Position measuring instrument

A position measuring instrument having a scanning unit for generating position-dependent analog signals that are triggered in a trigger stage at a predetermined trigger threshold voltage in order to generate digital scanner signals and to form position measurement values, the position measuring instrument having a testing device coupled to the scanning unit, the testing device comprising:

• means for varying either one of the trigger threshold voltage or the analog scanner signal so that in one state the trigger threshold voltage is within the allowable amplitude in normal operation of the analog scanner signal and in a further state the trigger threshold voltage is outside the allowable amplitude in normal operation of the analog scanner signal;
• further comprising a logic circuit coupled to the output of the trigger stage for monitoring the digital state of the output of the trigger stage, the logic circuit generating an error signal as a function of a change of the digital state under prescribed conditions.

A position measuring instrument having a scanning unit and a scale with a plurality of division tracks for generating a plurality of position-dependent analog signals that are triggered in trigger stages at a predetermined trigger threshold voltage in order to generate digital scanner signals and to form position measurement values in an evaluation unit, the position measuring instrument having a testing device coupled to the scanning unit, the testing device comprising:

• means for varying either one of the trigger threshold voltage or the analog scanner signal of one of the trigger stages so that in one state the trigger threshold voltage is within the allowable amplitude in normal operation of the analog scanner signal and in a further state the trigger threshold voltage is outside the allowable amplitude in normal operation of the analog scanner signal;
• further comprising a logic circuit coupled to the output of the one trigger state for monitoring the digital state of the output of this trigger stage, the logic circuit generating an error signal as a function of a change of the digital state under prescribed conditions and when the analog scanner signal of the one trigger stage is tested, the generating of an error signal occurs as a function of the states of further digital scanner signals.