Review: UNI-T UT61E digital multimeter

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…)

I was just thinking: Maybe that the meter wants to see AC current (going one way then the other).
In my application I have no current or 2A, but never a negative current. Could that be the reason why it’s not working?

It is not supposed to be that, because the DMM shows DC range.

If you have enough time could you please try to measure the strobe frequency with your UT-61E? Just to check if it’s working on yours.
That would be very kind. :slight_smile:

I’ve also posted the same question on EEVBlog as I’m sure there are many people who could know the answer there.

Now I got time to test it. You where correct, the problem is that it requires AC. Pulsing current is not enough, it must go negative, before the frequency and duty cycle will work.

Thank you HKJ for testing this as I don’t have the equipment to do this (easily).
That’s quite annoying that it requires to go negative.
And it’s strange that it allows to display frequency in DC mode as it can’t do it!

Thanks HKJ, you are the best! :slight_smile:

Thanks for the review, it was great! I do like the computer connect feature, but I myself forked out enough $$ for a Fluke 87 and I couldn’t be happier.

Thank you HKJ for the nice review!

I am experimenting myself now with logging the current of BT-C3100 charger, quite some fun :)

To me a more logical approach of estimating the discharged capacity from UT61E log file is by first calculating the mean pseudo-constant current draw for a subset of the logged data and then multiplying this number with the runtime of this data subset.

For example the DMM recorded 3000 data points including preceding and succeeding zeros {0,0,-199,-204,…,-213,-195,-197,0,0,0}miliamps, then the average current draw would have been {0+0-199-204-…-213-195-197+0+0+0}miliamps divided by 3000. The DMM needs 1500 seconds to record the 3000 points, so the runtime is (1500/3600) hours. Putting everything together we get

discharged capacity =

= ( {0+0-199-204-…-213-195-197+0+0+0}mA / 3000 ) × (1500/3600)hr =

= {0+0-199-204-…-213-195-197+0+0+0}mA × (0.5/3600)hr =

= {0+0-199-204-…-213-195-197+0+0+0}mA × 0.00013888889hr =

= {0+0-199-204-…-213-195-197+0+0+0}*0.00013888889 mAh

We could also drop the zeros to get a more meaningful mean current:

= ( {0+0-199-204-…-213-195-197+0+0+0}mA / 2995 ) × (1497.5/3600)hr = same result.

BT-C3100 is a fun charger and its mAh readings are not too far off that i could care less

The latest version of the UT61E PC software can be downloaded from here:

http://www.uni-trend.com.cn/product/2014_0504_231.html

The last tab leads to this link:

优利德科技(中国)股份有限公司-优利德科技(中国)股份有限公司 (15.1MB BA3E4CDA, 2014-04-15)

This can work for NiMH, but with LiIon you do only have a constant charge current during the CC phase. The CV phase has a constant declining current, there summing all mAh (or mAs) charged into the battery works better.