Apparatus for the automatic detection of counting errors in a displacement measuring system by encoding and counting

Claim 1

Apparatus for the automatic detection of counting errors in a displacement measurement system by encoding and counting comprising a measuring scale, sensor means including n analyzers each emitting on displacement before said scale a sensing signal, a generation network providing from the sensing signals counting impulses each corresponding to a displacement of an increment, a determination circuit connected to said generation network for determining the direction of count, a counter of said impulses, a plurality of output terminals for said counter furnishing in binary code the value CE registered by said counter, each of said terminals corresponding to a bit, the combination of said sensing signals furnishing the value CL from the sensor means in a sensing code having n positions to distinguish 2n increments within a graduation of said scale, a subtractor circuit for subtracting said value CL from the value CE, a memory circuit for the difference CE - CL at a time chosen as origin of the sensing, a coincident circuit receiving the instantaneous difference CE CL and the memorized difference and alarm means actuated by said coincident circuit upon non-coincidence of these differences.