New Devices for Precise Angle and Length Measurement Using Special Capacitors and Voltage Dividers

The angle and length transducers ("Circap" and "Lincap") utilize a circular or linear capacitor which consists of four rings or four cylinders, respectively, divided into two segments. A rotating or laterally moving shield increases the capacitance in one segment and decreases it in the other. The position of the shield is indicated by the voltage drop across the unshielded parts of these segments. This voltage is measured in an ac excited bridge using a precision inductive voltage divider. Prototypes of the Circap and Lincap have been constructed and tested. Results show that angle can be measured with a standard deviation of about 0.1" and length with a standard deviation of about 0.2 μm.