UNI-T UT61E Multimeter teardown photos.

[Nisei]

Correct, TL175
I got them with my Fluke 177. Sold the 177 but kept the TL175 leads. I really like them.

[mos6502]

Only issue is if you have pitted and/or dirty leads, which they usually are even when new out of the box. Cleaning them with contact spray helps a lot.

Had the same problem. Tried all kinds of chemicals. Acetone. Alcohol. Window cleaner. It helped a little, but it wasn't 100%. Then I tried this:



(A small brass wire brush.)

Scrub scrub scrub. Result: PERFECT. When I rub the probes together in buzzer mode, the resistance never even goes above 0.2 Ohms. Before, when did the same thing, the resistance would spike to hundreds of ohms. The formerly shitty Uni-T probes are a joy to use now.

[naughtilus]

Great idea with the brush.  The stock leads are not great, but certainly not terrible like the ones found on 830 DMMs.

[ocw]

I haven't seen much information on the sensitivity of the frequency counter in the UT61E other than it's not the best.  The manufacturer rating of 220 MHz along with the meter's banana plug input is a bit of a oxymoron.  220 MHz and the normal banana plug leads don't get along.  So, I made a banana plug to BNC shielded cable.  I fed the output of a Ramsey COM3010 service monitor directly to the meter when its 0 dBm output level was adequate.  When needed, I added a 16 dB amplifier.  It's 40 mW output was inadequate above 101 MHz.  Even starting below that frequency, greater frequency resolution is generally required dictating use of a frequency counter anyway.

I measured the sensitivity of the frequency counter portion of the UT61E as:

        UT61E      
FREQ    COUNTER SENSITIVITY      
         
1 Hz            >3.43 V   > +24 dBm   
2 Hz           171 mV   -2.3 dBm   
10 Hz   105 mV   -6.6 dBm   
60 Hz   105 mV   -6.6 dBm   
1 kHz   105 mV   -6.6 dBm   
10 kHz   117 mV   -6.0 dBm   
100 kHz   117 mV   -6.0 dBm   
0.5 MHz   165 mV   -2.6 dBm   
1 MHz   165 mV   -2.6 dBm   
4 MHz   200 mV   -1.0 dBm   
12 MHz   243 mV   +0.7 dBm   
25 MHz   243 mV   +0.7 dBm   
30 MHz   243 mV   +0.7 dBm   
35 MHz   243 mV   +0.7 dBm   
40 MHz   267 mV   +1.5 dBm   
50 MHz   385 mV   +4.7 dBm   
60 MHz   385 mV   +4.7 dBm   
65 MHz   554 mV   +7.9 dBm   
70 MHz   777 mV   +10.8 dBm   
75 MHz   873 mV   +11.9 dBm   
80 MHz   873 mV   +11.9 dBm   
85 MHz   1.10 V   +13.8 dBm   
100 MHz   1.20 V   +14.6 dBm   
101 MHz   1.35 V   +15.6 dBm   

Given the low resolution of the counter I didn't go into detail confirming its accuracy, but I never saw a sign of any significant error.

I also measured the frequency response of the AC voltmeter portion of the meter.  Since I'm more concerned about its validity for frequency response measurements, I measured the response +/- 1 dB.  I found that to be 5 Hz to 68 kHz.  The response was down 1 dB at 5 Hz and up 1 dB at 68 kHz.  At 60 Hz I measured its AC voltage accuracy as +0.155% (well within its 0.8%+10 rating).

[mos6502]

ocw, that's very interesting. I think above a few MHz, the capacitance of the leads becomes a big issue. Have you tried using extremely short leads? Or a BNC to banana Adapter?

Here's a schematic of the UT61E: http://docdro.id/EbNqMPt

As you can see, the input circuitry of the frequency counter is very simple (the stuff around R35).

I'm having some issues with the frequency input of my UT139C, but it did measure up to 27MHz correctly, even though it's only spec'd to 10MHz.

Have you tried the duty cycle measurement? It would be interesting to know up to what frequency that would be halfway accurate.

[ocw]

I must have made a good banana plug to BNC cable--I didn't see a significant change when instead of using the cable, making it clumsy and using a banana to BNC adapter instead.
I'm not sure what duty accuracy you are looking for, but this is what I measured on the UT61E:

Freq    Waveform           D Cycle
100 MHz   Sine           5.0%
90 MHz   Sine           6.7%
80 MHz   Sine           15.3%
70 MHz   Sine           25.0%
60 MHz   Sine           30.7%
50 MHz   Sine           34.9%
40 MHz   Sine           41.3%
30 MHz   Sine           42.1%
20 MHz   Sqr 50%   44.8%
15 MHz   Sqr 50%   45.9%
15 MHz   Sqr 32%   35.0%
15 MHz   Sqr 68%   58.6%
10 MHz   Sqr 50%   46.9%
5 MHz   Sqr 50%   48.0%
1 MHz   Sqr 50%   49.4%

The duty cycle reading being displayed on the UT61E depended on the input voltage.  If that voltage was just enough for an accurate frequency reading, the duty cycle reading would be low.  Double the voltage and the duty cycle reading would be much more accurate.  Since I was unable to increase the RF voltage for the higher frequency readings, the accuracy of their duty cycle readings seen was compromised by that.

 

[mos6502]

Great job, thanks! Of course, the measurment of the duty cycle depends on the trigger level, so it's really only meaningful for square wave signals. But it looks like the duty cycle measurement is useful to at least 1MHz. 

Duty cycle measurement is really useful for a lot of things. E.g. if you wrote a multitasking scheduler for your microcontroller, you can set a pin at the beginning of your task and reset it at the end of your task, and by measuring the duty cycle you can directly see how much of the CPU time that task consumes in percent.

[ocw]

I forgot about the higher output power available from my HP 3200B VHF generator.  Taking it to a metered output of +23.5 dBm/224 mW/3.346 V (1.7 dB beyond its rating) the UT61E was able to measure its output frequency up to 225 MHz.  Uni-Trend hasn't over-rated it.  But, there's a reason why their specs don't show its counter's sensitivity.

[xZero]

Is this one still worth consideration in 2015? Or is there something better for same price? 
Thanks in advance!

I was on cheap one, and finally gonna move to something better with PC connection.
I work primarily with electronics and informatics (hardware).

[mos6502]

Is this one still worth consideration in 2015? Or is there something better for same price? 
Thanks in advance!

I was on cheap one, and finally gonna move to something better with PC connection.
I work primarily with electronics and informatics (hardware).

Do you need the PC connection? If not, I'd go with the newer UT139C. Much better construction, faster display, actually has input protection, temperature measurement, real fuses and has a backlight. Only 6,000 counts, but unless you have specific requirements, that's perfectly adequate.

[xZero]

Thanks for the reply.

But yes, I do need PC connection, and that's the feature I've been missing on all multimeters I had (cheap ones).
Looking from my point of view, by my needs, UT61E seems like perfect choice, I've just wondering can I get something better/newer with same capabilities for the same price?
Since UT61E is few years old, I expected price to be lower as well, however it seems that it holds it price since then.

[mos6502]

22,000 counts and PC interface is pretty much unparalleled at this price point. So yeah, buy it. Forgot to mention, the burden voltages are also worse on the UT61E vs. the UT139C. Really, I would get the UT139C as well. Each has features that the other one is missing. I'm thinking of getting a UT61E myself to complement my UT139C.

[xZero]

Since I'm limited with price at the moment I'm gonna buy UT61-E as it have what I need and later I may go for UNI-T UT71D. Having spare multimeter can't be bad.

Or, what if I buy Mastech MY64 as first hand, since I'm out of any right now... It's pretty cheap, and seems to be decent temporarily.

[mos6502]

Wat. That one doesn't have a PC connection.

Anyway, this one is cheaper and better than the Mastech you mentioned:

[Lightages]

Just remember that the UT61E,and the UT71D do not meet their CAT ratings. Use them for electronics use and they are are good buys. The UT139C is a much better built and safer meter but has less features.

I have zero confidence in anything made by Mastech and would recommend the Uni-T models before anything made by Mastech.

[mos6502]

I have zero confidence in anything made by Mastech and would recommend the Uni-T models before anything made by Mastech.

Bingo! 

Another option would be the DT-4000ZC:



http://www.ebay.de/itm/Digitek-DT-4000ZC-TekPower-TP4000ZC-Data-Logging-Multimeter-with-Temperature-/200912705694

Pretty decent meter, very cheap and it has RS232.

[xZero]

Wat. That one doesn't have a PC connection.
...

Yeah I noticed that, but for price I didn't expected it.

Thank you for your effort guys, I'm realy happy to see al that responses and I had took a look at every of DMM recommended, and so I decided to go for UT61E for now, and after when I get some more money for some better one. It's good to have more than one.


As I said I'm electronic hobbyist, and sometimes I "mess" up with household installations and such voltages, but my very first generic DMM (DT-SOMETHING) had cost me only 10USD and It lasted for 5 years, and I did use it to measure amperage up to 20A, measure DC/AC voltage up to 200/500V for electronic tasks, for car electronics etc and it did all pretty well. It had bad probes, and unusable capacitance tester. I killed it by measuring voltage from DC/AC converter (12VDC -> 90VAC) because I forgot to change from DC to AC. That one was almost visually/feature identical as Mastech MY64 with exception that protection cover was yellow.

[niclasf]

I have done a combination of many of the UT61E modifications.
I have used a PIC16F688 to add more modes to the yellow and blue function buttons.


I have also added a LPF mode, but I am not sure how I can verify that it works.

[NicolasCalisto01]

Yes, is a nice multimeter hack

[groff]

niclasf wrote:

I have done a combination of many of the UT61E modifications.
I have used a PIC16F688 to add more modes to the yellow and blue function buttons.

Yes, very good work.   I found your c file on foogadgets but can I get hex file? Can you attach it on foogadgets or on this forum?

[niclasf]

Now you can download it in the download section in bitbucket, https://bitbucket.org/foogadgets/ut61e-modification/downloads/ut61e-mod.hex

Enjoy!

[groff]

Thanx 

[jbuszkie]

I have done a combination of many of the UT61E modifications.
I have used a PIC16F688 to add more modes to the yellow and blue function buttons.


I have also added a LPF mode, but I am not sure how I can verify that it works.

Do you have pictures of the mods?  I tired to go to the forum post in the foogadgets blog but it doesn't seem to work.

Thanks!

Jim

[niclasf]

I have uploaded the pictures from the modification, https://bitbucket.org/foogadgets/ut61e-modification/downloads

[MrMacman2u]

I have done a combination of many of the UT61E modifications.
I have used a PIC16F688 to add more modes to the yellow and blue function buttons. (popped out the link -MM2U)

I have also added a LPF mode, but I am not sure how I can verify that it works.

Excellent... no... Outstanding work niclasf!

I just bought this meter and this is, literally, an even better modification than the one I was in the middle of making using an ATTiny 85 since I wasn't going to bother breaking out the LPF!

Now I need to step it up and figure out how to hack in the temperature function using the ADF pin since that the chip supports temp too.

I'm working on other hardware upgrades as well including setting in metal inserts to use machine screws for the battery compartment and case, solid input jack upgrades to replace the cheapo splits, and installing the missing MOV's.

I'll document all the changes and post them here.