Multimeter with continuity test buzzer that responds immediately ?

[SolderSucker]

In the interests of science and curiosity I took the back off mine and grabbed a photo - looks like I have the inferior 'blob' (COB) version - should I try for a refund and seek out the 'better' model?

BTW, as it can't be made out in the photo, the 8 pin chip at U3 has the following markings:

T24C02A
19m0F3

Board photo below (note: there's no components on the other side, I removed it and checked).

[HKJ]

In the interests of science and curiosity I took the back off mine and grabbed a photo - looks like I have the inferior 'blob' (COB) version - should I try for a refund and seek out the 'better' model?

It looks fairly decent at a quick glance. It has 3 MOVs, and two PTCs, the fuses are ceramic, but the 10A probably too small for CAT III 600V.

[exe]

I didn't read the whole thread, but I want to comment . If continuity testing is all you need, then I recommend and aneng 8002 or 8008. They are, in my opinion, instant.

[schmitt trigger]

Warning, Warning! Addiction Alert!

If you want to become a true, red-blooded EEVBlog member, you will require to own *at least* two meters. 

Some members here have a dozen in their collection, and expensive ones to boot!
In addition to pedestrian instruments like  400 Mhz oscilloscopes, and vector network analyzers. 

You have been warned.

[AVGresponding]

In the interests of science and curiosity I took the back off mine and grabbed a photo - looks like I have the inferior 'blob' (COB) version - should I try for a refund and seek out the 'better' model?

It looks fairly decent at a quick glance. It has 3 MOVs, and two PTCs, the fuses are ceramic, but the 10A probably too small for CAT III 600V.

Yes, it's a BS1362 type, and I can't see how that can exceed CAT I, as the maths implies a required breaking capacity of 333A @ 600VAC for CAT II and 3kA @ 600VAC for CAT III.
A brief outline of CAT ratings as they apply to multimeters
Datasheet of the fuse in question

Mine doesn't have a BoB, seems to be rev 4 with the OP's being rev 5, but looks the same re the input protection:

[rsjsouza]

I reviewed this meter a while ago (attached photo) and it did not have the blob, although the input protection looked fairly similar and the 10A fuse, although looking like a BS1362, it was instead rated for 600V.

I don't see a problem with the blob per se and, if nothing else changed, it should still be a good meter. This is very different than the shameful case of the UT61E model mentioned before, where the revisions werw quite different in the input protection.

[exe]

it was instead rated for 600V.

Wow, are we discussing continuity testing of high-energy circuits? 

I have three types of DMMs in my drawer: cheap and fast anengs for 95% of work, K2000 when I need precision, and 121GW lidl multimeter for mains.

[indman]

From my practice, Chinese multimeters with a blob processor deteriorate much more often. The blob is much more sensitive to PCB deformations, shocks and overloads. I also see that placing all the parts on the same side of the board does not increase the reliability of the entire circuit. I would like to see the reverse side of the new board to see how well the mode selector tracks are routed. This is just my opinion, you may not agree with him.

[AVGresponding]

I reviewed this meter a while ago (attached photo) and it did not have the blob, although the input protection looked fairly similar and the 10A fuse, although looking like a BS1362, it was instead rated for 600V.

I don't see a problem with the blob per se and, if nothing else changed, it should still be a good meter. This is very different than the shameful case of the UT61E model mentioned before, where the revisions werw quite different in the input protection.

It is a BS1362 type. If you look at the datasheet, which is for the actual fuse that came fitted in mine, it's rated for a 200A breaking capacity @ 600VAC, and 10kA @ 250VAC.

I personally wouldn't use it on anything other than SELV stuff, I have Flukes for serious work. It's perfectly adequate as an electronics hobbyists meter.

[Gyro]

it was instead rated for 600V.

Wow, are we discussing continuity testing of high-energy circuits? 

Just what I was thinking. This doesn't seem to be part of the OP's requirement.

I don't know why people don't just build simple continuity testers. For example, the attached one (from EPE - Everyday Practical Electronics back in 1989) has a threshold of around 1R for continuity, 1M for isolation. I built one based on this circuit back then and it still works well to this day, as far as can be perceived, its response is instantaneous. Probe voltage is around 200mV, with reasonable input protection - not mains (although if safely constructed, it would probably smoke rather than exploding - especially if fusible resistors were used). I've always remembered this article as an example clarity - an ideal project for beginners that's actually useful.

I tweaked the audio circuit to two tones - continuity and isolation, and to start ticking quietly after about 30 seconds idle time as a battery saving reminder. It lives on the shelf above my bench to this day, I always use it in preference to a DMM if I'm trace out a board due to the resolution and instantaneous response. Of course, the range of available low current opamps is much wider these days - I can't remember what I used, not an LM308, probably something I had to hand.


Edit: The only time I've had it apart in the last 30 years was to add a front panel label and switch the input jacks to shrouded ones so that it could accept modern test leads.

[SolderSucker]

it was instead rated for 600V.

Wow, are we discussing continuity testing of high-energy circuits? 

Just what I was thinking. This doesn't seem to be part of the OP's requirement.

I don't know why people don't just build simple continuity testers.

OP here - in my case I was looking to replace my increasingly erratic Extech EX330 - I needed a relatively cheap and relatively basic meter that must have a fast continuity test. I only test boards running at 5 volts DC or lower (well, okay, also +12 volts DC for old sound circuits, -5 VDC too). That's pretty much it.

[bd139]

It’s fine then.

Incidentally I repaired my washing machine and rewired my house with a very dodgy UT61E.

[AVGresponding]

It’s fine then.

Incidentally I repaired my washing machine and rewired my house with a very dodgy UT61E.

Impressive you got so much wire out of it. Personally I'd have used 2.5mm² LSF T+E.   

[Fungus]

BTW, as it can't be made out in the photo, the 8 pin chip at U3 has the following markings:

T24C02A
19m0F3

Any 8-pin chip inside a multimeter is probably an EEPROM that stores the calibration data.

(unless it's a Hioki)

[bd139]

It’s fine then.

Incidentally I repaired my washing machine and rewired my house with a very dodgy UT61E.

Impressive you got so much wire out of it. Personally I'd have used 2.5mm² LSF T+E.   

 

To be fair the wire in the washing machine was better than 1950s stuff in the walls 

[rsjsouza]

it was instead rated for 600V.

Wow, are we discussing continuity testing of high-energy circuits? 

Just what I was thinking. This doesn't seem to be part of the OP's requirement.

I didn't start it. My message was intended to clear a question about the front end of the revised UT139C, nothing less.

It is a BS1362 type. If you look at the datasheet, which is for the actual fuse that came fitted in mine, it's rated for a 200A breaking capacity @ 600VAC, and 10kA @ 250VAC.

Thanks. I thought the BS1362 types were only 250V rated.

[AVGresponding]

Thanks. I thought the BS1362 types were only 250V rated.

Full specifications are only available from the BSI or third party agents for not inconsiderable sums of money.

Since it's not something that directly concerns my work, I can't get my employer to pay the £170 or so that it costs, unlike with other things to do with fire alarm regs, emergency lighting regs, general wiring regs, building regs etc.

Lacking the intention to part with said cash, I'm forced to speculate; either the 600VAC rating is part of the BS1362 (1973) spec, perhaps pertaining to possible phase-phase faults, or it's simply the manufacturer (Bussman in this case) has had them additionally certified so they can be used in other applications, such as marginal Chinesium DMMs...

[AlexTee]

Could you please watch this video and tell me if this a not an unusual behavior for a cheapo DMMs like UT161D (the certified version of UT61D+) to momentary interrupt beeping in continuity test? As I understand, it is quite slow at determining resistance, which causes beep interruption until the reading drops low enough to engage back the beeping to indicate a short circuit. My concern is that it stops me from reliably judging about circuit condition, because this brief interruption would make me think the PCB has bad contact. Each time I have to guess whether it was PCB or meter.
Would you keep such DMM or better get rid of it and invest in more reliable product?

https://youtu.be/0HC-WeQ5inA

[Fungus]

Could you please watch this video and tell me if this a not an unusual behavior for a cheapo DMMs like UT161D (the certified version of UT61D+) to momentary interrupt beeping in continuity test?

No it isn't. Lots of meters do it. It can be dirt on the probes, on the DUT, whatever...

his brief interruption would make me think the PCB has bad contact

Some meters latch the signal and make it sound continuous. I'm sure the owners are happy but which version is the truth?

[AlexTee]

Could you please watch this video and tell me if this a not an unusual behavior for a cheapo DMMs like UT161D (the certified version of UT61D+) to momentary interrupt beeping in continuity test?

No it isn't. Lots of meters do it. It can be dirt on the probes, on the DUT, whatever...

his brief interruption would make me think the PCB has bad contact

Some meters latch the signal and make it sound continuous. I'm sure the owners are happy but which version is the truth?

There is no dirt on probes, they are brand new, deliberately cleaned gold plated ones. If there was a dirt, it won't latch the sound immediately. Hm, I thought it is obvious from the video, that the problem is not with probes at all, but with slow measurement of resistance, which kicks in shortly after intial latching. And when it starts measuring, for some reason it starts off by jumping to higher reading, which causes sound interruption, then dropping down to 0.

And when you state, that a lot of meters do that, hm, at least other 2 meters I own never interrupt beeping unless probes are released.

[Fungus]

I watched the video. Yeah, that meter is weird.

[AlexTee]

I watched the video. Yeah, that meter is weird.

Yeah, that's what I mean. While being a minor issue it still annoys me. Imagine you're testing a complex PCB path, each time the sounds breaks, it triggers you into false assumption there might be something wrong with the PCB itself. I doubt I can get used to it. Probably will keep this one as a backup and invest in a more reliable product.

[rsjsouza]

Not only the break is bad, but its latch is terribly long - I can see you release the probes and the meter still beeping for 1/3 to 1/2 second.

I would definitely consider returning the meter - since there are no other tests around for either the UT161D or the UT61D+, it is impossible to know if this is intrinsic to this version of the meter or a defect on your unit.

[AlexTee]

Not only the break is bad, but its latch is terribly long - I can see you release the probes and the meter still beeping for 1/3 to 1/2 second.

Well, this is a bit tricky. If I release the probes just before the resistance measurement procedure kicks in, the beeping stops almost immediately (but very tiny delay's still present).

So, probably, there are two internal software routines invoking one after the other: the first one is executed whenever a short circuit is detected (via a hardware interrupt trigger implemented using external pull up on some I/O port), and then it jumps to the other routine, which executes much slower compared to the first routine. The cycle starts over whenever the second routine is exited (when reading returns to OL) with the first fast-responding routine ready to kick in next time a short circuit is re-detected. The manual states that the buzzer should come on if the tested circuit resistance is <50 Om, so I probed a 15 om resistor, but the meter didn't invoke the first routine, and proceeded with the second one, causing a significant delay. The user manual doesn't state the response time, and now I can see why. They just circumvented the hardware limitations by introducing two-stage continuity test and we as users of this gimmick should consider it as a feature, not a bug. Please, avoid this meter at any cost. I'm lucky I paid only 40 USD for this BS.

Here is the new self-explanatory video: https://youtu.be/Daagvz40it0

I wonder how more expensive DMMs from top brands behave when there's a small resistance in place. Do they still respond fast enough? Please, test on your meters, this is an interesting topic to discuss.

[rsjsouza]

I wonder how more expensive DMMs from top brands behave when there's a small resistance in place. Do they still respond fast enough? Please, test on your meters, this is an interesting topic to discuss.

It is not uncommon to see meters being able to have a working continuity mode with values larger than 0Ω and I can tell the ones I have from Keysight, Fluke, Brymen, etc have a hardware-implemented latch to indicate these values in the buzzer and, in some models, in an LED as well. So, the UT161D resembles the AN870/RM219 and the UT61E, where at 0Ω (or very near) the response is absolutely instantaneous but for values above a few Ω, you can clearly notice the buzzer is slower and, in the case of the AN870/RM219, it also lingers a bit after the probe release (the UT61E releases the buzzer immediately). However, both the UT61E and the AN870/RM219 do not have the stupid double beep.

However, brand name and price are not the only factors for a decent implementation or not. The Fluke 101 and the Amprobe AM530  are top tier brands but are very slow, while the Richmeters RM113D is quite fast (including a LED anunciator). So, your best bet is to look around for tests on the internet and see what it suits you.