Review: UNI-T UT61E digital multimeter

Holy Mother! HKJ

A review on a DMM? Only on BLF :-)

Thank you for taking the time and making the effort to do this. That is so awesome.

I NEVER read a DMM review before although I've seen them. I read this though :-)

Actually sounds a like its a lot of functionality in a cheap meter.

And pilotptk: Good one on the clamp meter.

I figured it out with Excel2010, the UT61E graph is presented in the F e n i x post. Thanks again HKJ for the support, as always!!

to whom it may concern, recalibration of the UT61E isnt necessary imho but it is possible. FOI, some users buy a little product called DMMCheck and do the adjustments on their own.

@HKJ or anyone to whom it may concern for the RS232 converters issue

Nowdays serial is obsolete,so connecting to Pc is not possible for those who does not has a serial port,but I found some RS232 convetor to USB in Deal Extreme,many consumer reported that some converters are not working,based upon my observation I found that the better converters are those which has FTDI chips and not prolific chips,since I am not that technically sound plz suggest which will work for Unit 61E,I have chosen these in Deal Extreme based on the customer reviews which are as follows.

1>http://dx.com/p/usb-2-0-to-rs232-adapter-0-8-meter-9656
(highly praised by a user)
2>http://dx.com/p/rs232-to-usb-convertor-cable-2537?rt=1&p=2&m=3&r=2&k=1&t=1&s=48530&u=2537
(Prolific PL2303)

3>http://dx.com/p/usb-2-0-to-rs232-ii-serial-cable-adapter-converter-black-80cm-123347?rt=1&p=2&m=3&r=2&k=1&t=1&s=48530&u=123347
(FTDI based converters)

4>http://dx.com/p/usb-to-rs232-dongle-with-extension-cable-5859?rt=1&p=2&m=3&r=2&k=1&t=1&s=48530&u=5859
(Highest Numbers of reviews)

5>http://dx.com/p/bafo-usb-to-rs232-converter-5947?rt=1&p=2&m=3&r=2&k=1&t=1&s=123347&u=5947
(Best built Quality)

6>http://dx.com/p/usb-to-rs232-serial-port-adapter-transparent-green-24512
(Cheapest Price)

Where I have had the most problems with the serial converters is the driver (When I last checked all the supplied drivers was for Win XP), especially with Prolific PL2303.

I solved the problem by buying locally from a company that did supply working Win 7 drivers (Sandberg).

I cannot say which one of the adapter is best or works, that would require that I tested them.

I have ordered but not yet received my UT61E. I am reading the manual and doing other research prior to having my hands on the real meter.

The current measurement would indeed have a “funny” resistance. Looking at the UT61E’s schematic floating around on the web, it looks like they use shunts with dual diode in parallel depending on the range.

  • With the max (10A) range: 0.01ohms, two zener diodes back-to-back (~~~~) then in parallel.
  • With other ranges, shunts are: 9, 90, and 900 ohms, in series and 9/900 are in parallel with two diodes (one in reverse). The 900-90-9 are in series then series with a 2ohm where. Drops appears to be measured at left of 900 (900+90+9+2) or left of 9 (9+2) depending on setting

Since diodes are not linear devices, the resistance would depend on the voltage and current. So the resistance will not be a fixed value as in a regular resistor alone but a resistance that changes with I and V. I am no electronic expert. I am not sure exactly why the diodes are there. My best guess is the diodes are to limit the voltage drop across the shunt so it can switch to the higher range without having the lower ranges reading a voltage way too high for it. (Any expert out there? Enlighten me if my guess is wrong.)

If the schematic is right (found it on the web somewhere, doesn’t mean it is accurate): For the 10A range with 0.01ohm shunt, the burden voltage should not have much affect. A 10A current would drop a mere 0.1 volt drop. The 1.2% error at 10A would give a +120mA error, plus 50-count giving total error of + 170mA. Since the 50-count alone would represent 50mA, measuring anything below 1A would not be very good with a 50mA uncertainty minimum.

Next best is the mA range with 9ohm in parallel with 2 diodes then series with a 2ohms shunt. The diodes+shunt would manifest itself as somewhere below 11ohms - the diode makes the actual resistance current/volt dependent so how much below 11ohms is hard to say. Inserting that into a say direct drive LED with a 50ohm current limiter, the 11 ohms would introduce a 20% increase in current limit resistance - the 50ohms limiting resistor is now a 61ohms limiter. That current measurement will be rather useless.

Using a 0.1ohm shunt and the lowest voltage range for low current (220mv) would in theory give better measurement. The shunt will be able to measure up to 220mV which equates to 2.2amps. The accuracy at that range would be (according to the manual) 0.1% accuracy giving error at –0.22mV. The five count error makes total error–0.27mV or 2.7mA.

So, it looks like I need to find some 0.1ohm shunts.

I have also seen the schematic (now).

The diodes protect the unused range, i.e. is 90 and 900 ohms are in series, when using the 90 ohm resister the diodes are used to lead the current around the 900 ohm resistor. That is the reason for the "funny" resistance in ampere and it does not affect precision "only" burden voltage.

I hate flipping through the manual to look for the %accuracy/specs each time I change the dial on my meter. So, I cut and pasted the UT61E’s spec for all the selections into a single-page layout. Small prints, but I can see all the %accuracy for all the ranges on this little poster on my wall.

Thought other UT61E may find this useful. If you like it, feel free to use it.


I was going to upload the PDF file here, but I see there is no upload option. So here is a link to EEvBlog under UT61-E teardown photos where you can find the PDF file.

Link to all specs on a single page

Great job, thanks for it!!

:)

i can't believe that i paid only 24.50€ for this baby (incl. discount codes, dinopoints, gift cards, afaicr). best flashaholic related purchase ever!!

HKJ, if you keep the HOLD-button pressed, the DMM will go into AUTO HOLD-mode ;)

No, it is a timed hold: It will lock the reading after some time.

oh i see, thanks!

but it's almost as good as AUTO HOLD :)

It is not, auto hold only has to be activated once and they you can take any number of measurements.

i never saw real AUTO HOLD in extended action.

will watch more youtube vids!!

:)

*FMI*

i've been doing extensive charger tests xp4 and whatnot. anyway my ut61e ran down the 9V battery. i use the ut61e that much, it's now the 5th or so new battery in it since i bought it 2.0yrs da ago. the DMM is able to operate with a cell at 5.455V offline resting voltage. after a few seconds of usage, the online voltage of the cell would drop below 4.855V and that's where the ut61e scrambles the LCD display and shuts down. the youtube reviewer tested the low voltage dmm operation in more detail with a constant voltage source. in reality, cell voltage isn't constant, so in practical terms a cell with ~5.5V offline resting voltage is pretty much the lowest you can go, since as soon as you set it online the cell does a huge voltage drop within seconds and the ut61e shuts off.

and fresh brand-new 9V alkaline has 9.6V offline resting voltage.

and true, my battery tester shows RED, dead cell. at 5.455V, the cell *is* dead. no wonder that the ut61e shuts down operation.

so i don't get it why the youtube reviewer examined how low the ut61e can go.

silly stuff.

lol

Modify it to run from regulated power supply?

Five batteries in two years is not bad.

I guess that I replaces batteries once a month or more, but then my most used DMM (A Fluke 189) is between 50 and 100 hours runtime each week.

today i am trying to manually measure the Eneloop AAA discharge capacity on a new ;) (hehe.. ) nimh charger which does display discharge capacities. the displayed capacities are a bit on the low side —compared to specs and C9000 results (Refresh&Analyze, Break-In)—, that's why i am doing this exercise. the UT61E comes in handy particularly for its stable unfailing logging capability. the serial cable was included in the package but i also bought the original USB cable from DX.

another beautiful point about this particular model is, because of its popularity the device gets continuously improved through invisible internal hardware revisions and users all over the world write their own PC LINK software (for Windows, Python, Linux, ..). I am satisfied with the original old Win software v4.01 on the CD-ROM but for our information, these are alternative programs compatible with UT61E:

The wiki site does not list the best tho:

There is also an entertaining and impressive UNI-Trend 12min company video (English lang, 118MB, slow download, use D/L manager).

So how does the kreisl measure discharge capacity?

Simply by logging the current I(t) over the entire time t with HKJ's measurement method:

One ends up with a data column for I(t) and one for t in Excel. Mathematically the discharge capacity is the integral of I(t) over time t, that simple. In a RL experiment this must be approximated by the sum of I(t)×∆t where ∆t=const.=1/f=1/(2.00Hz)=0.5s, because the updating frequency of UT61E is exactly 2Hz.

[quote] Discharge Capacity

= ∫ I(t) dt

≈ ∑ I(t)×∆t = I(t)*∆t = ∆t * I(t)

= 0.5s * 1h/(3600s) * 1000mA/(1A) * I(t)

where I(t) must be measured in the ampere "A"-setting, e.g. 0.201A [/quote] In other words, the amps just need to be added and this sum must be multiplied with that factor, e.g.

(0.201+0.200+0.200+0.197+0.199+0.202+…)*0.1388888…*1mAh

That doesn't sound too hard, does it? ;)

The discharge test is still going on, i'll post my result here when i am done with everything stay tuna.

EDIT:

test done. saved as *.XLS-file, opened with Excel, then simple Sum function:

So we get in 3h33min24s:

|Discharge capacity| = 5600.236 * 0.13888888… = 777.81055555… ≈ 777.8 ≈ 778mAh

The same cell (from brand-new 4-pack) discharged from the same starting condition (i.e. charged at 400mA in C9000 and after completion left in charger for 18hrs) gives the C9000 discharge result 795mAh (in 4h24min), which sounds realistic given the "Sanyo mAh-scale" and their "800mAh"-rating. That's a minor discrepancy of 17mAh.

Maybe HKJ's measurement method which certainly increases the resistance between plus and minus poles of the metal contact plates of the charger (contact resistance + battery + tin foil + multimeter with leads + tin foil + contact resistance = 479-880mΩ total, instead of ~48mΩ total) influenced the system and falsified the result. Therefore we're repeating the discharge test twice: without UT61E on the new charger, and with UT61E on the C9000. after these 2 tests we'll know which of the three devices are consistent with each other and which device is a poor product.

EDIT: tests done.

C9000 current measurement test failed, see below post.

the "without UT61E on the new charger"-test was very successful. I got the same low discharge capacity and time for completion was also the same: 3h33min30s, amazing! It means that my discharge capacity measurements on the new charger are valid in the sense that they do NOT influence or falsify the charger's behavior (although it does so on the C9000!). Furthermore, my UT61E measurements are also fairly accurate, after the Sanyo scale.

What's our take home message?

  • C9000 is very accurate with mAh-readings but also very/too sensitive to non-Eneloop or 1yr+ old cells because the "HI6H" resistance threshold is very low whereas all other chargers on the market do not have any such threshold. Trying to read (charge/discharge) current of a C9000 channel on your DMM in series is a practically an insurmountable challenge! Just give it up already :P
  • On other chargers, discharge capacity (amateur) measurements with an accurate logging meter such as the UT61E is possible, easy, and fairly accurate. If you own a battery analyzer, then it is a very instructive exercise to compare your own capacity measurements (from calculations with UT61E data) with the capacity readings of the battery analyzer.

i’ve been looking at this DMM for some time now but still haven’t bought it…just one question: can you try to press and hold the hold button for a few seconds and see if the hold on display will blink and then in the next 5 or 6 seconds it should function as on some expensive flukes i.e. not just freeze of the reading…EDIT: i still don’t quite understand difference between real hold function and this “semi-hold”

It does not include "Touch and hold" as the Fluke meters.

It has "Hold" that freezes the display immediately and it has "Delayed hold" where the display freezes after a few second.