But not immediately. I tested 400V occasionally, but couple of them died while testing 12V. I am wondering it 400V weaken the meter.
The old CenTech meters are 1000V, but the new models are 250V. Why even bother to have 50V more than the next range of 200V. Perhaps it's just same design with new label, when they got enough reports/complaints.
I am wondering if it's worth picking up some of the older 1000V models off ebay.
Buy Fluke, or at least Extech.
Fluke aren't perfect. I once accidentally touched the anode of a TV line output valve (tube) when testing with a Fluke meter. It killed the LED display.
John
On a sunny day (Sat, 31 Dec 2022 11:30:18 -0800) it happened John Larkin snipped-for-privacy@highlandSNIPMEtechnology.com wrote in snipped-for-privacy@4ax.com:
On recommendation of somebody here I bought 4 multimeters on ebay for the amount of 4$something a piece. All 4 are still working...
Quite accurate. too.
Guess I was lucky.
On a sunny day (Sat, 31 Dec 2022 12:49:05 -0800 (PST)) it happened John Walliker snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:
I once did that with my scope probe. Called the importer, got a new input chip, fixed it..
Did you try them with 400V?
I used a Fluke 83 when I was earning my keep. It survived sitting in a pickup year around in Nebraska weather and trips through wet cornfields. I might've left it set on ohms while checking a 480 volt circuit but I don't remember. I think it survived that also. Is Triplett any good nowadays?
On a sunny day (Sat, 31 Dec 2022 15:19:07 -0800 (PST)) it happened Ed Lee snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:
Very likely, measured PMT supply stuff, but a searh for 'multimeter' in my own postings in my own newsreader found these:
##On a sunny day (Tue, 8 Nov 2011 08:07:17 -0800 (PST)) it happened George ##Herold snipped-for-privacy@teachspin.com wrote in ## snipped-for-privacy@o9g2000vbc.googlegroups.com>: ## ##>On Nov 8, 6:13 am, Jan Panteltje snipped-for-privacy@yahoo.com wrote: ##>> Killed one of the new 3 dollar 40 cent multimeters ##>>
##>> OK, they are only 1 kV, and I went to 1900 V and higher. ##>> So this is the third dead multimeter, ##>> it shows very erratic readings now on all ranges, ##>> chip CMOS isolation pierced I think, actually ##>> it may have seen as much as 2700 V and that while changing voltage ranges= ##>. ##>>
##>> So, anyways, I have some nice analog 100 uA (IIRC) huge meters somewhere ##>> in the attic, will add a resistor and make an analog HV meter for this PM= ##>T stuff. ##>> Or maybe some HV attenuator box for the second (and last Chinese meter). ##>> sniff sniff. ##>> At least now I have a spare 9 V battery, ##>> See good in bad :-) ##>
##>High voltage, the death of most DMM's? I killed a 'good' ~$50 DMM ##>many years ago when I hooked it up to the spark from an old 5 HP lawn ##>mower engine that wouldn't run. I was 'convinced' that the spark/ ##>switching circuitry was no good. In retrospect a little resistor ##>string could have saved me from kicking myself all day! ##>
##>
##>George H. ## ##What I think happened is that I switched ranges, while still voltage in the HV capacitors. ##In these simple PCB range switches then the CMOS input possibly gets the full ##current via the series resistor, but could be anything else of course. ## ##I looked in the attic, found 2 huge analog meters, but those turn out to be 1 mA fsd. ##That is too much load to measure stuff like this. ##So, went to ebay and ordered a 50 uA analog multimeter for 6 dollar 55 inclusive shipping: ##ebay nr 160573395515 from China. ##Cannot even buy a stand alone meter for that here. ##I also ordered 3 extra digital multimeters, the same as the other ones, 3 dollar 40 or something. ##^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
So that explains why I have still 4 working ones :-) Meters now in use since 2011, no more problems.
230 V mains AC also OK, measured that many times.:-) Life goes on
High voltage can destroy resistors, but this seem to be quite fast.
Lot of folks live in countries where line voltage is 230V. So 50 volts makes a lot of difference.
I know nothing about CenTech meters. But I have several "DT830B" meters. Available schematics shows 3 resistors in series for 1000V. My oldest one have 2 resistors. Newest one have single resistor. Standard miniature resistors are rated for 250V, one can get better ones, but I doubt that one can get cheaply 1000V capable ones. Still, meter is marked as 1000V DC, 700V AC (the same as old meters).
This is for 250V DC. AC range remains at 250V as well. Peak to peak 250V AC is close to 400V DC. So, if it can handle 250V AC, it should be able to handle 400V DC.
They eliminated 0.2 cents worth of resistors. Ignore temperature and voltage coefficient effects. Maybe some of that is mathed out?
Chinese product prices ratchet towards cheap, and the specs ratchet deep into the lies region. Chinese amps and volts and per cent are about 10:1 off from SI standards.
It's our fault for buying the cheapest stuff on Amazon or ebay.
Is any Chinese stuff really good? Rigol is. Extech is good but isn't all Chinese.
On a sunny day (Sat, 07 Jan 2023 08:44:30 -0800) it happened John Larkin snipped-for-privacy@highlandSNIPMEtechnology.com wrote in snipped-for-privacy@4ax.com:
I have several of those Chinese 3$40 multimeters in use every day, and an analog one too. Most 'Chinese' stuff is OK, and much has US or Taiwan made chips in it.
My Chinese AC / DC clamp on meter died, but more because it mechanically sort of fell apart, got a Voltcraft, not sure where that is made,,, works great. Have a Voltcraft soldering station too, now in use for 10 years or more. Lots of small modules from China from ebay.. My drone is super! China too. My Tecsun SW LW AM FM SSB radio, my Baofeng 2 way radio, my satellite receivers, my terrestrial TV receiver.. etc etc But from the US? Microchip PIC micros are OK... Oh and LCD modules, OLED modules... all from ebay Wow my Huawei 4 G USB modem sticks (have 2) SUPER SUPER
US better get their trip together, just sanctioning the competition does not do it you guys need to produce cheaper faster better,, Like you hinted, why buy a Tek if a Rigol is cheaper and maybe better.
PTC+TVS can help but isn't generally reliable. The combo still has failure modes.
For signal-level stuff, depletion fets are good current limiters. I knew the guy who designed some nice Fluke benchtop DVMs and he used long strings of jfets as HV current limiters in the ohms sections.
The world needs a really good 2-terminal bulletproof current limiter.
The failed cenTech meters come on with display but no meaningful readings. I don't see any PTC. There are glass fuses. One failed open but another one intact.
I got an auto ranging meter. I will measure 400V with a 4:1 resister divider. I only need to know between 90% to 100% of 400V anyway.
No, voltage and resistance only. I can probably calculate I=V/R. I still have a few cenTechs for measuring current. BTW, the failed meters still work with High Amp (HA) mode, with a separate lead connector.
Yes, display is large and good, even has back light at night.
That's the CenTech i am talking about. I got 1 partial (bad LCD), 2 fail (bad LV and LA) and 4 good one.
Got load of them at Harbour Freight Tool between $0 and $4. They used to give it away with purchase, but cost $4 to $6 now.
Auto-off after 15 minutes. Definitely not keeping back light on too long. Or the 2xAAA batteries won't last.
If you are going to be working on HV circuits (>240 V) ONLY use DMMs with a CAT certification (which cheap Chinese meters don't have).
Which doesn't tell you much.
"The latest UL standard for electrical test instruments is UL 61010B-1, which is a revision of 3111-1. It specifies the general safety requirements, such as material, design, and testing requirements, and the environmental conditions in which the standard applies. UL 3111-2-031 lists additional requirements for test probes. The requirements for hand-held current clamps, such as the current measuring portion of clamp meters, are included in UL 3111-2-032.
UL standards are gradually being harmonized with similar international standards, such as those published by IEC. Until this is completed, there may be significant differences between each group's standards. For example, IEC 61010-1 2nd Edition includes requirements for voltage-measuring instruments in CAT IV environments. UL 61010B-1 doesn't."
What Flyguy might be saying - if he knew what he was talking out - is that there are safety standards for multimeters. In the US they are published by the Underwriter Laboratory.
There are also international safety standards.
A chinese multi-meter might well not conform to an American Underwriters Laboratory standard, but will probably conform to the relevant IEC standard, which isn't going to be much different.
A cheap chinese meter might be truly cheap and nasty, and correspondlngly dangerous, but anybody who sold it to you would risk being sued if it was.
It's more likely to be cheap because it was produced in high volume, rather than because the manufacturer cut any corners. I've ran into one American instrument that didn't meet their published specifications, which is a slightly different kind of problem - it wasn't certainly wasn't cheap.
Meters are rated for certain usages. That is where the CAT number comes into play. The cheap meters may be rated for home low voltage/current usage. Others rated for higher voltage /current.
I have a couple of $ 300+ meters and some of the 'free' Harbor Freight meters. None of the $ 10 to $ 50 meters. I worked with some 480 volt circuits that had fuses up to 300 amps. No way would I use any meter that I did not know it was CAT rated for the service. I would use the China meter on my home electronics that may have 500 volts in them but the current was an amp or less, but no way on a 240 volt+ circuit that had over a few amps, especially 100 or more amps supply.
If you had ever seen any Fluke or other safety films where the less expensive meters had been set on the ohms or current ranges and put across the high amp circuits no one would even think about using the meters that are not CAT ( or maybe some other standard) rated for the application.
As far as the sueing, all they have to say is the meter was used outside of its ratinng.
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