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AC Lift System – Position Monitoring
The unit also requires an absolute measurement of lift position. This is
achieved through the use of a potentiometer. The potentiometer is turned
by connected gears in the lift motor, which changes the wiper resistance.
With +3.3V DC applied across the potentiometer, the center wiper
connection will be a variable voltage (between 0 and +3.3V DC), dependant
on the position of the lift. This variable voltage is applied to the
input of a 16-bit A/D converter which converts the analog voltage into a
16-bit binary numeric representation that the processor can understand.
As the voltage returned by the potentiometer changes between 0 and 3.3V
DC, the corresponding A/D values change between 0 and 65507. In this way,
the processor can keep track of where the lift is positioned.
It is important to note that since the potentiometer is mechanically
connected to the gearing of the motor, it would be highly unlikely for a
lift motor to go out of calibration without having some damage that
needs to be repaired. See the section, Troubleshooting the Incline System (on
page 55) if this occurs.
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