how about UT70D multimeter as one of the higher end China made multimeters?

[Rhythmtech]

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.

[Kiriakos-GR]

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 .   

[Rhythmtech]

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?

[Kiriakos-GR]

From today its here 

https://www.eevblog.com/forum/index.php?topic=660.0

[tempo]

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

[onemilimeter]

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.

[Kiriakos-GR]

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 .  
  

[tempo]

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

[Kiriakos-GR]

Gary it makes more sense, to compare models ..  

The Fluke ones, are not all build equally.  

[Kiriakos-GR]

Oh no, spare me with this Flagship " confrontation " .   

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 .