What's the point of hold or auto-hold in DMMs? Ever seen a properly working one? - Page 1
Forum section: electronics / general

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 12:36:21 pm
content: I always thought that Hold function was supposed to be for when a measurement requires both hands, and full attention to the probes. The DMM was supposed to figure out when the measured value is stable enough, than freeze the measured value for a few seconds, so to give me time to disconnect the probes then watch the display.My Metrix mtx3283 doesn't work like that on either hold or auto-hold. Hold only freezes the display at the moment it was pressed, while auto-hold doesn't seem to be doing anything. It only holds the value if it differs less than +/-100 counts, on a 100_000 counts DMM.That's an expensive DMM, it was the top model from that line. It has No-Hold, Hold and Auto-Hold, and it was $800-$1000 new, don't recall exactly.I remember having the same frustration with some Fluke at a former workplace. I don't recall what model of Fluke it was, but I recall the frustration that it didn't hold the value until it was safe for me to read it. It required two dudes, one to keep the probes, the other to voice read the display.What's the point of having hold or auto-hold in DMMs? Ever seen a properly working one? Does anybody uses the hold/auto-hold in practice, or hold is in fact just a useless feature, good for marketing hype only?Why would I need Auto-Hold if I can afford to look at the display while probing?And why would I need Hold anyways? mtx3283 is slow, 3 measurement/second or so, it's not that the display is so fast that it can't be read.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 21, 2023, 01:01:44 pm
content: It works pretty well on my Metrix MX-57EX, a long press on the "HOLD" button activates auto-hold. It's not as fast as the Touch-hold on the F87V, but it's usable. Same for the Tek DMM912, and Agilent U1401B.There are times when the probing is either so fiddly or dangerous that youreallyneed to focus your attention on that rather than the meter display. Auto-hold is great for this.Normal hold is only really useful if you don't have logging capacity and you need a reading at a specific time and you can't remember the reading long enough to write it down...

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 01:10:16 pm
content: How did you use it?Auto-hold in mtx3283 doesn't remember the number when you disconnect the probes, so to afford to safely turn the head sideways and read the display.

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2023, 01:31:53 pm
content: I rarely use it but when I've tested it, it works fine on all 4 Fluke handhelds I have--27, 116, 189 and 289. The one I use the most, the 27 is very simple--long press on HOLD button until it beeps to engage AUTO-HOLD, connect the probes and take a reading until it beeps (usually very prompt, less than 1 second) and then the reading will be frozen on the display until you take a new one. I'd be surprised to see any decent meter not have this feature working properly. I'm not familiar with your meter, but I suspect either you aren't actually engaging the autohold or perhaps it doesn't actually have it.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 21, 2023, 01:40:42 pm
content: Press and hold the "HOLD" button until there's a second beep and the "MEM" annunciator starts flashing on the display. When it detects a stable reading, it'll beep to say it's caught a fish, and you can remove the probes.NB: This works on the MX-57EX, I have zero experience of the MTX3283

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 01:43:00 pm
content: Quote from: bdunham7 on April 21, 2023, 01:31:53 pmThat's the problem. What does it means "take a new one"? For Metrix mtx3283 it means the measured value changes with more than 100 counts. So if I disconnect the probes to afford to safely turn my head away from the probing are to the DMM, in less than a second the DMM will beep again and auto-hold on zero, which defeats the whole "keeping for you to read" idea.mtx3283 has a graphic LCD, it writes "AUTO HOLD" in clear, just that it doesn't remember long enough to be of any use.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 21, 2023, 01:54:17 pm
content: Maybe they fooked up the FW in that model?The MX-57EX doesn't detect disconnected probes as 0V or ∞Ω, nor does that happen on any of my other handheld meters with auto-hold, though the U1401B is a bit odd in that it gives you about three seconds to make a probulation after you press the button, which is less useful. I haven't checked how well it works on any of my bench meters.

author: Fgrir
author_rank: Regular Contributor
timestamp: April 21, 2023, 01:57:55 pm
content: Quote from: RoGeorge on April 21, 2023, 12:36:21 pmIt works great on my 34465A, and the list view makes it awesome for taking a bunch of measurements where I'd rather not look away from what I am probing.

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2023, 02:07:09 pm
content: Quote from: RoGeorge on April 21, 2023, 01:43:00 pmThat doesn't sound like a good implementation. Let me try my Fluke 27.......so I set a power supply to 3.00V and set the meter for AUTOHOLD. I touch the probes, the meter beeps and displays 3.0xx volts. I remove the probes and the display stays at 3.0xx volts, presumably forever. I reverse the leads, the meter beeps and displays -3.0xx volts. I reverse them again back to the original setup and touch them, it beeps and reads 3.0xx volts. I remove them and without adjusting anything, I touch them again and the meter beeps again and displays 3.0xx volts again, but perhaps a few digits off--so it is looking at a change from zero/open to some stable reading. You don't have to reset it manually. I can confirm this by setting the power supply to 2.00V, then with the meter still holding the previous 3.0xx volt display, when I touch the probes the meter beeps and changes to 2.0xx volts.The only glitch I was able to observe was when trying it on AC mains. It held the 118.8V reading for a few seconds, but then dropped down to a much smaller reading like 0.423 or something. The issue there is autoranging--it will drop down into the lower ranges and see a bit of stray noise as a new non-zero reading and capture that. The fix is to just set it manually for the expected range. Perhaps this might help in your case.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 02:31:37 pm
content: Quote from: bdunham7 on April 21, 2023, 02:07:09 pmThank you. Mine holds the number after it beeps, but only until the next measurement differs more than 100 units. That's written in the mtx3283 user manual:QuoteSo, mine is faulty by design.

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2023, 02:40:31 pm
content: Quote from: RoGeorge on April 21, 2023, 02:31:37 pmIf they include zero/open as a stable measurement that differs by more than 100 counts and thus replaces the old reading, then yes I'd say it was pretty useless......but are you sure that is the case? Will a 0.000V (or close) reading actually cause the old reading to disappear? Or is it downranging and then reading noise? Can you try manual ranging?

author: AVGresponding
author_rank: Super Contributor
timestamp: April 21, 2023, 02:52:04 pm
content: Quote from: RoGeorge on April 21, 2023, 02:31:37 pmCan you change the settings? I've just been playing with my bench meters and while the 34401A and TTi 1906 both work pretty well like the handhelds, the K2000 and K2015 are a bit finicky to set up; you can adjust the % at which it triggers a new reading and also the number of counts, and the measurement rate also has a big impact, on fast it holds for less than a second, but on slow it holds pretty much indefinitely.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 03:34:19 pm
content: mtx3283 is a handheld DMM, not a bench DMM, auto-hold is described at page 18 in the user manual and it has no extra settings:https://www.aemc.com/userfiles/files/resources/usermanuals/Multimeters/MTX_3281-3282-3283_EN.pdfQuote from: bdunham7 on April 21, 2023, 02:40:31 pmThat's what I'm complaining about. Either manual or autorange, my mtx3283 does the same.For example:- set manual ranging, DC 10.0000V full scale, Auto-Hold, measure a NiMH 6 cells battery- it beeps once when it reaches a stable measurement: +7.7882V- after disconnecting the probes, the display changes almost instantly (100 counts means 1.0mV on this range)- but it doesn't beep yet- then about half a second later, after the display changed about 3 times (without any beep),- it sees again a stable enough value, and it beeps and shows: +0.0029V while I keep the probes in the air

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2023, 03:50:48 pm
content: That sounds like a legitimate complaint. Whoever programmed that perhaps just didn't fully understand the concept! It sounds like the sort of thing that would merit a firmware update if that is possible.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 04:05:23 pm
content: I've looked for FW updates and couldn't find any on the producer's site (Chauvin-Arnaux). My understanding is this line of instruments are made with a proprietary ASIC. I suspect that probably the bug is in the ASIC chip, thus not fixable. I doubt that after so many years nobody noticed and no FW update was released.Could be, as well, that I have a defective mtx3283, while other mtx3283 are working just as expected.

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2023, 04:14:10 pm
content: Quote from: RoGeorge on April 21, 2023, 04:05:23 pmIt doesn't sound like the sort of thing that would go wrong, but it might sound like the sort of thing that would be addressed with an update and nothing mentioned if it was not feasible to apply the update to existing units. So if other (newer?) ones do work correctly, that's why.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 21, 2023, 05:25:33 pm
content: Seems it's dumb by the factory, and not something fixable. Mine has firmware v1.17, the one in this video has firmware v2.03 and still has the Auto-Hold the dumb way, see at minute 38:40https://youtu.be/BtlWO8TIkO8?t=2320

author: thm_w
author_rank: Super Contributor
timestamp: April 21, 2023, 10:31:23 pm
content: What a joke, and regular hold is useless too unless you have three hands. Making the entire button never used by 99% of people.Wasn't there some patent? They trademarked the name but not sure if the behavior was patented, can't seem to find it.https://patents.google.com/patent/US20090140721A1/enhttps://patents.google.com/patent/GB2194348A/en

author: tautech
author_rank: Super Contributor
timestamp: April 21, 2023, 11:07:36 pm
content: Just basic functionality that should work as intended and standard requirement for any decent bench DMM.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 22, 2023, 07:45:04 am
content: Quote from: RoGeorge on April 21, 2023, 05:25:33 pmThat's very disappointing, a clear step backwards from earlier designs. Is there anyone here with knowledge of how responsive C-A are to technical enquiries? This would seem to be a faulty implementation requiring a FW update.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 22, 2023, 08:20:05 am
content: The video is from 2012, I don't think they still sell those models.My best guess is they knew, but they have had no way to fix that faulty auto-hold.It's even more amazing this thing was designed for electricians, and it was designed to hang on the belt. No way one can probe, then look at its own belt without risking a short-circuit.Not to say measuring a vibrating circuit, like for example the alternator of a motor and so on.Look at this flyer, poor guy might die pretty soon if he keeps measuring like that:https://docs.rs-online.com/6e0e/0900766b80a57a09.pdf

author: AVGresponding
author_rank: Super Contributor
timestamp: April 22, 2023, 06:37:21 pm
content: That's a serious facepalm moment from a company that normally produces pretty good stuff. As well as the MX-57EX I have a rather nice F21 clamp meter, which has a manual hold button, easily pressed with the thumb while clamped onto a cable.Though for probing stuff I use either my F87V or T5-1000 at work.

author: tszaboo
author_rank: Super Contributor
timestamp: April 22, 2023, 09:11:33 pm
content: So it's just a bad implementation.I've used a Keysight handheld one, had the Bluetooth on it's back. Used auto hold. I could measure 10 points on a PCB, and log all the measurements (and only those) and it sent it through the BT to my PC which was running excel, making statistics from several boards in no time. Mind you this was before Keysight broke all it's software implementations for that benchvue crap, back then you could do this without paying them extra for software.

author: mwb1100
author_rank: Frequent Contributor
timestamp: April 23, 2023, 07:37:21 am
content: Brymen BM78x also has a good autohold. As far as I know the BM78x is the only Brymen meter series with the feature. It differs from Fluke's a bit in that it doesn't freeze the display at each stable reading, it just latches it internally. Then when you remove the probes it will display the most recent stable (and significant - ie., not 0V or OL Ohms) reading. However when it has latched a value, if the reading becomes unstable it will clear the latched value until it stabilizes again. If you remove the probes during the "unstable" state, it will display "-----" instead of the last stable value (which is what a Fluke would display).Either is a reasonable approach. And both cover the normal use: turn on autohold, probe a signal, set the probes down (so you can write/type your finding for example) and the value you probed will still display on the meter.