Design a motion sensor

[supro]

I am trying to design something that will sense how much of a movement a certain part of the body makes (such as jaw), but I'm not sure what would be the best method.

One method is using video camera and image processing, but it might not be as sensitive as I would like.
Another one has 2 surfaces connected by a light spring. One is connected to the jaw and is move-able while the other one is static. Both have a wires attached to them. One of the wires has AC current running through it which produces current (magnetic induction) in the other wire. Because of the jaw movement, the distance between cables will change which will cause a changed in the current in one of the wires that can be detected by a signal analyzer.

Any better suggestions or comments?

 

[Siniša]

I would mount acceleration motion sensor on the jaw. It can give you complete complex motion that jaw (or other parts of body) can produce. You need 6 axes of motion detected (3 linear and 3 rotational) to fully define motion. Now this might be overkill for your application and you might need only one inear sensor for your case. Your description says very little about purpose of measurement, range, resolution and accuracy and options, even if you restrict yourself to acceleration sensors only, are plenty. As skin is not rigidly attached to that bone, depending on speeds involved and mass of the sensors, some error might occur due to small ammount of skin streching. Again, this might be irelevant in your case.

There are plenty of semiconductor manufacturers that make MEMS based acceleration sensors, Analog, Motorola,... Be more precise to get more precise answer.

Added after 3 hours 30 minutes:

 

[supro]

Thanks for the reply.

I need a sensor to detect any kind of jaw movement - whether it is caused by eating, biting, or anything else. I am not sure about the resolution but it has to be very sensitive. I don't care about the direction of movement as long as I can sense there is some kind of movement.
I am looking at jaw first because its geometry is more complicated than a whole-body movement. If I can find something for jaw, I'll use the same thing for the body.

I'll look into the accelerometer.

 

[kender]

A similar question about the motion of the wrist was brought up here: **broken link removed**

I'd like to invite your question to a group dedicated to sensors: **broken link removed**. There's a good number of active sensor experts in this group. Some of them come from the biomedical device area.

- Nick