timestamp: November 14, 2017, 02:24:27 am
content: It would help us help you if you told us the make and model number so we know if that is normal or abnormal behaviour.

author: castironman
author_rank: Contributor
timestamp: December 03, 2017, 01:47:28 pm
content: Thank you for your help, it is a Southwire 14070T. I believe it is a CEM re bagged meter. It had some problem with it and Southwire replaced it but the new one still goes back to 0.00 and I think that makes it to have a slow autorange. Thank you.

author: retiredcaps
author_rank: Super Contributor
timestamp: December 03, 2017, 07:38:12 pm
content: Some Southwire multimeters are rebadged CEM Instruments. Yours is a DT-965T.http://www.cem-instruments.com/en/Product/detail/id/1332

author: retiredcaps
author_rank: Super Contributor
timestamp: December 03, 2017, 07:41:39 pm
content: Quote from: castironman on November 14, 2017, 12:34:48 amI haven't read the manual, but most CEM meters are 2 times/sec display update speed.What you describe above sounds like the correct behaviour for the meter as it starts at the lowest range 0.000 (6V), then goes to 0.00 (60V) and then settling in on the correct 9V reading. If it is 2 times/sec update, then the autoranging speed seems glacial especially if you are used to a faster or manual range multimeter.edit: manual says measurement rate is 3 readings/sec nominal athttp://www.southwiretools.com/tools/m/file.get.do?file_id=1955but doesn't specify the screen update rate? That is, measurement rate and screen display update rate isn't necessary the same.

author: retiredcaps
author_rank: Super Contributor
timestamp: December 03, 2017, 07:47:17 pm
content: Just as a reference, the Fluke 87V says in their manual (clearly)SpecificationsDisplay: Digital: 6000 counts updates 4/sec; (Model 87 also has 19,999 counts in high-resolution mode).

author: retiredcaps
author_rank: Super Contributor
timestamp: December 03, 2017, 08:07:10 pm
content: BTW, if you are willing, can you take it apart and post some pictures of the pcb inside? I don't think we have seen one of these yet?If not, no worries.

author: IanB
author_rank: Super Contributor
timestamp: December 03, 2017, 08:12:44 pm
content: Quote from: castironman on November 14, 2017, 12:34:48 amI did a spot check on a couple of meters I own. One of them shows "over range" for a short period while the auto-range settles. The other blanks the display for a short period before settling.I see nothing wrong in principle with showing 0.000 then 0.00 before settling. It's just a different way of doing things. Why are you worried or bothered by it?

author: retiredcaps
author_rank: Super Contributor
timestamp: December 03, 2017, 08:13:23 pm
content: CEM's marketing/photoshop division clearly needs some education. It shows 0.000VAC while the selector switch is in the off position.Even Southwire's stock photo is wrong. While it shows 120VAC with the selector switch in the V, the hold icon is missing from the lcd display (should be bottom left). Unless measuring with no probes attached is really 120VAC.Fail for both companies and both should be in the stock image FAIL thread.