to measure current in DAQ should we use rms value or DC avereage value

[dani@575]

to measure current in DAQ should we use rms value or DC avereage value

[johnsold]

What kind of signal are you measuring? Does it have interference or noise on it? What will you be doing with the results?

Lynn

[crossrulz]

In short: RMS is a good measurement for AC signals, average is a good measurement for DC signals.  So which do you have?

[dani@575]

i am taking measurement for single phase or 3 phase voltage and current and display it on front panel voltage measurement is valid but doinh with current measurement i suffer some problem should i take dc avg value or rms value for measurement 

when i take dc average value it give result as i want but doing with rms valur it give wrong result according to my circuit sitution. As, we know in ac case rms value is used for measurement but it give wrong result so guide me in this regard 

THANK YOU 

[dani@575]

i am taking measurement for single phase or 3 phase voltage and current and display it on front panel voltage measurement is valid but doinh with current measurement i suffer some problem should i take dc avg value or rms value for measurement 

when i take dc average value it give result as i want but doing with rms valur it give wrong result according to my circuit sitution. As, we know in ac case rms value is used for measurement but it give wrong result so guide me in this regard 

THANK YOU 

[johnsold]

The question still remains: What are you doing with the results? There is no universal right answer to the average or rms question.

Is your current waveform asymmetric about zero? That would produce a non-zero DC component.

Please ask more specific questions. Saying "it gives wrong result" does not provide any useful information. Is it wrong by 0.0001% or by 10% or by 100%? Does it produce an error but no result?

If you test the Averaged DC-RMS.vi with a simple signal like a sine wave with an offset, you will see that the DC output matches the DC component of the input while the RMS output includes both the DC and AC omponents.

Lynn

[dani@575]

sir, i am taking single phase voltage and current measurement using DAQ. As , we know rms value is used for ac measurement but using in daq it give wrong result What should u suggest about rms or average dc value in current measurement 

[Zwired1]

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@johnsold wrote:

The question still remains: What are you doing with the results? There is no universal right answer to the average or rms question.

Is your current waveform asymmetric about zero? That would produce a non-zero DC component.

Please ask more specific questions. Saying "it gives wrong result" does not provide any useful information. Is it wrong by 0.0001% or by 10% or by 100%? Does it produce an error but no result?

If you test the Averaged DC-RMS.vi with a simple signal like a sine wave with an offset, you will see that the DC output matches the DC component of the input while the RMS output includes both the DC and AC omponents.

Lynn

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Try posting your data and VI with a comment "I was expecting this value (x) and I get this (y)" and then ask the question "can anybody explain why this is happening?".  All of Lynn's questions are appropriate and remain unanswered by your latest post " it give wrong result ". 

[johnsold]

When you do the RMS calculation, are you using EXACTLY an integer number of complete cycles of the power line frequency waveform?  Using fractional cycles can generate errors.

Lynn