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Phantom readings with Pulse Oximeter?


#1

I can’t get my Pulse Oximeter to correctly detect the probe attached and detached conditions. It seems to always detect a pulse even with no finger. The three values returned are all over the range.
pulseOximeter_Heartbeat:67==8==67
pulseOximeter_Heartbeat:67==8==67
pulseOximeter_Heartbeat:56==8==94
pulseOximeter_Heartbeat:65==8==95
pulseOximeter_Heartbeat:60==5==94
pulseOximeter_Heartbeat:65==8==95
When a finger is in, it would sometimes show these same values and sometimes it thinks that there is no finger. It actually thinks that there is no finger when there is a finger more than when there is no finger.
I also have similar handlers for the probe connected and disconnected events. But they are rarely invoked. Probe connected happens when the Spider powers on and then almost never again.
Do I have a bad sensor?
Here’s the code, am I missing something?


        pulseOximeter.Heartbeat += new PulseOximeter.HeartbeatHandler(pulseOximeter_Heartbeat);

        void pulseOximeter_Heartbeat(PulseOximeter sender, PulseOximeter.Reading reading)
        {
            string s;
            if (!pulseOximeter.IsProbeAttached)
            {
                s = "pulseOximeter_HeartbeatLast:" + pulseOximeter.LastReading.PulseRate.ToString() + "==" + pulseOximeter.LastReading.SignalStrength.ToString() + "==" + pulseOximeter.LastReading.SPO2.ToString();
            }
            else
            {
                s = "pulseOximeter_Heartbeat:" + reading.PulseRate.ToString() + "==" + reading.SignalStrength.ToString() + "==" + reading.SPO2.ToString();
            }

            Debug.Print(s);

        }


#2

I havent seen one of these used yet as the seeed modules are pretty new. When you post code can you use the code tags so the code gets formatted properly (makes it easier to read :))
I know that Seeed run a tech support forum too so it would be worth posting there as well as here.
http://www.seeedstudio.com/forum/


#3

I’ll try to post in the seeed site.
Thank you.


#4

Will give a try on our end.


#5

Hi Gus,
I consulted with Michael Dodaro at Integral design. His sensor sometimes gives bad data at the beginning, but it works after a while. I retried mine many more times, but still could not get it to work correctly.
How can I get a replacement?
Thanks,
Mario

BTW, my current sensor doesn’t work either. I have posted the problem. But no one has an answer. Just a thought, could the A2D converter on my Spider be bad instead of these sensors? I’m sot sure of the hardware architecture.


#6

I found the problem. My Spider was plugged into a USB hub which apparently did not provide enough power to the Oximeter. I can now get readings like Mr. Dodaro. But like him, it takes about ten seconds to get reasonable readings. And if you move your finger, it would take another few seconds.
I have to get that external power working:-)
Thanks everyone.
PS The current sensor is another story. It still doesn’t work.


#7

5-10 seconds for stabilisation is normal even with commercial medical devices, movement artifacts too. :wink: