Multemeter Digits Vs Counts - U1272A Keysight  - Page 1
Forum section: electronics / beginners

author: 2X
author_rank: Frequent Contributor
timestamp: July 18, 2023, 08:03:40 pm
content: Hello,I have a query. The U1272A multimeter of the Keysight writes that it is a multimeter of 4&1/2 digits and 30000 counts. A multimeter of 4&1/2 digits can show only up to 19999 which this is 20000 counts. What am I missing?U1272A Handheld Digital Multimeter, 4.5 Digit, IP54https://www.keysight.com/us/en/product/U1272A/handheld-digital-multimeter-4-5-digit-ip54.htmlMultimeter – What Do Digits and Counts Mean?https://instrumentationtools.com/multimeter-digits-counts/

author: mwb1100
author_rank: Frequent Contributor
timestamp: July 18, 2023, 08:41:59 pm
content: They could/should have called it 4 3/4 digits (the 3/4 coming from it being able to display 0-3 as the most significant digit). I imagine the 4 1/2 is just a copy/paste or some other simple typo.I think most people pay attention to the counts rather than the fractional digits version of that spec since it's just plain easier to understand. For example how many digits is the 22000 count UNI-T UT61E? It's something more than 4 1/2 digits (20000 counts), but not up to 4 3/4 digits (30000 counts)

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2023, 08:42:46 pm
content: "4-1/2 digits" is an ambiguous statement: it means more than 4 and less than 5, but is interpreted differently between vendors.A sensible statement is "2000" or "40,000" counts, even though pedantically the meter only goes to 1999 or 39,999.(That's one less, innit?)

author: Benta
author_rank: Super Contributor
timestamp: July 18, 2023, 09:16:39 pm
content: My Fluke 179 has 6000 counts (0...5999) and is called a "3-1/2" digit multimeter.Most standard DMMs go to 1999 or 19999 and would be called 3-digit or 4-digit meters.

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2023, 09:18:07 pm
content: Most vendors list their 2000 count (1999 max) as "3-1/2 digit".https://www.mouser.com/c/test-measurement/multimeters-voltmeters/digital-multimeters/?number%20of%20digits=3%201%2F2%20Digit&type=Hand%20HeldSome older voltmeters only went to 999 or just past 1000 counts, but that's not so common anymore.

author: Veteran68
author_rank: Frequent Contributor
timestamp: July 18, 2023, 09:29:24 pm
content: Quote from: TimFox on July 18, 2023, 08:42:46 pmAs an old software engineer, I've long started counting at 0, so I don't consider that pedantic at all. 0-1999 is 2000 counts. 0-39999 is 40000 counts. Totally intuitive to me!

author: TimFox
author_rank: Super Contributor
timestamp: July 18, 2023, 09:37:58 pm
content: Don't get me started about Y2K and the current millenium.

author: tooki
author_rank: Super Contributor
timestamp: July 19, 2023, 01:22:34 pm
content: Quote from: Benta on July 18, 2023, 09:16:39 pmNo. Those are also 3.5 or 4.5 digits. (3 and 4 digits would be 999 and 9999, respectively.)The only thing multimeter vendors agree on is that a first digit that can’t go all the way to 9 is a fractional digit, with an initial “1” already counting as half. Some vendors use 3/4 for higher counts, some don’t. There’s no mathematical formula or anything, it’s just marketing decisions.

author: tooki
author_rank: Super Contributor
timestamp: July 19, 2023, 01:36:01 pm
content: Quote from: 2X on July 18, 2023, 08:03:40 pmThat last link is wrong. There are ample examples of n.5-digit meters with a first digit capable of more than 1.There’s no standard. A half or 3/4 digit simply means a digit that can’t do 0-9, which is what each “full” digit can do. There is no agreed-upon meaning beyond “half-digit = less than 9” and “3/4 digit = more than 1 but less than 9”. Many manufacturers choose to only use “half”.I think I’ve even heard of a manufacturer referring to a 2/3 digit. Don’t ask me who it was, though, I don’t remember.Examples from my bench:Keithley 197 meters are 5.5 digits, 220,000 countsKeithley 2015 is 6.5 digits, 1,200,000 countsKeysight U1252B is 4.5 digits, 50,000 counts

author: rsjsouza
author_rank: Super Contributor
timestamp: July 19, 2023, 01:41:19 pm
content: Quote from: tooki on July 19, 2023, 01:22:34 pmPrecisely. The fractional number of digits as 3-1/2 and 4-1/2 representing 2000 and 20000 count was a very solid concept in the eariler days of mass produced DMMs.However, when the number of counts started to become higher (4000 5000, 6000 and their multiples), things started to become crumpled into the -3/4 or -5/6 naming suffixes, with no real convention to it.

author: tooki
author_rank: Super Contributor
timestamp: July 19, 2023, 01:49:57 pm
content: Exactly. And it’s even less clear when you have some limitations on the second digit, too, like the Keithleys I mentioned that have 220k and 1200k counts. (Which are formally specified as 1M counts +20% overrange on the K2015.)

author: Siwastaja
author_rank: Super Contributor
timestamp: July 19, 2023, 02:03:23 pm
content: And sometimes that tiny detail matters. One could think a 4000 or 5000 count meter is nearly the same, but if you need to measure lithium ion charge voltage (4.2V) with good resolution, then that simple "20% difference" becomes a 10x difference as you need to switch to next range on the 4000 count thing.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 19, 2023, 04:03:11 pm
content: That "number of digits" is a prehistoric and in today's modern world a meaningless number. It's only carried by inertia into the present and future. Just stating the maximum number it can display (with rounding to make it a nice round number) is much more sensible.There have also been some oddball meters which for example have a max display count up to 24000It's just like LGQBXGA monitors. No sensible person even attempts to decipher all those resolution numbers. It's much easier to just use the number of pixels.Quote from: Siwastaja on July 19, 2023, 02:03:23 pmAnd it goes on...Voltages up to around 5V are the most common in electronics, and a 6000 count meter covers that nicely. I find the difference between 6000 count and 10000 count meters rarely significant. And when you go up to 20000 coun't it's of course a 2000 count meter with "just" an extra digit, and the cycle repeats.But much more important then the display count. Buy some decent DMM if you want reliability. I bought a few of those AN8008 things, discovered that newly bought 1% resistors were out of spec, measured them with another DMM (then measured in spec) and then discovered the contacts in those aneng meters are not reliable.