LabVIEW
pulse oximeter
Hi Doraemon,
I don't know if you've ever had a chance to make a pulse oximeter before, but they are actually pretty fun to do (although it can be frustrating at times). Essentially the first thing that you need to know is if you are going to simply use a premade oximeter and just read the voltages coming out of it, or are you going to try to get your very own LEDs and photodiodes and try to make your own.
The main things to remember is that you are looking at two different output voltages. One from a red LED, and another from an infrared LED. The basic principle of the whole thing is sort of like what you probably did as a kid, taking a flashlight, holding it to your hand at night and and seeing your bones. As seen in the picture below, the two different LEDs will have different voltage levels depending upon the saturation of the hemoglobin with 02.
If you want more detailed information, then check out this site, as they seem to have some good basic info. Be careful just doing a Google search for more information on pulse oximetry, as you tend to find some very boring results. Somehow us scientists and engineers have a knack for making cool subjects boring when we write about them.
Now getting to the LabVIEW portion of everything
As you can see in the above figure all you are really looking at is two voltages. That means you will simply need to have two separate analog input channels measuring the voltages coming from the different LEDs.
Honestly, the LabVIEW part should be the easy part of everything. When I've done these in the past the biggest pain was making sure that all of my transducers were working properly. Once that is set, then you can easily pull things in thru the DAQ board and begin taking measurements.
Best of luck!
I don't know if you've ever had a chance to make a pulse oximeter before, but they are actually pretty fun to do (although it can be frustrating at times). Essentially the first thing that you need to know is if you are going to simply use a premade oximeter and just read the voltages coming out of it, or are you going to try to get your very own LEDs and photodiodes and try to make your own.
The main things to remember is that you are looking at two different output voltages. One from a red LED, and another from an infrared LED. The basic principle of the whole thing is sort of like what you probably did as a kid, taking a flashlight, holding it to your hand at night and and seeing your bones. As seen in the picture below, the two different LEDs will have different voltage levels depending upon the saturation of the hemoglobin with 02.
If you want more detailed information, then check out this site, as they seem to have some good basic info. Be careful just doing a Google search for more information on pulse oximetry, as you tend to find some very boring results. Somehow us scientists and engineers have a knack for making cool subjects boring when we write about them.
Now getting to the LabVIEW portion of everything
As you can see in the above figure all you are really looking at is two voltages. That means you will simply need to have two separate analog input channels measuring the voltages coming from the different LEDs.
- The Pulse will be really easy to see because the voltages will be going up and down easily showing the systole and diastole of
the heart. You should be able to simply plot one of the two lines
on a waveform graph and see the heartbeat (keep in mind that pulse
oximetry is VERY sensitive to noise artifact).
- The Oxygen Saturation is a little more difficult to measure and may require some custom scaling. However, even this should not be too difficult as it is just a matter of comparing the two different voltages and figuring out what the difference is and how exactly that relates to a percentage. If you get a percentage of less than about 90%, then you may want to head straight to the nearest hospital or stop smoking.
Honestly, the LabVIEW part should be the easy part of everything. When I've done these in the past the biggest pain was making sure that all of my transducers were working properly. Once that is set, then you can easily pull things in thru the DAQ board and begin taking measurements.
Best of luck!
Hi Doraemon,
I did these quite a few years ago back in college, but I'll tell you what I can remember. Basically you are going to have to source an LED with a wavelength of 660 and 910 nm. Once you find those it's actually a really simple circuit. You might need some filters and such on it, but the basics look a lot like this:
You'll have to forgive my artistic (non)-abilities. There are probably some other details that I'm forgetting, but hopefully this will at least give you an idea. I remember it was pretty simplistic. However, keep in mind that you're dealing with non-visible light, so it may be difficult to confirm that the LED works.
If you are building something like this from scratch it's probably a lab of some sort, if that's the case, then try asking around for a professor as they have likely done something like that before. Somebody around a university should have a schematic of this type of circuit.
If this is for a commercial application, then I highly recommend getting a pulse oximeter that is already made as it will be MUCH easier to deal with and will save you days of work (and time = money). To find that, just do a Google Search.
Have fun with this,
I did these quite a few years ago back in college, but I'll tell you what I can remember. Basically you are going to have to source an LED with a wavelength of 660 and 910 nm. Once you find those it's actually a really simple circuit. You might need some filters and such on it, but the basics look a lot like this:
You'll have to forgive my artistic (non)-abilities. There are probably some other details that I'm forgetting, but hopefully this will at least give you an idea. I remember it was pretty simplistic. However, keep in mind that you're dealing with non-visible light, so it may be difficult to confirm that the LED works.
If you are building something like this from scratch it's probably a lab of some sort, if that's the case, then try asking around for a professor as they have likely done something like that before. Somebody around a university should have a schematic of this type of circuit.
If this is for a commercial application, then I highly recommend getting a pulse oximeter that is already made as it will be MUCH easier to deal with and will save you days of work (and time = money). To find that, just do a Google Search.
Have fun with this,
Message Edited by Otis on 09-12-2005 04:30 PM
