Sensor apparatus - for an elevator with a hanging position measuring tape - for detecting a critical change in length of the position measuring tape - comprising a carrier - with a mounting element - for mounting the carrier on a stationary part of the elevator, - comprising a carriage - on the carrier, - comprising a tape holder - on the carriage - with at least one securing element - for securing the position measuring tape in a fixed location and - for roughly setting the length position of the position measuring tape, - comprising a guide device - between the carrier and the carriage - with guide elements on the carrier and on the carriage - for, in the parallel direction of the position measuring tape to be mounted, - displaceably securing the carriage to the carrier, - comprising a tensioning device - between the carrier and the carriage - with engagement elements on the carrier and the carriage and - with a tensioning element - which is secured to the engagement elements - in order to move the carriage counter to the direction of the positioning tape to be secured and - in order to be able to tension a secured positioning tape, - comprising a detection device - for detecting a critical displacement of the carriage on the carrier on the basis of a critical change in length of a position measuring tape to be mounted and for outputting a signal in the event of a detection, - with at least one activation element - for identifying the position of a critical displacement and - with a sensor - for detecting the activation element in the event of a critical displacement, - wherein the activation element and the sensor - are alternately secured on the carrier and the carriage, characterized in that - an adjusting device is provided - in order to be able to set the distance between the at least one activation element and the sensor, - with at least one adjusting element - on the carriage and the tape holder - for setting the position of the tape holder with respect to the carriage in a parallel direction of the position measuring tape to be mounted - in order to be able to adjust the length position of a position measuring tape to be mounted with respect to the carriage, - or on the carrier and the carriage - for setting the distance between the at least one activation element and the sensor. - for an elevator with a hanging position measuring tape - for detecting a critical change in length of the position measuring tape - comprising a carrier - with a mounting element - for mounting the carrier on a stationary part of the elevator, - comprising a carriage - on the carrier, - comprising a tape holder - on the carriage - with at least one securing element - for securing the position measuring tape in a fixed location and - for roughly setting the length position of the position measuring tape, - comprising a guide device - between the carrier and the carriage - with guide elements on the carrier and on the carriage - for, in the parallel direction of the position measuring tape to be mounted, - displaceably securing the carriage to the carrier, - comprising a tensioning device - between the carrier and the carriage - with engagement elements on the carrier and the carriage and - with a tensioning element - which is secured to the engagement elements - in order to move the carriage counter to the direction of the positioning tape to be secured and - in order to be able to tension a secured positioning tape, - comprising a detection device - for detecting a critical displacement of the carriage on the carrier on the basis of a critical change in length of a position measuring tape to be mounted and for outputting a signal in the event of a detection, - with at least one activation element - for identifying the position of a critical displacement and - with a sensor - for detecting the activation element in the event of a critical displacement, - wherein the activation element and the sensor - are alternately secured on the carrier and the carriage, - an adjusting device is provided - in order to be able to set the distance between the at least one activation element and the sensor, - with at least one adjusting element - on the carriage and the tape holder - for setting the position of the tape holder with respect to the carriage in a parallel direction of the position measuring tape to be mounted - in order to be able to adjust the length position of a position measuring tape to be mounted with respect to the carriage, - or on the carrier and the carriage - for setting the distance between the at least one activation element and the sensor.