Measurement of narrow gap between two hot metal workpieces - by determn. of capacitance between surface of one piece and metal sensor located on other piece

摘要

The workpieces are esp. at temps. above 300 deg.C.; and a sensor is located on one workpiece(I). The sensor consists of a substrate made of an electrically-insulating refractory and coated with a layer of metal(II) facing the other workpiece(III). The surfaces of metals(II,III) form a capacitor, the capacitance of which indicates the distance between metals(I,III). The height of the sensor substrate prevents the occurrence of parasitic capacitance effects. The sensor substrate is pref. made of Pyrex glass (RTM); ceramic; vitreous silica; Th02; Si02; Mg0; or alumina. Metal layer(II) is pref. Au; Cu; Ni; or Ti. Used for accurate determn. of a gap which is a few hundredths of a mm in length. Standard capacitance curves can be determined for each temp., and variations in the gap of ca. 1 micron can be detected.