UNI-T UT61E Multimeter teardown photos.

[user4963]

measure the values ??of the capacitor can write one of these?

Please

[Lightages]

I might be able to do that tomorrow

[user4963]

thank you.Lightages

[Rick Law]

...Plus more multimeters is always priceless and enables to do alot more things....Unless they come out with a multimeter with multiple isolated channels, those things are hard to beat when combined.

I am reasonably happy with the 61E.  I already have 3 others - 2 radioshack and a DT830B.  But I actually was thinking about getting a couple more  DT830B's when I was playing around with boost circuits:
In Volt, in current, out Volt, out current, drain current, that is 4 right there.  I could use another one to do adhoc readings.

One of my 4 is a DT830B, $6 DMM, not bad.  I use it as my volt meter for my PSU.  It actually performs better than the other cheapos from Radio Shack (4-8 years old).  So I was considering getting a pair of DT830B.  But I hate all those stuff on my table leaving me so little space.

I would not invest in another mid-low end DMMs.  If I would get more DMMs, I will probably aim for a higher end ones or real cheapies.  Mean time, I just got my ATMega328 as Volt/Current meter working on a breadboard and ordered parts to transfer it to PCB.  I divided up the 6 ADC's as 3 pairs of volt+current (switch-selectable) 0 - 5/15/30Volt and fixed 0-4Amp (using a 0.1ohm as current sense and amplified with OpAmp).  The two pairs I have working gets me +-1% to 4% accuracy.  Not bad when I have not yet calibrated them yet.  After I get the parts, I can get the 3rd pair working, transfer it to PCB, and then I'll do some software tricks (the ADC under-reads at low ranges).  If I can bring it closer to 1-2% using my UT61E as "accurate" reference, I just may end up using the ATMega as my PSU's volt+current.  All three channels shares common ground, so it took me a while to figure out how I would make that work for me.  If the thing works (at +- 1-2%), I don't need the DT830B's as volt/current meter.  If it doesn't, well, I learned a lot trying to get it working so far.

Please keep us posted on how your Atmega328 meter reading project is going - I'm sure some folks would be up for trying your design if you want to share it.  Thx

As promised...

https://www.eevblog.com/forum/microcontrollers/an-implementation-of-atmega328-volt-logger-the-dinometer-a-learning-project/

[Benik3]

I suppose that it's the best choice under 75USD?

Only thing which disappoint me is the resistance for measuring of high currents :/

[Lightages]

user4963:

Sorry I haven't had the time to check the parts for you yet. I will get to it soon.

I suppose that it's the best choice under 75USD?

I am not sure I would say it is the best choice for under $75, but it is one of the best. There are the Digitek DT4000ZC and the DT2843R which are very good values for the money too. The DT2843R measures RMS AC+DC whereas the UT61E only does AC. The DT2843R has very slow continuity test but has very low burden voltage on the current measurements. The best buy depends on your needs between these.

[Benik3]

OK thanks, I will look at it

[Lightages]

Actually, If you are in the US and willing to spend $78, have a look at this:
https://www.eevblog.com/forum/buysellwanted/great-deal-on-amprobe-am-270-!!!-us-only-(/

[Benik3]

I'm from Czech Republic :/
But how much cost normal shipping from US to CZ? If there will be someone to buy it for me...

[Lightages]

This is why everyone needs to put their country in their profile, or say what country they are from before asking anything.

[tmammela]

Is it possible to calibrate resistance or current measurement in this meter? There seems to be many pots inside it but I've only seen discussion about dcv calibration. I have a dmmcheck plus incoming so I would have all needed references.

[george graves]

WOuld like to know as well.

[Benik3]

This is why everyone needs to put their country in their profile, or say what country they are from before asking anything.

I thought that I choose it in registration, but now I see that I don't have the flag on my profile.
Never mind, repaired

[ModemHead]

Is it possible to calibrate resistance or current measurement in this meter? There seems to be many pots inside it but I've only seen discussion about dcv calibration. I have a dmmcheck plus incoming so I would have all needed references.

In my experience, it's not common to see calibration adjustments for resistance or current on manually-calibrated (trim-pot) handhelds.  Closed-case calibration units can of course calibrate any function/range using stored offsets.

A dual-slope integrating A/D converter is by its nature ratio-metric. Measuring resistance is done by passing a current through a reference resistor and the unknown resistance. The ADC measures the ratio of the voltages across the two resistors by switching it's reference input to the voltage across the known resistance.  The ratio of the voltages is also the ratio of the resistances, since the current is the same.

This means the accuracy of the resistance range is based mostly on the tolerance and tempco of the resistors used as the 'known'.  These are often dual-purposed from the voltage divider.  How close the multimeter comes to a known resistance measurement is a good indication of the quality of the parts in the front end, but not of the DCV calibration.  The DCV calibration is usually done by tweaking the voltage reference, and that isn't even used during resistance measurement.

For current ranges, it's measuring the voltage across the shunts, so both the DCV calibration and the tolerance and tempco of the shunts come into play.  Calibrating just the current without affecting voltage would require tweaking the shunts.

[tmammela]

For current ranges, it's measuring the voltage across the shunts, so both the DCV calibration and the tolerance and tempco of the shunts come into play.  Calibrating just the current without affecting voltage would require tweaking the shunts.

Thank you. So no resistance calibration, that's fine. So ideally if I calibrate dcv it also calibrates current?

[ModemHead]

So no resistance calibration, that's fine. So ideally if I calibrate dcv it also calibrates current?

I took a look at the UT61E schematic and I can't spot any trim pots that would affect the voltage off the shunts.

However, I do see a 10K pot in line with the ohms voltage sense (VR3).  Not sure how much effect that would have on a high impedance input, but it may tweak the ohms readings?

Be careful with your adjustments, you don't want to make it worse.

[mrflibble]

Mmmh, quick check on ebay shows they go for < $60 these days. Is the UT61E still the budget model to go for, or are there other nice deals to be aware of? I noticed the Digitek DT-2843R and Digitek DT-4000ZC being mentioned as well, but those don't quite have the resolution of the UT61E...

[Wytnucls]

Still the cheapest option for a new sturdy 4 1/2 digit TRMS meter with autoranging. It is not a perfect meter by any means, but quite usable and probably the best value for a hobbyist on a budget.

[Rick Law]

Still the cheapest option for a new sturdy 4 1/2 digit TRMS meter with autoranging. It is not a perfect meter by any means, but quite usable and probably the best value for a hobbyist on a budget.

I agree.  Very good meter for the money.  I did very careful research before I purchase it.  I was not sure that this time around in returning to play with EE if my interest would not fizzle out as it did the last couple of times, so I was not willing to spend a lot of money with a new meter.  I went the low cost route.

Having own the UT61E for a year now, I can say I am very pleased with it.  I would have like it had it been say 60,000 count, twice as accurate, backlid, auto-off... etc, etc, etc.  But that would have been 3x 4x or 10x what I was would have to spend.

Good value for the money is important in my decision.  My diddling around requires nothing more that a percent or two accuracy.  This far exceeded my need and at a very low cost.  So in my case, I am very pleased with it.

Rick

[mrflibble]

Thanks! Looks like the UT61E is the one to go for. Or rather, it was the one to go for right now, and has become the one to maybe go for in the future. It's bloody typical. You look for a used 5 1/2 digit meter for quite some time, cannot find it for a decent price, and then decide ah fuck it I'll go for a new 4 1/2 digit handheld meter. So you invest some time into researching the various option, decide on a certain meter, do your last sanity checks (posting in this thread) and then ... an affordable 5 1/2 digit meter pops up. Isn't that always the way...

So I picked up an HP 3478A for $150 shipped.  Not nearly as cheap as some of those  cheap offerings I sometimes see in the US, but such is life.

Chances are I will still get me a UT61E since it does look like a pretty nice meter, but the purchasing date suddenly got pushed back. Relative importance and allocation of limited moneys and all that.

Edit: grammar happens to people who proofread.

[Wytnucls]

The UT61E has a strange 'Peak Hold' implementation.
Usually on other meters, 'Peak Hold' displays very fast measurements of the AC sine wave positive peak voltage, with a max/min around that voltage.
On the 61E, 'Peak Hold' goes through a calibration first and then displays The Max (positive) and Max (Negative) of the sine wave voltage, with slow updates of about 2 samples per second. The bar graph keeps on displaying the TRMS voltage for that sine wave, instead of the peak voltage.

[Robomeds]

Still the cheapest option for a new sturdy 4 1/2 digit TRMS meter with autoranging. It is not a perfect meter by any means, but quite usable and probably the best value for a hobbyist on a budget.

Since you said "new" I would agree.  If you are willing to shop ebay and live in the US (one or both will be 'no' for many people) I think you can do much better.  For the same money I've seen these meters used, all of which strike me as better than the UNI-T
Amprobe AM140 (Brymen with 500,000 count display)
http://www.ebay.com/itm/Amprobe-AM-140-TRMS-Digital-Multimeter-With-Leads-WOW-NR-/161166659089?pt=LH_DefaultDomain_0&hash=item2586480e11
BK version of this meter (an ancestor of the current Agilent meters)  Note this is 40,000 count but has very good accuracy.
http://www.ebay.com/itm/Hioki-3801-Digital-HiTester-Multimeter-/290889897049?pt=LH_DefaultDomain_0&hash=item43ba639459
BK 5390 (a favorite of mine).  Rare on ebay but I got one for $35 and did a tear down of the meter.  0.025% DC, water proof (a need I haven't needed ) and 50k count. 
A number of old bench meters. 

[lagman]

I just received my UT61E that I ordered when I saw that everyone is happy with it. And I like it!
Unfortunately I'm unable to use the data logging function using the serial cable and a USB to serial adapter. (http://dx.com/p/usb-to-rs232-dongle-with-extension-cable-5859)
The adapter is plug and play and I can see it linked to COM4 in "device manager". I installed UT61E v4.01 exe and connected to COM4 but I get nothing...

It's the first time I use RS232 so maybe I'm doing something wrong?

[Benik3]

Maybe different voltage output?
RS232 can be +-5V, +-10V, +-12V or +-15V.
Or there is also TTL +-3.3V but it's not probably this...

[lagman]

Hum... I know absolutely nothing about RS232. 
I suppose that being powered by USB it can't be more than 5V. I looked at RS232 pinout and couldn't find a power pin!?
I checked all pin voltages on the USB to RS232 adapter and all are at 0V apparently. Is that normal?