A look at the Uni-T UT210E

[joeqsmith]

First graph is with the UT210E inside the degauss coil.   Scale is 20A/division or 80Ap-p.  The second graph is from my gauss probe.  Showing about 500 gauss peak.    I may need to drive it harder.

[joeqsmith]

Joe, what's that cool-looking shiny thing in the background (two handles, several buttons)?

Visit here often?   

Still not enough, apparently.

Thanks, Joe. Beautiful work. Going to check out your other vids too.

Thanks for the compliment.  I tried to give that 70's look.   There is always the long thread where I post about the latest tests at:

https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

[bitseeker]

Curious how you people are doing it or if it's not been a problem yet?     

I only use it with relatively low currents. Not a problem yet.

[flywheelz]

Same here.

At what type of current the problem appears?  Newb question, is the problem still there after ZERO?

P.S. I am blown away by your one of a kind DVM torture tests 

[bitseeker]

High DC currents or high AC currents that are interrupted sufficiently above/below zero. In other words, large amounts of flux can leave the clamp magnetized. If the condition is bad enough, zeroing the meter may not work or may not leave enough headroom to make measurements.

[joeqsmith]

With the new PTC, it's now about 630 gauss peak.  This increased the time to about 500ms.   

[joeqsmith]

Short clip showing using magnets to bias the UT210E.   Need to remember to hold the button in longer.... Too much coffee.   

https://www.youtube.com/watch?v=0lyMiAKfOjU&feature=youtu.be

[bitseeker]

Good demo. That degausser is working really well.

[joeqsmith]

I think it's good enough now that I'll start working on the box for it this weekend. 

[bitseeker]

To match the pulse gen?

[Circlotron]

Why does the current waveform go non-sinusoidal when it is tapering off?

[joeqsmith]

To match the pulse gen?

Why does the current waveform go non-sinusoidal when it is tapering off?

The power here is pretty poor so I never see a nice looking wave looking at the line.  However, as the flux decays the wave does have a double hump thing going on.  It's always there but just not as pronounced.   

Let's see if you can answer your own question with a few clues.   Again, to be clear the circuit is a fuse, push button, PTC and coil all placed in series and driven off the AC line. 

In the attached plots, the yellow (channel 1) is the output from the gauss sensor.  Red (channel 2) is the AC line voltage and Blue (channel 3) is the current.   

76 shows the entire process as I toggle the button.
77 shows the start of the cycle.
78 shows later in the cycle.

What is the thermal response time of a PTC? 
If the PTC were replaced with a resistor do you think we would see the same strange shape?

[joeqsmith]

Picked out some of the better looking sections.  Epoxied then and used some 150, 200, 300 and 600 grit.  Sealer and stain.   Needs some dry time before I can do anything more with it. 

[bitseeker]

Looking good.

[joeqsmith]

Looking good.

Thanks. First coat of poly applied.   Wife is home so can't just toss it in the oven.  Sitting over the office lamp curing (none of this LED rubbish).  Should be able to finish it up over the weekend. 

[SeanB]

Non sinusoidal current waveform is a PTC artefact, it is designed with a small amount of voltage dependency, so the current pulses get shorter and smaller as it heats up, leading to the magnetic field degrading fast but evenly as it heats up. It also has to have a very low current flow when hot, so that it does not lead to dot crawl on the CRT display with the residual current that has to flow with the device hot.

If making one using an old CRT TV set you can just cut the board section out of the power supply, but make a note of the connections, as most CRT monitors use a 3 wire degauss posistor, which has 2 thermal elements in there, one to provide both the heating and the reducing current, by being a PTC unit that heats up, with the resistance limiting the current to a peak when cold and reducing it as it heats up. The second is a NTC unit across the coil itself, but in very close thermal contact with the PTC heater ( simply by being on the other side of the contact plate connected to the middle pin) so that as the PTC heats up the NTC drops in resistance, shunting the current away from the coil, dropping the magnetic field to a much lower level when hot.  That way the heating current does not flow through the coils when hot, eliminating the dot crawl on a CRT computer monitor, as this typically has a much smaller dot size than a TV set, which would mask this crawl in most cases simply as it was smaller tham the dot pitch.

[joeqsmith]

After 3 coats of high gloss poly, wet sanding between coats and adding four rubber feet.   

[bitseeker]

That's a deep finish alright. Are you going to give it a metal faceplate too?

[joeqsmith]

Let's not get too carried away.  It's still a UNI-T after all.      

The camera has a hard time with it. Peace out.   

[bitseeker]

Not the Uni-T!

[Digital Corpus]

I wanted to measure the current of my alternator in my car, but in fiddle with other things, I left the meter on there when I started it. The starter is ~1.8kW so I definitively put a whole lot of amps through that coil. It provided about a 300-500 mA offset from magnetising the coil. I flipped the meter over, started the car again and removed it the offset. Just thought I'd share.

As for the work you all have been doing on hacking this little sucker, holy crap I like what has been done. My current week is packed, but going out to 6,000 counts and flipping the start order of the modes is definitely on the list. Thanks for the work you all have done.

[SeanB]

That's a deep finish alright. Are you going to give it a metal faceplate too?

Bit hard unless he has a slot in it, otherwise it will be a shorted turn on the coil. Even then the gap is easy to short out with a metal object ( the things going into there is generally ferrous) which makes for some interesting sparks.

[Behemot]

Anyone willing to test two new eeprom mods?  It gives two new functions in 2A mode.  Its reported on the Russian site that these functions still have the full count even after zeroing out (i.e. doesn't go back to 2000).  The LCD does not show a "." in the read out.

Update:  Tested the DCA 0000 function in 2A and it truly works even after zeroing out. 

Code: [Select]

       old      new
 A7: 00 1C - DCA 0000 in 2A mode / SELECT slot 3
 B7: 00 1D - ACA 0000 in 2A mode / SELECT slot 4

That group is really digging into it.  So is the decimal gone as they suggested?

With my programmer working again, I tried these changes.  Currently I have the meter default to DCA/DCV. 

If I turn on the 210E, then select the 2A mode, the decimal is shown.  Zero out the meter, the decimal is still shown.  Putting more than 2A through the meter will over range it. 

Turn the meter back off and on, then again select the 2A mode.  Don't zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.

Turn the meter back off and on, then again select the 2A mode.  Select AC, the decimal is shown.  Now select DC, the decimal goes away.  Don't zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.  However the meter now starts beeping at about 600mA. 

Turn the meter back off and on, then again select the 2A mode.  Select AC and then DC.  Zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.  However the meter still beeps at about 600mA and there is no decimal.

So it's not a real clean setup IMO.   Maybe I missed something.

Oh man, this range mode seems very appealing. But what about the strange behaviour joeqsmith was writing about? Has it been corrected?

[flywheelz]

Anyone willing to test two new eeprom mods?  It gives two new functions in 2A mode.  Its reported on the Russian site that these functions still have the full count even after zeroing out (i.e. doesn't go back to 2000).  The LCD does not show a "." in the read out.

Update:  Tested the DCA 0000 function in 2A and it truly works even after zeroing out. 

Code: [Select]

       old      new
 A7: 00 1C - DCA 0000 in 2A mode / SELECT slot 3
 B7: 00 1D - ACA 0000 in 2A mode / SELECT slot 4

That group is really digging into it.  So is the decimal gone as they suggested?

With my programmer working again, I tried these changes.  Currently I have the meter default to DCA/DCV. 

If I turn on the 210E, then select the 2A mode, the decimal is shown.  Zero out the meter, the decimal is still shown.  Putting more than 2A through the meter will over range it. 

Turn the meter back off and on, then again select the 2A mode.  Don't zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.

Turn the meter back off and on, then again select the 2A mode.  Select AC, the decimal is shown.  Now select DC, the decimal goes away.  Don't zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.  However the meter now starts beeping at about 600mA. 

Turn the meter back off and on, then again select the 2A mode.  Select AC and then DC.  Zero out the meter and place more than 2A through the meter.  It does not over range and reads the correct value.  However the meter still beeps at about 600mA and there is no decimal.

So it's not a real clean setup IMO.   Maybe I missed something.

Oh man, this range mode seems very appealing. But what about the strange behaviour joeqsmith was writing about? Has it been corrected?

You need to disable the OL alarms.  I haven't done it but I think its writing FFs from 16 to 1C.  joeqsmith has done it. I am sure he will share what he did.

[Behemot]

Thanks, I'll wait for his response.