switch actuator 145 does not extend below the level of the foot platform 15 but is contained with the housing 144 which mounts to the foot platform 15 the switch actuator 145 includes a head 148 and a shaft 150 which is slidably mounted within a channel 168 within the housing 144 the housing 144 also has two chambers 164 166 a switch rod 152 is mounted within chamber 164 at pivot point 155 and connects at one end to the shaft 150 of the switch activator 145 mounted on the other end of the switch rod 152 is a magnet 157 which is disposed a fixed distance from a hall effect sensor 160 flat spring 162 ensures that switch actuator 145 remains in an extended position within the concave formation when not depressed by the ball of a foot in operation when the ball of a person 39 s foot contacts the switch activator 145 the head 148 and shaft 150 are depressed and slide into the housing 144 along channel 168 the switch rod 152 pivots about pivot point 155 so that magnet 157 is brought into proximity to hall effect sensor 160 the hall effect sensor 160 can be advantageously used for several purposes first it can merely act as an on off switch to detect when a person 39 s foot has been properly placed against the ball locator within the foot well of the device 10 or 11 second since the hall effect sensor 160 generates an increasingly stronger electrical signal as the magnet 157 draws closer this signal can be used to determine the relative size of the ball of the foot of the person being measured the more the switch activator 145 is.