03-06-2017 04:57 AM
Hi,
Can any body help me out of this dilemma? I need to know how to calculate spO2 from photo transistor output. In depth explanations are most welcome!!!
I have done this calculation before by using the below formula.
Ratio (R) = ((AC rms of Red LED)/DC of Red LED)) / ((AC rms of IR) / (DC of IR))
spO2 = 110 - 25xR
Is this correct?
03-06-2017 05:48 AM
Hi dhans,
so you have some device named "photo resistor" without providing specific information (manual, spec sheet) for that device.
And you have a formula where you don't provide any information on (sources, datasheets, explanations).
You want us (in a LabVIEW programming forum) to discuss the validity of that formula for your (rather unknown) device without providing any in-detail information!? Really?
03-06-2017 05:59 AM
Hi buddy,
Here I have given all details of my pulse oximeter project.
I am using nellcor DS -100 A probe which contains Red LED, IR LED and one photo transistor.
Using labview I alternatively on and off Red and IR LEDs. I save an output of photo transistor for both Red LED and IR LED in two different arrays. Then I implement an algorithm said above and some filtering process for smoothening the waveform.
Since the output of photo transistor is current I needed to convert current to voltage using an op amp called ' MCP602' . This op amp has two channels. I took out output from 1st channel and connect it to the filter circuit in order to remove DC components from output signal. From that signal I do some calculations to get an expected output waveform.
Just I need to check whether my algorithm and logic implemented in labview is correct and to know the proper alogrithm and chnages.
03-06-2017 07:27 AM
Hi dhans,
I need to check whether my algorithm and logic implemented in labview is correct and to know the proper alogrithm and chnages.
I cannot comment on your algorithm as I don't know anything about the specific physical properties you are using in your setup…
But I can comment on your VI:
- I don't see any error handling
- I do see a lot of unneded local variables
- I see some "funny" other things
I recommend:
- use a state machine approach like "INIT", "IR LED", "RED LED", "Analyse"…
- keep relevant values in shift registers (maybe in typedefined clusters) to get rid of local variables
- enforcing dataflow by outputting boolean values in case structures is just bs: that's why I recommend a state machine…
- implement error handling on your hardware communication functions!
03-06-2017 10:15 AM
Hi GerdW,
Thanks for the reply.