if found an empirical correlation between distance and horizontal prox value. It is a fit to a quadratic polynom function, written in integer arithmetic.

 p=prox.horizontal[number] if p>1200 then distance=(p/331)*(p/330)-((5*p)/61)+204+80 else distance=-1 end

The 80 at the end reflects the fact, that the corr var measured between sensor and object. But the distance here is measured from the centre of the hole (in Thymio) and the object.

And be careful the values depend on the used sensor (and maybe other things).

Here is my original data (for white,brown and black (paper) objects)

#dist #white #brown #black 0 4450 4420 3210 10 4430 4430 3200 20 4410 4290 2460 30 4120 3550 1360 40 3450 3010 50 3010 2630 60 2680 2370 70 2460 2180 80 2280 1930 90 2100 1740 100 1930 1520 110 1790 1270 120 1520 130 1330 140 1000

Basil

Does someone knows the correlation between sensor values and the actual distance to an object?

For example, when Thymio measures the prox.horizontal or prox.ground.delta value of 300 or 1000 to an object, what is the distance to this object?

Does a formular exist to calculate the measured value to a distance?

Best
Discovery_42