UNI-T UT71D review

[Wytnucls]

My UT71D meter has very high current consumption when it auto-powered off. I couldn't measure it yet but it drains the battery overnight if I forget to power it off.

Is it a problem with my unit or is a design flaw? Do you guys have this issue?

The drain on the 9V battery while in 'auto power off' mode (DCV position) should be 40uA (measured with Keithley 2000 on the 10 mA range).

[joeqsmith]

I had ran a similar test some time ago with a Fluke 87V, Extech EX540 and the Brymen BM869s.   The Extech was by far able to detect the shortest pulse of the three.   I picked up a UNI-T 181A and thought I would add it to the mix. 

These were similar but with a 2V peak rather than 3.   Again, I would grab a scope and really have no need but I do find it interesting that the 181A is not even close to what you saw with your 71D. 

To illustrate the fast transient capture of the 71D, I fed it a 3V 10uS pulse at 50Hz from a function generator. The meter easily registers the pulses and displays the pulse voltage in 'Peak Hold' mode, all the way down to 100mVpp.
Most meters need a minimum repetitive pulse duration of 250uS for proper capture.
Peak Hold data can be logged to the computer in real time, at 15 samples per second.

[Wytnucls]

It is a feature of the Taiwanese Cyrustek ES51966 IC (peak capture patent 476418), as fitted to the UT71D. Uni-T may have overlooked its existence, as it isn't mentioned in the manual.
The UT181A uses a different IC, which probably lacks the fast transient capture capability.
The Fluke 867B and its lesser siblings are the only other meters I know of, that can match the 10us transient capture of the 71D.
The FLIR DM93 should be able to do it too, as it uses the same IC as the 71D, but it isn't documented.

[joeqsmith]

Thanks.  I was wondering more if they felt this was an important feature why they did not implement it on their newer meter.    I had a look at the patent.  They don't really talk about what drove it other than cost and battery life unless I missed something.  I can't think of one time that it would have come in handy.     

I am curious, what do you use it for?   

[Wytnucls]

This thread is a meter review and as such, looks at all the features of the UT71D. What I use the meter for is irrelevant.
Like I said, I don't think Uni-Trend paid much attention to the glitch capture capability of the IC they chose to fit in their meter. The same goes for FLIR.
Fluke on the other hand, made it an important feature of the 867B, seen as a convenient and cheaper alternative to a bulky oscilloscope in the field. I'm pretty sure someone found it useful then.
Most meters have a peak capture feature. In this instance, the 71D happens to do it better than most other meters.

I also looked at the patent, but couldn't make much of it, as I don't read Mandarin. There are schematics of the circuits involved, but I haven't looked at them in great detail.

Here is the link if anybody wants to have a go at it:
http://twpat-simple.tipo.gov.tw/tipotwoc/tipotwekm

[joeqsmith]

No problem.  I just figured you would have some idea what to use this feature for.   Fluke's site does talk about using it to capture line transients (even with the 87V).  I don't see there being enough information to do much good.  Did you try capturing anything higher than the 3V?  Something more on par with some sort of simulated line transient?     

The patent engine has a translate feature.   Attached is the English translation. 

[Wytnucls]

There isn't much to gather from the patent. It is used like any peak detect feature on any multimeter. The only difference is that it is more sensitive that most (10us for a repetitive transient with lowest amplitude 100mV on the 4V range).
Line voltage transient detection may be one use. Picking up current transients on a 4~20mA loop may be another. Logging is available in Peak mode, at 15 readings per second.
Characterizing the whole Peak mode would be time consuming and would require some substantial testing gear. This is something most manufacturers haven't done properly either.
I'll leave that task to someone who may actually need the feature and is willing to devote some time testing the meter over the whole voltage and current gamut.

http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/dmms/under-used_functions
http://www.tek.com/sites/tek.com/files/media/document/resources/Peak_Detection_AN.pdf

[joeqsmith]

I had not thought about the 4-20mA.   Did you try to see if it could capture that same even in this range?  I was only looking at voltage when I ran those quick checks.   

Line voltage transient detection may be one use. Picking up current transients on a 4~20mA loop may be another. Logging is available in Peak mode, at 15 readings per second.

[Wytnucls]

I did try to capture a fast mA current transient with the meter, but my gear is not really up to the task, so the test is not conclusive.
Let me know if you're successful on your side with another meter and I'll try to replicate your set-up here, if possible.

[joeqsmith]

I was thinking to use a resistor in series with the meter and pulse the voltage to get the 4 to 20ish.   

I started out with 0.5Hz 50% just to get things setup
181A read 20.017/4.002
869s read 20.022/4.002

At 50Hz, 500uS pulse
181A reads 20.11
869s reads 20.9

50uS pulse
181A reads 20.13
869s reads 9.4 ***

20uS pulse
181A reads 17.74
869s reads 8.5

Now the funny one is the Extech which was really good in voltage mode.   In current mode even with a 5mS pulse, it could not detect it. 

 

Went back to repeat the voltage test with the Extech and realized I had forgot how to use the peak mode.  I then tried the peak detect in current mode and it worked.       It also turns out the 181A needs a fair amount of time to settle.  Several seconds (5 or more)     The Brymen on the other is correct.   

Here is the new data for the Extech and the UNI-T.
 
50uS   EX540 19.86mA,  UT181A 20.13mA
20uS   EX540 19.86mA,  UT181A 20.16mA
10uS   EX540 19.85mA,  UT181A 20.13mA
5uS     EX540 19.80mA,  UT181A 20.17mA
2uS     EX540 18.68mA,  UT181A 15.97mA
1uS     EX540 15.43mA,  UT181A 10.94mA


Thinking back, what was the fastest 4-20 I ever worked on.....   

[Wytnucls]

Someone was having difficulties with the internal logging features of the meter.
Here is a digest of procedures for proper operation:

There is no memory delete prompt as such.
All one can do is append a new batch of data to the existing data in memory or choose to overwrite the existing data from the beginning.

To store new data in memory:
Press STORE key
Press HOLD key if you want to overwrite old data, otherwise skip this step
Press STORE key to set recording interval (then + key repeatedly to set from 0 to 255 seconds) (Hold + key continuously for fast scroll)
Press STORE key to start recording
Press EXIT key to stop recording

To review stored data:
Push STORE key for 1 second (RECALL)
Select sample with + or - keys
Press HOLD key to send all stored data in memory to computer via USB

At any time, to send a single measurement reading to the computer via USB, push MAXMIN (SEND) key for 1 second then EXIT.

[Wytnucls]

Here a link to the early version 1.10 of the logging software, for anybody who needs the RecallData function which was deleted from the later version 3.0.
RecallData allows you to download stored data to the computer, specifying original logging start time and interval, instead of default settings.

https://www.dropbox.com/s/9c5nrzuwx40800h/UT71C_D_E_setup.exe?dl=0

[Wytnucls]

The graph on the old version is also more useful, as the one on the new version doesn't allow scaling.
For instance, here is an old 9V battery voltage recovery graph in real time, after a large load was removed (500 seconds):

[gerrylix]

Here a link to the early version 1.10 of the logging software, for anybody who needs the RecallData function which was deleted from the later version 3.0.
RecallData allows you to download stored data to the computer, specifying original logging start time and interval, instead of default settings.

https://www.dropbox.com/s/9c5nrzuwx40800h/UT71C_D_E_setup.exe?dl=0

Thanks again for uploading the 1.1 version the other day.
Sadly the "Recall function" for multiple storage entries isn't working with any version.
After hours of trying v1.1 and v3 i switched over to an open source project called sigrok!
The sigrok cli (https://sigrok.org/) with the right commands parsed all of my 174 datapoints in 1 second.

Install sigrok cli then use Zadig, that came with it, to exchange the already installed USB driver of the USB-serial/USBHID-serial with the zadig one.
Afterwards head over to the cmd prompt(i prefer http://cmder.net/ over windows one but not neccesary) and "cd" the folder where sigrok-cli.exe resides and use:

sigrok-cli --driver uni-t-ut71d:conn=VID.PID --continuous -o test.txt -O analog
(USE VID and PID of the right USBport, i.e.: 1a86.e008)
-o specifies the outputfile
-O specifies the format
-V shows the fileformat

After that, start the DMM and follow the instructions to recall from Wytnucls.
Hint:
Use USBdeview(http://www.nirsoft.net/utils/usb_devices_view.html) to find the correct USB port and VID/PID.
Never use "sigrok-cli -scan" with the UT71D or the hardware hangs and you may have to disable+enable the port .

Greets

[Wytnucls]

Sadly the "Recall function" for multiple storage entries isn't working with any version.
After hours of trying v1.1 and v3 i switched over to an open source project called sigrok!

Are you saying that you can't transfer data from the 71D memory to your computer?

[gerrylix]

Exactly, i can't transfer it to the offical uni-t software.
The DMM is running through the entries and sending them but the software only gets the first entry, doesn't matter which version i use.
Normal logging is possible, in "live" mode but stored values aren't transfered.
Maybe it's because of this:
"The communication parameters are 2400 baud, 7o1. However, the vendor software opens the serial port with 8n1 settings, so the vendor protocol descriptions are slightly off. "

[Wytnucls]

I don't have a problem here on Windows 10, with UT71D version 1.10. Just tried 180 entries, which all transferred. The only problem is that the graph seems to stop after 142 points.
The transfer is lightning fast.

Tried a transfer again, 210 data entries, with a higher starting voltage. Everything went through, including all points on the graph.

[gerrylix]

I don't have a problem here on Windows 10, with UT71D version 1.10. Just tried 180 entries, which all transferred. The only problem is that the graph seems to stop after 142 points.
The transfer is lightning fast.

Tried a transfer again, 210 data entries, with a higher starting voltage. Everything went through, including all points on the graph.

Damn, then its maybe an issue with win7 pro.
Tried it on two different machines.

Facinating that sigrok has no problems getting the datapoints under win 7.

[Wytnucls]

It was transferring perfectly too on my old Sony Win 7 machine. I am surprised to hear that yours has a problem.
Try reinstalling the software perhaps.

[gerrylix]

It was transferring perfectly too on my old Sony Win 7 machine. I am surprised to hear that yours has a problem.
Try reinstalling the software perhaps.

Tried to reinstall v1.1 and v3 two times.
Once on my small log-netbook and on my main machine, both seem to have the same issue.

I have to say i became a fan of the sigrok lib after one day.
Maybe i'll build some GUI around the library for my DMM's and dataloggers.

Thanks for the effort Wytnucls 

[Breizh13]

Hello all from France,

this week I received my UT71D from Batronix DE. Nice meter except the stand which is too small, and so, the meter is too inclined.

My problem is with the recalling datas feature. It don't work on windows Xp and Windows 10. I tried release V1.0 and V3.0 with the same poor result.

When I do that
"To review stored data:
Push STORE key for 1 second (RECALL)
Select sample with + or - keys
Press HOLD key to send all stored data in memory to computer via USB"

I just get the first record.

And when I check the "Recall data" option on the the V1.0, nothing append!!

I could see that I am not the only one with this problem. Can aanyone give us help to solve that?

PS: I sent an email today to the vendor. Maybe he can help.

Philippe
Salon de Provence
France

[Wytnucls]

Batronix is selling the newer version of the UT71D, with the 1000V HRC fuses. I suspect the download feature might not work properly on that meter anymore. Contact Batronix for an explanation or have a look at the Sigrok software.

[Shock]

What differences are present on the PCB just different fuse holders and fuses?

[Wytnucls]

I presume it would be erroneous software loaded at the factory, if all new meters behave the same way.
A few components were moved to make room for the fuses, but it is essentially the same meter.

[abraxa]

I have to say i became a fan of the sigrok lib after one day.
Maybe i'll build some GUI around the library for my DMM's and dataloggers.

There is sigrok-meter btw, which runs fine on linux but since we don't use Windows really, we would appreciate it if someone would be willing to figure out what's needed to make it run on Windows as well. Probably just the python bindings for libsigrok. If you'd be willing, you'd have a GUI right away instead of having to write it
Either way we're glad you find sigrok useful!