I hope people in the industry have more sense and know how.

Notice I said: people. I did not say: people in industry.

 

People without training shouldn’t be messing with high voltage. Accidents happen even with training. Fluke will not protect you from ignorance.

 

People without training shouldn’t be messing with high voltage. Accidents happen even with training. Fluke will not protect you from ignorance.

I couldn't agree more.

 

Go ahead and change the batteries and see if that solves the problem. My best guess is that they selection dial switch has worn contacts. A drop f squirt of contact cleaner might restore good operation.

Yes, I've just had some time off to pop some fresh cells in. I brought my Elenco M-1700 (hey- it came with an associates degree at a tech school several years ago) from work where It collects dust, so I have some kind of reference at least. Just testing some small solar panels for open circuit voltage and current. The Uni-T still measuring low mA readings and is more accurate with the full amp jack and setting. Going to take it apart tonight and clean as you and rsjsouza suggested.

Although it gets heated, I appreciate EVERYONE'S input about meters- their role, safety and quality.
It's good communicating with people who have passion, and interests about SOMETHING

 

The two things that completely upset me about the current DMM market are:
- The fake CAT ratings, which would mostly fool people that would have basic knowledge about electricity/electronics (enthusiasts, hobbyists). That, tied to the joint mA with V/Ω input, makes it really easy to give (at least) a scare to the user - or the loss of a limb.
- The absolute garbage quality control in certain brands and models, with loose parts inside (I have seen springs, screws and rotary switch contacts), flux and grime residue (I have seen very low resistance across input terminals, protection devices and switch contacts), bent parts inside and others.

Also, I agree that not all budget meters can be considered "toys", but identifying one from another requires a level of expertise that goes beyond the spec sheets and the markings on the device.

At last in my rant, Uni-T does not do any favours to their users by having a base model name (UT61, UT136, UT210, UT139, etc.) and a soup of suffix letters that indicate quite radical differences in features and form (UT61A/B/C/D/E, UT136 A/B/B+/C/C+/D, UT210A/B, UT139A/B/C/E/S...). In particular the UT61E, which even comes in two versions: one for the general market and another fully loaded with protection to meet EN61010 ratings with a TÜV mark.

 

Agreed on the CAT ratings... I had to do a lot of research to find a decent one, I did run across this guy who spends a lot of time and his own money to test multimeters and oscilloscopes on EEVblog. He performs his own high voltage testing based on CAT transient requirements.

https://www.eevblog.com/forum/testg...ot-appear-to-meet-their-claimed-safety-specs/

https://www.eevblog.com/forum/reviews/a-list-of-recommended-multimeters/

https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/

Still my $13 meter with 6,000 count and HRC fuses... amazing.

 

Don’t even call the free Harbor Freight one a multimeter or put it in the same category as the others. I have about 5 of those and they’re good for the 9V battery. If you paid anything for one it’s too much.
View attachment 176067

I would say it's better in some ways than my first Fluke. Sometimes it's really all you need.

 

Hey if they only put an auto shut off and those probes are just not dependable. Also no continuity beep. My first meter was an AW Sperry. It’s over 25 years old and still pretty good. Wait I take that back I did have an older analog meter or two.

 

The old Fluke did come with better probes but manual on/off and no continuity beep. My first analog meters were the same way. With the HF being free, other than filling landfills, it's hard to fault it. IMO, the bad meters are the ones with a high price tags and poor performance.

I have looked at several Flukes and they have all performed very well against my tests. Many of these were from China. I've also looked at several Brymen products which have also done very well.

The links to the FAQ and data I've collected may be found here:
http://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

 

Joe keep up the good work.

My son stuck a free HF meter in a wall socket and blew it up scaring us. He was ok but the meter died violently. I was scratching my head looking at the CAT II 1kv rating. I’m sure he had it in the wrong setting.

Never had an issue with a fluke other than not knowing that the 113 only reads up to 60k ohms or my Sperry. I have no issues probing for high plate voltage on tube circuitry.

This Thsinde just boggles my mind. It’s a little slow to settle but built well and useful so far.

 

My son stuck a free HF meter in a wall socket and blew it up scaring us. He was ok but the meter died violently. I was scratching my head looking at the CAT II 1kv rating. I’m sure he had it in the wrong setting.

He probably plugged the probe at the unfused 10A input, which would obliterate the meter regardless of the range it was set (it has a dead short between the COM and the 10A input).

Even on a Fluke or other A-brand, if the probe is inserted in the A or mA terminal the event could be a bit scary as well. However, no modern Flukes have unfused inputs and therefore this would certainly tame the event.

 

Have to share this. I was at a local surplus store and asked to look at one of the UNI-T meters. I was shown an AC outlet with which to test the meter. The black input jack is surrounded by red on the plastic case and the black input jack was mostly surrounded by red on the case, when I went to plug the red lead into the black input jack the sales girl cried "Aaaaahhhh..NO, NO, NO!" Heavens,what if I were to plug the meter into the AC outlet backwards?

Still have that meter on the bench. The Fluke is stored safely nearby.

 

Joe keep up the good work.

My son stuck a free HF meter in a wall socket and blew it up scaring us. He was ok but the meter died violently. I was scratching my head looking at the CAT II 1kv rating. I’m sure he had it in the wrong setting.

Never had an issue with a fluke other than not knowing that the 113 only reads up to 60k ohms or my Sperry. I have no issues probing for high plate voltage on tube circuitry.

This Thsinde just boggles my mind. It’s a little slow to settle but built well and useful so far.

Hard to say what your son was doing with a meter and wall socket. Without supervision and education, a few things could have happened. The meter's high current shunt is not fused. Connecting the leads to the high current shunt and proceeding to probe the AC could be a problem. The low current input is shared with the voltage input. Even with the leads connected properly, obviously selecting the current mode would be a bad idea. It is fused but the fuse type varies meter to meter.

Depending on what the plate supply is, it seems unlikely that it would damage the free meter if the voltage is under a KV. I've taken them to a KV fairly often and have never seen them breakdown. They have changed the range on the newer meters from 1KV to 250V or something like that.

There was a video floating around of a TV show where they were selling products. The person demonstrating the meter plugs it into the wall socket and proceeds to turn the knob to the current setting. They got a bit of a bang from it.

The video you link, I don't think they explain what was going on. I assume they were running the surge test but that's a guess. It's similar to the tests I run in that the open circuit voltage profile I use, ether meets that standard, or is double the FWHH. But the combo generators also spec the current waveform. This is where I differ. Many people don't seem to grasp that. I test with a maximum of 20 Joules which isn't much. Basically, as I stated from the beginning, I was never out to prove if these meters were safe or met their specified safety ratings. My only goal was to see how electrically robust they are and I don't need a lot of energy to damage them.

 

He probably plugged the probe at the unfused 10A input, which would obliterate the meter regardless of the range it was set (it has a dead short between the COM and the 10A input).

I'm not so sure it would obliterate the meter. Something would open up eventually. Maybe the CB.

I ran that test with the leads and I can believe the leads in some cases would open up before the meter.

 

I'm not so sure it would obliterate the meter. Something would open up eventually. Maybe the CB.

I ran that test with the leads and I can believe the leads in some cases would open up before the meter.

Joe, hyperbole was added for effect.

(but it is absolutely certain the meter would be in much worse shape than if a fuse was fitted)

 

There was a video floating around of a TV show where they were selling products. The person demonstrating the meter plugs it into the wall socket and proceeds to turn the knob to the current setting. They got a bit of a bang from it.

I posted a while ago a similar video - perhaps that is what you remember. A Brazilian talk show presenter was trying to show how to use a "Harbor Freight-like" DMM when she was trying to measure a 220VAC outlet. With a poor contact, she thought about moving the range switch and suddenly a small "bang" was heard - perhaps due to the V/Ω/mA shared input.

 

I suspect that is the same video. I think the first time I saw it was on Reddit.

I attempted to run one of the free meters while in it's highest voltage setting across my half cycle line simulator. This obviously exceeds the 20J I mentioned earlier. If you read the comments, someone had asked "You had it in the 750V mode but what did you run through it ?" and I responded with 4KV. After being on Youtube for a while, I think that was a bad answer as there is a good chance the person asking wouldn't have any grasp of the waveforms being applied. They may have very well went away thinking I hit the meter with 4KV DC. I've had people write me that I was connecting them directly to a capacitor bank. They of course don't understand that the waveshape is present even with no load and that the generator itself absorbs the excess energy which is converted to heat in the output network.

For the actual surge test, the transient rides on top of the actual AC line where I am just trying to simulate the transient riding on top of a half of a cycle. Any of the better meters I have looked at are not effected by this test as they don't break down. So there's no path to dump that half cycle into. The free meter, like so many of the low cost ones I look at, doesn't have any sort of input protection combined with the creepage. In this case the leads did act as a fuse.

 

I suspect that is the same video. I think the first time I saw it was on Reddit.
I attempted to run one of the free meters while in it's highest voltage setting across my half cycle line simulator. This obviously exceeds the 20J I mentioned earlier. If you read the comments, someone had asked "You had it in the 750V mode but what did you run through it ?" and I responded with 4KV. After being on Youtube for a while, I think that was a bad answer as there is a good chance the person asking wouldn't have any grasp of the waveforms being applied. They may have very well went away thinking I hit the meter with 4KV DC. I've had people write me that I was connecting them directly to a capacitor bank. They of course don't understand that the waveshape is present even with no load and that the generator itself absorbs the excess energy which is converted to heat in the output network.

Yes, with such broad audience venue like Youtube, one cannot be too cautious in providing answers to questions. In replies on my channel, I tend to try to set the stage before actually answering the question - the issue is that the replies end up becoming too extensive.

So your generator outputs half cycle (1/120s) of 4kVpeak into the load, right? I saw this on a video of yours a long time ago but I keep forgetting about the exact parameters.

 

No doubt there were some Darwin wannabe's watching my tests, seeing some meter being tested at 8KV and thinking they could hook it to their MOT with a continuous 2KV and everything would be fine. Flip side is the people who comment about why would I ever expect a meter that say's right on it that it can handle 600V, to handle 8KV. Maybe a few of them have learned something from these tests but I doubt it.

There are two generators used during the half cycle test. One generates a high voltage low energy waveform, the other low voltage high energy one. The high voltage generator is the same one used for my normal tests. When I run the half cycle test, the high voltage generator is set to 4KV peak, 100us FWHH with a 2 ohm source (not the 50us FWHH called out by the IEC standards). Rise times are in the order of 1.2us and the decay is exponential, limited to about 20J. Again, the same waveform I use for the normal testing.

Basically, this generator is what is causing the meter being tested to breakdown. The only time I will consider running this test is IF the meter brakes down during the normal test. The high voltage generator triggers the low voltage generator which will in turn output a higher energy waveform that will also decay exponentially over a half AC line cycle. The excess energy is once again absorbed internal to the generator. I would need to dig up my notes but I want to say this generator is setup for 660Vpeak. I wanted something common that I knew EVERY meter I looked at should handle with no troubles. The energy available is in the order of 600J.

The transients I use could certainly be lethal, which is why I am very cautious when running these tests. Still they hardly compare with the real test, so you never will see a meter come apart with my tests like you will with the IEC tests. But again, that was never the goal.

I don't collect any data from the half cycle test. It's really there to provide some sort of idea how the meter being tested behaves with a little higher energy.

 

After taking it apart and cleaning it up with isopropyl and microfiber (don't have contact cleaner on hand) it's still the same results. Really likes to show 2mA. In this case it should have read around 39mA which I tested with the old Elenco meter. Looks like I'll be doing some meter shopping soon. I appreciate all the input.