I am sort of a beginner to all this. I'd like to interface an arduino with one of these sensors to get accurate and reliable readings of linear "string pull distance".
My thought was to get the analog one, which seems like it would work by supplying an input voltage and the encoder linearly varies the output voltage as the string is pulled through some internal voltage division or something. My worry is that if the input voltage was unsteady, it might affect the output voltage readings.
I've just watched this video that describes how rotary encoders work on with two digital channels (Rotary Encoder Tutorial with Arduino Code - YouTube) and now I'm convinced that the digital sensor will work as well.
Any advice on which type (analog/voltage dividing or two-channel digital) will be more accurate and reliable over the long term?
My worry is that if the input voltage was unsteady, it might affect the output voltage readings.
For an analog input the DAC will return between 0 and 1023 as a fraction of the supply voltage. The analog device you have linked is simply a potentiometer where you supply the voltage. Assuming that there is minimal loss in the wire, the V you supply will be the same as at the Arduino, so not absolute voltage reference is required (eg, if you have 4.5V supply, the DAC will work in steps of 4.5/1024 V or just under 4.5mV).
more accurate and reliable over the long term
The pot based sensor will degrade over time as the wiper and carbon wear down. The digital sensor probably relies on mechanical switching, so it will also eventually fail. How quickly both of these happen will depend on how hard you drive the sensor mechanically.
I personally have a preference for digital sensors as the calibration factors can be better controlled in software, and it is likely to give you a better resolution (this depends on the mechanical setup), but I guess that either can really do the job you described.
Thanks for your reply! I'm worried about the analog one in the sense that if the supply voltage varies over time or doesn't stay exactly 4.5V (or whatever is chosen), the output may change and recalibration may be required to keep displacement accurate. Is this the case, or was I misunderstanding your reply to this question?
I think we will go with the digital. Appreciate the advice!
Then the output of the DAC will still be measured correctly as the proportion of that voltage. It is more likely that the resistor becomes non-linear as the part that 'moves' the most gets work first.