Having trouble with power and power factor form EPM_Power.VI

[johnsold]

Are the voltage and current measurements synchronized?  I do not have most of your subVIs so I cannot see what is in them and have never used the niDMM.  It looks as though the DMM functions are initialized each iteration of the loop and called asynchronously.  If there is not some hardware synchronization, the phase angles will be completely random.

Lynn

[Scott_B]

I don't believe that the voltage and current are syrcronized.  The subvi's and VI's are not my doing, they are actual NI Lab VIEW VI's.  The current phase readings are completely random and this may be why.  How would I sycronize the current and voltage?

Scott

[johnsold]

I am not familiar with your measurement hardware, so I do not know if it is capable of doing it this way.

Generally you create an analog input task with two (or more) channels.  Then every time you take a sample it measures both channels.  While the samples are not truly simultaneous, they timing offset is usually small and can be calculated if necessary.

If your hardware cannot handle two channels in one task, see if you can run both A/D converters from the same sample clock.  Next best is to use heardware triggering and trigger both devices with the same pulse.

Lynn

[Scott_B]

I tried to use the analog inpute  task, but it doesn't see the thermocouple car.  I have tried other ways to syncronize the Measurements but, nothing works. 

[Sean_N]

I realized I didn't post the modified code with the 3 phase VI.  I attached it now.  I'm not sure what thermocouple card you have or what kind of channel you were creating.

[Muruganandhan]

we are doing same concept . can we calculate power factor using NIELVIS ? and how it is possible ? pls reply soon ...thanks in advance

[CertifiNATEtion]

Hi Muruganandhan, 

This is an old thread, it would be a better idea for you to post a new question for the community to see. 

As long as you are not exceeding the board voltage/current limits there is no reason you should not be able to measure the power factor using the NI-ELVIS. 

-N