Using the UNI-T UT61E to measure 20 Amperes

[@MarcoFranceschini1971]

Great new one, shunt resistor Joe...for the UNI-T UT61E.

[@SBHSGA]

Maybe you could start selling a kit for the UT61E? Call it the JS upgrade package? Just kidding - great video - and that 61 is becoming quite the device! BTW - I get my Brymen 869S in the mail today. TME in Poland is a great outfit.

[@joesmith-je3tq]

Enjoy the new meter.

[@BrassLock]

Thanks for uploading this test Joe. I wonder if a scaled-down mini Peltier style of thermoelectric cooler would allow handheld devices to handle more than 20 amps, or for longer than is currently recommended.

[@joesmith-je3tq]

Like the other post about the micro fan, we still need to remove the heat. A Peltier is not efficient and would create a lot more heat that we need to deal with, not to mention all that wasted energy needed to run it.

[@otnica]

A couple of ventilation holes on the case will help keeping the temp under control.

[@joesmith-je3tq]

They go to all that work to design the interlocking case for safety and you think we should drill holes in it?

[@otnica]

Experimenting or redesigning? The case was designed for a 10 Amp max current shunt and not for your increased 20 amp. Despite using a larger shunt there is a substantial heat dissipation increase. Other options besides melting the case could include asbestos insulation of the shunt. But, perhaps if you just keep the meter for bench work, a safe enviroment, the couple of HOLEs could do it. All a matter of priorities of choice. BTW, I like your very comprehensive evaluations of DVTMs. Keep up the good work!

[@joesmith-je3tq]

I could run it with an external shunt, use the UT210E, remove the back cover all together, go to a smaller resistance and add a gain stage, lower the Watt density, use Teflon..... Adding a few holes is not going to do much. Maybe a fan with a lot of venting. Try some of your own ideas and post the results. I am interested.

[@hdmalpas]

Have a look into the ET201 it is supposed to be 20A, it is not just a DMM but also an oscilloscope?

[@felixcat4346]

Very nice tutorial. How can i measure the resistance and amperage of a component ,like a light bulb while it is loaded using 2 multimeters? The one measuring resistance could get damaged.

[@joesmith-je3tq]

There is something called ohms law. You should look it up. You could do this measurement with one meter.

[@joesmith-je3tq]

Right, if Joseph is playing with 220 AC line voltage and a light bulb, a meter may not be a very safe way to play with it. I attempted to look at some non-resistive AC loads with a scope for fun. kzbin.info/www/bejne/ZmWsaKF-dsR7rq8

[@mdzacharias]

I just had a funny thought (to me anyway...) How about a magnesium shunt? :-)

[@joesmith-je3tq]

Think it would burn a UNI-T to a crisp?

[@mdzacharias]

Aw, now you gotta do it...

[@glenslick2774]

So the watt density figures in watts / mm^2, or watts / inch^2, is that based on the surface area of the current shunt (Pi * diameter * length)? This is the first place that I have seen watt density units being used and was unsure exactly what they meant at first.

[@joesmith-je3tq]

Surface loading or Watt density is normally something you would consider when designing heaters. Yes it is based on the Wattage and surface area.

[@otnica]

a micro fan; could it help?

[@joesmith-je3tq]

In real life, this would never be a problem. The manufacture's will derate the current input based on the design. In the case of my little experiments, I still need to get the heat out of the case. Drilling holes in the case is not an option. Using metal to conduct the heat outside the case is not an option. The best idea would be to reduce the resistance like some of the cheaper meters I looked at. The 61E does not have a programmable gain so an external amplifier would need to be added. Personally, I use other means to make current measurements. What's the voltage drop of the UT210E at 100A. haha. Also the large external shunts, LEM sensors and what not depending what I am trying to do.

[@JackZimmermann]

Could you lower the burden voltage on the multimeter just by choosing the right fuse? I remember from one of your earlier videos where you showed how much drop there was on the fuse.

[@joesmith-je3tq]

Slightly. Putting a 30A slow blow fuse into a handheld meter to get low burden in the mA range may not be the best idea for other reasons and is not going to win you the MacArthur award. Always replace the fuse with the manufacture's recommendation.

[@JackZimmermann]

Haha! Good advice. Just curious if there is a large difference between fuses of the same rating. Unlike someone I know, I don't have a stack of exploded multimeters with fuses. :)

[@joesmith-je3tq]

You haven't lived until you have a stack of exploded multimeters.. I can't answer your question. I am pretty limited in what I have for the larger fuses like this. They all seem to come with the three major brands and they don't have the same break currents. Higher current rating will typically have a lower resistance. But you can see it's minimal.

[@JackZimmermann]

To be fair, I wouldn't dare even to be in the same room when you start up your high voltage gear. Been bitten twice by 240 volts and once when shorting out the CRT on a Mac 128k during repair back in the eighties. Young, dumb and full of ... The CRT was by far the worst experience. But as usual, you get lax after a couple of hundreds of repairs. I which I had money (working on a startup right now), then I would send you a bench multimeter to test. Quite curious of the difference. As always, great videos! I learned a lot.

[@joesmith-je3tq]

I appreciate the thoughts of those wanting to send in meters to tests. For now I can't really see asking for money to run the tests. It's really out of my own interest as I have time. If anyone else can benefit from the data I collect, all the better. When I was very young I started playing with TV sets, with some guidance from my dad. Now we have Google to give us guidance. Lot's of free advice out there.... The main generator with the VF display is fairly safe. Not much energy and it turns it's self off when the test is done. This includes discharging the bank. The connectors I use are normally covered so I don't really come in contact with anything. Now that small one that sits on top used to simulate a half cycle line condition. That is not one to play with. The safety is really just turn the thing on and stand back. That long PEX discharge probe is the only safety feature.

[@AlexandreJasmin]

What about the low-z voltage range on some meters? How much power will it dissipate at high voltage?

[@joesmith-je3tq]

I have a few meters that have this feature and they use one or more PTCs to pull it off. So it's not a constant resistance. Looking at one meter as an example, at 120VAC applied there is 4.7mA through it, so a little under 600mW. When cold, the meter has a resistance of around 3K which would be closer to 40mA.

[@zx8401ztv]

Did your new shunt return back to exactly the value you set it?. I was just wondering if a once heated shunt is altered slightly. Like the adaptive backlight, thats what all meters should have :-)

[@joesmith-je3tq]

If you are asking about the shunt, it depends. Many of the shunts I tested are no longer considered conductors. It seems to have something to do with the melting temperature. If you run the shunt below this, it's not going to change. If you really want to know if the meters displayed current returned to normal once it cooled, yes. You could repeat this with your meter but read the manual as they may limit the time you can measure for. Also, many cheap meters may not have the resolution needed to detect the change. The free HF meter may not show any drift. 3 or 3.5 digit meters would have to be really crappy... Never mind, some are!! haha I do like that backlight as well. Every time I pull that meter out for an experiment, I think why isn't that in my Brymen!

[@joesmith-je3tq]

I am in the process of running this test on several meters just for you. I'll put this followup video on-line today which should help answer your question.

[@zx8401ztv]

Yep you did a smashing job with that linear light, just the right illumination to countermand the darkness, very clever :-D. I came back to see if i had a reply as i didnt get a notification, i think youtube is being messed around with again :-(. Check your subscriptions.

[@zx8401ztv]

Thankyou :-D, i bet the cheap shunts change after a hot test, crappy material i would expect :-D

[@joesmith-je3tq]

I ran a long test yesterday with several meters where I ran them all at 5A and let them settle. Then zeroed them out and let them sit and cook. I then took them to 10A and back to 5A. They all returned to normal, except the 61E I modified. I then took the 61E to 20A and let it cook, then back to 5A and after a very long time it returned to the previous value. When I aligned the UT61E, I used the Brymen as a reference and the PCB was cold. I suspect the problem is that pot they have sits right next to shunt and fuse which heat up. But now I have a fair amount of thermal mass so things lag. These UNI-T meters are not always the best layouts. I think the thing to do is remove the pot. The way they set it up, that thing is WAY to sensitive anyway. UNI-T is trying to make money with these cheap meters, so you can't expect too much out of them.

[@newsogn5148]

what software is that I can't tell?

[@joesmith-je3tq]

LabVIEW

[@kaybhee6]

what software is that

[@joesmith-je3tq]

Custom

[@tanishqbhaiji103]

dumb idea: why not temperature compensate a fuse and use it as a shunt to reduce the burden voltage

[@joesmith-je3tq]

Use a clamp and get the burden to 0.

[@caio1998caio]

joe, I heard you talking about Dave's meter, is he working on a new one?

[@DoRC]

Arduino Eletronico he sure is. the 121jw and it looks like it's gonna be a sweetheart.

[@caio1998caio]

Could you link me some video/somethig about this new meter? Couldn't find a thing about it.

[@joesmith-je3tq]

They mentioned it will have a higher voltage diode check mode as well which if you play with higher voltage diodes may be a nice feature. They also mention about it having a lower burden voltage.

[@caio1998caio]

Thanks for the help guys, I'll join EEVBlog forum. Also, higher diode check voltage is pretty handy, shurely if I have the money when it comes out, 'll buy it.

[@klystron44]

Certainly believe in getting your money's worth out of your meters. How about external shunts? I use one of 30A, like your video's.

[@joesmith-je3tq]

Most of these meters were bought only for these experiments. The only one I actually use is that Brymen BM869s. It is rare I use a handheld multimeter to directly measure current. The UT210E gets a fair amount of use as a DC current clamp.

[@sepertude]

Get DT4282 and make detail review, nobody did it yet. Or some used Gossen from ebay.de

[@joesmith-je3tq]

Buying a used meter for these tests is just a bad idea. I would have no history about the meter and the previous owner could have stressed the meter causing it to skew the test results. The amount of time it takes to run one, it's just not worth any perceived savings.