Use an Average responding (No True RMS) multimeter as harmonics detector

[Kiriakos GR]

Few years back Agilent (Keysight ) introduced in the market multimeter model U1242B.
This specific DMM came with one special function named as:  Measuring Harmonic Ratio

Recently I did some investigation to find out more about this implementation, in simple English I wanted to find out how they did it.
Description of this feature sounds attractive at the ears, but is it something special? 

Further reading of Keysight U1242B user manual shown that there is no any detailed explanations (U1241-90063.pdf) .
Now in another document (Application Note 5989-7040EN.pdf ): Detecting Harmonics in an AC Signal   
They do say more and all that this feature is all about this is one simple comparison of measured voltage in  True RMS mode and also at Average responding ACV mode.

Cheap UPS output this is heavily dis-formed emulated sine-wave, at  220V one average responding multimeter will measure about 180V ACV when one True RMS meter will measure all signal components and reading will be 220 ACV.

U1242B has the ability to deactivate temporarily it True-RMS ADC,  then takes a second measurement and compares it with the one with ADC turned on.
Measuring Harmonic Ratio delivered by U1242B this is not a measurement comparable with any other measuring tool (power analyzer) , but rather one simple indication in which calculated percentage this is hypothetical.

Alternative way for some one to perform such a comparison this would be by using side by side one average responding meter and one True RMS.

From the other hand nowadays that Oscilloscopes pricing this drops down every few months,  it might worth getting one if you are serious about troubleshooting electrical installations and single-phase  power quality issues. 

[giorgos]

Indeed. Many times when I managed to measure the output of a common UPS , with a no true rms multimeter , the indicated output voltage seems to be lower than 230V . I speak for many years back, when I had not have my HIOKI DT4225 yet 

[Kiriakos GR]

I am now counting seven years of time about making the choice to be able to conduct reliable measurements in UPS systems and single devices by the use of advanced multimeter. 

http://www.ittsb.eu/fluke87v-gsm.html

Prior 2010 industry of test and measurement tools was limited to only a few reliable brand names  (USA & France).
Back then reliable multimeter were in the price tag of 400 EUR,  and about that price were one clamp meter probe with bandwidth of 20KHz or more.
 
In 2011, mainly industry of Taiwan and other countries, them focused more at manufacturing of fast True RMS meters, and at the same them be more wisely priced.
Back then I was encouraged to start my Blog by a female marketing product manager from Taiwan, because she sensed that I am crazy enough to handle all responsibility that comes with such an mission. 
   
At 16 March 2017 I am counting four years as Oscilloscope user.
I have use my Oscilloscope to more than 600 applications.
Within 2017 they are only two multimeter them coming very close to what one Oscilloscope can do (both are at the price range of 450 EUR).