If you need to read it very quickly you could use a non-differentiated Custom function driven with a Norm.ON contact so the ADC function is executed at every scan of the ladder logic.
For really time-critical mission you could use an interrupt input to trigger the custom function that will measure the ADC continuously for a period of time (e.g. during motion). E.g. you could use a For next loop to measure ADC continuously for 10,000 cycles during motion which will ensure that you measure the ADC readings during the whole time when the device is moving.