Long range capacitive proximity sensor for human body detection

Other Hardware Sensors
1

Does anyone know what the practical distance limit is for human body detection?
Is there an optimum oscillator frequency range?

The 'super long range' industrial sensors commonly available only seem to work up to 80mm or so and are designed for detecting things like bottles on a production line.
(http://rechner.com.au/products/long-range-capacitive-sensors/.)

I would like something that can detect a person approaching some weighing scales, so a light can be turned on before they step on.
The sensor doesn't need to be particularly compact, it can even sit on the scale if need be, providing that it is thin and flat.

Capacitive looks attractive because the sensor hardware is cheap, simple and rugged. I hope to use the signal processing power of the Arduino for noise and interference rejection.

Mike

2

I've experimented with this - sensing someone up to a few meters away but as soon as you get to large distances, everything starts to affect the values (temperature, humidity, EM radiation etc).

With some fancy code you can probably get a pretty good idea of whether someone's there or not.

3

would like something that can detect a person approaching some weighing scales, so a light can be turned on before they step on.

I would use a PIR for that; directed at some to be determined angle ..

4

Try here: