GB1330702A - Method of and apparatus for measuring dimensional changes - Google Patents

Abstract

1330702 Measuring dimensions DEFENCE SECRETARY OF STATE FOR 23 June 1971 [25 June 1970] 30900/70 Heading G4H Changes in the dimension of an object (10, Fig. 1, not shown) are measured by moving in steps a pressure sensor 20 (Fig. 2) until a bridge 38 is balanced, the steps being simultaneously counted in a counter 56. As described the bridge output after amplification, is fed to three threshold detectors 44, 46, 48. When the level of the highest detector is exceeded, gate 72 is enabled so that high frequency clock pulses are applied (1) to increment the counter 56 and (2) to drive in a forward direction a reversible stepping motor 30 moving the sensor 20. When the amplifier output falls between the levels of detectors 46 and 48, gate 64 is enabled so that low frequency pulses are applied to the counter and motor. The resolution of the system is represented by the difference between the levels of detectors 44 and 46. If the output drops below the level of detector 44 gate 52 is enabled to supply high frequency pulses to decrement the counter and drive the motor in the reverse direction. The count may be displayed. The apparatus may be used for measuring changes in the diameter of a cylindrical surface of a workpiece supported in a vertical spindle lathe.