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PSoC Lock-in vs. AD630 based Lock-in | Cypress Semiconductor

PSoC Lock-in vs. AD630 based Lock-in

Summary: 1 Reply, Latest post by odissey1 on 03 Sep 2015 11:19 AM PDT
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ad8172a_1469691's picture
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Hi everyone-

I'm looking into building a lock-in amplifier using the PSoC 5LP prototyping kit to measure the intensity of, effectively, a light source. My current set-up is similar to Fig 9 (attached) from this college lab manual. Using a commercial lock-in, things work totally fine, but I'm trying to scale down the size of my setup and would like to build a lock-in on the 5LP. 

The only question I have is, should I do this all in software in my PSoC? Or would it be best to implement a lock-in with external components (most notably the AD630 synchronous demodulator) and then use the onboard ADC of the 5LP for digital readout of the LIA value?

I've read this guide from cypress on implementing a LIA with a PSoC, but the conclusion made me rethink doing everything in software. 

Just wondering if anyone has some insight I'm lacking. I appreciate any and all help!


user_342122993's picture
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there is a lock-in demo demo project posted here (scroll down):


Note that (if) you have external reference input from mechanical chopper, you may need to phase-shift (depending on modulation frequency and your photo receiver response time). In commercial lock-ins there is typically a PLL circuit to do that, but if receiver's response is fast then you don't need it. If you modulate laser source than the above project should work fine without modifications.




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