Author Topic: Handheld meter robustness testing (Read 1262180 times)

joeqsmith · « **on:** June 06, 2015, 12:54:30 am »

N2IXK · « **Reply #1 on:** June 06, 2015, 01:09:35 am »

Any muiltimeter with a legitimate Cat III rating can handle Cat II circuits.

The higher the Category rating, the higher energy the meter is safe with. You can always use a Cat III or Cat IV meter on lower rated circuits, but not the other way around....

joeqsmith · « **Reply #2 on:** June 06, 2015, 01:14:38 am »

After doing many searches on this site, I see a lot of posts about how meters are rated and tested. There were even a few posts where people attempted to put some high voltage on them. To be clear, my plan is not to do an insulation test. I am interested in surge. My plan is to construct a small generator that I will use to weed out the worst meters. If any meters are working after my basic test, I plan to further test them to the actual standards.

CAT III 600 would require the surge use a 2 ohm source with a 6KV peak (3000 Amps peak). This would ride on top of the AC. Nasty stuff. CAT II uses a 4KV peak with a 12 ohm source (333 Amps peak). The test is the standard 8/20 waveform with a short applied or 1/50 with an open.

A few good articles if you are interested:

http://www.grainger.com/content/safety-digital-multimeter
http://cp.literature.agilent.com/litweb/pdf/5990-4578EN.pdf
http://faculty.riohondo.edu/jfrala/fluke_multimeters_-_abcs_of_multimeter_safety_multimeter_safety_and_you_application_note.pdf

joeqsmith · « **Reply #3 on:** June 06, 2015, 01:49:15 am »

To start out, I need a generator that can create something close to the CAT II waveform. You saw from my first post my quick generator. This thing could hardly do much of anything.

Over the last few days I built up several circuits, blew up every bench supply I have (an repaired them) and am close now to what I am looking for.

My plan to do a sort of hybrid waveform. I plan to limit the peak to 2KV but stay with the 2 ohm source. I also plan to limit the duration of the pulse (not sub 1.0us like my first throw together setup). I plan to cut it in half. For a CAT III meter this will be no problem what so ever as it is 1/3 the peak and half the duration with the same impedance.

The second generator I cobbled up worked fairly well with a 12 ohm source but I wanted something that could do the above and put out that full 1000 Amps.

The DOE Handbook Electrical Safety is available on-line. I have played with KV low current equipment most of my life from TV and radios to modern test equipment. So I am not concerned about this little project. However, I thought it would be interesting to highlight a few paragraphs from this document.

To create the waveform, I have been using a 500mA wall mount supply. I use this to create a high voltage signal that is rectified and stored into a bank of capacitors.

In Fig. 3-4. Complete electrical hazard classification system showing 5 major groups and 54 classes. You can see capacitors are called out as Classes 3.x. They are broken down by operating voltage.

13.7.3.3 Safety Practices
An analysis of high-voltage circuits should be performed by a qualified person before work
begins unless all exposed energized parts are guarded as required for high-voltage work. The
analysis must include fault conditions where circuit current could rise above the nominal rated
value. Depending on the results of the analysis, any of the following may apply:

1. If the analysis concludes that the current is above 5 mA or stored high-voltage capacitive
energy is above 1 joule for voltages between 100 and 400 V DC, or above 0.25 joule for
voltages equal to or greater than 400 V, then the work is considered to be energized work
and should be performed in accordance with Chapter 2, "General Requirements" and/or
Chapter 3, "Hazard Analysis." See Chapter 3 for details on electrical hazard classification.
2. If the analysis concludes that the current is between 0.5 mA and 5 mA and between 0.25
and 1 joules, then the worker may be exposed to a secondary hazard (e.g., startle reaction)
that must be mitigated.
3. If the analysis concludes that the current is below 0.5 mA and below 0.25 joules, then the
worker exposure is minimal and no special precautions are required, even for high voltage
circuits.

From above, I plan to run the storage caps at 2KV. Well above the 400V limit. Looking at Fig. 3-9. Hazard Classes 3.x, capacitors, > 400 V, we can see that for 1-10 Joules, it is considered Class 3.3d. This is a Red colored box.

10) A red Class (X.3) indicates injury or death could occur by proximity or contact; often
the hazard is shock, contact burn, or arc-flash burn; engineering controls are
necessary for operation (e.g., listing or equipment approval), and administrative
controls are necessary for electrical work in this Class.

It should be obvious what the above means....

joeqsmith · « **Reply #4 on:** June 06, 2015, 01:53:39 am »

After making some calculations for the controller and output stages I ran a quick simulation of both. Attached you can see the simulated response with a 1Meg and a 0.1 ohm load attached. Not quite a 1000 Amps in the simulation.

joeqsmith · « **Reply #5 on:** June 06, 2015, 03:38:02 am »

Here is the final test generator. No high voltage is exposed except at the banana connectors that plug into the target. I was going to run it from batteries and still may. There are two banana jacks on the side used to supply the power. The key is plastic and is used to disable the unit. The cable is silicone and the connectors are a CSCB series, both rated for much higher voltages than I plan to run.

In the picture, you can see the damaged BK meter with the Pearson current transformer. This is a 5000A 20MHz part, PN 410.

Looking through Amazon, there is not a great way to search for CAT ratings. Interesting is that all the work that was put into the DVM spreadsheet and all the concern for safety, I can't seem to find them rated by CAT an fuses. I read through the forum about meters that don't meet their specs.

Halvmand · « **Reply #6 on:** June 06, 2015, 11:03:48 am »

Interesting. Looking foward to se some test results.
Do you have any meters in mind for destruction?

I would personally like to see the fluke ripoff get exited.
http://www.ebay.com/itm/F14129-Aimometer-MS8215-Auto-Range-Digital-Multimeter-DMM-AC-DC-Voltmeter-Amme-/261831441592?pt=LH_DefaultDomain_0&hash=item3cf65ebcb8

Halvmand · « **Reply #7 on:** June 06, 2015, 11:08:18 am »

Oops. That is only CAT II rated.

Fungus · « **Reply #8 on:** June 06, 2015, 12:50:35 pm »

Quote from: joeqsmith on June 06, 2015, 12:54:30 am

However, after a quick search on the internet, it seems there are many low cost CAT III rated meters available. I would like to know if any of these can handle CAT II.

Anything that's CAT III is also CAT II.

Quote from: joeqsmith on June 06, 2015, 12:54:30 am

Why am I only interested in testing them at CAT II? Well that's about the only thing I would ever dare use any hand held meter for.

The difference between CAT II and CAT III is very subtle in practice.

You can't tell if a mains socket is CAT II or CAT III just by looking at it. It's mostly to do with the distance from the circuit breakers (ie. the length/inductance of the wire between you and the distribution panel).

Quote from: joeqsmith on June 06, 2015, 12:54:30 am

Well that's about the only thing I would ever dare use any hand held meter for.

Me? I wouldn't use anything less than CAT III for regular mains work and I'd want a meter which I KNOW is CAT III, which in practice means Fluke. The numbers printed on the front of certain other brands of meter have been shown to be lies many times in these forums.

A Fluke 101 can be had for under $45, is easy to find, and comes with proper covered probes for mains AC work.

For that price I don't see any point in using anything else.

G0HZU · « **Reply #9 on:** June 06, 2015, 01:20:46 pm »

Quote

Me? I wouldn't use anything less than CAT III for regular mains work and I'd want a meter which I KNOW is CAT III, which in practice means Fluke. The numbers printed on the front of other brands of meter have been shown to be lies many times in these forums.

A Fluke 101 can be had for under $45, is easy to find, and comes with proper covered probes for mains AC work.

For that price I don't see any point in using anything else.

The only thing I'd add to that is that for the vast majority of today's hobbyists, one should rarely need to directly measure the mains voltage with a meter anyway.

I avoid it as much as possible and use a sealed 'meter in a plug' if I'm curious about what the mains voltage is. Otherwise, I'd rather debug any mains wiring inside a piece of electronics gear with the unit switched off and unplugged from the mains and after a discharge.

To put this in perspective, I don't think I've measured the mains voltage directly with a DMM for many years. Obviously it would be different if I was an electrical engineer working on domestic or commercial power distribution etc but I'm quite happy to use basic DMMs (here and at work) for most low voltage electronics work. But I always keep them well away from mains voltage (230V AC here in the UK).

joeqsmith · « **Reply #10 on:** June 06, 2015, 03:47:20 pm »

Quote from: Halvmand on June 06, 2015, 11:03:48 am

Interesting. Looking foward to se some test results.
Do you have any meters in mind for destruction?

Yes, I have started to make a list.

Mastech MS8264, 8261, 8217 and 2008B. The Extech MN15A. The UNI-T UT90A.

I don't care if it had a bad review, was shown to have a glass fuse or appeared to have no protection at all. I don't care what color it is, how many features it has or how many digits. I am looking for anything under $50 with a CAT III 600V rating and fused current or clamp. I am not affiliated with any company and have no bias towards any manufacture of hand held meters. So any meter that meets the above, I would add to the list.

Quote from: Fungus on June 06, 2015, 12:50:35 pm

A Fluke 101 can be had for under $45, is easy to find, and comes with proper covered probes for mains AC work.

I'll check. I have another Fluke in mind and am not apposed to testing more of them if they meet the criteria.

Currently I am working on a short video showing how the generator works and the waveforms it produces. I was looking around the room for loads, and there was an LED bulb that would no longer turn on. I connected the bulb to the generator and zapped it. You know, that thing came back to life! I kid you not! I screwed it back into my fixture and it is still on. Maybe a lead free solder joint failure.......

Fungus · « **Reply #11 on:** June 06, 2015, 04:23:46 pm »

Quote from: joeqsmith on June 06, 2015, 03:47:20 pm

Quote from: Fungus on June 06, 2015, 12:50:35 pm
A Fluke 101 can be had for under $45, is easy to find, and comes with proper covered probes for mains AC work.
I'll check. I have another Fluke in mind and am not apposed to testing more of them if they meet the criteria.

Under $42.50 delivered to your door: http://www.ebay.com/sch/i.html?_nkw=fluke+101

joeqsmith · « **Reply #12 on:** June 06, 2015, 05:44:16 pm »

I closed my Ebay's account many years ago but I did find it on Amazon for under $50, ships direct from China with free shipping.

As I plan to buy one higher cost DVM, I started to look at the warranty and manuals. Let's look at the 101 manual.

Quote

LIMITED WARRANTY AND LIMITATION OF LIABILITY
This Fluke product will be free from defects in material and workmanship for one year from the date of purchase. This
warranty does not cover fuses, disposable batteries, or damage from accident, neglect, misuse, alteration, contamination, or
abnormal conditions of operation or handling.

Would a manufacture consider purposely testing their products, misuse or abnormal? I guess we will find out.

For the first tests I plan to use my homemade surge generator to test all of the meters. One thing that may not be clear is for my basic home surge tests, I am not going to inject on top of the input signal. Surge would normally ride on the AC and would be tested +/- at 0, 90, 180 270. It should be clear what this means as far as the peak voltages. My concern is not so much the peak, but the energy available from the line after an arc. When I made this video showing the effects of having the surge on top of a 24V DC source it's not hard to understand why.

https://www.youtube.com/watch?feature=player_detailpage&v=ZeRkEKBYdzw#t=64

joeqsmith · « **Reply #13 on:** June 07, 2015, 01:18:07 am »

Here's the first of what will be several videos showing the my homemade scaled down surge generator in operation. You can see the output waveform with various loads attached.

Halvmand · « **Reply #14 on:** June 07, 2015, 06:30:07 pm »

Great video.

I think this one from amprobe could be a fun test:
Amprobe AM-510 for 44 $ on ebay
http://www.ebay.com/itm/Amprobe-AM-510-Commercial-Residential-Multimeter-with-Non-Contact-Voltage-New-/351412552068?pt=LH_DefaultDomain_0&hash=item51d1d20184

This too:
Amprobe AM-34 for 45 $
www.ebay.com/itm/Amprobe-AM-34-Cat-III-AUTO-Digital-Multimeter-/271867163408?pt=LH_DefaultDomain_0&hash=item3f4c8bb310

Or this one if it would drop just a tinsy bit in price and be available outside europe. From your video you don't sound european.
PeakTech 2015. It has really good features i think. Could not find a teardown of it, but some of the higher end models seems well build.
http://www.peaktech.de/productdetail/kategorie/multimeter/produkt/p-2015.html

blackbird · « **Reply #15 on:** June 07, 2015, 07:36:15 pm »

I would like to see the Elix AL72D tested. It is a cheap multimeter sold by ALDI and some other discount supermarkets. They claim CATII and maybe it will survive the 750VAC or 1KVDC.

This model is also sold as the Range RE93A and I think under many other 'brands'.

The retailprice of this multimeter is somewhere between €10 and €15.

MarkL · « **Reply #16 on:** June 07, 2015, 09:18:38 pm »

joeqsmith:

I'm interested in your surge generator. Perhaps a schematic would be helpful.

How are you triggering the discharge of the capacitor bank? Or are you just charging it until it arcs over in the DUT?

joeqsmith · « **Reply #17 on:** June 07, 2015, 09:25:15 pm »

Quote from: Halvmand on June 07, 2015, 06:30:07 pm

Great video.

I think this one from amprobe could be a fun test:
Amprobe AM-510 for 44 $ on ebay

This too:
Amprobe AM-34 for 45 $

Or this one if it would drop just a tinsy bit in price and be available outside europe. From your video you don't sound european.
PeakTech 2015. It has really good features i think. Could not find a teardown of it, but some of the higher end models seems well build.

Thanks. Glad you enjoyed the sparks.

I like that 510. I looked for the PeakTech but it does not appear available. I assume there are many more that fall into this price/rating range.

Quote from: blackbird on June 07, 2015, 07:36:15 pm

I would like to see the Elix AL72D tested. It is a cheap multimeter sold by ALDI and some other discount supermarkets. They claim CATII and maybe it will survive the 750VAC or 1KVDC.

This model is also sold as the Range RE93A and I think under many other 'brands'.

The retailprice of this multimeter is somewhere between €10 and €15.

I looked for this meter and could not find it. However, I am really looking for CAT III 600 and up.

I have now added some test lead points and a ground clip.

joeqsmith · « **Reply #18 on:** June 08, 2015, 02:46:36 am »

You saw the sparks fly from my old BK that was CAT II rated. Then you saw the sparks fly from my old Fluke.

Against my better judgement, I decided to sacrifice one more meter to the surge god. After seeing how bad the Fluke arced and blowing the control IC off the BK, I thought it would be good to tape it. The DM-301 appears as cheap as they come. It has no CAT rating at all. There are no CE or TUV marks. There is no brand name on it but it was made in Korea. I picked it up in a Sears outlet just to have a handheld. It got used a lot and is in pretty rough shape now. The LCD is cracked and I no longer use it so putting it on my scaled down surge generator is no problem.

In this video I talk a little about how I plan to go about evaluating the low cost meters. I also talk a little about the 1010 standard and how I base my pass/fail criteria on it.

When you start looking at 5 seconds between transients, 5 transients per mode, say 3 connectors testing all combinations, say 10 modes, and both positive and negative.... Well that's a very very long time to test each meter. This can make for a VERY boring video. If you ever had to test a product to these standards, you know what I mean. It's a lot of waiting.

As you watch this video, I stripped out most of the dead time waiting for the tests. I also did not show every dial setting being tested. I did leave some of it in order to show how slow this testing can go. So if you get bored watching, just fast forward.

If you are looking for a video where 1K resistors are measured and I talk about how big the fuses are, how soft the rubber case is or how the plastic feels or the colors of the plastic, these videos will not be for you. But if you want to see some low cost meters getting hit with the surge, get some popcorn. I plan to increase the energy to each and every one of them to destruction. Only one meter will come out on top and I don't care which brand or where it was made.

Once I have found the best of the low cost meters that I have purchased, then next question I need to answer is can a higher priced name brand meter go up against it.

Without further adieu, setting the bar low as it gets, here's the no brand name DM 301. Enjoy
https://www.youtube.com/watch?v=pInd17ibzDg&feature=youtu.be

joeqsmith · « **Reply #19 on:** June 09, 2015, 01:26:49 am »

Tonight I increased the voltage from my homemade surge generator until the unbranded DM-301 failed. This will be the starting point for testing the new meters. If the new CAT III 600 rated meters I order can't out perform this super low cost unrated meter, well, those would be some very poor meters. The bar is set low.

Short clip showing the breakdown.
https://www.youtube.com/watch?v=USwqyjUD-jw&feature=youtu.be

ivan747 · « **Reply #20 on:** June 09, 2015, 02:47:24 am »

May I suggest the Amprobe AM220? It has what would appear to be HRC fuses but are really normal fuses with a ceramic tube, no sand and potentially no vacuum.

joeqsmith · « **Reply #21 on:** June 11, 2015, 01:27:32 am »

I have narrowed my search for a higher end meter test against what ever low cost meter survives to the highest energy surge. Keysight's U1272A, Fluke's 28II or the 87V. All are in roughly the same price range. Leaning towards the Keysight only because I have not had any failures with my HP meters and you saw what happened with my first Fluke.

If anyone out there has actually ran surge tests on these and have an idea where they fail, it would be helpful. I would rather have the more robust meter of the three for my testing.

ivan747 · « **Reply #22 on:** June 11, 2015, 03:30:25 am »

Dave hates (feline) cats. If you rename the thread he might see it.

Mark · « **Reply #23 on:** June 11, 2015, 09:43:20 am »

Quote from: MarkL on June 07, 2015, 09:18:38 pm

joeqsmith:

I'm interested in your surge generator. Perhaps a schematic would be helpful.

How are you triggering the discharge of the capacitor bank? Or are you just charging it until it arcs over in the DUT?

I am also interested in this as I am working on surge testing at the moment, it would be interesting to compare home made vs professional unit. Can you post your schematic JoeQ?

joeqsmith · « **Reply #24 on:** June 11, 2015, 11:00:39 am »

The BK 2703C, Mastech MS8264, Amprobe AM-510, Extech MN16A, Fluke 101 are now on order. Does the Fluke 101 come out on top? Do they all outperform my unbranded DM-301?

Quote from: Mark on June 11, 2015, 09:43:20 am

I am also interested in this as I am working on surge testing at the moment, it would be interesting to compare home made vs professional unit. Can you post your schematic JoeQ?

While I mentioned it in Part 2, for any questions about surge generators refer to the IEC 61180-1.


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Author Topic: Handheld meter robustness testing (Read 1262180 times)

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