ok. spend some time with the data sheet and it makes sense now!
the enable-pins would activate only one chip at a time, and then i can use the address-pins to get the 4 consecutive 8-bits (32bit data) and only the activated chip would send back results on the shared data bus.
the other option seems to be to do pin change interrupts and do my own counting on the arduino. so i can reset the counter myself (which i will do regularly with a reed switch positioned at angle 0).
would you say going with the external-decoder is more advisable, will produce more accurate data?