DMM Continuity Speed question. - Page 1
Forum section: electronics / testgear

author: BillyO
author_rank: Super Contributor
timestamp: August 31, 2025, 05:03:14 pm
content: Simply put, what is the response time that is considered acceptable for most purposes?25ms?50ms?1ms?Chime in folks.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 31, 2025, 05:14:09 pm
content: I think measuring speed like that is kinda funny. People test with AWGs or whatever other method to see what the response time of the meter is, but it doesn't usually account for notifying the human.Speed mostly matters if you're swiping cute little tiny chips with lots of pins, and you don't want to pause on each pin.

author: tooki
author_rank: Super Contributor
timestamp: August 31, 2025, 05:24:44 pm
content: Quote from: BillyO on August 31, 2025, 05:03:14 pmWell, the Fluke 87V, which has possibly the nicest continuity testing out there, is specified as detecting 1ms shorts and opens.

author: BillyO
author_rank: Super Contributor
timestamp: August 31, 2025, 05:29:38 pm
content: Quote from: tooki on August 31, 2025, 05:24:44 pmI think the Brymen BM786 beats that by a factor of 100, but do we really need anything that fast for most purposes? I have some meters here that are at around 25ms, but they don't sound, to me anyway, 25 times slower than the Fluke or 2500 times slower than the Brymen.

author: floobydust
author_rank: Super Contributor
timestamp: August 31, 2025, 05:31:34 pm
content: Speed matters when you are trying to locate a bad connection. Like in a cable, connector, switch etc. and wiggling things. This is why I like scratchy, it has good use.I have old DMM's (no MCU) that are quite high speed scratchy but still need good connection time for making the "big beep".I think an aspect people are missing is the debounce time for qualifying to make a beep, and if that debouncer resets with bounce happening within that duration.So I see at least three different methods for the continuity beeper, some of them are so sloowwwwwwww.

author: tooki
author_rank: Super Contributor
timestamp: September 07, 2025, 11:41:48 am
content: Quote from: BillyO on August 31, 2025, 05:29:38 pmThe manual for it says “Response time: <100μs”. (So a factor of 10 faster.) But it also says it’s unlatched, which means you can’t really compare them.I don’t know howyourears and eyes work, but mine would never be able to detect a beep or blink of 100μs. I have made videos showing how 1ms shorts and opens are either practically or entirely undetectable with an unlatched meter. (I’ll find the links and post them later.) The Fluke makes it possible to clearly detect 1ms shortsand 1ms opensbecause it is latching.

author: Fungus
author_rank: Super Contributor
timestamp: September 07, 2025, 01:41:00 pm
content: Quote from: BillyO on August 31, 2025, 05:03:14 pmI'd say sub 10ms.Quote from: tooki on August 31, 2025, 05:24:44 pmThe best continuity tester is on an $8 Aneng. These aren't even gold probes, they're what comes with the meter.(nb.The LED is bright - much brighter than it looks in the video)Quote from: KungFuJosh on August 31, 2025, 05:14:09 pmSee video.

author: tooki
author_rank: Super Contributor
timestamp: September 07, 2025, 02:25:18 pm
content: Quote from: Fungus on September 07, 2025, 01:41:00 pmThat’s just a plain old unlatched continuity tester, as found on gazillions of meters. (Granted, with a visible indicator, which most lack.)Here’s the videos I did some years ago demonstrating 1ms opens and shorts on an unlatched meter and a Fluke 87V:

author: BillyO
author_rank: Super Contributor
timestamp: September 07, 2025, 02:40:59 pm
content: Quote from: tooki on September 07, 2025, 11:41:48 amLess than 100us can be considerably less than 100us.I don't how your ears or eyes work either but in this video the Brymen (near the end) goes from 12ms pulses to 61us pulses and the length of the beep does not change, and is perfectly audible. The backlight flash is also perfectly visible. At least to my eyes and ears. It may not be latched, but it certainly has a minimum length notification.

author: David Hess
author_rank: Super Contributor
timestamp: September 07, 2025, 05:12:31 pm
content: Quote from: KungFuJosh on August 31, 2025, 05:14:09 pmThat is the test I would use. As pointed pointed out later, whether the continuity function latches or pulse stretches matters here if it is too fast.My meters are all old, and fast enough, as I suspect most meters are, but I know some meters have been way too slow in the past.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 07, 2025, 09:36:15 pm
content: Some guess...If you wan to test for connectivity to a big IC with (for example) 20 pins in a row and you "ratchet" a probe over that row in about 500ms (which is already quite slow, but very realistic), then reaction time must be below 25ms to detect continuity.The biggest limitation would be false positives because of decoupling capacitors. (Dave mentioned this in one of his Brymen video's) Decoupling capacitors will give short continuity blips when probed as the capacitor charges, and thus passes some current. Dave mentioned that Brymen made the reaction time slower to prevent these false detections, but I rather have some false positives and a faster response time myself. When you are reverse engineering a bigger circuit with a lot of connections, then the vast majority of the pins you're checking will be signals, and not Power / GND. Also, when you are probing Power / GND, you quickly enough learn to recognize the short blips from such capacitors.According to Dave, Brymen tuned the software to not give a false positive on a 100nF capacitor, but that seems silly to me, as there are usually tens to a 100 of these things parallel to each other.And overall, when you're beeping though a handful of wires, this is completely irrelevant (and people will comment on that). But if you're laying out the whole netlist of a circuit with the size and complexity of a commodore 64 (Just to give a complexity indication), then a reliable and fast beep is really essential.C64 has around 20 DIP 14/16 chips and 10 bigger IC's with 24 to 40 pins, and a bunch of passives and connectors.A rough estimate, that is: >>> 20*15 +10*30 + 200 = 800 pins. And for each of them, you have to check connectivity against the other 799. That is over half a million connections to beep though!But of course you can greatly reduce this by using brain power. RAM IC's will be mostly parallel to each other, and so do other places where the data or address bus is used. It's mostly the control signals combined with glue logic that needs a lot of beeping.Also, if you're really concerned about reducing false positives, then maybe using a low voltage (100mV) low impedance tester may be a good choice. You could also use a fast ADC and then analyze whether your probe has a "jump", or whether it's charging a capacitor.

author: tooki
author_rank: Super Contributor
timestamp: September 09, 2025, 06:20:55 pm
content: Quote from: BillyO on September 07, 2025, 02:40:59 pmThat model was originally latched; it depends on the firmware version. That's clearly the latched version, and thus not a valid counterargument.Not to mention that a "minimum length notification" is literally what latchingis.

author: BillyO
author_rank: Super Contributor
timestamp: September 09, 2025, 06:41:41 pm
content: Quote from: tooki on September 09, 2025, 06:20:55 pmIt's a Brymen BM786. It's not exhibiting the behavior you claim. So, now you move the goalposts.Your intellectual dishonesty is showing.Here is what is says in the manual:QuoteFurther, see the attached. A screen shot from the latest manual's specification on this. Where, precisely, does it say it is "unlatched"?QuoteCall it what you like and don't be childish. You are the one that incorrectly insisted it was not "latched" when clearly it effectively is.

author: IanJ
author_rank: Unknown
timestamp: September 10, 2025, 07:00:00 am
content: Measured by my wee DMM continuity tester. The BM786 is the only meter to beat my tester.The times measured are what reliably give repeatable tones without skipping etc.Example MARK Examples (minimum) at 250ms SPACE:- Brymen BM257 = 38ms- Fluke 85 III = 0.9ms- Fluke 87 = 0.9ms- Agilent 34405A = 25ms- Keysight 34461A - 1ms (needs Space = 300ms)- Agilent 34401A = 20ms, but will work lower but gives continious tone- Brymen BM786 = Better than 0.01ms- V&A VA38 = 0.1ms (beep varies in volume to point it's hardly audible though, obviously not using a fixed beep length)- Fluke 17B MAX = 30ms (courtesy of EEVBlog YT video)Here's my DMM Continuity Tester:https://www.ianjohnston.com/index.php/projects/124-project-062-dmmcontinuityIan

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2025, 07:55:07 am
content: Much prefer the way Joe Smith tests DMM continuity with an AWG.....Set AWG with a square wave start and increasing its frequency until DMM starts missing pulses.Set AWG for a Pulse @2Hz then start reducing its duty cycle to find the shortest pulse it will reliably detect.I followed his methodology for SDM3000 bench meter tests:https://www.eevblog.com/forum/testgear/siglent-new-bench-dmm-sdm3055/msg4840136/#msg4840136

author: nctnico
author_rank: Super Contributor
timestamp: September 10, 2025, 08:10:22 am
content: It is not only about detection speed but also cycle time. How long does it take for a DMM to be ready for the next measurement? When I measure continuity, I test A-A, A-B, B-B while moving only one probe at a time to make sure the probe tips make contact. So 3 measurements done quickly. And I want instant feedback about what I'm doing. A slow DMM might start giving a beep when I lift the probe which is utterly confusing to use.

author: Aldo22
author_rank: Super Contributor
timestamp: September 10, 2025, 08:57:08 am
content: Quote from: nctnico on September 10, 2025, 08:10:22 amExactly, I said that earlier, and I'm trying to compare the DMMs as objectively as possible with the SG.But not everyone seems to agree with that.https://www.eevblog.com/forum/testgear/looking-for-best-continuity-multimeter-under-500-usd-handled-or-bench/msg5990083/#msg5990083

author: tooki
author_rank: Super Contributor
timestamp: September 10, 2025, 09:02:50 pm
content: Quote from: BillyO on September 09, 2025, 06:41:41 pmHonestly, I think you owe me an apology. Not only is your tone entirely uncalled for (I was not even the slightest bit rude to you), but I also suspect that you severely misread my reply, because I did not say the things you claim I said!Anyway, this isn’t “moving the goalpost” or being intellectually dishonest, it’s literally a point that could not be more salient. I never said a latched meter can’t be fast, and the Brymen in the video shows that.Quote from: BillyO on September 09, 2025, 06:41:41 pmYou highlighting “continuous” doesn’t mean anything, because every continuity tester beeps continuously when it’s got uninterrupted continuity.However, the manual makes absolutely clear that it’s unlatched in newer firmware. It says, on page 17:QuoteScreenshot attached so there’s no question as to the veracity of the quoted text.I do not know whether the listed specs were changed along with that firmware change. But at the time that I wrote “The manual for it says “Response time: <100μs”. (So a factor of 10 faster.) But it also says it’s unlatched, which means you can’t really compare them” (which, I remind you, I wrote before you posted the video), I did not know that the old latching firmware wasalsosub-100μs. But my statement is valid for the BM786 you can buytoday.Dave has, so far, made TWO videos about the BM786’s changed continuity test. So I’m not making it up. If you watch the latest one of those,https://youtu.be/9lC-k5yU9W4?si=EF_UpgEfiM8DDpHpyou can plainly see and hear that the version in the video you shared is the latching version, because the unlatched versions are VERY different.Quote from: BillyO on September 09, 2025, 06:41:41 pmWTF? You made up a term that literally just describes what a latching continuity function is and tried to act as though it’s somehow different. It’s not. Me pointing that out is not being childish.Quote from: BillyO on September 09, 2025, 06:41:41 pmHuh? I very clearly said the one shown was the latched version! It was YOU who said “It may not be latched, but it certainly has a minimum length notification.”My exact words:Quote from: tooki on September 09, 2025, 06:20:55 pmI said is that that MODEL has switched from latched to unlatched, which is absolutely true, and Dave has provided the proof in videos.Now, as shown in the video of the latched BM786 you shared, those do seem to have exceptionally fast, latched continuity.What I was trying to get at, about it being not valid is that because that model changed, you can’t get that anymore, so what you now have available is the unlatched version which is no better than any other unlatched continuity tester. Every unlatched tester is fast, but also doesn’t help you hear very short transients.I’m sorry if I wasn’t more clear on that point. But in no way did my responses warrant the rabid hostility you have exhibited!!

author: floobydust
author_rank: Super Contributor
timestamp: September 11, 2025, 01:59:32 am
content: Hard to discuss anything given the amount of berating happening latelyContinuity function is composed of two monostables and an astable, as I know it. Is that how it still is, as we reinvent the wheel? I dislike the term "latching", there is no latch FFS.It seems to be the debouncer that people circle jerk about.My go-to multimeter for chasing down bad connections or PCB tracing uses this circuit, a CD4030 and CD4069 for the piezo. The CD4030 is a weird beast and I notice some glitches trying a CD4070 on the breadboard.Those skilled in the art might notice the voodoo. The trigger is from the LCD Continuity icon XOR'd with the backplane.About an 80usec response time and 70msec duration beep at over 4kHz. From 1980, 45 years ago lol. The wheel is still round.It just works really good, with in-circuit capacitors and semiconductors, bad connections, and quick enough to zip a few dozen IC pins in a sweep.No MCU, no firmware, no interrupts/polling or sloppy comparator thresholds.But there are many other important specs to a decent continuity function - but off topic.