Review: UNI-T UT61E digital multimeter

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.

well the C9000 test failed and that's probably the reason why nobody on the WWW ever did a thorough technical analysis of the Maha: the tin foil (or aluminum foil) method increases the total resistance between the C9000 metal contacts by such an amount that the C9000 returns the infamous "HI6H" error message and stops the program. with the UT61E connected in series to the C9000 neither an Eneloop CHARGE nor DISCHARGE program can be executed. premature ejac ejection yikes!

did anyone on the WWW ever measure the C9000 current as displayed on the LCD? well i tried to measure its current with my UT61E but the C9000 wouldn't let me. that's disappointing and frustrating. and it reveals a clear disadvantage of C9000: it has serious difficulties with handling slightly poor cells (e.g. VARTA ACCUCELL 1.5yrs old) and it can absolutely not handle poor cells (any old NiMH's other than Eneloop), especially not charge them. Discharge should be possible with poor cells but still remains a challenge: premature ejac is typical in such cases, meaning C9000 is not able to evaluate their discharge capacities (nor are other charger-analyzers btw).

I am still doing the "without UT61E on the new charger"-test to get an indication if the inclusion of a DMM in the system influences the (discharge test) results. Hopefully not.

So far i cannot claim that, if C9000 displays "399mA" current, the actual current really is 0.399A, and tbh the 4h24min discharge time for "795mAh" sounds a bit fishy, but the charger returns plausible, consistent, realistic, reproducible, accurate mAh-readings and that's more important than discrepancies between displayed and actual currents. The latter just makes it harder to verify the mAh-measurements.

nobody asked you kreisl to post all this so why you're writing, whom are you talking to?

erh .. haha. never mind ;)

:shy:

Thanks for the review, I got the same DMM and I’m quite happy. Two things:

  1. On mine, when I press for a long time the Hold button it enters a mode similar to the one on Flukes and other. Which means that I can apply the probes, then hear a beep and it will hold the voltage it was at when it beeped.
  2. Did you succeed to find a USB to RS232 adapter that works with that DMM? I bought one but it never worked… I get a virtual COM port but no data comes out. I haven’t any RS232 device to find if the problem is the DMM or the adapter unfortunately.

No, it is not like Fluke:

On the UT61E you start a time and it will capture one measurement

On Fluke it will capture a measurement each time the voltage is stable, i.e. after activating auto hold once you can do any number of measurements.

I do have a some USB RS232 to version COM port adapters, but I do not remember if I have tried them with the UT61E.

Oh ok. I never had a Fluke. :slight_smile:

Can you tell me what RS232 to USB works well for you? If you have time could you please test it with UT61E?

I got a few of this model: http://www.sandberg.it/support/USB-to-Serial-Link-9-pin one or two years ago and they have worked fine.

Note: I have not used them for my 24/7 logging, only for shorter tests.

Thank you very much. :slight_smile:

www.dx.com/p/150054

Yes but as said in HKJ’s review it’s better to have a Serial adapter as it’ll create a COM port that can be used in an other software.

One more question:
I just realized that on the A range, pressing the yellow button enables Hz mode. Pressing it again gives the duty cycle.
So I tried to put the probes in serial on my flashlight. I get a current reading but when I switch to Hz or Duty Cycle it doesn’t work.
I’m doing that to get the frequency of the strobe mode and the frequency and Duty Cycle of PWM at low mode.

Am I doing something wrong? I checked the manual and it says max frequency 1khz so it should work.

It sounds correct enough, some possible problems can be:

  • Current draw to small for frequency measurement.
  • The current draw is not "clean", i.e. the driver uses a buck or boost converter that pulses all the time.

My LED driver is direct drive. There is just a MOSFET to control PWM for low mode and strobe.

Current is about 2-3A. It should be enough I guess.

Here is a picture (in case I have something wrong…)