how to calculate the phase difference between two square wave (acquired from two channel in one DAQ)

[TIMZX]

Hello everyone ,

 I need a quickly help that as below :

I am trying use PCI-6220 to acquired six signals from one rotation encoder (channel A, channel B,channel Z ,and their non-signals) .The encoder out signals will be square wave and 4000pulses per revolution. I set it rotation at 300rpm speed. I need show every square wave of six out channels in waveform and measure the A-B phase difference to check if the value is correct (designed value should be 90deg) .

I have no idea how to measure or calculate the phase difference of two square wave base on synchronizate to acquire these two square wave from two channel on the PCI-6620....

Anyone can give a idea how to calculate the phase difference with two square wave ?

Thank a lot and Thanks again...

Tim

[johnsold]

Tim,

Locate the rising edges of both A and B by sample array index numbers. Find the difference in index for successive samples of A. Find difference in index for an A edge and the next B edge. Divide by the difference in A. Result is fraction of period. To get phase in degrees multiply by 360.

Lynn

[TIMZX]

Lynn,

Thank you for your response , But I have a little confuse on how to locate the rising edages of both A and B by sample array index numbers. can you give me a program that  demonstrate what you show me ...Please.

Thank you very much 

Tim 

[johnsold]

Tim,

What version of LV are you using?

Lynn

[TIMZX]

Lynn,

   Labview8.2 full .

Thanks again

Tim

[johnsold]

Tim,

Here is a simple rising edge detector for one channel.

Lynn

[TIMZX]

Thank you very much !!!

Thanks again .

Tim

[pattousai]

hi, sorry to bother, but my labview version is 8.0, so i cant open this VI 😕

i wonder if you guys cant post the picture (jpeg or whatever) of this vi


thanks a lot


see'ya

[johnsold]

Here is an 8.0 version.

Lynn

[U_TTT]

Hi Lynn,

Can you also add further for finding phase difference from two channels ? 

Thanks in anticipation.