Setting up of quadrature signals.

摘要

A readhead 10 traverses along a scale 12, producing square wave signals in quadrature on lines 24,26. These are counted by an external counter 28 to indicate the position along the scale. The square waves cannot be used to monitor the orientation and stand-off of the readhead 10 relative to the scale 12. To achieve this, therefore, circuitry within the readhead 10 monitors the sinusoidal quadrature signals from which the square waves are produced, and gives a simple go/no-go indication on a LED 62 when these signals have an acceptable amplitude and are in an acceptable quadrature relationship. <IMAGE>