I am trying to build an encoder interpolator using an Arduino, because commercial interpolators are very expensive.
I am using a Baumer ITD42 encoder, which outputs a 1Vpp differential signal on two phases (A and B).
I understand that the differential signal can't be used to drive the Arduino analog input pins directly, so I got a pair of LTC1286 serial ADCs. These are advertised as having differential inputs.
However when I wired up the encoder to the LTC1286's I am only getting the positive-going part of the waveform. The negative-going part gets clipped at zero.
My understanding is the Baumer encoder outputs are actually centred about 2.5V and are 1Vpp (i.e. they go from 2V to 3V). But this is not what I am getting. The maximum count I get from my LTC1286 is about 450 counts - which is 500mV with the ADC reference set at 5V.
Any ideas? (of course a differential amplifier would work, but I'm trying to reduce the parts count as much as possible, and used the LTC1286 precisely because it has differential inputs).