Two meters show different amperage

[robertd]

Clearly the root cause of this problem is that you have more than one meter. If you had only one you wouldn't have this problem.

An error of +/- 2% won't get you to 2x the current. Any chance one of those "measurement loops" has two turns of wire, to give it more sensitivity for small currents? I would try swapping the loops, or the meters.

 

[Joey94]

I tried everything. Changing the loops the meters .. at this picture the middle one is on 10x

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[ptonsparky]

Take all but one loop out. Place each meter individually in the same window. What does each show?
Next window?
Next?

 

[robertd]

I tried everything. Changing the loops the meters .. at this picture the middle one is on 10x

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What happens if you try that setup with a nonreactive load, like a heater or non-electronic light bulb or a toaster?

 

[gar]

211025-1648 EDT

Joey94:

Your problem is that you do not know how specific meters work. This means you need to do some study, and perform controlled experiments.

I my previous post I commented on some aspects.

You need to create some specific circuits that are well controlled, and that you understand the signal that these circuits can produce.

For one circuit I would suggest that you have a sine wave generator, adjustable frequency, of a constant peak amplitude, but adjustable, as the fundamental source, a gate ( switch ) that can be turned on at a positive zero crossing, off at either a positive or negative zero crossing, and a counter to determine the number of output cycles. Then use this source to test your different meters,

You can learn a lot from such experiments.

.

 

[Joey94]

What happens if you try that setup with a nonreactive load, like a heater or non-electronic light bulb or a toaster?

With a nonreactive load they all give the same measurements.


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[gar]

211025-1648 EDT

Joey94:

Your problem is that you do not know how specific meters work. This means you need to do some study, and perform controlled experiments.

I my previous post I commented on some aspects.

You need to create some specific circuits that are well controlled, and that you understand the signal that these circuits can produce.

For one circuit I would suggest that you have a sine wave generator, adjustable frequency, of a constant peak amplitude, but adjustable, as the fundamental source, a gate ( switch ) that can be turned on at a positive zero crossing, off at either a positive or negative zero crossing, and a counter to determine the number of output cycles. Then use this source to test your different meters,

You can learn a lot from such experiments.

211025-2332 EDT

I will continue with a comment on your 2126 post of today.

If you use as an input a sine that you turn on at t=0 and leave that signal on for at least 10 seconds, then I would expect that you would get reasonably consistent readings because this provides a consistent signal vs time over the transient response time of the different meters.

See some of my different waveforms vs time, P1 thru P9, at
http://beta-a2.com/EE-photos.html
.

The signal levels of each of these waveforms vary grossly vs time.

How different meters respond to different waveforms vs time is dependent on the meter design, and construction. An oscilloscope provides me the best way to see what happens vs time. Note: the inductor, and tungsten lamp provide roughly a half cycle pulse at 60 Hz. One half cycle is 8.3 milliseconds at this frequency.

.

.

.

 

[Sahib]

With a nonreactive load they all give the same measurements.


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The meters back to the suppliers for checking and issuing calibration certificates.

 

[gar]

211026-0631 EDT

Sahib:

There is probably no reason at all for meter recalibration. You do not seem to understand how meters of different designs nay vary in their res[ponse to short time signals.

.

 

[Sahib]

.

The meters back to the suppliers for checking and issuing calibration certificates.

211026-0631 EDT

Sahib:

There is probably no reason at all for meter recalibration. You do not seem to understand how meters of different designs nay vary in their res[ponse to short time signals.

.

gar:
The OP in his last post said for nonreactive loads, the meters gave same max measurements. A noninductive load such as heater draws a surge current of much shorter duration than an inductive load. But the OP meters were able to display same readings but not in the case of longer duration surge current of kitchen inductive load. So I think something wrong with the meter circuits.

 

[gar]

211026-0729 EDT

Sahib:

See my scope plot at P5 at EE-photos.html

There is no inrush current. Note: this waveform was produced by turning AC power on at a voltage peak.

.

 

[Sahib]

https://electronics.stackexchange.com/questions/332439/starting-inrush-current-of-a-resistor-heater

 

[ptonsparky]

https://electronics.stackexchange.com/questions/332439/starting-inrush-current-of-a-resistor-heater

Gars usage of ‘Inrush’ is very specific and if I understand correctly, the term is limited to transformers current when first energized.

 

[wwhitney]

The OP in his last post said for nonreactive loads, the meters gave same max measurements. A noninductive load such as heater draws a surge current of much shorter duration than an inductive load. But the OP meters were able to display same readings but not in the case of longer duration surge current of kitchen inductive load.

That's to be expected with different sampling rates. For the short duration peak, it's too short for either to sample, and they both give a lower max reading than the instantaneous. For the long duration peak, the one with a faster sampling rate can see more of the peak, so it gives a higher max reading than the other.

Cheers, Wayne

 

[Sahib]

That's to be expected with different sampling rates. For the short duration peak, it's too short for either to sample, and they both give a lower max reading than the instantaneous. For the long duration peak, the one with a faster sampling rate can see more of the peak, so it gives a higher max reading than the other.

Cheers, Wayne

Excellent.
Only sampling rates of meters to be checked by OP for confirmation.

 

[Joey94]

Sampling Frequency: 3 samples per second
For all three meters


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[wwhitney]

Sampling Frequency: 3 samples per second
For all three meters

Does that spec apply to MAX mode, or just normal mode?

Regardless, your observed behavior is, I think, best explained by a difference in how the MAX mode works on each meter, causing a difference in accuracy of capturing the transient peak.

Cheers, Wayne

 

[hbiss]

I think it should be clear at this point that we have uncovered that the readings are very much subject to the meters being used and the results can vary a great degree from meter to meter. Probably something most of us didn't know.

These tests should lead us to conclude that if greater accuracy is required other methods should be employed. The "MAX" function on at least the meters being reviewed should be only considered a rough approximation.

-Hal

 

[gar]

211026-1923 EDT

I do not see how this discussion can proceed in any meaningful way unless you know precisely what the meter design is with respect any peak or maximum function.

The words "peak" or "maximum" have to be defined.

Given no other information I would assume an AC signal would be full wave rectified, and that either peak or maximum would be the highest instantaneous value to occur. This measurement I can accomplish with an ideal bridge rectifier loaded with a storage capacitor, and followed by a DC voltmeter.

Clearly my assumption does not correspond with the results of early posts in this thread.

Therefore, one has to find out how a particular manufacturer designs their meter, or how a particular meter is designed.

.

 

[hbiss]

Therefore, one has to find out how a particular manufacturer designs their meter, or how a particular meter is designed.

And what the design goal was for that function- is it supposed to be accurate under all conditions or just give a ball park indication. Really, they aren't charging thousands for these meters.

-Hal