how can I catch heart beat signals  - Page 1
Forum section: electronics / testgear

author: NateDuong
author_rank: Contributor
timestamp: July 27, 2015, 09:24:22 am
content: Dear everyone,I am thinking about what know of machines in RF lab can catch heart beat signal,In the RF lab with spectrum and network analyzers, also have Function generator and more.They are just working on signal with high frequencies, but heart beats are very low frequencies about 1.17 to 10 Hz.Any ideal, everyone?Thank you.Regards,Nate Duong.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 27, 2015, 09:38:06 am
content: The minimum requirement is:You need to make a differential measurement with 2 probes close to the heart and a third probe for grounding, away from the heart.Use a differential signal amplifier and a scope and you will see the heart beat signal pretty well.The professional requirement is much more difficult.

author: Psi
author_rank: Super Contributor
timestamp: July 27, 2015, 09:48:42 am
content: I wonder if you can catch it with one of the ATMegas that has the 200x differential gain mode. That would be kinda cool to try.

author: Ivan7enych
author_rank: Regular Contributor
timestamp: July 27, 2015, 10:08:33 am
content: Also you will need to make a low pass filter to cut out anything higher than 30-40Hz (especially AC 50Hz noise and its harmonics 100, 150Hz ...).May be 2..4 order lowpass filter with 20-40Hz threshold + additional 50Hz rejection filter.

author: Psi
author_rank: Super Contributor
timestamp: July 27, 2015, 10:10:20 am
content: Or maybe just a few bitshifts and additions

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 27, 2015, 10:23:23 am
content: maybe optical sensing using a pulse oximeter finger probe?

author: HighVoltage
author_rank: Super Contributor
timestamp: July 27, 2015, 10:23:52 am
content: Good point on the low pass filter.I played around with this a little, a long time ago.Here is a good PDF from TI:Heart-Rate and EKG Monitor Using the MSP430FG439

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 27, 2015, 10:32:02 am
content: Are you only interested in beats per minute or the recording of the electrical waveform (EKG) pattern?

author: babysitter
author_rank: Frequent Contributor
timestamp: July 27, 2015, 10:38:42 am
content: The heartbeat results in a pressure wave forwarded by vessels to the tissues.The ratio of tissue to blood changes momentarily.If you connect a impedance probe to the skin, you will see different resulting impedances as that of tissue is different to that of blood.Please, please, please report your findings to me!

author: VK5RC
author_rank: Unknown
timestamp: July 27, 2015, 11:30:22 am
content: Be VERY careful , once you have a good skin contact (low resistance) as you need to measure the voltages involved about 20mV amongst the 'soup' of mains voltage, you want to be very careful of ground loops or DC offsets, a few 10s of mA across your chest can be very nasty.

author: NateDuong
author_rank: Contributor
timestamp: July 27, 2015, 11:50:13 am
content: Quote from: HighVoltage on July 27, 2015, 10:23:52 amPapers you gave me really helped a lot,Thank you very much,Best Regards.Nate Duong.

author: NateDuong
author_rank: Contributor
timestamp: July 27, 2015, 11:51:50 am
content: Thanks every one, for ideals,I will figure them out, and will report the results to all of you.Best regards,Nate Duong.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 27, 2015, 12:35:29 pm
content: Use color amplification on high-ish speed camera images.http://people.csail.mit.edu/mrub/vidmag/If you are going to measure using probes with body contact. You might start reading about medical grade isolated power supplies.

author: amyk
author_rank: Super Contributor
timestamp: July 27, 2015, 01:45:09 pm
content: If your heart is beating at 10Hz something isverywrong...

author: _Wim_
author_rank: Super Contributor
timestamp: July 27, 2015, 08:10:08 pm
content: Quote from: amyk on July 27, 2015, 01:45:09 pmI think that is called overclocking...

author: hendorog
author_rank: Super Contributor
timestamp: July 27, 2015, 10:49:33 pm
content: It has been done using RF as well - i.e. non contact:http://www.technicaljournalsonline.com/ijaers/VOL%20I/IJAERS%20VOL%20I%20ISSUE%20I%20%20OCTBER%20DECEMBER%202011/16%20IJAERS.pdfhttp://etd.fcla.edu/UF/UFE0017533/xiao_y.pdf

author: VK5RC
author_rank: Unknown
timestamp: July 27, 2015, 10:49:53 pm
content: The necessary bandwidth can be calculated using the no 1 rule of thumb , bw(Hz)=0.35/RT(secs). Rise times can be around 20ms or so. Mains interference gets right in there.A good trace quality allows a lot more interpretation than heart rate, 'The ECG made easy' has been used by medical students for decades. You also need 10 channels for a full '12 lead ecg'.

author: aargee
author_rank: Frequent Contributor
timestamp: July 29, 2015, 01:32:41 am
content: Analog Devices had (has?) some good info on ECG. They build chips to deal with this and their info is a good read.

author: torch
author_rank: Frequent Contributor
timestamp: July 29, 2015, 07:30:23 am
content: Quote from: _Wim_ on July 27, 2015, 08:10:08 pmYou can say that again. At 3Hz, we switch from monitor mode to defibrillator mode.