Author Topic: how about UT70D multimeter as one of the higher end China made multimeters?  (Read 37065 times)

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Offline slburris

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Anyone tried the UT70D multimeter?  It's a 79,999 count meter with decent specs:

http://www.uni-trend.com/UT70D.html

I think a rebadging of it is the Sper Scientific 840077.  It available from
Amazon for $135.  The UT70D seems to be on Ebay for a similar amount.

Anyone got some PCB pictures of this thing?

Scott
 

Offline armandas

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The closest I could find was this PCB of UT70A model. You might be interested in pictures of UT71 series though: https://www.eevblog.com/forum/index.php?topic=332.msg3421#msg3421
 

Offline Kiriakos-GR

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Anyone tried the UT70D multimeter?  It's a 79,999 count meter with decent specs:
Nop..
But never the less, it looks interesting, and has an 54 megabytes large as "user's  manual".  

Quote
Your Multimeter is an intelligent digital one, a precise
instrument with a resolution of 80,000 counts and up-to
-date automatic computer calibrating function.

High resolution A/D converter and micro-controller data
processing technique is adopted in the Meter, featured
with intelligence, high precision and multi-functions. The
Meter can be widely used in laboratory field service,
domestic and other applications. All the functions and
ranges have full overload protection.

In addition to the conventional measuring functions, it is
equipped with a RS232C standard serial port for easy
connection with computer to realize macro recording and
monitoring and capture of transient dynamic data,
displaying change of waveform during the measurement,
providing data and evidence to engineering technicians
for scientific research. This is also a highly applied digital
multimeter of good performance with display back-light.
« Last Edit: May 14, 2010, 08:43:49 pm by Kiriakos-GR »
 

Offline saturation

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Those trimmer are old tech, e.g. VR7 marked in the photo.  Modern DMM no longer use them.  Its more likely to drift with time, temp, shock and vibration.
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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Well If some one seeks good points to argue ... ;D
He should read the Users manual.

About True RMS specs , 1000V 40 ~ 400Hz 
Capacitance tester up to 100uF
Display refresh time 5 per second. 
Sleep mode 30 min, buzzer makes five beeps before fall in to sleep .. ( No shit )  :D :D
 

Offline Mechatrommer

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i just ordered a Uni-T UT70B from ebay. I'll take a blind shoot on it for about $70. Lets see if i have a hit :) Thanx guys for info here.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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i just ordered a Uni-T UT70B from ebay. I'll take a blind shoot on it for about $70. Lets see if i have a hit :) Thanx guys for info here.


Some one is overexcited here ...  ;D

I will only nag about it , about the resolution... other than that looks fine ..
 

Offline Mechatrommer

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i've surveyed from ut60 to ut71 range. IMO, ut6x is quite nice in spec, except they are not auto ranging. auto ranging start from ut70 series, ut71 series is way too expensive for my taste n needs. so it leave me with ut70's. i got most interested at ut70A coz it has great range in 20uA-10A, ut70B got 200uA-10A, but after some 5 minutes meditation, i choose UT70B coz it has R232 connection to PC which i asume data logging capability. hope i'm not mistaken on this. i saw some youtuber post about it (using QBasic to get data out of UT70B).

about resolution? i've been very happy with my SUNWA $20 DMM in term of reading, so i think, with this $70 DMM, i should not be dissapointed by it. if i am/will, then be ready for rant time!
« Last Edit: June 02, 2010, 12:22:51 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Mechatrommer

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sorry.. correction. the UT70B range is 400uA-10A. NOT 200uA-10A. o well, hope it can read something :P
and also i just noticed... the UT70A is not auto ranging...
UT70C or UT71A could be (a little bit) better than UT70B... with around $20 addition.
« Last Edit: June 02, 2010, 01:55:43 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Mechatrommer

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i just change the order, add a $20, and ask to replace the model to UT71A, so no more UT70B
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline cybergibbons

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I find their product naming conventions really hard to follow. It seems that the series name is only really to do with the case and LCD and not very much to do with the features.
 

Offline Mechatrommer

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yup. sometime it is quite overlapping between 70 and 71 series, or even 60's. escpecially in the range. when we go from 60abcd up to 71abcde, the range is going up and down and up again. i think i need all the spec display together to get a better picture (just like parametric table). but generally going from a to d or e version means price going up. the 70d is more expensive than 71a even if the higher "71" number. thats why after making 2nd review, i've change my mind to UT71A due to:

1) greater uA range at low side (200uA on UT71A compared to 400uA on UT70B)
2) USB connection compared to RS232 (not sure whats it for, no review on this online, i hope its for sending data to PC)
3) greater count accuracy, 3999 for 70B, 20000 for 71A
4) with carrying case
5) 71A looks more pro and sexy! oh yeah baby! :)

and all this is just for $20 addition, i think its worth it.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Mechatrommer

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my only concern with this "new technology" DMM is that reading/update speed. i dont understand why more expensive DMM's are very slow at even continuity check where my $20 can do that in split second. similar to other V and A reading too.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline slburris

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So I went ahead and picked up a Uni-Trend UT70D multimeter.
I took it apart and it looks a bit different than the earlier UT70 series. 
No pots to adjust for one thing.

I threw up a quick web page with some photos at:

http://random.electroscott.com/ut70d.html

Time will tell how good this meter is compared to my Flukes.

Scott
 

Offline cybergibbons

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2) USB connection compared to RS232 (not sure whats it for, no review on this online, i hope its for sending data to PC)

I'd be very interested to see this as well - there's not much mention of it in the manuals. I can imagine it is just a USB->Serial bridge and works pretty much the same as the older RS232 interface.

I do recall reading somewhere that one of the lower meter (UT61D maybe) output a serial representation of the 7 segment display bars, rather than actual numbers....
 

Offline saturation

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Its inherent in design, consider if they fail to consider this item, what else can they overlook?

FWIW you won't get this issue with an reputable DMM, like a Fluke that you'll have for a lifetime.


my only concern with this "new technology" DMM is that reading/update speed. i dont understand why more expensive DMM's are very slow at even continuity check where my $20 can do that in split second. similar to other V and A reading too.

Best Wishes,

 Saturation
 

alm

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One issue is that you need longer integration times for higher accuracy, but it's technically perfectly feasible to do thousands of readings per second in 3.5 digit mode (recent Agilent DMM's), although not for $100. But if they use the same type of ADC in both models, the more accurate model would need longer integration times.
 

Offline saturation

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Thanks for this work, and good photos.  I agree with your conclusion, use it for low voltage work.

Some comments on its design.

There are a number of solder repairs visible on the back, here's just one zoomed in:



The 9V battery connector has barely any strain relief

glass fuses are a no-no for any CAT level meter, it should be at least HRC or equivalent

That foil shielding appears flimsy; hopefully it stays clear of the PCB to prevent shorting; similar designs are adhesive and stick to back of the casing to reduce risk of shorting





So I went ahead and picked up a Uni-Trend UT70D multimeter.
I took it apart and it looks a bit different than the earlier UT70 series.  
No pots to adjust for one thing.

I threw up a quick web page with some photos at:

http://random.electroscott.com/ut70d.html

Time will tell how good this meter is compared to my Flukes.

Scott

« Last Edit: June 05, 2010, 01:58:31 pm by saturation »
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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FWIW you won't get this issue with an reputable DMM, like a Fluke that you'll have for a lifetime.



I do not have faith  in this "marketing statement" .
especially by having in mind , the negative and poor behavior of Fluke , to any one who got an used meter.
Not that the ones with sealed ones, will get any better services ..
The Fluke forum is locked ... so no room for complains !!  
I do not see any day/night deferences at the " low end "  Flukes, in comparison with many others branded competitors ..


About baptizing the UNI-T as low voltage , the damn Flukes does not gain any FAME ...

This UNI-T are fabulous ,  even the PCB are ready to accept large HRC fuses ,
but the silly American asses ( Buss and others ) , they charge for them " an fortune " ..

If I was an manufacturer of DMM's, I would use also acceptable "middle cost" FUSE solutions.

Comparing apples with apples ,  the 300$  UNI-T  will have no deference from the FLUKE 87-5 .

  

  
« Last Edit: June 05, 2010, 04:47:20 pm by Kiriakos-GR »
 

Offline neikalo

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I had one of these. I gave it away because I didn't trust it:



(This one was the second with the same problem).

It had a terrible continuity buzzer, poor backlight, and a weired analog bargraph marked 0-10 instead of 0-8 (it's an 80000 count meter). 10 meant 100% of range.

The PC software was pretty basic as well, but it did work.

I paid a lot for it (GBP100). A Fluke replacement was over three times the price but many times better. I never looked back.
 

Offline Kiriakos-GR

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Oh yea this fantastic video ... will blame the UNI-T  for a life time ..  :P

I will have to make my own video , to blame the FLUKE 87-5 about it poor performance as frequency meter ..

I was testing my own tone generator , and I had to amplify the signal with 5W amplifier so to get reliable readings ..
With 0-600mV  input level , it should be hyper sensitive as frequency meter too !!

Or ...
I had to use the output of the tone generator as input on my amplifier ( square signal) , so to have acoustic output,
and another output of my generator ( sine signal ) , as input for the Fluke !!  

Pictures here ..  
https://www.eevblog.com/forum/index.php?topic=629.0

I have 50/50 % , love & hate feelings for the top Fluke , thats why I consider my opinion as less biased.  ;)


    
 

Offline Kiriakos-GR

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and a weired analog bargraph marked 0-10 instead of 0-8 (it's an 80000 count meter). 10 meant 100% of range.

This sounds like a bad joke ...  the analog  bar-graph .. it called as analog because it is ....
Its an second separate meter on a single display ..

Has nothing to do with the main " Digital counts"  meter !!   

 

alm

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Except that the analog bar is based on the same ADC, which has the same digital counts (plus a few extra for auto zero). It's not like the resolution is limited by the LCD display. If the bar graph indicates 9, that would mean 90% of 80V = 72V. Are you seriously suggesting this is intuitive?
 

Offline Kiriakos-GR

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For any such details , just read the manual ..

http://www.uni-trend.com/manual2/UT70DEng%20ManualLVD.pdf

Analog  = analog  

scale 0-10  =  0-10 volts  0-1000 volts  etc etc  

Metrix (France ) had build even an DMM with analog needle and digital LCD in one package.    

Here is the proof , that the UNI-T does have 0-1000 scale !!  :P
Page 17 ...
« Last Edit: June 05, 2010, 10:18:30 pm by Kiriakos-GR »
 

alm

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For any such details , just read the manual ..
I did, and it took ages to download (slow site):
Quote from: UT70D manual, page 34
For example, when 80V range is selected, the full-range value of the analog display is 80V, and as the full range is uniformly divided into 10 grades, each grade denotes 8V; If the input is 40V, the high-lighted bar-shape will be at the position indicated by the number 5.
5 = 40V? This is completely stupid, they should have just used the scale between 0 and 8 instead of requiring the user to memorize 8/10th fractions.

Analog  = analog  

scale 0-10  =  0-10 volts  0-1000 volts  etc etc  

Metrix (France ) had build even an DMM with analog needle and digital LCD in one package.    
I know it's technically possible to combine an analog and digital meter (Fluke did this in a wideband RMS meter, ironically it also indicated 0 to 100%), but that's a lot more expensive than just sampling from the same ADC in low-resolution high-speed mode, which is what almost any DMM does.

Here is the proof , that the UNI-T does have 0-1000 scale !!  :P
Congratulations, the bar graph scale does work correctly at one range setting! I'm impressed.
 

Offline Kiriakos-GR

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Here is the proof , that the UNI-T does have 0-1000 scale !!  :P
Congratulations, the bar graph scale does work correctly at one range setting! I'm impressed.

Yes it does  ;D  ;D  ;D   
 

Offline saturation

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I'm not sure why you had issues with your Fluke 87V for a simple measurement, my 20 year old 85I reads true today as it did when new per the original calibration data for series 1; I just spent some time checking its calibration with some new equipment I have that was calibrated in March and April this year.  

I saw the 70D video in the past, while it could have just be a 'fluke' ;D if you read the comments on the video, he was not alone.  

There are other favorable reviews elsewhere though, particularly those looking for a low cost data logging DMM, which is helpful if it were reliable and read accurately.   So I have some interest in a meter than works like Fluke but isn't in its price range, but I'm not convinced you'd want to invest time and energy collecting important data with this Uni-T.  I wouldn't hesitate to buy it for low voltage or DC use in the field, but I think you can do that with a cheaper DMM.

The spec sheet is a bit misleading:

http://www.uni-trend.com/UT70D.html

If this is true, for an 80,000 count DMM its accuracy is more closer to 8,000 count.  The last digit has little value.  

For e.g.: specs report 0.05%+10 digits in the 8V range [ but the manual Kiriakos shows that at 8V its really 20 digits.]

8.0000V ~ 7.9960-8.0040,  + 10 digits  ~ high as 8.0050.  That's quite a bit of variation unless you ignore the last 2 digits.  Likewise, the reported accuracy of the ACV and other ranges to a high of 20-120 digits, reinforce the last 2 digits unreliable, at worst.  

The manual page 34 shows what Alm already suggested, its full scale represents the same scale as the digits, so in this example, it would be 8v, and the scale represents 8/10 for every digit.  Luckily most folks use the analog scale as a relative reference or real time trend, rather than to measure a value.

The penultimate voltage range is 800V then finally 1000V, which seems like a unusually small increment given the way a DMM scale is made.  I think this is more to keep in line with the limits of CAT III safety which limits input at 1000V AC or DC, for transients up to 8000V.





FWIW you won't get this issue with an reputable DMM, like a Fluke that you'll have for a lifetime.



I do not have faith  in this "marketing statement" .
especially by having in mind , the negative and poor behavior of Fluke , to any one who got an used meter....

If I was an manufacturer of DMM's, I would use also acceptable "middle cost" FUSE solutions.

Comparing apples with apples ,  the 300$  UNI-T  will have no deference from the FLUKE 87-5 .






Oh yea this fantastic video ... will blame the UNI-T  for a life time ..  :P

I will have to make my own video , to blame the FLUKE 87-5 about it poor performance as frequency meter ..

I was testing my own tone generator , and I had to amplify the signal with 5W amplifier so to get reliable readings ..
With 0-600mV  input level , it should be hyper sensitive as frequency meter too !!


Or ...
I had to use the output of the tone generator as input on my amplifier ( square signal) , so to have acoustic output,
and another output of my generator ( sine signal ) , as input for the Fluke !!  

Pictures here ..  
https://www.eevblog.com/forum/index.php?topic=629.0

I have 50/50 % , love & hate feelings for the top Fluke , thats why I consider my opinion as less biased.  ;)


    
« Last Edit: June 06, 2010, 12:48:19 am by saturation »
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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I'm not sure why you had issues with your Fluke 87V for a simple measurement...........  


For the price that it costs , I have no tolerance with such quirks.  

Or even with the other issue that it does at High resolution , when the voltage gets under the 19.999
it turns normally to the normal resolution { 20.00 },  but I have to drop 4 volts , so to enter again at the high resolution.
Thats not right ... simple as that.  
It should turn to high resolution , just by a millivolt drop from the 20 volts.

If this one costs 500 EUR , and it does not do it right , how much I need to spent for true perfection?   1000 EUR ?  

If so, no one haves the right to blame the economic UNI-T .
 

alm

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If this one costs 500 EUR , and it does not do it right , how much I need to spent for true perfection?   1000 EUR ?
Nothing is perfect ;). I'm sure much richer people have spend a lot more money to find that out.

If so, no one haves the right to blame the economic UNI-T .
But it doesn't hurt to make potential buyers aware. This isn't a 'who has the biggest meter' game, or about who's right or wrong, nobody here has personally designed any of these meters. Everyone just gives his or her opinion, and if you combine them all, you might get something resembling an objective description of the meter.
 

Offline Kiriakos-GR

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Well at the price level of the specific Fluke , that is mainly my problem , I have no people to " combine "  their observations ..

Even so, I am starting to believe again at the old Greek principal " That simplicity works always best in anything "

So there is no need , for super complicate instruments , with bugs that no one are able to fix.
 
And before I let this ranting of my, to over for good ,
I will also nag  about the display  of the fluke 87-5 , due the poor viewable angle . ( up - down)
And  the super silent beeper .... all those hard plastics as multimeter case, plus the rubber in between 
the plastic covers ,  plus the rubber holster ,  cause the beeper to sound with so low volume ,
that no one will be able to listen in it ... specially at the famous " industrial environment " .
What the damn FLUKE had in mind about that ? " industrial environment " + low volume beeper !!       
 
Even at my bench I had to stop any noise source and  even the music (radio),  so to listen it .. 
I am truly thinking to drill the Fluke, so to get some sound of it ..

All my other low priced DMM's have an powerful beeper ...  how can I blame them ?
 
 

Offline slburris

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I did a few more tests of UT70D, comparing with my Fluke 87-V and Fluke 8505A 6.5digit bench meter.

Using a Malone voltage standard to test with:

http://www.voltagestandard.com/Home_Page_JO2U.html

This is supposed to by 0.01% accurate at 5V.  I got the following
measurements (note I just turned everything on, didn't let stuff warm
up, so your mileage may vary):

87-V: 5.000
8505A: 5.00022
UT70D: 5.008

Hmm, so it does indeed look like the last digit should be ignored
and the manual says it's += 10 digits for accuracy.  Not clear to
me if you could trust the last digit for relative measurements.

On to resistance.  I used a 500K resistance standard, accurate to
+- 0.05%.  Here are the results:

87-V: 500.0K
8505A: 499.93K
UT70D: 498.6K

Other notes:

I don't experience the OL at turn out as shown in the youtube video someone
posted.

The continuity test is only moderately responsive and sounds a little scratchy.
I think some meters pulse stretch the continuity results -- this one does not.

I agree that the analog bar graph is pretty useless for measurements.  It does
update lightning fast though, so I would use it just to see if the input was varying.
Looking at the manual, the graph updates 50 times/sec, and the digital display
5 times/sec.

The foil shielding is more durable than the photo would show.  It's encased in
pretty tough plastic, and is grounded via the ground input lug.

Scott
 

Offline slburris

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More measurements.

I connected the Fluke 87-V and the UT70D to line voltage and the results were:

87-V: 119.5VRMS 59.98Hz 50.0% duty cycle
UT70D: 120.0VRMS 59.98Hz 50.01% duty cycle

Next, I generated a 100Khz sine wave at 1Vpp with a signal generator

87-V: 100.00Hz, 46.4% duty cycle
UT70D: 100.01Hz, 50.65% duty cycle

Next I tried measuring two capacitors:

2200uf

87-V: 2261uf
UT70D: failed, checking manual shows this is beyond the range of the meter

0.002uf

87-V: 3.09nf
UT70D: 2.77nf

Scott
 

Offline saturation

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Thanks Scott for the updates.  Good to know results particularly knowing of the instruments you're referencing the Uni-T against.  Please keep them coming.

The 8505A is a Fluke DMM?  I think its has rated accuracy much over the 0.01% Malone reference.

On the DCV referenced against the Malone standard, that gives the 70D a DC accuracy of 0.1556%, a bit off from the published 0.05%.  Even with the 10 digits extra, it would rate at 0.06%.  The 87V DC accuracy here is 0.0044%

For the precision resistor, using the 8505A as a reference then the
87V is 0.014%
70D is 0.266%

Note, on the measurements without higher reference device, its hard to know who is off, the 87V or the 70D.  It would be great if you could measure them against the Fluke 8505A.

Caps tend to have high tolerances so what's printed on the device may only remotely be what its true nF is.  Again, best to measure it against a higher accuracy device.

Thanks for the clarification on the foil shield, its well built for it then, my err.



More measurements.

I connected the Fluke 87-V and the UT70D to line voltage and the results were:

87-V: 119.5VRMS 59.98Hz 50.0% duty cycle
UT70D: 120.0VRMS 59.98Hz 50.01% duty cycle

Next, I generated a 100Khz sine wave at 1Vpp with a signal generator

87-V: 100.00Hz, 46.4% duty cycle
UT70D: 100.01Hz, 50.65% duty cycle

Next I tried measuring two capacitors:

2200uf

87-V: 2261uf
UT70D: failed, checking manual shows this is beyond the range of the meter

0.002uf

87-V: 3.09nf
UT70D: 2.77nf

Scott

I did a few more tests of UT70D, comparing with my Fluke 87-V and Fluke 8505A 6.5digit bench meter.

Using a Malone voltage standard to test with:

http://www.voltagestandard.com/Home_Page_JO2U.html

This is supposed to by 0.01% accurate at 5V.  I got the following
measurements (note I just turned everything on, didn't let stuff warm
up, so your mileage may vary):

87-V: 5.000
8505A: 5.00022
UT70D: 5.008

Hmm, so it does indeed look like the last digit should be ignored
and the manual says it's += 10 digits for accuracy.  Not clear to
me if you could trust the last digit for relative measurements.

On to resistance.  I used a 500K resistance standard, accurate to
+- 0.05%.  Here are the results:

87-V: 500.0K
8505A: 499.93K
UT70D: 498.6K

Other notes:

I don't experience the OL at turn out as shown in the youtube video someone
posted.

The continuity test is only moderately responsive and sounds a little scratchy.
I think some meters pulse stretch the continuity results -- this one does not.

I agree that the analog bar graph is pretty useless for measurements.  It does
update lightning fast though, so I would use it just to see if the input was varying.
Looking at the manual, the graph updates 50 times/sec, and the digital display
5 times/sec.

The foil shielding is more durable than the photo would show.  It's encased in
pretty tough plastic, and is grounded via the ground input lug.

Scott

Best Wishes,

 Saturation
 

Offline saturation

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Maybe there is something subtly wrong in your DMM, you did buy it used from eBay as I recall?

https://www.eevblog.com/forum/index.php?topic=354.15

Also in that thread you did a voltage test, but if you have access to such equipment maybe you should do a full calibration across all the ranges.



I'm not sure why you had issues with your Fluke 87V for a simple measurement...........  


For the price that it costs , I have no tolerance with such quirks.  


Or even with the other issue that it does at High resolution , when the voltage gets under the 19.999
it turns normally to the normal resolution { 20.00 },  but I have to drop 4 volts , so to enter again at the high resolution.
Thats not right ... simple as that.  
It should turn to high resolution , just by a millivolt drop from the 20 volts.

If this one costs 500 EUR , and it does not do it right , how much I need to spent for true perfection?   1000 EUR ?  

If so, no one haves the right to blame the economic UNI-T .
« Last Edit: June 07, 2010, 12:09:04 am by saturation »
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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Maybe there is something subtly wrong in your DMM, you did by it used from eBay as I recall?

https://www.eevblog.com/forum/index.php?topic=354.15

Also in that thread you did a voltage test, but if you have access to such equipment maybe you should do a full calibration across all the ranges.


I have no true issues with the DMM , thats why I am holding my horses  about any true debate.   :)

Some quirks , are software related issues , some others are about the design of it,
and about the sensitivity of it as frequency meter ,  I  own an true Japanese frequency meter from LEADER 0~150MHz, that its does not fool around.

Its all about price tag and expectations.
I was expecting more perfection from it, as " package ".

I am not surprised , that the specific UNI-T performs decently .

Even so, when we test DMM's  its best to use the same cables set  ;)  
  


  
« Last Edit: June 06, 2010, 08:35:18 pm by Kiriakos-GR »
 

Offline slburris

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Bah, my first attempt to post this got eaten!

The Fluke 8505A is a 6.5 digit benchtop multimeter.  For DC volts,
it's rated to be within 0.001% +- 8 and for resistance it is
0.003% += 1. 

As you can see, it's far better than any voltage or resistance standard I
have....

The 87V is rated DCV 0.05% +-1 and resistance 0.2% +-1.  So if all the
math is right, the 87V is doing much better than spec.

For capacitance, I don't have anything to compare against.  The only
equipment I have is the 87V and now the UT70D.  I'd like to get
a real LCR meter, but I haven't yet.  I know Dave likes the Smart Tweezers,
but I'm still looking at the Agilent U1731B for $276 from Newark.

http://www.home.agilent.com/agilent/product.jspx?nid=-34196.920242.00&cc=US&lc=eng

I'll see what other tests I can come up with.

Scott
 

Offline slburris

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OK, time for more multimeter abuse.

Probably most people use frequency counters instead of
multimeters to measure frequency, but I ran some more
tests just for fun.

Here's the setup.  I used a Wavetek 288 signal generator
to generate sine waves.  I'm feeding the output to both
the Fluke 87-V multimeter and the UT70D.  As well, it
goes to a Racal-Dana 1998 frequency counter that is
using a Trimble Thunderbolt as a GPS locked 10Mhz external
frequency reference.  I'd say the frequency measurements
of the 1998 will be extremely accurate :-)

The signal generator is set to produce 1Vpp and terminated into
50 ohms.

At 100Hz, the results are:

1998: 100.004Hz (many more digits of accuracy, but not important for this test)
87-V: 100.00Hz
U70D: 100.01Hz

Now at 1Khz:

1998: 1000.046Hz
87-V: 1000.0Hz
U70D: 1000.1Hz

Now at 100Khz:

1998: 100.00455KHz
87-V: 100.00Khz
U70D: 100.01Khz

Now at 200Khz, beyond what the U70D is specified for:

1998: 200.009Khz
87-V: 200.0Khz
U70D: 199.71Khz

Next, I pushed the limits of the frequency to see what the meters
could do.  The U70D is only specified up to 100Khz and the 87-V
up to 200Khz.

The U70D started displaying completely wrong values above about 250Khz
then eventually only displayed zeros.  The Fluke 87-V worked up to about 660Khz,
then displayed only zeros.  The Fluke never displayed any nonsense numbers -- it
either displayed the correct frequency or zero.

OK, going back to 100Khz, I started dropping the amplitude of the signal to see
where the meters would drop out.  The U70D stopped working below 0.93Vpp.
The 87-V stopped working below 0.07Vpp (no, that's not a typo, more than 10X
lower amplitude).

I'm really coming to appreciate what a nice meter the 87-V is.

Scott


 

Offline Kiriakos-GR

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Well Scott, it looks that you know, what you are doing, but I need to see pictures,
so to cheer up .  :)

With words I build castles .. too

The 600KHz one ... and the low 0.07Vpp
« Last Edit: June 07, 2010, 08:36:37 am by Kiriakos-GR »
 

Offline slburris

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You know, I'm going to hold back my opinion until I see the results of Dave's $100 multimeter
test.  I wonder if he's going to test any UniTrends, and if so which ones?

I really wanted a multimeter with capacitance measurement, so that knocks some of the
cheaper meters out for me.  Ignoring that, I kinda like the VC99 for 1/3rd the price of
the UT70D, but Dave really doesn't seem to like that one.

Scott
 

Offline EEVblog

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You know, I'm going to hold back my opinion until I see the results of Dave's $100 multimeter
test.  I wonder if he's going to test any UniTrends, and if so which ones?

Yes, the UT61D, it's in the mail.

Dave.
 

Offline Kiriakos-GR

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slburris has made a detail testing there............

Sorry but I did no see it ..  other than words.
 

alm

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What's the point of pictures? Unless you take great pains to show every single wire and control setting, it contains less information than written text. Either you trust someone to do a correct and unbiased test, and you accept their numbers, or you don't, and no amount of data will convince you. Pictures of the setup are quite rare in science, especially if it's standard equipment.
 

Offline saturation

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You can make a simple high pass filter to get a good measure of capacitance, and I presume you have a scope but you can do this with just Vac on the DMM:





http://www.play-hookey.com/ac_theory/hi_pass_filters.html

Since you have a reference signal source, a reference resistor of 500K, and you have an 'unknown' roughly .002 uF cap then fc = 159.15 Hz when the Vacout ~ 0.707 Vacin






Bah, my first attempt to post this got eaten!

The Fluke 8505A is a 6.5 digit benchtop multimeter.  For DC volts,
it's rated to be within 0.001% +- 8 and for resistance it is
0.003% += 1. 

As you can see, it's far better than any voltage or resistance standard I
have....

The 87V is rated DCV 0.05% +-1 and resistance 0.2% +-1.  So if all the
math is right, the 87V is doing much better than spec.

For capacitance, I don't have anything to compare against.  The only
equipment I have is the 87V and now the UT70D.  I'd like to get
a real LCR meter, but I haven't yet.  I know Dave likes the Smart Tweezers,
but I'm still looking at the Agilent U1731B for $276 from Newark.

http://www.home.agilent.com/agilent/product.jspx?nid=-34196.920242.00&cc=US&lc=eng

I'll see what other tests I can come up with.

Scott

Best Wishes,

 Saturation
 

Offline slburris

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I guess I'm not clear on what the pictures are being requested for. 
Nevertheless, here are some shots of everything I've been talking about.

First up, we have the units under test, the Fluke 87-V and the UT70D
sitting on top of the Racal-Dana 1998 counter, currently displaying
the 100Khz signal from the signal generator.

Next, at the bottom of this stack, we have the WaveTek 288 signal
generator set to 100Khz.  The Tektronix 2236 oscilloscope and
Tektronix 1240 logic analyzer are not used in this testing.

Next we have the Trimble Thunderbolt GPS disciplined oscillator feeding
a TAPR TADD-1 RF Distribution Amp (http://www.tapr.org/kits_tadd-1.html).
That's used to distribute the 10Mhz standard to multiple instruments.
 

Offline slburris

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More pics,  here we have two Fluke bench meters, the 8505A and the
8502A.

Lastly, we have the 0.05% resistance standard and the 0.01% voltage
standard.

Scott
 

Offline slburris

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Can you believe the Racal Dana 1998 was a $60 find on Ebay?  I think
I lucked out on this one.

Counts to 1.3Ghz.  It's not a bad counter by itself, but since it can take
an external 10Mhz reference (like good equipment should), it's much more
accurate than it was originally designed for when fed the output of the
Thunderbolt.  I've also got an HP 5328A counter which can take an external
frequency standard, but it's huge compared to the 1998.

I've seen some cheap 1.3Ghz counters on the market, like the Mastech MS6100,
an 8 digit counter.  I'm not sure how much I believe the specs.  No external
frequency input, so it can't be nearly as accurate as my current counters.
Maybe once Dave's finished destroying every multimeter on the market, he can
take apart some of the counters from China. 

Scott
 

Offline Kiriakos-GR

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About the 87-5 , I have move my interest, beyond the common leads measurements.  ;)

More details , in specific thread .  :)


.
« Last Edit: June 07, 2010, 08:17:29 pm by Kiriakos-GR »
 

Offline saturation

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You have very highly capable gear.  What made you consider the UT70D?

Based on your prelim observations, $100 is an acceptable price point, but a most compeling feature against competition in its price range is its data logging RS232 feature.  Hopefully these reading are stable over time to make logging any data worth it.

I raise a skeptical flag as the spec sheet and the simple measured results show it doesn't live up to it, except in the frequency counter.  The good news is these prelim specs are acceptable but not what is publicized as its specs, compare to what Fluke reports vs what you actually measure.

For extra confidence, I'd remeasure it at a later date, and with a variable power supply check the accuracy of the added ranges against the Flukes on both Vdc and Vac to check its linearity, just as you did sweeping up the frequency spectrum, and also check its response against a square wave.


Can you believe the Racal Dana 1998 was a $60 find on Ebay?  I think
I lucked out on this one.

Counts to 1.3Ghz.  It's not a bad counter by itself, but since it can take
an external 10Mhz reference (like good equipment should), it's much more
accurate than it was originally designed for when fed the output of the
Thunderbolt.  I've also got an HP 5328A counter which can take an external
frequency standard, but it's huge compared to the 1998.

I've seen some cheap 1.3Ghz counters on the market, like the Mastech MS6100,
an 8 digit counter.  I'm not sure how much I believe the specs.  No external
frequency input, so it can't be nearly as accurate as my current counters.
Maybe once Dave's finished destroying every multimeter on the market, he can
take apart some of the counters from China. 

Scott

Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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Sorry to see this Kiriakos, but it again suggest your your Fluke is damaged or in need of calibration.

I am not aware of what you think, that you have see ..  
But I will not start explaining here, of how this digital clamp works in detail.

I had spent hours , taking measurements , and learning how to properly use , this new setup.  
The only that I can tell , its that the clamp , has an "Auto Zero" calibration + 1.5% accuracy .
  
« Last Edit: June 07, 2010, 08:31:11 pm by Kiriakos-GR »
 

Offline saturation

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Sorry Kiriakos I did not see the picture clearly until I saw your clamp meters.  I removed my message, my apologies!

Sorry to see this Kiriakos, but it again suggest your your Fluke is damaged or in need of calibration.

I am not aware of what you think, that you have see ..  
But I will not start explaining here, of how this digital clamp works in detail.

I had spent hours , taking measurements , and learning how to properly use , this new setup.  
The only that I can tell , its that the clamp , has an "Auto Zero" calibration + 1.5% accuracy .
  
Best Wishes,

 Saturation
 

Offline Rhythmtech

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Sorry to see this Kiriakos, but it again suggest your your Fluke is damaged or in need of calibration.

I am not aware of what you think, that you have see ..  
But I will not start explaining here, of how this digital clamp works in detail.

I had spent hours , taking measurements , and learning how to properly use , this new setup.  
The only that I can tell , its that the clamp , has an "Auto Zero" calibration + 1.5% accuracy .
  

Is that 1.5% of reading or full scale? What is the range of the current clamp? In the mV scale the 87 has ± (0.1 % + 1) of reading, so it could contribute ~.101 of error at 1 mV. What is your current source? It looks like the current clamp is set to 1mV/A output, while there is a 10mV/A setting, which might give a much better reading.
 

Offline Kiriakos-GR

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Sorry Kiriakos I did not see the picture clearly until I saw your clamp meters.  I removed my message, my apologies!


No problem ..      ;)
I know that you are an positive thinking person , thats why I respect your opinion,
most of the times .   :D
 

Offline Rhythmtech

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Sorry to see this Kiriakos, but it again suggest your your Fluke is damaged or in need of calibration.

I am not aware of what you think, that you have see ..  
But I will not start explaining here, of how this digital clamp works in detail.

I had spent hours , taking measurements , and learning how to properly use , this new setup.  
The only that I can tell , its that the clamp , has an "Auto Zero" calibration + 1.5% accuracy .
  

Is that 1.5% of reading or full scale? What is the range of the current clamp? In the mV scale the 87 has ± (0.1 % + 1) of reading, so it could contribute ~.101 of error at 1 mV. What is your current source? It looks like the current clamp is set to 1mV/A output, while there is a 10mV/A setting, which might give a much better reading.

Which thread is this on?
 

Offline Kiriakos-GR

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Offline tempo

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #54 on: November 05, 2010, 04:11:19 pm »
This is a good topic for me as I am considering buying the UT-70D.

Lots of useful measurements but as far as I could see (late coming here) none on True RMS current reading of non sine waveforms.  

Could an owner of one please try that for me and see how it performs.  A simple test would be to take some AC, from a transformer secondary winding and put it through a diode into a load and measure current.  How accurate is the UT70D compared to say a Fluke (some folks seem to have lots of great gear around).

What happens if the diode is shorted out? Does the 70D reading increase by 1.414 times.  Of course the voltage from the transformer would have to remain the same.  Possible with the primary on a Variac.

thanks
« Last Edit: November 06, 2010, 09:26:17 am by tempo »
 

Offline onemilimeter

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #55 on: November 07, 2010, 07:30:56 am »
Those trimmer are old tech, e.g. VR7 marked in the photo.  Modern DMM no longer use them.  Its more likely to drift with time, temp, shock and vibration.

Hi...

Interested in learning that trimmer is no longer used in modern DMM. What're the techniques used in modern DMM to do the job? Is it using digital potentiometer/trimmer?

Thanks.
 

Offline Kiriakos-GR

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #56 on: November 07, 2010, 10:10:49 am »
This thread looks a bit old  by reviewing it today   :)    

@tempo  

Such comparisons over "True RMS"  , needs specialized instruments " calibrators " .

An easy "Home test"  to check if an DMM, it does work as  "True RMS" ,
are to measure the output of an Uninterruptible power supply .
http://en.wikipedia.org/wiki/Uninterruptible_power_supply

If the Mains voltage are 220 , the capable DMM it will measure the same output,
even if the Mains get interrupted.  ( UPS working alone) .
The non capable DMM will measure about 140V as output.

@onemilimeter
The digital  Multimeter , specially the Non-auto range ones,  they do have trimmers .
The most common to find trimmer , even if the " Non-auto range one " has no second ,
are the one that adjusts the accuracy over DC .

Most modern "auto range"  ones (not all ), are using programmed  chips, that some are able to re-calibrated , and some not .  
  
« Last Edit: November 07, 2010, 10:15:09 am by Kiriakos-GR »
 

Offline tempo

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #57 on: November 07, 2010, 10:28:02 am »
Thanks for the reply.  However, I didnt see anything wrong in my simple comparison test, assuming someone had a UT70D and a supposedly much better Fluke.

Gary
 

Offline Kiriakos-GR

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #58 on: November 07, 2010, 10:35:47 am »
Gary it makes more sense, to compare models ..  

The Fluke ones, are not all build equally.  
« Last Edit: November 07, 2010, 10:37:42 am by Kiriakos-GR »
 

Offline Kiriakos-GR

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Re: how about UT70D multimeter as one of the higher end China made multimeters?
« Reply #59 on: November 07, 2010, 10:53:14 am »
Oh no, spare me with this Flagship " confrontation " .    :D

The Video of Dave , about the 100$  DMM ( the No2 if I remember correctly ) ,
it did show that the Tested Uni-T , was more than capable, to measure voltage at high frequency.

But the bottom line are , that only an exclusive Uni-T product range benchmark ,
will separate the top dogs from the average ones .

     

 
 


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