Exposed, incremental linear encoders are the feedback system of choice from the axes of high precision CNC machine tools. The problem is that the measuring standard (scale) of an exposed encoder is fastened directly to a mounting surface on a machine and can become coated with oil, coolant or dirt, as can the reticule that scans the scale. Signal stability and quality, and hence the integrity of information fed back to the control system, can be adversely affected.

Heidenhain’s ASIC HSP 1.0 provides a stable measuring signal that is unaffected by even severe levels of contamination. The intelligent circuitry compensates for fluctuations in signal amplitude due to interference, providing a low-noise output that maintains interpolation accuracy of the machine axes.

The signal processing ASIC constantly monitors the scanning signal from a Heidenhain linear encoder. If changes are detected, it compensates for the resultant deviations to establish the original signal quality, so that interpolation deviation and position noise do not increase. The signal retains its ideal form and its amplitude stays nearly constant at 1 VPP. Even if the ASIC’s control limit were to be exceeded, due to increasingly heavy contamination, it would not result in an abrupt failure of the signal, which would instead only slowly decrease in amplitude.

If it does, the HSP 1.0 readjusts it by increasing the LED current. The resulting increase in LED light intensity scarcely affects the noise level in the scanning signals, even when there is a high degree of signal stabilisation. This is in contrast to systems where the gain is made in the signal path, which increases the noise level.