Capacitive sensor arrangement for a liquid or gaseous medium, and method of making the same

摘要

A capacitive sensor for measuring characteristics of liquid or gaseous media has at least two outer carrier boards and a spacer plate that keeps the two outer boards at an exact dimensionally stable spacing from each other. A sensor capacitor is formed by a hollow space in the spacer plate flanked by two metal coatings forming capacitor plates on the inwardly facing surfaces of the outer boards. Two or more capacitors can be formed by stacking the desired number of boards and spacer plates. Ports are provided for the medium to flow into the hollow space or spaces preferably in the spacer plates. Further ports for pressure equalization inside and outside the sensor are formed either laterally in spacer plate margins or directly in the outer boards. A multitude of such sensors is manufactured simultaneously by printed circuit board techniques that provide the required capacitor plate forming coatings on the inwardly facing surfaces of the boards and the required conductor leads as well as metal screening against adverse field influences. The individual plates and boards are stacked, aligned and bonded and then cut along connector strips to form the individual sensors. Lead-through contacts are formed prior to the cutting.