Fast continuity mode on DMM : Can be explained  - Page 1
Forum section: electronics / general

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: September 10, 2011, 02:13:21 am
content: I have the impression that some people have a small difficulty to translate correctly what they watch in all those videos in relation with the continuity speed found on some DMM units.I think that I have to clarify few factors, so this myth to have an end.Yes it is a myth.Why?Some years back the continuity mode or function was a dedicated tool.If you had move the range switch to the continuity mode, the DMM behaved with the maximum speed as response, and the beep sound was instant.Later on, some manufacturers they started to mix the continuity mode with the resistance measurement mode.This move started to cause some hysteresis in the performance (speed) of the continuity mode, because the DMM had to measure first the resistance and Beep if the resistance is low as 0-100 ohms, so low resistance belongs to the sphere of what we describe as sort connection.The continuity mode also got married with the Diode testing mode,and because of that, it also become slow in the area or responsiveness.Let’s make a first synopsis:1) True continuity mode = 100% fast or Zero delay2) Continuity + Ohms mode = 95% fast or 5% delay3) Continuity + Diode mode = 70% fast or 30% delayThe above synopsis is what happens with the Fluke 87V and 28II.But what really maters are that none of that Fluke DMM has a true continuity mode.Any multimeter that has a dedicated continuity mode, can easily take the victory in this case, because it will be 100% fast.How we can tell if the continuity mode are:1) Single?2) Mixed with Ohms mode?3) Mixed with Diode mode?The answer is really simple, there is symbols next to the range switch!!What Dave admires in all those reviews?He admires the faster behavior of the continuity in the mixed modes.It is known that they are slow, and so the faster device wins the credit.Still even me that I love him, I have to scream at him and protest,Because he never explained in depth in those reviews, the essence of the continuity mode. LOLLast round:The technical part of what causes the hysteresis,It is known.One DMM could had slow CPU and it needs more time to calculate and respond,and usually the one with the slow CPU, it would also had a slow beeper circuitry.More responsible than anything today is the CPU, and I would describe all those latest DMM, as computers dressed as multimeters.Currently those Fluke 87V and 28II are the true winners in the mixed Continuity + Ohms mode, even the latest Agilent U1272A it looks to be slower but equally fast at both modes.a) Continuity + Ohms mode = 90% fast or 10% delayb) Continuity + Diode mode = 90% fast or 10% delayWe say goodbye at the 300$+ rangeand we get down to the 100$ one.The faster DMM at the 100$ shootout was had a dedicated True continuity mode,But the reviewer forgot to point out this detail. !!There is no chance one 100$ DMM to have fast continuity mixed mode, this is simply impossible.But it could have a single super fast continuity mode, but this is a mater of choice.Its up to you, to select the one that does well what you have as primary need in your head.It’s pointless to nag about the continuity response, if you had selected the DMM mostly because of the low price factor.

author: Lightages
author_rank: Unknown
timestamp: September 10, 2011, 04:46:09 am
content: UniTrend UT10A slight delay, 30ms?, not latched, mode soft selected using mode button: $12.70 USDUniTrend UT33C instant, not latched, continuity mode shared with diode test: $16 USDUniTrend UT71E BIG delay, 1/2 second, latched, mode soft selected using mode button: $200 USDRadio Shack 22-807 instant, latched, mode soft selected using mode button: $30 USD in 1995?Hung Chang HC-3500T instant, latched, dedicated mode on dial: $80 USD in 1986Conclusion?Your theory is wrong. Price and type of selection for continuity mode has no direct relation to the reliability and speed of the continuity response time.Conclusion 2?Unitrend has wild variability in the performance of their designs that are not related at all to their price. My best meter from them for this specific criteria was on the low end of their price scale AND shared diode test with continuity.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 10, 2011, 05:59:54 am
content: i dont care! and i dont care latched or not latched. when i want to continuity test, i'll simply grab my $10 DMM that can do instant beep upon short instead of my latched $100 DMM! i dont care, i'm willing to buy the $10 DMM even 100 unit if all i care is continuity test! dont mention to me the Fluke, i wont give a sh*t if its continuity test, no matter how charming the latched sound is.

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2011, 07:57:54 am
content: I don't see how it's impossible for a cheap multimeter to do a fast mixed mode continuity test. All that's required is a separate comparator (the cheap LM393 will do) to switch the piezo on/off. It shouldn't matter how long it takes for the display to update, the continuity function can easilly designed to be instantaneous.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 10, 2011, 08:39:05 am
content: Quote from: Hero999 on September 10, 2011, 07:57:54 ambut most manufacturers opt not to.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: September 10, 2011, 02:23:20 pm
content: Quote from: Lightages on September 10, 2011, 04:46:09 amThere is no any theory of my on the table, I had offered to you and to all, for free, an valuable information.No one needs to pay 800$ for getting those instruments and find out how they stand about the continuity response.Quote from: Lightages on September 10, 2011, 04:46:09 amThe true problem in such comparisons, is that we do not have a way to actually accurately measure,the delay in mS.If we had .... I would add another two questions.a) how fast is the first activation of the continuity mode.b) how fast it is with a repeatable rate.

author: SgtRock
author_rank: Unknown
timestamp: September 11, 2011, 05:42:02 am
content: Dear Kiriakos:--I use the DJ method to measure the response time of beepers. I just click the probes together and try to play "Waltzing Matilda" in double four time, also known as Swing Trot, and used for really fast dance numbers. Best RegardsClear Ether

author: vk6zgo
author_rank: Super Contributor
timestamp: September 11, 2011, 06:39:14 am
content: I can use the continuity function,which is also the diode test,on my Fluke77 as a Morse code practice oscillator,so it is pretty fast.I hardly ever use it for continuity. I was brought up on analog VOMs,so I look at the display on Ohms,which is very fast,considerably faster than the Uni-T meters I have tried.Another reason for using the Ohms range is that the beeper may not show up a high resistance joint of around 50-100 Ohms,where the resistance reading will.VK6ZGO

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: September 11, 2011, 07:53:41 am
content: Quote from: SgtRock on September 11, 2011, 05:42:02 amI am like a corpse right now, did not sleep all night working on my B&O TV set,I did manage to fix every little issue, but because of my victory, my adrenaline fall to the lowest levels,due the fact that I finally I feel relaxed and winner, and I was ready to crash my head on the keyboard, due the lack of sleep....And then ...... I read your message ... and visited even the youtube so to find the Matilda song...And by hearing it I am laughing for five minutes now...I think that I will start training my self with the Jingle Bells , before I got to anything faster ...LOL