Abstract An improved humidity sensing element of the electrical resistance-dependent, metal oxide type in which the metal oxide is sintered to achieve a stable cross linked porous metallurgical matrix. In the preferred embodiment, the humidity sensing element of the invention is produced by coating a dielectric blank to which an electrode system has been applied with a metal oxide selected from a group including the oxides of Group VIII, Period 4 of the Periodic Table, preferrably Fe2O3, applying a slight amount of compression to the coating and releasing the compression, heating the coated blank to a sufficient temperature and for a sufficient length of time to achieve sintering of the metal oxide and thereafter impregnating the cooled coating of the sensor with a reversably hygroscopic humectant material such as polyethylene glycol, for example.
A MOISTURE SENSITIVE ELEMENT COMPRISING SPACED METAL ELECTRODES, A SINTERED ELECTRICALLY INSULATING METAL OXIDE COATING OVERLAPPING SAID ELECTRODES, SAID OXIDE HAVING A CHARACTERISTIC HUMIDITY-DEPENDENT ELECTRICAL RESISTANCE, AND WHEREIN SAID SINTERED METAL OXIDE STRUCTURE IS OF A POROUS NATURE, THE PORES THEREOF BEING IMPREGNATED WITH A REVERSIBLE HYGROSCOPIC HUMECTANT MATERIAL, AND ELECTRICAL LEADS ATTACHED TO SAID ELECTRODES.
Claim 2
Dependent Claim
56 words
A MOISTURE SENSITIVE ELEMENT COMPRISING SPACED METAL ELECTRODES, A SINTERED ELECTRICALLY INSULATING METAL OXIDE COATING OVERLAPPING SAID ELECTRODES, SAID OXIDE HAVING A CHARACTERISTIC HUMIDITY-DEPENDENT ELECTRICAL RESISTANCE, AND WHEREIN SAID SINTERED METAL OXIDE STRUCTURE IS OF A POROUS NATURE, THE PORES THEREOF BEING IMPREGNATED WITH A REVERSIBLE HYGROSCOPIC HUMECTANT MATERIAL, AND ELECTRICAL LEADS ATTACHED TO SAID ELECTRODES.
Claim 3
Dependent Claim
22 words
The moisture sensitive element of claim 1 including a substantially inert dielectric blank space member upon which said metal electrodes are applied.
Claim 4
Dependent Claim
33 words
The moisture sensitive element of claim 2, wherein said metal oxide is one selected from a group consisting of the oxides of Group VIII, Period 4 of the Periodic Table of the Elements.
Claim 5
Dependent Claim
13 words
The moisture sensitive element of claim 3 wherein said metal oxide is Fe2O3.
Claim 6
Dependent Claim
15 words
The moisture sensor of claim 1 wherein said humectant material is a stable hygroscopic polymer.
Claim 7
Dependent Claim
12 words
The moisture sensor of claim 5 wherein said humectant is Polyethylene glycol.
Claim 8
Dependent Claim
15 words
The moisture sensitive element of claim 6 including a moisture-permeable membrane superimposed over said coating.
Claim 9
Dependent Claim
15 words
The moisture sensitive element of claim 7 wherein said moisture-permeable membrane is polyvinyl alcohol sheet.