Digital Holter with PIC ?!

[BrianT]

Go to the Texas Instruments site and have a look at their Medical Applications Guide. There are also plenty of ECG front ends on the web if you can't find the TI pages. You can simplify the front end to just an instrumentation amplifier and an opamp. You need a three electrode ECG system to reduce 50/60 Hz interference and movement artifacts. The signal input electrodes go to left chest and right chest and the common mode (anti-interference) output signal goes to the right ankle - perhaps the belly in a mobile system.

The ECG signal is 10 microvolts to a few millivolts so you need a sensitive amplifier, preferably with an inbuilt notch filter to kill the mains interference.

My ECG recorders turn on every ten minutes and record a ten second 'tape recording' of the animals heart data plus environmental data. The PQRS signal is pretty fast so the sampling rate must be about 200 samples per second or you will miss the heart beat. Once you have got stable 'tape recordings' you can then set about devising an algorithm to extract heart rate or interbeat variability or whatever you are looking for and save just a two byte number rather than a 2048 byte block.

Because the input signal is so low, you cannot have any other systems running during the signal capture phase or the local interference will overwhelm your results. I store the data as a 2048 byte block in the PIC 18F4620 internal RAM and then write the data as 8 x 256 byte blocks out to the external flash. I am using multiple M25P64 memory chips.

In summary, you can make a holter recorder with an analog front end and a PIC processor.

HTH
Brian

[Eugeniu]

Thank you Brian for your usefully informations . I have find " Medical Applications Guide " from TI . I am reading it . I understand that your ECG is self- makeing , is it ?

> In summary, you can make a holter recorder with an analog front end and a PIC processor.

This is so imprtant ! I'll try to do it .(with some / more help)

[Eugeniu]

Thank you Brian for your usefully informations . I have find " Medical Applications Guide " from TI . I am reading it . I understand that your ECG is self- makeing , is it ?

> In summary, you can make a holter recorder with an analog front end and a PIC processor.

This is so imprtant ! I'll try to do it .(with some / more help)

Apologize me for this double email (it's my browser problem )