ITTSB.EU Blog Forum
AC Power Meter | PSU | UPS evaluation | Battery Testers - Chargers | CCTV => AC Power Measurement of appliances & Technical discussion => Topic started by: Kiriakos GR on September 05, 2024, 09:48:18 AM
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IEC61000-4-7 Testing and measurement techniques - General guide on harmonics and interharmonics measurements and instrumentation, for power systems and
equipment connected.
About this standard I care more of how this relates to instrumentation.
This standard specifies methods used in harmonic measurements.
The harmonics can be measured without grouping, with grouping and with sub-grouping.
The advantage of grouping and sub-grouping is more steady measured harmonic current values with fluctuating loads.
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Personally when i think as potential buyer of a new digital power meter (bench top), I am trying to find a good balance between product price and my actual needs.
I am now using IEC standard release date as indication of the age that a specific digital power meter this were designed.
For example, any new instrumentation that support IEC61000-4-7 (IEC 61000-4-7:2002/AMD1:2008), this is product design of year 2008 and later.
Further note that IEEE 519-2014 makes reference to IEC 61000-4-7 and requires measurements to be made with sub-grouping.
IEC website reports, standard stability up to the year 2025.
This translates that IEC it might upgrade it or not at 2025 and later.
The advanced digital power meter is the one able to perform:
a) THD of V & I Total Harmonic distortion.
b) Analysis of harmonic component per order, 1~50.
c) V & I harmonic distortion percentage per order
e) V & I actual value per order
A new question this now arises, is it worth any potential buyer to wait and see of what IEC will decides in the near future?
Another question that bothers me, this is of how much worth in cash, a newcomer digital power meter from China, which support IEC61000-4-7?
In the positive side of things, AC power meter bandwidth, this is standardized at 2022 at 2.5 kHz.
At DC power meter bandwidth, there is still an open race, and this is relative to switching frequency of diode.
Consumer level pulsing power supply they operate at 80 ~100 kHz
Fast Charging for EV this has different operating frequency.
High-End PSU for telecommunications they might have switching frequency up to 1 MHz.
For us engaging primarily with consumer level products, DC bandwidth over 300 KHz this is out of interest.
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At another scenario, and if detailed Harmonic measurement this is not needed as requirement.
We might aim for a AC digital power meter Class 0.1
Bandwidth 2 KHZ
Which will deliver THD that we can trust, along of V,A,PF and Hz.
Such a design this is named as production line instrument.
It is unfortunate that such digital power meter, they are not coming along with PC software.
While the power meter supporting Harmonic measurement IEC61000-4-7 they do come with PC software.
Regarding Low power measuring sensitivity, I have no problem to pair with any instrument that can measure 0.03 Watt .. 30mW and above.
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More food for thought.....
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This is typical for measurements according to IEC 61000-3-2, IEC 61000-3-12, IEC 61000-4-7, EN 61000-3-2, EN 61000-3-12 and EN 61000-4-7 where a 200 ms window is required for a 50 Hz fundamental frequency.
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I am some how lost here, GW Instek for example presents compliant power meter to EN 61000-4-7, when their top tier GPM-8330/8320 it has different data update timing per situation.
Copy / Paste from their documentation.
1) When the data update interval is 100 ms the numeric display 10 items display update interval is 200 ms.
2) When the data update interval is 100 ms or 250ms and the numeric value display is set to
Matrix or ALL Items display update interval is 500 ms.
3) The waveform display update intervals are approximately 1s
4) Accuracy changes caused by data update interval:
When the data update interval is 100 ms, and Auto, add 0.05% of reading to the 0.1 Hz to 1kHz accuracy.
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No there is no love sentiment between me and GPM-8330/8320, I do dislike the steeping of current ranges
0.5 A/1 A/2 A/5 A/10 A/20 A.
500mA as smaller range this is too large for my taste.
From the other hand, GPM-8310 while it seems as a complete solution, fastest data update interval this is 250ms, and this makes it slow and not compatible to EN 61000-4-7.
At the end of the day, if you care to select an instrument at 1500 Euro price point, every little detail counts. ;)