Exposed incremental linear encoders are the feedback system of choice for the axes of CNC equipment requiring very high positional accuracy, such as metrology equipment and precision machine tools.
However, the measuring scale of an exposed encoder is fastened directly to a mounting surface on the machine and can become coated with oil, coolant or dirt, as can the reticle that scans the scale.
Signal stability and quality, and hence the integrity of information fed back to the control system, can therefore be adversely affected.
With this in mind, Burgess Hill-based Heidenhain (GB) Ltd (
www.heidenhaingb.com) has developed HSP 1.0, a new application-specific integrated circuit (ASIC), which provides a stable measuring signal that is said to be unaffected by even severe levels of contamination.
The circuitry compensates for fluctuations in signal amplitude due to interference, providing a low-noise output that maintains the interpolation accuracy of the machine axes.
The ASIC constantly monitors the scanning signal from a Heidenhain linear encoder. If changes are detected, the circuit compensates for the resultant deviations to establish the original signal quality, so that the interpolation deviation and position noise do not increase.
According to the company, the signal retains its ideal form, while amplitude stays nearly constant at 1Vpp (peak to peak).
Even if the ASIC’s control limit was 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.
Heidenhain has also introduced enhanced accuracy data for its exposed linear encoders, to enable design engineers to refer to more-detailed information when selecting the appropriate encoder for an application.