Abstract: A displacement sensor comprises a measuring head which measures displacement by variation in frequency of an oscillator due to movement of a core in a coil. The signal from the oscillator is used to gate a high frequency crystal clock into a counter. The count is representative of the change in frequency of the oscillator and thus the displacement to be measured. The count is compared by a microprocessor with a look-up table stored in the memory during initial calibration. The operating and processing electronics connected to the sensor head are mounted in a connector which can be directly coupled to connectors of other sensors to form a bus connecting multiple sensors to a data logger or computer.