Big Clive's "Trashy" meter, unboxed ( Duratool D03047 multimeter )

[floobydust]

My home has a tiny little service coming into from a small distribution transformer.  Nothing like what feeds for the buildings where I worked.    Outlets at my house are several feet from the main feed and are behind small CBs which are behind another small one.  Worse thing that will happen if I pull an outlet and short the wires, I blow a CB.  Hardly CAT III or risk of an arc flash. 

Same here. That's why I wasn't worried about measuring the mains with my Big Clive special.

Knowledge is power.

Ignorance is bliss. Like a chinese fortune cookie, "May your multimeter's spacings be auspicious".

I think so far it's magical opinion and unicorns telling us the DT830 is OK at x volts. Or we can argue it's the requirements at fault - the IEC overvoltage categories are wrong. Not that the product has ever been tested or evaluated to meet its fake claims.
Strange for EE's to discard science for a cheap "trashy" cause.

"Hardly CAT III" you'd need to run a Dranetz to convert speculation and gut feel to fact. I've used loggers in facilities to see if power is a problem with equipment failures. Like making a measurement with some test equipment 

[Fungus]

I think so far it's magical opinion and unicorns telling us the DT830 is OK at x volts.

I never said "DT830".

The Big Clive special is a "D03047" - it says so right there in the title.

"DT830" covers a million variants so I could never make a blanket statement like that.

Not that the product has ever been tested or evaluated to meet its fake claims.

What fake claims are those? "CAT I"??

[EEVblog]

Maybe you could be the whistlindiesel of the test gear world.

I might do it if there was a crowd funder for it.
I doubt any company would give one for nix to be specifically overload tested.

Ok, I draw the line HERE

[Fungus]

Maybe you could be the whistlindiesel of the test gear world.

I might do it if there was a crowd funder for it.

I'm not sure that's how it works.

Maybe you could start by running over some working Fluke 8060As in your car.

[Gyro]

Using DMMs on the mains is somewhat overrated (no pun intended). In a lot of cases it rather akin to beginners getting their first fancy scope, having nothing to look at other than the cal output, and being hypnotically drawn to the nearest mains outlet.

Most use cases are establishing whether mains is present or not, rather than measuring its voltage to within a few volts. Electricians use proper 2-pole testers for such purposes, together with a simple proving unit. These are inevitably at least 600V Cat III. The cheaper professional ones have a basic LED bargraph voltage display, the slightly more expensive ones, an LCD voltage readout too. They normally have a basic continuity and phase rotation tests too, with the same Cat rating. No finger-trouble  controls, captive probe lead, and they still give a live voltage indication even if the batteries are flat or missing.

Decent qualtity second hand 2-pole testers can be picked up quite cheaply on ebay (Don't go to Ali!). When you get one, you should carry out the inspections detailed in the manual - check for cracks, lead damage, tug test etc. And verify that they indicate correctly. Proper safe isolation procedure requires indication verification before and after checking the circuit of interest. That's where the battery powered proving unit comes in. You can get those on ebay too, but it's easy enough to make your own with a simple self oscillating inverter - this is pefectly safe to do, if you don't get a reading on the proving unit then any test on the mains circuit is automatically invalid.

Most measurement tests involve a safely isolated, dead circuit. Once the circuit is proven dead and preferably locked off with a clip on the breaker, you can perform resistance measurements etc. Proper second hand insulation and continuity testers (again with the comfort of Cat rating), are again easily available on ebay. They will probably be past their calibration date, but are very easy to verify with a bunch of low and high value resistors and a Cat 1 1kV DMM.

The only other live tests are beyond the capabilities of a DMM anyway. Ze / PSC (prospective fault current) tests require a dedicated tester as does RCD trip current / trip time. RCD testers are also pretty cheaply available too (again they may be past cal, but if an RCD trips at 1 x In and holds at 0.5 x In then it is good enough. RCDs have test buttons anyway.

In summary, there is very little reason to be using a DMM on a live mains circuit.

[joeqsmith]

"Hardly CAT III" you'd need to run a Dranetz to convert speculation and gut feel to fact. I've used loggers in facilities to see if power is a problem with equipment failures. Like making a measurement with some test equipment 

Several years ago I had Dranetz come in for a visit to demonstrate their latest products.  After the sales demos, I started to ask about their testing.  After all the point is we would be using it to capture various events.  Normally companies will leave the products for a few weeks to get a feel if they are fit for the job.  So I asked them about subjecting it to the various safety standards.   They had no problem with this, so I invited them to attend.  We all had a fun time that day.

[joeqsmith]

I think so far it's magical opinion and unicorns telling us the DT830 is OK at x volts.

I never said "DT830".

The Big Clive special is a "D03047" - it says so right there in the title.

"DT830" covers a million variants so I could never make a blanket statement like that.

Not that the product has ever been tested or evaluated to meet its fake claims.

What fake claims are those? "CAT I"??

Sadly, I suspect they missed the whole point of these measurements with the free DT830 meter were on a CAT1  low energy circuit.   I would have thought that when I stated that the one power supplies current limit kicked in with the input impedance of the meter, something would have clicked.   

I'm not going to get all concerned about my home toaster repairs and my CAT III outlets because it's just not the same thing.

So what's the supply impedance at those socket outlets?

I'll try and make a few measurements today with my tiny home wires.  I assume you will do the same so we have something to compare.  If not, I can measure some larger circuits.   

[joeqsmith]

The robustness of bench meters is effectively stamped on the front. Both of mine (Keithly and Keysight) are CAT II 300V. That screams "I'm delicate please don't hurt me!"
No need for testing, just assume all bench meters are delicate snowflakes.

Or test them to a common standard and see how they shake out which is what David is asking about.   No big deal to benchmark them.   

Sure, but I'd bet few people would care. It's not like you'd use that as a buying decision for a 4 digit priced bench meter.
And if you thought there are a lot of people complaining about blowing up DMM's is pointless, wait until you blow up expensive high end bench meters.
But hey, knock yourself out.

David Aurora had asked me so I responded.  No big deal.   I do agree that there are few people in the world who are interested in electronics.  Guessing your point is few people would watch but that's true of all my videos.      

I have a friend who owns a motorcycle speed shop and was talking with them about their business.  They made the point of suggesting to go for a drive and count the number of cars vs bikes.   Now take that small percentage of bike and ask how many of them race.  Then how many of that small segment drag.  Not many of us but we have fun.   

As I mentioned, I did ask about robustness of the HP meters before buying them.  It's the only test equipment that I would care about due to it being used to measure several hundred volts  (not to mention the small transients it can get exposed to). It's not like my other equipment that is limited to a < 50V with warnings of ESD damage everywhere.   

[joeqsmith]

I'm not going to get all concerned about my home toaster repairs and my CAT III outlets because it's just not the same thing.

So what's the supply impedance at those socket outlets?

I'll try and make a few measurements today with my tiny home wires.  I assume you will do the same so we have something to compare.  If not, I can measure some larger circuits.
[/quote]

I assume because we are talking commercial vs industrial, you want to keep this below 250V? Are you wanting any other metrics or just the impedance for the three legs?   

[David Aurora]

The robustness of bench meters is effectively stamped on the front. Both of mine (Keithly and Keysight) are CAT II 300V. That screams "I'm delicate please don't hurt me!"
No need for testing, just assume all bench meters are delicate snowflakes.

Or test them to a common standard and see how they shake out which is what David is asking about.   No big deal to benchmark them.   

Sure, but I'd bet few people would care. It's not like you'd use that as a buying decision for a 4 digit priced bench meter.
And if you thought there are a lot of people complaining about blowing up DMM's is pointless, wait until you blow up expensive high end bench meters.
But hey, knock yourself out.

Not primarily, of course. But if you're scratching your head between models that stack up very similarly (as many meters do), and one is shown to be better built than the other, that's a no brainer. At that price point they're all going to agree on a 9 volt battery or a 10k resistor, so build quality or even little things like display visibility/control layout/fan noise etc start to dominate (for me, anyway). Teardowns are one way of comparing build quality, stress testing is another.

Also, I should clarify (although Joe clearly gets it) that I'm not saying let's try to set fire to top notch instruments and destroy them just for a laugh. I'm saying I'd like to see how different models cope under stress. Same as most other meter tests- can they tolerate a decent voltage when in wrong modes? What happens if you exceed the max voltage or current ratings, does the protection work properly or does damage occur? What happens if there's a spike on the input? What happens if the meters own supply voltage drops during measurements (e.g. during a brown out)? What happens if you flick between front/rear terminals during high voltage/current measurements? And so on.

I think the price of these things is all the more reason to do stringent testing rather than just rubber stamping them because of the price, brand or accuracy. People run these tests and more before declaring a $20 meter good or bad, why not a $5000 meter?

[IanB]

Some meters have a multi-gigaohm input impedance, and while I don't know how this is implemented, I would guess the input more or less is going directly to the gate of an FET? If that is the case, is there any way these can have robust input protection?

[David Aurora]

I'm making an analogy. A sensitive mechanical instrument should be treated with mechanical care. Similarly, a sensitive electrical instrument should be treated with electrical care.

You're kind of making the same mistaken assumption as the OP here that everything is always controllable- it's not. Devices fail while under test, surges happen, test points can be mislabeled, probing mistakes happen, etc.

There's no mistaken assumption here. If you drop your expensive micrometer on the concrete floor and put it out of alignment, that's tough on you, time to buy a new one. Similarly, if you blow up your expensive bench meter by accident, that is similarly tough on you. Time to replace it or get it repaired. What you don't do is get the probes from that expensive meter and recklessly stick them in unknown circuits. If you do that you have only yourself to blame for mishaps.

If you're only ever sticking your probes in circuits you know back to front, that are well documented and are guaranteed to be behaving correctly I've got to assume you're unemployed. Jesus Christ. From one day to another all sorts of shit lands on my bench for inspection, often already worked on by cowboys or DIYers. Just the last few disasters that spring to mind are a power switch where a terminal had somehow internally shorted to the actuator, a tube amp where some numb nuts had wired the 450V B+ directly to the input jack, missing insulation between transistors and heatsinks, incorrectly connected transformers... the list goes on. Surprises happen and sometimes your probes find something you weren't expecting, welcome to the real world.

I have a small question for everyone in this thread: do your lightbulbs have a CAT rating on them? When you twist a bulb into its socket, do you ever worry about it exploding in your hand? Do you wear safety glasses and rubber shoes when you change a lightbulb?

A DMM may be connected to the mains for a few seconds at a time to take a reading, and there is only one of them. All the lamps in your house are connected to the mains 24/7 and switched on for hours at a time. They could explode, cause a fire, or cause human injury. The risk is vastly higher than with using a DMM.

Why are there many threads about meters, and no threads about household appliances and electrical devices? There are millions more of the latter, and a proportionately higher hazard, statistically.

I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess 

[Grandchuck]

I am curious if there are any auto mechanics on this forum?  EV battery voltage can be as high as 800V.  And, the energy stored is significant.  What does this group (auto mechanics) do about using instruments safely?

[Fungus]

I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess 

What if it's a two (or three) way switch and you don't know if it's on or off? Do you rewire your house first?

[wasedadoc]

I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess 

What if it's a two (or three) way switch and you don't know if it's on or off? Do you rewire your house first?

The neon screwdriver would come out of that drawer in the kitchen that has the non-cooking items such as string, Stanley knife, spare keys, candles, fuse wire, tap washers etc.

[IanB]

The neon screwdriver would come out of that drawer in the kitchen that has the non-cooking items such as string, Stanley knife, spare keys, candles, fuse wire, tap washers etc.

You forgot the rubber bands and batteries 

[Fungus]

The neon screwdriver would come out of that drawer in the kitchen

Make sure it's a certified CAT III screwdriver, not a fake Chinese one

[Gyro]

Some meters have a multi-gigaohm input impedance, and while I don't know how this is implemented, I would guess the input more or less is going directly to the gate of an FET? If that is the case, is there any way these can have robust input protection?

In the case of the Datrons that I'm familiar with, there's a 100k 10W resistor chain before the bootstrapped protection diode (well, JFETS and Zeners) network on the Hi-Z input ranges. I'm not as familiar with other brands.

[switchabl]

I have a small question for everyone in this thread: do your lightbulbs have a CAT rating on them? When you twist a bulb into its socket, do you ever worry about it exploding in your hand? Do you wear safety glasses and rubber shoes when you change a lightbulb?

I realize that this is a rhetorical question but the thread seems to have gone sideways anyway. So, here is a fun fact: a lightbulb ("self-ballasted LED lamp for general lighting services by voltage above 50 V") has to be tested to a withstand voltage of 4 * nominal line voltage + 2000 Vrms between the contacts and any accessible parts for 1 minute in an environment with >91% humidty. Around here that works out to roughly 4kV peak.

[AVGresponding]

Using DMMs on the mains is somewhat overrated (no pun intended). In a lot of cases it rather akin to beginners getting their first fancy scope, having nothing to look at other than the cal output, and being hypnotically drawn to the nearest mains outlet.

Most use cases are establishing whether mains is present or not, rather than measuring its voltage to within a few volts. Electricians use proper 2-pole testers for such purposes, together with a simple proving unit. These are inevitably at least 600V Cat III. The cheaper professional ones have a basic LED bargraph voltage display, the slightly more expensive ones, an LCD voltage readout too. They normally have a basic continuity and phase rotation tests too, with the same Cat rating. No finger-trouble  controls, captive probe lead, and they still give a live voltage indication even if the batteries are flat or missing.

Decent qualtity second hand 2-pole testers can be picked up quite cheaply on ebay (Don't go to Ali!). When you get one, you should carry out the inspections detailed in the manual - check for cracks, lead damage, tug test etc. And verify that they indicate correctly. Proper safe isolation procedure requires indication verification before and after checking the circuit of interest. That's where the battery powered proving unit comes in. You can get those on ebay too, but it's easy enough to make your own with a simple self oscillating inverter - this is pefectly safe to do, if you don't get a reading on the proving unit then any test on the mains circuit is automatically invalid.

Most measurement tests involve a safely isolated, dead circuit. Once the circuit is proven dead and preferably locked off with a clip on the breaker, you can perform resistance measurements etc. Proper second hand insulation and continuity testers (again with the comfort of Cat rating), are again easily available on ebay. They will probably be past their calibration date, but are very easy to verify with a bunch of low and high value resistors and a Cat 1 1kV DMM.

The only other live tests are beyond the capabilities of a DMM anyway. Ze / PSC (prospective fault current) tests require a dedicated tester as does RCD trip current / trip time. RCD testers are also pretty cheaply available too (again they may be past cal, but if an RCD trips at 1 x In and holds at 0.5 x In then it is good enough. RCDs have test buttons anyway.

In summary, there is very little reason to be using a DMM on a live mains circuit.

Ah, the good old days... sadly, my Fluke T5-1000 uses 2x AA (rechargeables work fine, which I prefer even though I can get free industrial Duracells at work), as do many two-probe testers these days.

In point of fact, a DMM does have a place in the electrician's toolbag. The continuity test that a pair of Steinels or an installation tester can do has a maximum of a few hundred ohms, the insulation tester function can only measure by using 250V or more, at 1mA, which is death for many things you might find connected to your fixed wiring.
A real case scenario for this happened a few weeks back, when we were trying to track down an earth fault on a fire alarm. The insulation tester I had brought had a maximum resistance reading of 200kΩ, before the insulation test ranges. The installation tester had continuity only. The earth fault, as it turns out, (I took my F87V in the next day...) was around 360kΩ, so we couldn't see it with any of the testers (it wasn't possible to remove all the fire alarm devices on a section, and naturally enough, that was the offending section) at the first attempt. Still, we got a full weekend of overtime out of it, so no complaints...

Also, though I don't get to play with UPS's at work these days, you definitely need a DMM for that, also if you're playing with VFD's, and almost all PLC /automated machinery.


One of the electricians that joined us recently has a bloody neon screwdriver; I keep threatening to throw it in a skip if he leaves it unattended. If he wields it anywhere near a DB or panel board, I will rugby tackle him to the floor and smash that piece of shit with a club hammer.

[Gyro]

One of the electricians that joined us recently has a bloody neon screwdriver; I keep threatening to throw it in a skip if he leaves it unattended. If he wields it anywhere near a DB or panel board, I will rugby tackle him to the floor and smash that piece of shit with a club hammer.[/color][/font][/b]

Do it! It's your H&S duty as well as being fun.

[floobydust]

I think so far it's magical opinion and unicorns telling us the DT830 is OK at x volts.

I never said "DT830".

The Big Clive special is a "D03047" - it says so right there in the title.

"DT830" covers a million variants so I could never make a blanket statement like that.

Not that the product has ever been tested or evaluated to meet its fake claims.

What fake claims are those? "CAT I"??

Post #1 the input jack board markings "830B.2XB", main board "832.2" so I see it as a DT832. "DT" for Duratool? KT logo maybe Ketai. They go for less than USD $1.50 ea. in bulk 
With the fake "EN 61010 Cat. I 500V label" Interesting on Alibaba 99% of DT830B, DT832 etc. show a "61010" or "Cat. x" label. Farnell is getting some extra. Others majority of them jacks say 500VAC "Cat. I 250V" or others 750VAC/1,000VDC Max. which I could believe if there is proof of test.

[themadhippy]

give me a trusty test lamp any day over a digital /led testers,no battery's to go flat and they draw enough current to avoid weird ghost  readings

bloody neon screwdriver;

bit of silver paper from a fag packet across the resistor soon makes the owner  chuck em away

[switchabl]

Post #1 the input jack board markings "830B.2XB", main board "832.2" so I see it as a DT832. "DT" for Duratool? KT logo maybe Ketai. They go for less than USD $1.50 ea. in bulk 
With the fake "EN 61010 Cat. I 500V label" Interesting on Alibaba 99% of DT830B, DT832 etc. show a "61010" or "Cat. x" label. Farnell is getting some extra. Others majority of them jacks say 500VAC "Cat. I 250V" or others 750VAC/1,000VDC Max. which I could believe if there is proof of test.

"DURATOOL is the registered trademark of Premier Farnell Limited"

I think it's safe to assume that they had it tested if they sell it under their brand. It is possible that they have requested some minor changes to make it pass. (Reputable EU sellers used to have their own version of some Uni-T meters with better fuses and different ratings printed on them so they would actually pass safety testing and be able to sell them legally.)

Like I said above, in this case "CAT I" almost certainly means "no overvoltage protection" (the manual, probably written by Farnell, carefully specifies "overload protection" for all modes, none of which exceeds 500V). So "CAT I 500V" is really not a very high bar. The difference in terms of clearances and insulation is something like 5x-10x compared to CAT II (aka "delicate snowflakes").

[floobydust]

I thought a ripoff of Duratool Taiwan.

Cat. I 300V is a 1,500V impulse, Cat. I 600V 2,500V and there is no "500V" mains category.
Cat. II 300V spacings is 1.5mm. If the multimeter's PC board layout was done professionally, that isn't hard to achieve. But this multimeter again shows a clown car for the traces, this is why without a spacings analysis or formal testing, it's a bit scary.
EE's strive to do good but occasionally fail and this is why testing is done.

Let's see Premier Farnell provide a test certificate of any kind. That should be a good laugh.