Signal conditioning circuit for trigger probe.

摘要

A touch trigger probe (11) has electrical contacts (10). A comparator (18) compares the resistance of the contacts (10) with a threshold, in order to generate a repeatable trigger signal when the contacts open. To ensure that the trigger signal can be generated reliably even if the resistance of the contacts (10) when closed should increase, the threshold set (on line 20) is variable. The threshold can, for example, be set by a sample and hold circuit (24) which tracks the resistance of the contacts (10) when closed.