Cheap meters.

[stj]

Re: Cheap meters.

yea, that pissed me off because i only had the 8002 for a week when that got posted about!

the hackability is good on those meters though - i change the time to power-off and fix the backlight on them.

[Th3_uN1Qu3]

Re: Cheap meters.

Saw Dave's review on the AN8008. The missing mA range is the only negative i'd give it for the price range. Accuracy is quite amazing. If you are only going to use it on low voltage stuff, it is definitely worth the money.

[redwire]

Re: Cheap meters.

The ZT109/AN8008 is pretty good deal for 9,999 counts, but not for mains-voltages use. It has some tiny 3.6x10mm fuses rated 250VAC and not sand-filled, not even 3mm gap. But benchwork it does pretty good.

I think you can enable the missing mA ranges, thermocouple etc. in the EEPROM.
I should try it but too lazy.

[stj]

Re: Cheap meters.

but not for mains-voltages use

complete bullshit - mostly spread by davey fans who never looked at a meter schematic or manual.

the 8001/2/8 are fine for mains.
the gaps are good, the soldering is clean and the probes are o.k.

the fuses are ONLY used for current mode, and the manual clearly states 36v DC or 25v AC is the safe maximum for current mode.

just like people bitching about the ut61e having 250v fuses - well it clearly states 250v on the front.
if your going to ignore the manual then natural selection will come into play!

[redwire]

Re: Cheap meters.

These cheap chinese multimeters have fake regulatory claims, so the question is- what voltage are they safe at?
It's good to know, as some are a garbage build with flux, solder gobs, bad PCB layout, crap probes etc.

I do high-voltage 400-600VDC measurements... should I use this meter for that, or PFC circuits- as many hobbyists do here.

Agree davey is about Cat. III for electricians on HV panels etc. and the meter's Cat. III/600V and Cat.II/1,000V claim is fake.

I looked at the PCB and it has a few spots with narrow gaps. One trace bypass the V fuse entirely, eek.
Yes $25 multimeter build quality is good and gaps seem ~1.5mm so OK for Cat. II and home use to 300V but the 250V fuses are too tiny. Fuses are also needed for voltage mode.

[stj]

Re: Cheap meters.

but the fuses wont blow in voltage-mode because there is nothing in the meter to create a load.

[redwire]

Re: Cheap meters.

If you are on anything other than Volts, i.e. ohms, and apply voltage, the meter's input clamp/TVS turns on. Or you grossly overvoltage the input and breakdown occurs. Then the meter unintentionally creates a load.

I should have been clearer about "voltage mode", meaning anything other than measuring current.
I thought it best to have a fuse blow instead of PCB traces or parts burning up.

But Fluke 87 has no second fuse, they use a spark-gap, two PTC's, fusible resistor there. Hmm.

On the AN8002/8008 the second 200mA fuse seems to protect the uA function only, and I thought it would save the tiny PTC and pulse out function etc.

I'm just saying this second fuse could be expected to interrupt high fault, same as the current-shunt fuse.


I've attached typical DMM input stage section, sans main input fuse. Not sure how the pulse out is protected.

[budm]

Re: Cheap meters.

I do not see any protection for V/Ohm unless J1A is installed, it looks like jumper.

[stj]

Re: Cheap meters.

J references are contact-pairs on the rotary switch

[budm]

Re: Cheap meters.

So it does not look like it has any protection in Volt mode at all.

[redwire]

Re: Cheap meters.

I looked into it more, and multimeters don't have a fuse on the voltage (non current) mode input, because this is also the ohms, continuity, diode-test input and the fuse's resistance gets in the way.
All you see is HV resistors and PTC to protect the ohms current-source.

These cheap chinese multimeters, most have very poor spacings, so an arc or breakdown would have nothing to limit the fault.

I know people shouldn't be using these "at high voltage" but the bogus labels say 600V or 1000V.

[Th3_uN1Qu3]

Re: Cheap meters.

They will do 1000V. But it's CAT II at best. If you are an electrician doing industrial or powerline stuff, you buy a meter that has passed regulatory agency testing. The Chinese meters are OK for hobby use. But i wouldn't try them on, say, a high power tube amplifier with HT supply higher than 200 volts.

I located my new 830B and have a 20MP camera at my disposal (Lumia 930 ). Want me to tear it down for you guys? It will be stripped down anyway as i want to build it into a power supply - was cheaper and faster than waiting for a panel meter from China.

[stj]

Re: Cheap meters.

i imagine it takes up a little more space than a panel meter from china!

[redwire]

Re: Cheap meters.

830B multimeter selling for $USD 3.79 well that's pretty cheap. DT830B as a kit for more dollars.
They seem to use the 'ol 7106 A/D IC.

I got one to carry around in the car, but it uses those crap 12V A23 batteries.
Glued a 9V battery outside it, lol

[eccerr0r]

Re: Cheap meters.

Those FWP Hazard Fraught Tools meters look like 830B's...

Though the HFT models do use PP3 batteries...?!

[eccerr0r]

Re: Cheap meters.

DT830B as a kit

I think I bought an 830 kit eons ago as a gift, and it actually had a true 7106 DIP40 in it. Now we get these die bonded to PCB crap :-(

[Th3_uN1Qu3]

Re: Cheap meters.

830B multimeter selling for $USD 3.79 well that's pretty cheap.

They can be found for under $2.

[eccerr0r]

Re: Cheap meters.

I have a small pile of the FWP (Free With Purchase (coupon)) Hazard Fraught Tools meters. They are indeed made cheap.

I have one meter that uses the A23, but it's not an 830 clone... and yes I hate the A23 - doesn't last long and hard to get cheaply...

Attached is one variant of the HFT meter - that has a backlight...

And speaking of pointless repairs, I did try to "repair" this meter multiple times - fixing broken probes, fixing the common connector and melting the case, and ... replacing the battery ... when all of these could have been "fixed" buy getting another free unit (This is my garage/automotive repair meter that I toss around...)

[stj]

Re: Cheap meters.

funny label on the battery. "(c) 2012 Sunbeam Products Inc"

i'd swear PP3 battery's have been around much longer than 2012!!
are they really claiming copywrite over it??

[eccerr0r]

Re: Cheap meters.

I think they're copyrighting the label design - not the battery. The label, which just like any artwork, can be copyrighted...