DMM Lead Arc getting voltage from power strip

[edpalmer42]

Given that the jacks don’t do current measurement, then the most likely explanation is that you inadvertently shorted the probe tips. Either to each other, or across line and ground (since the neutral and ground are connected back at the panel).

That would be pretty difficult to do on a north american receptacle. The slots for live and neutral are very narrow, in fact the probes on most DMMs insert very snug into them, which doesn't allow for any side-to-side movement of the probes so there's no way you'd be able to short the probes to each other, at least not without bending them.

It is possible however on poorly made power strips if the probes are relatively long for the probe to poke past the back of the receptacle and through the insulation of a wire, or a grounded chassis, but this would be rather unusual as most DMM probes are not much longer than a standard plug end.

The lead tip is about 3/16th longer than the plug spade. I was having a hard time getting a reading in the power strip. I do remember that and it was not like doing it in a wall receptacle, so maybe I did ground it out. It's a very good explanation.

That happened to me many years ago with an old 3-way adapter.  I pushed the DMM probe in and shorted to either the neutral or ground.  Quite an impressive light show!

If your power bar is screwed together, pull it apart and inspect it.  If not, unplug it (!!) and then see if you can get continuity to neutral or ground by probing into the hot lead with the smallest insulated wire you've got.  If you do, that power bar is dangerous!  Cut the cable off and throw it away!

[ozcar]

That happened to me many years ago with an old 3-way adapter.  I pushed the DMM probe in and shorted to either the neutral or ground.  Quite an impressive light show!

If your power bar is screwed together, pull it apart and inspect it.  If not, unplug it (!!) and then see if you can get continuity to neutral or ground by probing into the hot lead with the smallest insulated wire you've got.  If you do, that power bar is dangerous!  Cut the cable off and throw it away!

I’ll admit to doing that once too, also on a triple adapter – so long ago that power strips/boards/bars had not been invented (at least, I had never seen such a thing). It only took one probe to do it.

Perhaps two “melt points” might be visible on the probe?

Or, as suggested, if the power strip can be opened up, see if there is any way that the probe could have come in contact with two of the conductors, and look for “melt points” there too.

[DW1961]

Given that the jacks don’t do current measurement, then the most likely explanation is that you inadvertently shorted the probe tips. Either to each other, or across line and ground (since the neutral and ground are connected back at the panel).

That would be pretty difficult to do on a north american receptacle. The slots for live and neutral are very narrow, in fact the probes on most DMMs insert very snug into them, which doesn't allow for any side-to-side movement of the probes so there's no way you'd be able to short the probes to each other, at least not without bending them.

It is possible however on poorly made power strips if the probes are relatively long for the probe to poke past the back of the receptacle and through the insulation of a wire, or a grounded chassis, but this would be rather unusual as most DMM probes are not much longer than a standard plug end.

The lead tip is about 3/16th longer than the plug spade. I was having a hard time getting a reading in the power strip. I do remember that and it was not like doing it in a wall receptacle, so maybe I did ground it out. It's a very good explanation.

That happened to me many years ago with an old 3-way adapter.  I pushed the DMM probe in and shorted to either the neutral or ground.  Quite an impressive light show!

If your power bar is screwed together, pull it apart and inspect it.  If not, unplug it (!!) and then see if you can get continuity to neutral or ground by probing into the hot lead with the smallest insulated wire you've got.  If you do, that power bar is dangerous!  Cut the cable off and throw it away!

Excuse my language but FUCK ME. I got continuity. I'm sure that's what must have happened. I had to search a little, but I got it.

[Gyro]

Excuse my language but FUCK ME. I got continuity. I'm sure that's what must have happened. I had to search a little, but I got it.

Well it appears that I owe RockSeed an apology (well apart from the fuse [Edit: crap stuff] anyway).

Time to get the cable cutters! 

[DW1961]

Excuse my language but FUCK ME. I got continuity. I'm sure that's what must have happened. I had to search a little, but I got it.

Well it appears that I owe RockSeed an apology (well apart from the fuse crap anyway).

Time to get the cable cutters! 

Yeah I'm not such in a hurry to dismiss what the guy said about the fuses either. Remember we have a language gap too. I'll ask him for a schematic, if he has one. The unit seems to do exactly what they say and it doesn't in ANYWAY feel cheap, or light, or anything like that. The dial is positive and clicks firmly in place, the read out is clear, the backlight works well, and the measurements for voltage and current were right on according to my math calculations and comparing it to my other DMM. I know it can do all of those things and still be spooky, too. I'll see if there is a way to tear it down without destroying it. I asked if the fuses are replaceable.

I did see another DMM with only two leads and it said it could do everything with only two leads, no current lead. That is spooky, but I'd want to understand it before blowing it off.

Yeah that power strip. Man. "Get the cable cutters."

Done.

[DW1961]

Just got a reply back from RockSeed about replacing the fuses.:

Q: Are the fuses replaceable?

"Yes, just buy a universal voltage current fuse but pay attention to the size of the fuse"

He also said make sure the dial is correct for volts amps and AC DC, and I suppose that is because somehow they are doing everything with two leads, instead of splitting it into an dedicated amp plug.

[Gyro]

Well if there are any fuses, then he should be advising HRC meter fuses, not 'just universal' ones. I'm still not clear if there are any current ranges on the probes, or just on the clamp. Only the instructions will tell you.

I think you are duty bound to go searching for them now! [Edit: if he says they are replaceable, then they ought to be easy to locate] 

I think what he is doing is just giving generic multimeter feedback rather than anything specific to this particular product (still worrying advice on the arbitrary fuse choice though).

[tooki]

Given that the jacks don’t do current measurement, then the most likely explanation is that you inadvertently shorted the probe tips. Either to each other, or across line and ground (since the neutral and ground are connected back at the panel).

That would be pretty difficult to do on a north american receptacle. The slots for live and neutral are very narrow, in fact the probes on most DMMs insert very snug into them, which doesn't allow for any side-to-side movement of the probes so there's no way you'd be able to short the probes to each other, at least not without bending them.

It is possible however on poorly made power strips if the probes are relatively long for the probe to poke past the back of the receptacle and through the insulation of a wire, or a grounded chassis, but this would be rather unusual as most DMM probes are not much longer than a standard plug end.

The lead tip is about 3/16th longer than the plug spade. I was having a hard time getting a reading in the power strip. I do remember that and it was not like doing it in a wall receptacle, so maybe I did ground it out. It's a very good explanation.

That happened to me many years ago with an old 3-way adapter.  I pushed the DMM probe in and shorted to either the neutral or ground.  Quite an impressive light show!

If your power bar is screwed together, pull it apart and inspect it.  If not, unplug it (!!) and then see if you can get continuity to neutral or ground by probing into the hot lead with the smallest insulated wire you've got.  If you do, that power bar is dangerous!  Cut the cable off and throw it away!

Excuse my language but FUCK ME. I got continuity. I'm sure that's what must have happened. I had to search a little, but I got it.
(Attachment Link)

Thanks for the update!

It'd be interesting to see how the contacts are laid out internally. Clearly they're not designed to be probed, but then again, that's not actually a requirement for a receptacle. Given that it hasn't blown your home circuit breaker, I take it that no shorting occurs when only actual AC plugs are inserted?

[ozcar]

I'm still not clear if there are any current ranges on the probes, or just on the clamp. Only the instructions will tell you.

Looking at the picture of it, I don’t get any suggestion that it can measure current other than by the clamp.

And, somebody specifically asked the Amazon seller “Can this measure current with leads also?” and was told, no, only via the clamp.

[DW1961]

Well if there are any fuses, then he should be advising HRC meter fuses, not 'just universal' ones. I'm still not clear if there are any current ranges on the probes, or just on the clamp. Only the instructions will tell you.

I think you are duty bound to go searching for them now! [Edit: if he says they are replaceable, then they ought to be easy to locate] 

I think what he is doing is just giving generic multimeter feedback rather than anything specific to this particular product (still worrying advice on the arbitrary fuse choice though).

He said there is no way to get current reading from the leads, only the clamp and only AC. I can ask which fuse?

[DW1961]

It'd be interesting to see how the contacts are laid out internally. Clearly they're not designed to be probed, but then again, that's not actually a requirement for a receptacle. Given that it hasn't blown your home circuit breaker, I take it that no shorting occurs when only actual AC plugs are inserted?

No shorting when a normal plug 'was' inserted. 'Was' because the strip itself is now pushing daisies in the world's ever-growing plastic pile, and the wire (pure copper too) has just added 10 feet of what looks like 12 AWG copper wire to my collection.

[ozcar]

I can ask which fuse?

I’ll bet there is no fuse.

Your meter appears to be a re-badged BSIDE ACM81. That is the cheapest one of a trio of similar BSIDE meters, ACM81, ACM82, and ACM91. Comparison chart here: https://www.aliexpress.com/item/1970498378.html

Here is a review of the posh model: https://lygte-info.dk/review/DMMBSide%20ACM91%20UK.html

[DW1961]

I can ask which fuse?

I’ll bet there is no fuse.

Your meter appears to be a re-badged BSIDE ACM81. That is the cheapest one of a trio of similar BSIDE meters, ACM81, ACM82, and ACM91. Comparison chart here: https://www.aliexpress.com/item/1970498378.html

Here is a review of the posh model: https://lygte-info.dk/review/DMMBSide%20ACM91%20UK.html

OK I'm tearing it down! The review was for an older model, so I "hope" the dude wasn't outright lying to me. The one I have does now have a diode function too. Maybe they added a fuse? lol Thanks for that link. Now I know exactly how to disassemble it.

Does this look like it has fuses? They wouldn't be under the board? Also, the reply about having fuses was by "Amazon Customer" but was worded "Our products have. . . ." When I clicked on "Amazon Customer" I got an Amazon 404 error. Something fishy going on here. I mailed the seller directly this time through the Amazon email system. We'll see what they say.

[Gyro]

I see no fuses. 

The green blob is a PTC thermistor, to protect the Ohms, continuity, diode test etc. Q1, Q2, Q5 and Q6 are diode clamps (after the PTC).

R7A and R7B are high voltage resistors, probably the top of the voltage divider for the volts ranges. Likewise R4A and R4B (probably lower voltage range).

D1, D2, D3, and D6 will be the overload clamps for the output of the Jaw current transformer.

I can't see any evidence of current ranges on the Jacks.

Pretty much as expected, there's not a huge amount of protection on the Jacks for the Cat rating but pretty much as expected for the price range (try to avoid applying highish voltages when not on a volts range (it's always good practice to double check anyway).

Fuses are only useful for direct (on the jacks) current ranges, so it really would have been surprising if you had found any. That's what you get from generic Amazon seller advice - I'm sure he meant well though, just lacking information / knowledge, don't hold it against him.

[DW1961]

I see no fuses. 

The green blob is a PTC thermistor, to protect the Ohms, continuity, diode test etc. Q1, Q2, Q5 and Q6 are diode clamps (after the PTC).

R7A and R7B are high voltage resistors, probably the top of the voltage divider for the volts ranges. Likewise R4A and R4B (probably lower voltage range).

D1, D2, D3, and D6 will be the overload clamps for the output of the Jaw current transformer.

I can't see any evidence of current ranges on the Jacks.

Pretty much as expected, there's not a huge amount of protection on the Jacks for the Cat rating but pretty much as expected for the price range (try to avoid applying highish voltages when not on a volts range (it's always good practice to double check anyway).

Fuses are only useful for direct (on the jacks) current ranges, so it really would have been surprising if you had found any. That's what you get from generic Amazon seller advice - I'm sure he meant well though, just lacking information / knowledge, don't hold it against him.

You know I don;t know if it was the seller. It just said "Amazon Customer" but the answer started out "Our products. . . " So strange. I actually sent them an in Amazon email directly to the seller, so no way for them to avoid the question, fudge the answer.

Is there anything  can report from tearing it down that is either good or bad? I'll review it and add you analysis, if that's ok? Is it dangerous? Lacking in a way that is short lived? Anything you can think of.

[wizard69]

If the meter has a resistance capability I'd most certainly test the meter for proper operation on the resistance ranges.   This highlights the value of having a set of precision resistors or at least resistors that you have measure to a high degree of precision, in your possession.   They don't have to be of "calibration standard" quality but they should be well known as to their acutal values.   The nice thing here is that there are all sort of examples right here in these forums of how to create quick check standards.    I call them quick checks because the intention isn't to be good enough to calibrate in many cases but good enough to prove operation of the tool.

If the meter still works I have a hard time believing that the meter caused your problem.   It could be something you did or another factor.

By the way while this might rub many the wrong way meter leads are expendable wear items in my mind.   Be prepared to buy new ones any time the current ones are damaged, show contamination or have been stressed excessively.    I work in automation, with high voltage AC and DC systems, and frankly this is an area where you get no second chances.   I hate to even think about how much current could be discharged from some of the motor drive caps I have to deal with.   These are likely small caps compared to some stuff people work on  but they make me pucker every time I work on them.

[DW1961]

If the meter still works I have a hard time believing that the meter caused your problem.   It could be something you did or another factor.

Wizard. It was as bad power strip that allowed the leads to cross the neutral and positive.

[Gyro]

Is there anything  can report from tearing it down that is either good or bad? I'll review it and add you analysis, if that's ok? Is it dangerous? Lacking in a way that is short lived? Anything you can think of.

As I mentioned, the level of protection is what you would expect in that price range. If it was a Fluke or something then you might expect VDRs, maybe even spark gaps - but that stuff comes with higher CAT ratings and you didn't pay for an expensive fluke, so you wouldn't expect them. At the same time, for general indoor mains use (wall sockets) and low voltages it should be fine (pushing the probes through mains strip internal metal parts permitting  ). Don't go probing around the inlet side of your breaker panel or substations and you ought to be fine. If you're going to do that, then buy a Fluke and some anti-flash gear.

You can't pull it up for lack of fuses because you wouldn't expect fuses without current ranges on the jacks - and the fuse advice was from some anonymous Amazon user anyway, so far as you can prove.

Check its voltage, resistance accuracy against another meter and if you're happy with it and its operation, then there's really nothing to fault for the price. I can't see anything obvious in the construction.

[DW1961]

Is there anything  can report from tearing it down that is either good or bad? I'll review it and add you analysis, if that's ok? Is it dangerous? Lacking in a way that is short lived? Anything you can think of.

As I mentioned, the level of protection is what you would expect in that price range. If it was a Fluke or something then you might expect VDRs, maybe even spark gaps - but that stuff comes with higher CAT ratings and you didn't pay for an expensive fluke, so you wouldn't expect them. At the same time, for general indoor mains use (wall sockets) and low voltages it should be fine (pushing the probes through mains strip internal metal parts permitting  ). Don't go probing around the inlet side of your breaker panel or substations and you ought to be fine. If you're going to do that, then buy a Fluke and some anti-flash gear.

You can't pull it up for lack of fuses because you wouldn't expect fuses without current ranges on the jacks - and the fuse advice was from some anonymous Amazon user anyway, so far as you can prove.

Check its voltage, resistance accuracy against another meter and if you're happy with it and its operation, then there's really nothing to fault for the price. I can't see anything obvious in the construction.

Thanks. I gave it a good review and mentioned it's limitation, such as no DC current measurement.