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View Full Version : heart beat sensor


twinkle
December 15th, 2001, 04:42 AM
Does some one know how they work ? What I know about these HBS is that they seems to amplify a certain low frequency and that the range is only a few meters but they work through (concrete and steel) walls and that they realy good work
there is little to find on the web only in games but I know they are used here in the port by the customs searching for illegals which hide in sea cargo containers.

nbk2000
December 15th, 2001, 09:47 AM
There's two types that I know of.

1. RADAR detects the slight change in your chest cavity size while breathing and heart beat oscillation. Doesn't work through any metal object, but will through concrete and brick.

2. Low frequency oscillations caused by the cardioballistic impulse. This is the physical movement caused by your hearbeat. If you've ever been in a tub and noticed how, when you hold your breath, the water still moves you've seen it in action.

Won't work in buildings or anything in firm contact with the ground. Requires that the test object can move. Wheter it's a semi-truck or a boat, they can be moved by a heartbeat.

Uses the same technology as seismographs.

You'd either have to come up with an active counter-pulser to do the same thing as noise cancellation does for sound, or give them so many false alarms by planting mechanical "pulsers" in whatever it is that you'd be using (but before your need) that they stop using the damn things or ignore most of the alarms.

It'd also greatly tie them up if the pulsers where booby-trapped. Now, every time they detect something, they have to call the bomb squad and all that other shit because they don't know if they're going to find a person or a bomb.

This technology is also being applied to detect prisoners attempting to sneak out in trucks and what not. Very annoying development.

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twinkle
December 15th, 2001, 12:10 PM
but what is the range just a few meters or shorter I assume that the obstruction is between is most relevant and would indeed a low frequency generator with a frequency of about 70 to 80 pulses work for the radar type?