CS14 as alternative to a 4 bit absolute encoder.
The CS14 wide electrical angle of 330º gives the possibility to include up to 17 silver zones guarantying that there will be no voltage overlapping of contiguous positions. Let’s take a look at the particular case of 16 silver zones combined with 16 detents:
The step function that results from this configuration (see the graph on figure 1) makes it possible to differentiate 16 non overlapping different voltage levels from the collector output pin. (B in figures1 and 2)
The detents are set to position and fix the wiper contact on the surface of each silver zone thus absorbing any mechanical play and printing tolerances. The electrical contact between the metal surface of the wiper and the silver area minimizes the contact resistance.
The mechanical detents are evenly spread 22.5º±3º from each other along the circumference as it can be seen in the figure 2 drawing.
The endless rotation feature of the CS14 allows to move the wiper from the detent number 16 (U/Un = 100%) to the detent number 1 (U/Un=0%). During the transition between these two detents it will slide on a dead zone for a few degrees, meaning that at that moment there will be no electrical contact with the resistive track.
In order to cope with this, a pull-up or a pulldown resistor is to be introduced into the circuit design. ACP recommendation is the latter, a pull-down resistor whose value has to be at least 100 times the potentiometer nominal value. In that case, the collector pin output will be
0% (U/Un) when the slider transits on the dead zone.
ACP standard configuration is a potentiometer of 10K Ohm recommending a pull-down resistor to be equal or greater than 1MΩ. (Figure 3)
Connecting the collector terminal to the AD port of a microcontroller to feed the output voltage of said configuration will allow for the selection of 16 different functions.
The table below (figure 4) shows the equivalence between the output function of this potentiometer, indicating the tolerance at each detent, and a 4 bit digital encoder signal. In summary, a CS14 fitted with these features can be used as an alternative to a 4 bit rotary encoder.