Author Topic: Multimeters that do not appear to meet their safety specs. (updated frequently)  (Read 155825 times)

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Offline Macbeth

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Pah. You kids with all your silly CAT3 600V/1000V etc multimeters. Back in the day we would use AVO 8 analogue multimeters, 20k ohm per volt. MASSIVE calibrated scale with mirror strip for parallax, absolutely no worries measuring mains or even three-phase. 2,500v AC/DC readings not a problem. Tested to 5kV. No silly fuses - a sprung cut-out button was all that was needed.

My current AVO is a 1970's "Test Set No.1" which was a military spec and measures 3,000v AC/DC (and all other ranges are in the 30's instead of 25's). It can even read 30uA.

Obscure Ever Ready cardboard box batteries only needed for the resistance ranges.

We also worked on TV's and Radios that were all totally live chassis - no isolation at all. The highly (in)efficient voltages were all generated using a massive wirewound "dropper" resistor with taps for all the HV, LV, and finally the valve heater circuits. It was an electric bar fire in the telly. Yes, the metal chassis was directly connected often enough to 240V Live. More modern sets like the Philips G8 chassis (with the fantastic Nixie tube channel indicator) actually used high tech SCR chopper mode power supplies instead of the bar-fire dropper. Of course, no isolation, it was all live. Quite scary.

Somehow I survived to tell this tale. You know what? I'm perfectly happy with my shitty cheap VC99.  :scared: But for HV stuff I think I will just dust down that ancient Bakelite AVO 8 (Test Set No. 1).

ETA: A link for anyone interested in good old school stuff. http://www.richardsradios.co.uk/testsetno1.html
« Last Edit: November 29, 2013, 07:55:53 am by Macbeth »
 

Offline Macbeth

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This has been brought up before. The old equipment had several advantages. One of them was that components were much larger and so were clearances. Mechanical build quality was also orders of magnitude better. Another advantage is that you would generally set them down while measuring, as opposed to a hand held DMM that you hold in your hand. So even if the AVO meter explodes, it's much less likely to injure you. It won't comply to the latest safety regs, but I'd rather trust my life to an AVO 8 which was the best they could make at that time than a cheap and nasty VC99 from whatever brand.
Oh, I agree. Except the VC99 is too darn big to be holding in your hand anyway!. Come to think of it, I have never measured anything with a meter in my hand (even my shirt pocket sized super tiny autoranging DMM). I need my hands on the probes - the meter stays on the bench or wherever I can prop it up. Only clamp meters would be used in hand. But I don't do that sort of thing.

But I have to say, I also would trust a massive 2-3kg AVO with bakelite case than any meter when playing with HT voltages! That is over any CAT III meter whether its Fluke or Chinese crap! That is what I implied in my previous post.

Also, I think everyone should have an old fashioned 20k/volt analogue meter as well as an old fashioned 10-20MHz analogue scope. Why? Because they cost next to nothing and will end up in landfill otherwise - and you can learn so much more!
 

Offline oldway

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These ancient AVO are not as safe as you say:
- same input terminals for voltages and currents: this is wrong and dangerous.
- cut-out protection is very slow (actuated by pointer) and is not able to interrupt high energy and high voltage dc current.
I repaired several badly damaged AVO 7 and 8. Not so safe at all.

If you want to measure HV 5KV or more (in low energy circuits only !), it's a lot more safe to use a good quality HV probe.

If you are a Electrical field engineer working with 600V high energy busbars or a Power electronics engineer (as i am), working with DC drives Edo 500V 5000A, you will not use a cheapy 5 bucks multimeter...only high quality multimeters as Fluke, Agilent, Gossens...
« Last Edit: November 29, 2013, 08:44:08 pm by oldway »
 

Offline Lightages

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The Brymen 820 series do not appear to meet their rating either.

You are correct and as orjan- has posted it appears that only the top models of the New Brymens actually meet their true CAT ratings according to the latest CAT requirements. As has also been stated it certainly appears that the only difference is the quality of the fuse fitted. The circuit boards are shared amongst these different models.
 

Offline Lightages

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This discussion of old well built analog meters is interesting, but moot. They were designed for the times and with the knowledge and materials available at the time. They were also NOT CAT rated so they really have no place in this thread. I hope we can keep this discussion to modern available meters so as to help people select the right meter for their use.

If someone wants to start a thread discussing analog meters specifically I will be happy to add a link to the main post to the thread. I am sure there are people who like to consider an analog meter and would benefit from opinions aimed at that topic and older meters in general.
 

Offline calexanian

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There is something nice about a good VOM. Kinda like listening to a record warm fuzzy feeling kind of thing. It's part tool part artistic statement or something.

Hands Off My Digital Fluke!!! Hahahahaha
Charles Alexanian
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Offline TheBay

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I have never seen a G8 with a Nixie tube!, would love to see one.

I have worked on loads of Live chassis TV's back in the day, you could get a belt off the aerial socket on some sets if leaning against an earthed VCR lol! And idiots that put external speakers or headphone sockets on them  |O

Pah. You kids with all your silly CAT3 600V/1000V etc multimeters. Back in the day we would use AVO 8 analogue multimeters, 20k ohm per volt. MASSIVE calibrated scale with mirror strip for parallax, absolutely no worries measuring mains or even three-phase. 2,500v AC/DC readings not a problem. Tested to 5kV. No silly fuses - a sprung cut-out button was all that was needed.

My current AVO is a 1970's "Test Set No.1" which was a military spec and measures 3,000v AC/DC (and all other ranges are in the 30's instead of 25's). It can even read 30uA.

Obscure Ever Ready cardboard box batteries only needed for the resistance ranges.

We also worked on TV's and Radios that were all totally live chassis - no isolation at all. The highly (in)efficient voltages were all generated using a massive wirewound "dropper" resistor with taps for all the HV, LV, and finally the valve heater circuits. It was an electric bar fire in the telly. Yes, the metal chassis was directly connected often enough to 240V Live. More modern sets like the Philips G8 chassis (with the fantastic Nixie tube channel indicator) actually used high tech SCR chopper mode power supplies instead of the bar-fire dropper. Of course, no isolation, it was all live. Quite scary.

Somehow I survived to tell this tale. You know what? I'm perfectly happy with my shitty cheap VC99.  :scared: But for HV stuff I think I will just dust down that ancient Bakelite AVO 8 (Test Set No. 1).

ETA: A link for anyone interested in good old school stuff. http://www.richardsradios.co.uk/testsetno1.html
 

Offline Macbeth

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I have never seen a G8 with a Nixie tube!, would love to see one.

I have worked on loads of Live chassis TV's back in the day, you could get a belt off the aerial socket on some sets if leaning against an earthed VCR lol! And idiots that put external speakers or headphone sockets on them  |O

IIRC the telly was one of the posher ones, and even had an ultrasound remote control. It had 6 channel buttons 3x2 (more than enough for future expansion! lol!) and a single Nixie that I guess only went up to number 6. Philips or Pye? So long ago... But yes, I only ever saw one of them.

ETA: Those ultrasound remotes never did catch on, what with them sending the family mutt insane, and the TV picking up sounds like dropping dishes to change channels.  :-DD
« Last Edit: December 22, 2013, 08:59:16 am by Macbeth »
 

Offline Lightages

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Please I ask again: Keep this thread on the topic. This is to be a resource for people to refer to and not have to go through completely irrelevant posts.
 

Offline philpem

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Phil / M0OFX -- Electronics/Software Engineer
"Why do I have a room full of test gear? Why, it saves on the heating bill!"
 

Offline Lightages

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Thanks for the information Philpem. I already did put a general warning against these pieces of junk in an entry, "Any Meter with the model number "830"". There are people here on the forum that like them  :-//
 

Offline don.r

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Shippers: for the love of Pete and all that is holy, STOP USING UPS INTERNATIONAL!
 

Offline AlienRelics

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No need to even mention Cen-Tech, then?  :-DD
 

Offline torr032

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DT830B - risk of electric shock due to insulation defects / risk of flashover, not compliant with EN61010 / LVD:
http://unsafeproducts.eu/2013/09/13/digital-multimeter-dt830b-digital-multimeter/
http://unsafeproducts.eu/2013/11/08/multimeter-%CF%88%CE%B7%CF%86%CE%B9%CE%B1%CE%BA%CE%BF-%CF%80%CE%BF%CE%BB%CF%85%CE%BC%CE%B5%CF%84%CF%81%CE%BF-digital-multimeter/

I saw these multimeters in Germany, in December 2013. In Toom Baumarkt stores, probably the Germany biggest stores for selling tools.
 

Offline calexanian

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That is the Cen-Tech harbor freight meter. We break those apart and use them as panel meters in temporary setups, then throw them away! The harbor freight down the street sells hem for 2.99 every now and then.   :-DD
Charles Alexanian
Alex-Tronix Control Systems
 

Offline rexxar

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I just bought a Uni-T UT203 clamp meter, and the input protection is... well, there isn't any. It's supposedly CAT2/3, but the only protection is a PTC. There's not even a fuse, so if something goes short while you're measuring mains voltage, you're going to have a very nice explosion.  :-BROKE Blast protection is okay, there's rather deep walls, but I still wouldn't trust it. Additionally, there's no sort of isolation cutouts around the inputs, and a trace taps off the input and goes straight to the selector switch. I can see that arcing if you put a KV or two on it. (They also used a red wire to attach the common terminal?  :o)

Unfortunately, I'm stuck with it; being an unemployed college student, it's all I could afford, at around $40 on Amazon.  |O
 

Offline Lightages

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Actually the lack of fuses does not indicate that anything is wrong with the UT203. It is a clamp meter and fuses are only used for current functions. It might actually pass a full test according to its CAT rating but I doubt it.
 

Offline PedroDaGr8

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I just bought a Uni-T UT203 clamp meter, and the input protection is... well, there isn't any. It's supposedly CAT2/3, but the only protection is a PTC. There's not even a fuse, so if something goes short while you're measuring mains voltage, you're going to have a very nice explosion.  :-BROKE Blast protection is okay, there's rather deep walls, but I still wouldn't trust it. Additionally, there's no sort of isolation cutouts around the inputs, and a trace taps off the input and goes straight to the selector switch. I can see that arcing if you put a KV or two on it. (They also used a red wire to attach the common terminal?  :o)

Unfortunately, I'm stuck with it; being an unemployed college student, it's all I could afford, at around $40 on Amazon.  |O

Actually, there's no need for a fuse. Basedhe input jacks do not measure current. This means the input impedance on these jacks will always be in the megaohm range. Current surge will not be a problem. So the lack of a fuse is expected.

Based on the image I saw is rated CAT II 600C/ CAT III 300V. Based on the lack of current measurements on the input jacks and what I've seen of uni-t input protection this sounds a bit optimistic but far from unreasonable .

So in summary, it sounds like your meter DOES NOT belong on this list.

Sent from my EVO using Tapatalk

« Last Edit: January 19, 2014, 10:52:56 am by PedroDaGr8 »
The very existence of flamethrowers proves that some time, somewhere, someone said to themselves, "You know, I want to set those people over there on fire, but I'm just not close enough to get the job done." -George Carlin
 

Offline tzok

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DT830B - risk of electric shock due to insulation defects / risk of flashover, not compliant with EN61010 / LVD
These are VERY popular in Poland and are really cheap - you may buy them for less than 5€.
 

Offline sean0118

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Curiosity got the better of me while reading this thread, I took my cheap Digitech QM1523 apart. The 10 amps input is un-fused, but the "600V CAT II" input only has a glass 250V fuse. That's a bad thing right?

Terrible soldering as well, only two of the four fuse holder legs are soldered to the board. :(

« Last Edit: February 07, 2014, 09:59:10 pm by sean0118 »
 

Offline Lightages

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Yup that's pretty bad.  :palm: Not only is only fused for mA and uses the wrong fuse for the CAT rating, it looks horribly built. The other glaring issue is that whoever designed the circuit board just designed it as if it were a small signal board. No consideration for voltages creepage or clearance. On top of that, there appears to be no input protection at all. Keep this one for the car and low voltage electronics and keep it away from the wall socket! :scared:
 

Offline PedroDaGr8

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Yup that's pretty bad.  :palm: Not only is only fused for mA and uses the wrong fuse for the CAT rating, it looks horribly built. The other glaring issue is that whoever designed the circuit board just designed it as if it were a small signal board. No consideration for voltages creepage or clearance. On top of that, there appears to be no input protection at all. Keep this one for the car and low voltage electronics and keep it away from the wall socket! :scared:

This has to be one of the worst I have seen in a while! There is LITERALLY nothing between the 10A input and ground other than the CURRENT SHUNT!!!!!! :wtf: That thing is BEYOND unsafe!
The very existence of flamethrowers proves that some time, somewhere, someone said to themselves, "You know, I want to set those people over there on fire, but I'm just not close enough to get the job done." -George Carlin
 

Offline sean0118

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Thanks for your replies, I thought that might be the case. I have only ever used it for low voltage DC and now that's all it will ever be used for.

I found the manual and it does state that it has a 250V fuse, but then why mark it CAT II? I can't find the receipt, but these are still for sale at Jaycar. I know this is a global forum, but anyone know if there is an authority in Australia to report this to?

Also, it came with double insulated "CAT II" leads. Anyway to tell if these really are double insulated?  :scared:
 

Offline Wytnucls

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Yup that's pretty bad.  :palm: Not only is only fused for mA and uses the wrong fuse for the CAT rating, it looks horribly built. The other glaring issue is that whoever designed the circuit board just designed it as if it were a small signal board. No consideration for voltages creepage or clearance. On top of that, there appears to be no input protection at all. Keep this one for the car and low voltage electronics and keep it away from the wall socket! :scared:

This has to be one of the worst I have seen in a while! There is LITERALLY nothing between the 10A input and ground other than the CURRENT SHUNT!!!!!! :wtf: That thing is BEYOND unsafe!
Gossen made a meter without a fuse on the A range (MetraHit 23S). It had a CAT II 1000V rating.

Electrical Safety (23S only)
Protection Class II per EN 61010-1:2001
/VDE 0411-1:2002
Measuring Category II
Operating Voltage 1000 V
Pollution Degree 2
Test Voltage 5.2 kV~ per EN 61010-1:2001
/VDE 0411-1:2002

 

Offline PedroDaGr8

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Yup that's pretty bad.  :palm: Not only is only fused for mA and uses the wrong fuse for the CAT rating, it looks horribly built. The other glaring issue is that whoever designed the circuit board just designed it as if it were a small signal board. No consideration for voltages creepage or clearance. On top of that, there appears to be no input protection at all. Keep this one for the car and low voltage electronics and keep it away from the wall socket! :scared:

This has to be one of the worst I have seen in a while! There is LITERALLY nothing between the 10A input and ground other than the CURRENT SHUNT!!!!!! :wtf: That thing is BEYOND unsafe!
Gossen made a meter without a fuse on the A range (MetraHit 23S). It had a CAT II 1000V rating.

Electrical Safety (23S only)
Protection Class II per EN 61010-1:2001
/VDE 0411-1:2002
Measuring Category II
Operating Voltage 1000 V
Pollution Degree 2
Test Voltage 5.2 kV~ per EN 61010-1:2001
/VDE 0411-1:2002



How can you make that safe at 1kV? Maybe I'm just too much a noob but the though of 1kV across a 10mOhm shunt makes my hair stand on end.
The very existence of flamethrowers proves that some time, somewhere, someone said to themselves, "You know, I want to set those people over there on fire, but I'm just not close enough to get the job done." -George Carlin
 


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