Joe, after downloading your spreadsheet, it is not clear just what each of the cell pass/fails represent.
Members often ask of DMM recommendations, must they watch all your vids?
Joe, after downloading your spreadsheet, it is not clear just what each of the cell pass/fails represent.
"Fail" = Magic smoke escaped at the specified voltage.Members often ask of DMM recommendations, must they watch all your vids?
You could try watching one of them...
PS: They're not 'recommendations'. It only measures one tiny aspect of a multimeter (resistance to sparks).
When I opened the spreadsheet FIRST time the Column titles DID NOT appear, hence the reason for my post.
All good now.
Can I also say it seems obvious (at least to me) that the thread title has many overlook the excellent work you have done, but maybe not so with the addition of DMM in the title.
PS: They're not 'recommendations'. It only measures one tiny aspect of a multimeter (resistance to sparks).
Joe, I thought just the addition of "DMM" would enable more hits from a forum search:
Hear kitty kitty kitty, nope not that kind of cat. CAT III handheld DMM surge tests.
Anyway, I'll butt out now, please carry on with what history will show as magnificent work.
After six years of use, my Mastech MS9508 / Cen-tech P37772 LCD was starting to become intermittent.
Notice that the LCD is starting to pop out. The On and Hold buttons are letting some photons escape. Sparks are coming from the transistor test socket.
No holidays for you and your surge tester.
What meter to fun first in 2016? Would like to see that Keysight GDT protection in action
What meter to fun first in 2016? Would like to see that Keysight GDT protection in action
Maybe not the first meter, but it'd be nice to see a BM257 run at some point. You've run a lot of lower end Flukes and compared them to your BM869 as a comparison to Brymen meters, but it seems to me that a BM257 or similar would be a fairer comparison in terms of price range / size / etc.
Thanks for the videos. I've been watching them from the beginning and it will be interesting to see what survives in 2016.
I have a feeling the larger GDT devices will survive the test, but the other protective devices will certainly fail. The more common larger GDT devices will absorb enough energy to clamp a spike down to 1kV even if the spike is a direct lightning hit. The traces will vapourise, but the GDT will still be there unbroken in the carnage. Seen that in plenty of telecoms applications, where you find the green module blackened and burned, with nothing left of the incoming wiring, the IDC Krone socket, the PCB holding the GDT units or the earth wire, unless you used 10mm cable for it. About 10% chance the PBX after it has survived unscathed, they generally blow all the line cards, power supply and any extension card that ran into the incoming frame. The phones however typically will survive, unless they were in use when the lightning hit.
I just was thinking that instead of blowiing up a bunch of more meters, why not run a video on the protection devices that can be found inside. Run a PTC or two, some MOVs, gas discharge tubes, etc. This would give easy subjects to video, and some fun fireworks perhaps. It would also be much cheaper and easier to video. This would help illustrate the actual safety of the safety devices themselves.
no i dont have circuit in mind. its just an idea because the UNI-T PCB always come with unpopulated MOV. if say by putting in the MOV, and it can stand up to some more surge, it could be good news for some DIY-ers who are interested to mod it but do not know the result for a real surge.
There are a few things you should consider.....
There are many many different MOVs in the world. I would doubt they put it right across the inputs for example. So even if you knew the MFG and PN for the MOV, hooking it to the generator is not going to tell you much.
Even if you traced out that part of the circuit of the meter you are wanting to test, clearances would not be the same if I just threw something together. If your goal is to test a specific meter with some changes, I think to really know what is going to happen we would use the real meter.
Next is your statement about "...DIY-ers who are interested to mod it but do not know the result for a real surge."
First, let's talk "real surge". Let's just assume that the IEC standards represent a real surge. I have been involved with these tests from time to time. Believe me, if something goes wrong there it can be a real thrill. Even my little half cycle line simulator does not come close to the amount of energy we test to. And believe me, with all the comments people have talked about safety and how the meters have never been shown to be unsafe during my tests, the last thing you want is for someone who has no clue to modify their own meter and then think it would survive these tests or worse, somehow be safe. None of us want that. This is why there are real labs that run these tests.
Its fun to look at some of the mods people have done to their handheld meters. Some of those rat nests would light up on a real test and worse, after cutting holes in the case, may actually come apart. No thanks...
If the goal is to "harden" the meters front end, I tried to show how to make an attenuator for a meter. Once again, people started talking about safety, which was never the goal. It is a good way to protect the meters front end. That may be a better approach.
That said, believe me, I know what you are getting at and you are not the first person to ask me about this. My advice is just buy a better meter if you are concerned about it.
A little info on GDT and usage and turn on.
http://www.citel.us/gas_discharge_tubes_overview.html
Littelfuse datasheet, they are probably the devices installed.
http://www.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_gdt_catalog.pdf.pdf
they are rated to handle a pulse with a risetime of 1kV/us, so turn on is pretty fast. Failure is by going open circuit on the 2 terminal devices, though you do get safety ones that have a shorting bar that fails the device as a short circuit when it is ruptured.
Page 10 shows that it pretty much is turning on after around 300ns of the transient being applied, most of this probably due to lead inductance. They tend to stay on until the voltage drops below the holding voltage of around 140V, though they can easily clamp at over 1kV on a high energy pulse limiting the downstream side to that. Probably that is why they use 2 in series, so the voltage is clamped hard by the second stage to the breakover voltage of the second device.
PS: They're not 'recommendations'. It only measures one tiny aspect of a multimeter (resistance to sparks).
One?
The series resistance on the input does look like it will at least attenuate the pulse, though the survival of the resistor is not guaranteed, so it has a blast shield to keep the pieces more or less together. Then they cascade that again so it is likely it will safely absorb the pulse without blowing up, though the chances of it surviving are not that good it will at least absorb the test pulse. Low capacitance is a major advantage over a MOV, and the residual capacitance will likely help as well.
PS: They're not 'recommendations'. It only measures one tiny aspect of a multimeter (resistance to sparks).
One?
OK, more than one...