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Help required for sample and Hold

Hello,

 

I am working on a project Cerebral Oxygenation Monitoring. The concept is similar to pulse oximetry. I help already developed the hardware that includes the timing circuit , led driver for driving Red and IR Led, Amplifier and Filter Stage. I am getting the pulse signal but it is multiplexed signal corresponding to effect of both Red/IR Led. Now to separate it I need to use sample and hold circuit, whihc I can achieve with and IC LF398 but I want to minimise this part and directly take this multiplexed signal through DAQ Card in to LabVIEW and further create sample and hold in LabVIEW.

 

The sampling needs to be in synchronus with the Timing signal given to Red and IR. How I can achieve this in LabVIEW.

 

For eg: the Red Led is triggered with a pulse of 1 ms with a repeatation rate after 10 ms. So this timing pulse should trigger the sampling part.

 

 

Please Help.

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What (NI) hardware do you have?  Are you using CompactRIO, PXI, NI-USB?  If you want precision timing, you should be running LabVIEW with the Real-Time Module (which requires a processor capable of Real-Time).

 

BS

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Not sure what you need the HOLD part for.

 

Correct me if I'm wrong:

 

You have a 1 mSec pulse, every 10 mSec.

 

Each pulse triggers two LEDs:  RED and IR

 

You have a single signal which contains the processed (through the body, or whatever) responses to BOTH of those signals.

 

So, how does a S&H, hardware or otherwise, separate the two responses?

 

Is one delayed in time, relative to the other?

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com


Blog for (mostly LabVIEW) programmers: Tips And Tricks

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The only way to get the timing pulse is through hardware so you would connect that to the DAQ card. Doing a sample and hold in software would not be possible based on the information you have provided.
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@Bob_Schor wrote:

What (NI) hardware do you have?  Are you using CompactRIO, PXI, NI-USB?  If you want precision timing, you should be running LabVIEW with the Real-Time Module (which requires a processor capable of Real-Time).

 

BS


I will be using NI-USB 6008 for Signal Acquisition

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@CoastalMaineBird wrote:

Not sure what you need the HOLD part for.

 

Correct me if I'm wrong:

 

You have a 1 mSec pulse, every 10 mSec.

 

Each pulse triggers two LEDs:  RED and IR

 

You have a single signal which contains the processed (through the body, or whatever) responses to BOTH of those signals.

 

So, how does a S&H, hardware or otherwise, separate the two responses?

 

Is one delayed in time, relative to the other?


 

YES you are right, 1 mSec pulse, every 10 mSec. 

 

IMG_20140626_152552.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Above figure shows the trigger pulses generated using standard hardware. One triggers IR and other triggers RED. In above case  I had kept repetation rate 4msec

 

This is the signal which I may get

 

Sig.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now how do I separate both of these signals in LabVIEW

 

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I'm still not clear - your pic shows two distinct signals, yet you're asking how to separate them.

 

Is there some hardware piece that is multiplexing them?

 

Can you bypass that?

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com


Blog for (mostly LabVIEW) programmers: Tips And Tricks

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