Medical Sensor

[sardineta]

I am curious about baby's movments when a fetus is inside her mother.
So I am thinking if there is a sensor which can be employed to catch the baby's movement so I can reproduce that movement into a sound.

I have no idea which sensor can be used for this application. I have found some pressure sensors but I am not sure if it can help me.

What kind of sensor is the one I need?

Thanks in advanced

 

[stevez]

Take a look at stethoscope.com - more or less electronic versions of the traditional stethoscope.

Sound and mechanical movement are almost the same - a pressure sensor and microphone are very similar. The problems I see are sorting out the noises made by the fetus from all the other noise. That may be where software or filters might be of some use. Read thru some medical books and you'll find that there are lots of noises - many of which are quite useful in determining things.

 

[tansis]

**broken link removed**


https://www.electronics-lab.com/projects/science/019/

Most clinicians learned the art and science of auscultation using an acoustic stethoscope. While many models of electronic stethoscopes have been marketed over the years, none of them seem to do a very good job of emulating the most common forms of acoustic stethoscopes available.

Just out of curiosity...
Has anyone seen a doctor using an electronic stethoscope?

 

[sardineta]

Thank you.
I am thinking about the noise, yes I really know this will be the major problem here.

In fact the friction against the skin whill be a headhache but most the environment noise as the circuit itself.
Probably a fast MCU or a DSP will be necesary Or any special audio/filter IC can help me to stop the noise.

What you recommend me to use

 

[tansis]

There is a circuit on the web for noise cancelling headphones,
that may be of some small help, google should find it for you.
I seem to recall it's even been posted in this forum, try searching
here first.

 

[sardineta]

Considering the transducer I will use, and taking into considerations the similarities between pressure and microphone sensor I will use a Pressure Sensor

The part number is the MPX2202D and MPXM2202AS from Freescale
the first one is differential and the second one is absolute.

I really don't know exactly what is the advantages od using a differential or an absolute pressure sensor!?!?!

Thanks a lot for your comments and advices, I really appreciate that
If you can recommend me something, Thanks in advanced

 

[audioguru]

I don't think that an air pressure or fluid pressure sensor will measure motion. Doctors use ultrasound to "see" motion and even the gender of the fetus.
Doctors use a lubricant on the microphone head of an electronic stethoscope to stop friction noises.
There are electronic stethoscopes that frequency-shift the less than 30Hz frequency of heartbeats to about 350Hz so that our hearing, microphone and speaker or headphones hear it better.

 

[Gavilan]

Perhaps a very thin and flexible reflective skin patch, then use a mounted laser reflecting off the patch as close to perpendicular (the highest incident angle?) possible. Have the light reflect onto a photoresistor. Amplify the signal off the photoresistor and convert it to an audio signal? This has been used as a surveilance method for many years so the theory works. I have never heard of it used for such application as this.

Be carful when using any type of RF producing device. There are potential negative affects of exposure. A modern handbook on antenna design will give the frequency of greatest energy absortion as a 1/4 wave function of the human body length, but that is looking at the human body as a cylindrical conductor. Transparancies of the human nervous system are indicative of polarization with relativly high inductance when compared to the whole body cylinder. As the exposure frequency approaches the frequency of individual specific response (or near harmonic frequencies), the frequency is of much greater importance than field strength in terms of affect of exposure.

If it were not for the potential negative affects I would suggest linking the nervous system to a remote low power transmitter and monitoring the changes in transmitter circuit parameters. The three time differentiated functions of the heart muscles could most certainly be monitored, the potential is there for much much more.

This is not science - it is conjecture - but it never hurts to be careful.

Gavilan

 

[sardineta]

Yes, I found that an ultrasound sensor is the right sensor for this application, I have seen some medical equipment that use this kind of devices.

I don't find out a cheap and small (for a PCB) ultrasonic sensor, does anyone knows one?

Tansis, one of the circuits you gently send me do not get the vibrations from the skin surface, it is from the bell of a stethos, but it was great !

silla