The invention relates to methods for operating an inductive
proximity sensor, comprising the steps of exciting the inductive
proximity sensor by applying a
voltage signal in the form of a step function to the
voltage input of the
proximity sensor, in particular by applying a square-wave
voltage, Sampling the voltage
signal applied to the proximity sensor in order to obtain corresponding voltage values, Sampling the current flowing in the proximity sensor in response to the application of the voltage
signal in order to obtain corresponding current values, Summing up the sampled current values of a first time interval of the
step response, Calculating an
average current value based on at least one current value from a second time interval of the
step response following the first time interval, Calculating an average voltage value based on at least one voltage value from the second time interval, Determining a total
system resistance (Rtot ) based on the calculated mean current value and the calculated mean voltage value, and determining a normalized current signal (i Σ,norm ) by dividing the summed sampled current values of the first time interval by the calculated current mean value of the second time interval. The invention is characterized by looking up a
lookup table or by using a description of a two-dimensional relationship, e.g. by a polynomial, to determine the
inductance (L p ), where as input values to look up a corresponding
inductance (L p ) in the
lookup table the determined total
system resistance (R tot ) and the determined standardized current signal (i Σ,norm ) and comparing the determined
inductance (L p) with at least one predetermined threshold to infer the presence or absence of a nearby target object.