Principle of the sine/cosine measurement

A position encoder with sine/cosine interface 1 V_pp outputs two sine signals phase-shifted by 90° as analog voltages. Both signals are transmitted over two lines differentially as signal and counter signal, the voltage difference between the two lines giving the wanted signal in peak-to-peak volts. A level of 1 V_pp is usual. A full 360° cycle of the sine signal is designated as a period. Up to 10,000 periods per mechanical revolution are typical for rotary encoders.

If the rotary/linear encoder is moved, an occasionally high frequency alternating voltage is generated, which is subject to the known dynamic limits such as maximum input frequency and amplitude attenuation/level in the subsequent circuitry.
In extending the signal of a digital incremental encoder, which can only evaluate these full steps/cycles, the downstream circuitry can interpolate the two phase-shifted sine signals and thus determine the position n-thousand times more precisely, even within a cycle. For the EL5021 this period resolution by interpolation is 8 to 13 bits, depending upon the setting, and is equivalent to a 256 to 8192-fold micro-resolution of the interval.

Micro-increments The EL5101 Encoder Terminal uses a time-based micro-increment method for the same purpose, in order to also resolve digital encoder steps into up to 256 micro-increments.

In addition a further Reset/C signal from the encoder can be connected in order to mark a special position, e.g. the zero position. This signal can be used by the EL5021 for resetting or latching.