New UNI-T UT892 2000V AC/DC High Voltage Multimeter

[joeqsmith]

Who would trust Uni-T for safety or minimal honesty?
...  Have to see a teardown and BBQ lighter test lol.

We could get one and treat it as a special case, cause it's a special meter.  Maybe just test the 2kV input only.   I ran one of their high voltage sticks.  It died fairly early on as well. 

I’ll do that when it arrives with my Hipotronics HD140

I remember a few people using low current leakage testers to look at meters.   Even Dave did something similar.  Of course, they can provide enough current to prevent them from folding back.  Consider making a video of it when you run it.  I would like to watch.   Attached is a video I made to show a few cheap meters on my larger 1kVDC supply.   It appears the HD140 has a Max Trip Current AC Test 5 mA.  By comparison  I've taken out the small half amp HRC fuses with this this supply by accident.   This is the same supply I used to demonstrate to Dave that it is indeed possible to damage a DMM at 1kV after he had suggested otherwise (also attached).     

The UT892 manual says
"... withstand surge voltage up to 1000V..."
"Do not measure ACV/DCV voltage over 1000Vrms. It is possible to measure higher voltage but it may cause damage to the meter or user!"

so I'm assuming the usual functions have no decent input protection. That costs many pennies and the boss still wants a new Lambo 

??  So it's rated for 2kV but only use it to half the rated or you can damage it?     

[floobydust]

The UT892 manual says
"... withstand surge voltage up to 1000V..."
"Do not measure ACV/DCV voltage over 1000Vrms. It is possible to measure higher voltage but it may cause damage to the meter or user!"

so I'm assuming the usual functions have no decent input protection. That costs many pennies and the boss still wants a new Lambo 

??  So it's rated for 2kV but only use it to half the rated or you can damage it?     

It appears to be a normal (Uni-T) multimeter with the 'strong as bamboo' input protection, and the manual seems to refer to this - good for 1,000V typically... despite the Cat. III 600V rating which is a 6kV impulse...
The extra 2,000V input there are no specs for it. I assume it's just another 10MEG resistor array in series with the main divider string.
With no approvals and the owner's manual jibberish, who knows what voltage this thing can safely do before arcing internally.

[joeqsmith]

I couldn't tell you anything about safety but could determine at what level it is damaged.   

[Kleinstein]

Without a current range the safety may be a little better than with many other cheap meters.  No need to worry about a HRC fuses.
The separate 2000 V input has a good chance to also give better protection for the ohms circuitry. So at least that input can be relatively robust, not going to the switch for the ohms part.

I would not use it for higher mains voltage or CAT3 use, but it could still be a good meter for the few cases where you have 1000-2000 V with a limited current, like for PMT tubes or similar. Still 2000 V is only a rathersmall step up. The usual probe wires are typically only made with 1000V in mind. So to be on the safe side one would also need special test probes (at least 1).

[jhoffman]

Without a current range the safety may be a little better than with many other cheap meters.  No need to worry about a HRC fuses.

Less chance of a "high energy electrical explosion" (4th July Fireworks!!!) by accidentally connecting a multimeter in "current mode" to a HV power rail.

Removing "current mode" is a valid "safety feature".

Great point !!!

Replace the test leads with 8000 Series Probe Master Test leads and it might become a half decent HV VOLTMETER (I deliberately avoid the word multimeter).

Another point is that this UNI-T UT892 meter comes with a substantial rubber holster (for a $32 USD meter) so there's quite a bit of electrical insulation.

Given that there's no current mode and lots of insulation (just replace the test leads) this meter is beginning to appear as a viable HV VOLTMETER.

[Fungus]

I´ve got serious doubts about the 2000V range on a meter which costs "nothing".

Why? Voltage dividers are dirt cheap and there's no current ranges so they saved money there.

Then the UT-892 come along, for 42 bucks...
I got doubts. 

Even Fluke sells a $50 meter.

[Mechatrommer]

You falsely state "3 phase has nothing to do with 2KV" when you consider transient voltages in real world practical situations. Last time I checked we still use electric motors with coil windings which have a habit of generating back EMF when you switch them on and off.

if talk about transient, we can have 12V automobile producing 25KV (i got the shock once its not fun) and normal household appliances that can produce the same level intentionally. once i fixed a mains strobe when spark occur across a through hole resistor, about 1cm legs apart go figure what KV can do that, i covered the path with double sided tape acting as dielectric modifier, problem solved. transient is everywhere even in static.

I originally created this post in the interest of public safety and awareness to "bait" people to see who would bite.

so you are special kind of (troll) bot

[jhoffman]

Quote from: jhoffman on Yesterday at 07:09:31 pm

    I originally created this post in the interest of public safety and awareness to "bait" people to see who would bite.

so you are special kind of (troll) bot

I sensed (without at the time understanding why) that there was something "unusual" about this meter.

I will now buy this meter (replacing the original test leads for better ones) as in my humble opinion (after considering the evidence) that this is an excellent value HV voltmeter for $32 USD.

When you consider the PCB real-estate gained by removing current measurement circuitry (inc. the shunt and fuses) it becomes obvious that there is more PCB real-estate available for physical insulation separation to avoid internal HV voltage breakdowns.

I haven't seen a tear-down yet, but intuitively I've formed the opinion so far that this is a good HV voltmeter for $32 USD.

It's sold as a 2kV multimeter which in practice will "probably" work up to 6.0kV with some minor mods possibly required.

Mind you, I wont be holding onto this meter with my bare hands if I'm trying to measure the HV supply of a microwave oven's magnatron.

I simply used this forum as a "Litmus Test" just to gauge what others might be thinking.

[Kleinstein]

Before using this meter for higher voltage is may be a good idea to look inside first. There is a chance it can be reasonable made, but we don't know.
Besides the extra space from not having the amps ranges, the extra terminal also means there is no need to route the input to the switch / ohms ranges. The protection of the ohms ranges is often one of the weak points, more than just the voltage ranges.


With the often not so good fuses in cheap meters it may be a good idea to have a look inside first too, so one knows if the CAT rating is somewhat legit or a bad joke.

[Martin72]

Even Fluke sells a $50 meter.

Well, it says what...

I think I´ll try to get a UT892 and tear it down.
The other Uni-T, UT196 I try to let it order by our purchase man.
Amazon is not a problem to buy for us, but this one will be sold directly from china - Not so good for us..

[Martin72]

UT-196 was ordered, when arrived I´ll tear it down..

[Gyro]

...
When you consider the PCB real-estate gained by removing current measurement circuitry (inc. the shunt and fuses) it becomes obvious that there is more PCB real-estate available for physical insulation separation to avoid internal HV voltage breakdowns.

I haven't seen a tear-down yet, but intuitively I've formed the opinion so far that this is a good HV voltmeter for $32 USD.

It's sold as a 2kV multimeter which in practice will "probably" work up to 6.0kV with some minor mods possibly required.
...

At 6kV, a standard 10M Input divider will be dissipating 3.6W - that requires PCB real-estate and more than minor mods!

It's pointless going past 1kV (personally I would say 100V) with a 10Meg input resistance, the circuit loading gets too high.

[Kleinstein]

For the 2 KV range the meter is supposed to have 20 M ohms input impedance. So the higher range is more like with an additional resistor (10 M) in series to the normal divider.
So the divider would see less heat than the standard 10 M divider.

[Gyro]

I won't get on to my pet gripe about the 10Meg input resistance cop-out on DMMs then. 

[floobydust]

This multimeter is supposedly for work on VFD's and of course a bit silly in that a 2,000VDC bus yet OVC Cat. II 600V rating makes no sense.
I don't think you'll get that high a DC bus voltage in that AC environment. It's not a MV multimeter.

If you turn on the VFD LPF and look at a phase output, the 20MEG surely needs compensation to really get an accurate RMS voltage.
I'll bet it has none, they cost pennies and the boss will not get his new Lambo.

[NoMoreMagicSmoke]

I won't get on to my pet gripe about the 10Meg input resistance cop-out on DMMs then. 

I mean this sounds like a good read regardless!!!

[floobydust]

Obviously never been a member of the 20,000 ohms/volt club 
A multimeter for electricians should be in the other direction... LowZ. But not on the 2kV range.
Once I got burned with a multimeter 22MEG input resistance, measuring good mains voltage- yet the fuse was blown. It was dirt/CNC coolant on the fuseholder giving enough leakage current for the bogus reading. Costly mistake.

[PartialDischarge]

Just received the UT892, had only 15 minutes to play with it, here are some observations:

- It only displays up to 2200V then it shows OL
- From 1900V display turns red and beeps.
- 20Meg string is made up of 8 2.5Meg resistors, not shared with 10Meg input. At 2000V thats 0.025W per resistor.
- Although string is mounted at the board side edge, there is good creepage to the outside thru the enclosure lip. The first resistor in the string (R29) should have been placed earlier. Still the whole string can be covered by silicone-.
- Mine is reading 0.2% below at 1000/2000V scale, so very good
- Continuity mode works nice, is fast
- Display contrast is ok, does not have the low contrast problem.

[Gyro]

Thanks for being the first to bite the bullet.

An interesting meter (or manufacturere function combination choice). Thoughts that come to mind...

- As you say, they would have been better to put the 2kV chain further inboard.
- I was assuming that they would have added some more resistance in series with the main chain rather than having a separate one. Maybe they didn't want 1kV appearing on the main input jack?
- Funny that they have only 8 resistors in the 2kV chain versus 10 in the main one - that's 275V per (1206?) resistor at full 2200 count!
- I wonder what the voltage rating of that PTC is- although they have excluded the 2kV jack from the cat rating.
- It's amusing that the display goes red at 1900V... Because that's where things get interesting, right? 

Thanks for the first look!


P.S. I wonder if they have done anything different with the switch contact spacing?

[Fungus]

- As you say, they would have been better to put the 2kV chain further inboard.

Very obvious and would have cost them absolutely nothing to do it. I wonder what else they overlooked? 

- I wonder what the voltage rating of that PTC is- although they have excluded the 2kV jack from the cat rating.

How many volts would you need to apply to heat up a PTC in series with a 20MOhm resistor?

[Fungus]

What's the "live" socket for?

It appears to go through the range switch after the PTC. Seems dodgy to me...what's the clearances on the other side of the PCB?

[Fungus]

I would not use it for higher mains voltage or CAT3 use, but it could still be a good meter for the few cases where you have 1000-2000 V with a limited current

I'd want a much higher input impedance for that.

The small, high voltage supplies I've used tend to have very limited current. Even 20MOhm could be enough load to give an incorrect reading.

[Gyro]

- I wonder what the voltage rating of that PTC is- although they have excluded the 2kV jack from the cat rating.

How many volts would you need to apply to heat up a PTC in series with a 20MOhm resistor?

Ha, good point, the PTC isn't there for to protect the voltage function on normal meters is it!

[PartialDischarge]

I would not use it for higher mains voltage or CAT3 use, but it could still be a good meter for the few cases where you have 1000-2000 V with a limited current

I'd want a much higher input impedance for that.

CAT rating does not mean higher input impedance, it means higher clearance/creepage and higher power rating of passives.


I think the meter is fine, without current measurements which I seldom use it simplifies the board, protections and price of the meter. Also it has a 9V battery which will probably last longer than 2xAA.

[PartialDischarge]

So I decided to modify the meter, since I don't know how good those 2.5M resistors are, I replaced them with 2.4M ones that I have. Also I removed the PTC and put there the rest of the resistance minus a bit to compensate for the low 0.2% reading. Now it is measuring +-1V.