change detection instaed of X4 encoding

[orsogna]

HI

I 'd like to acquire some analog input using an external sample clock from an encoder. My problem is that I want an X4 encoding. Is it possible to use change detection.vi to detect the both falling and ring edges of both signals A and B of the encoder?I needt to now how,and if, with this method, apart the delay due to the multipexer for the multychannel acquisition, I have other delay or if it works as a normal external clock and (so sample clock/convert clock).

(PCI6221)

thanks

(PCI6221)

[Henrik_Volkers]

With the help of some external circuitry:

XOR A and B  -> x2

short RC delay -> x2d

XOR x2 and x2d -> x4  🙂

see XOR @ wiki 😉

your RC delay define the pulselenght you need to check with the minimim pulse lenght of your external trigger input. And use propper shielding and grounding to not disturb your analog signals.

Buffer the XOR, use the slowest logic you can use (fast transients are nasty)

Have fun

[Henrik_Volkers]

AND trigger on the rising edge , the falling one is by the RC delay and might produce more jitter and has a tempCo....

just in case this might be of intrest ..... 😉

[JB]

An LS7184 quadrature clock converter would be an easy and efficient solution.

• Leave MODE unwired for X4 counting
• Configure the pulse width (RBIAS) according to the frequency of your encoder's signal
• Use the !CLK output to trigger the acquistion.