POSITION MEASURING APPARATUS

PURPOSE:To realize a small size and to make it possible to select and utilize required functions by providing a master unit, a measuring unit and function units, and providing a constitution wherein each unit is connected to a data bus so that the unit can be freely attached and removed. CONSTITUTION:Various kinds of parameters of all units are stored in a master unit 3 which is connected to duplex data bus 6 so that the unit 3 can be freely attached and removed. The measured position value expressing the position of an object to be measured X is operated in a measuring unit 2A which is connected to the data bus 6 so that the unit can be freely attached and removed and connected to a detecting head part 1 based on the parameters. The specified processings are performed for the measured position values in an analog output unit 4 and a digital input/output unit 5 which are the functional units connected to the data bus 6 so that the units can be freely attached and removed based on the parameters. In this way, only the units having the required functions are assembled, and many kinds of the functions can be used. There is no useless parts, and the low cost and the small size can be realized.