Humidity sensing element

A method for producing a humidity measuring element, comprising the steps of:

• providing a non-conductive substrate;
• depositing on said substrate two separate closely spaced interdigitated thin metal film electrodes with fingers having a period less than the thickness of said substrate;
• overlaying said substrate and said electrodes with a first thin dielectric film of a water absorbing material whose dielectric constant varies with the amount of water absorbed;
• depositing over said first dielectric film an electrically conductive water permeable mesh, said mesh being deposited to a thickness such that it has openings which are substantially evenly distributed over its surface to provide its water permeable characteristic;
• and
• overlaying said mesh with a second thin dielectric film of water absorbing material.

A method for producing a fast responding humidity sensing element which will not be subject to influence from surface contamination, comprising the steps of:

• providing a non-conductive planar substrate of a certain thickness;
• depositing on said substrate two thin film interdigitated electrodes whose fingers are spaced apart by a distance such that the period of said fingers is less than the thickness of said substrate;
• depositing over said interdigitated fingers a first water absorbing polymer film whose dielectric constant varies with the amount of water absorbed, said film having the thickness necessary to obtain the response time desired for the element;
• depositing over said first polymer film a thin conductive mesh whose thickness is such that there are produced holes in said mesh which have an average spacing less than the thickness of said first polymer film;
• and
• depositing over said mesh a second water absorbing polymer film whose thickness is greater than the average diameter of the holes in said mesh but is still within the thickness range required to keep the elements response time within the required range.