[chrismorgan]

A technical error in one of the diagrams: Hall effect sensors are not binary, but one-dimensional, and are used so; their output voltage is directly proportional to the magnetic field strength. As for PIR sensors, fundamentally they’re certainly not binary, but I have no idea if they perhaps expose only a binary signal. A better example of a binary sensor might be an on/off switch.

[hornej]

thats a good point about the hall sensors. i'll update that. PIR sensors also output an analog signal, but in practice they are binary.

[relaxing]

There’s a funny autocorrect typo in the Adams quote: Zaphod -> Zappos.

[hornej]

lol, thanks. fixed it

[stingrae]

in practice they don't have to be binary

[mycall]

If you include time dimension, hall effect sensors are two dimensional.

[stingrae]

analog PIR is typically a differential signal between two receivers. The receivers are placed behind a fresnel lens (where the lenses are designed to point into each of the sensors). So when an IR source (like a person) walks in front of the sensor it creates a large spike, because they are being compared against a low IR area.

There is a form of PIR sensing where it behaves like a thermal camera at a very low resolution (sometimes as low as 2x2 pixels)

[hornej]

most hall effect sensor applications i've seen use a schmitt trigger and output a digital (on/off) signal

[choonway]

the only true binary sensor i can think of are good old fashioned mechanical switches.

[samatman]

Mercury switch on a bimetallic strip (old-school thermostat) counts, same basic principle.

[stingrae]

reed switch

[relaxing]

is an old fashioned mechanical switch.