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Topic: ADMINS: MOVE TO [SENSORS], THX. microwave sensors - fore and aft detection? (Read 336 times) previous topic - next topic

mattlogue

I plan to use uWave sensors in concert with PIRs and cameras for my home.

Do most (i bougt some cheap ones), microwave sensors detect motion both FORE & AFT? If it detects otion fore, how can one block it? Will I need 18ga steel sheet for it, or will al foil do the job? How much coverage (inch dia, whole unit, 2in beyond unit)...
Just because I live in the states don't mean I care

Paul_KD7HB

Do you understand what "Doppler sensor" means. It means it senses movement! Plain and simple.

Anything else you will have to modify the device to ignore either a + frequency difference or a - frequency difference.

Paul

Geek Emeritus

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Paul_KD7HB

this one is directional
Interesting device. I guess you would need to compare two readings to see if the second is less or more that the first, in order to determine the direction of travel.

Paul

mattlogue

What I don't understand here is DOPPLER Radar is supposed to measure velocity... that's how they detect tornados... a hook in the velocity radar image. So in THEORY, this device should measure velocity, it may be simplified to a digital signal output though...
Just because I live in the states don't mean I care

Paul_KD7HB

What I don't understand here is DOPPLER Radar is supposed to measure velocity... that's how they detect tornados... a hook in the velocity radar image. So in THEORY, this device should measure velocity, it may be simplified to a digital signal output though...
Wrong analogy! Think of the radar gun detecting the speed of a baseball. As shown on TV, the speed is a direct result of Doppler radar.

A tornado has an infinite number of velocities. Zero at the center and maximum somewhere on the outer edges. A tornado cannot be detected is it has NO rain or hail in it. That is what the radar detects, the velocity of an infinite number of reflecting particles. Through computation of the frequency of thousands of return signals, a computer can determine the maximum frequency shift of the return signal and from that compute the radial velocity of that reflection and that number is what you are given on the tornado warning or weather report.

If a radar signal is of high enough frequency and has enough power, difference in air pressure density can diffract/reflect that signal and indicate air turbulence.  The aircraft control system can warn aircraft about to fly into that turbulence.

In all cases, your return signal has to be the basis of calculation of velocity, not the velocity itself. And that requires calibration of your system.

Paul

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