Abstract An essentially full range resistance type relative humidity sensing element is produced by providing a dielectric blank, on which an electrode system has been applied, with a metal oxide coating, in a manner which produces a porous structure therein, and subsequently impregnating that coating with a humectant material. The metal oxide used is selected from a group, including oxides of the metals found in Group VIII, Period 4 of the Periodic Table, which exhibit electrical insulating properties, and wherein the amount of electrical resistance varies with the relative humidity of the environment to which it is exposed. The humectant material, which may be any nonvolatile, reversibly hygroscopic material capable of being retained in the porous oxide structure, such as polyethylene glycol, for example, reduces both the amount of electrical resistance and the magnitude of the change in that resistance produced in response to changes in relative humidity into a range readily measured by ordinary electrical resistance measuring devices.
A moisture sensitive element comprising spaced metal electrodes, an elecTrically insulating metal oxide coating overlapping said electrodes, said oxide having an electrical resistance which is humidity-dependent, said coating having a porous structure, the pores thereof being impregnated with a reversibly hygroscopic humectant material, and electrical leads attached to said electrodes.
Claim 2
Dependent Claim
50 words
A moisture sensitive element comprising spaced metal electrodes, an elecTrically insulating metal oxide coating overlapping said electrodes, said oxide having an electrical resistance which is humidity-dependent, said coating having a porous structure, the pores thereof being impregnated with a reversibly hygroscopic humectant material, and electrical leads attached to said electrodes.
Claim 3
Dependent Claim
27 words
A moisture sensitive element as claimed in claim 1, including a substantially inert dielectric blank member and a noble metal electrode system applied to said blank member.
Claim 4
Dependent Claim
35 words
A moisture sensitive element as claimed in claim 1, wherein said metal oxide is one selected from the oxides of the elements contained in Group VIII, Period 4 of the Periodic Table of the Elements.
Claim 5
Dependent Claim
15 words
A moisture sensitive element as claimed in claim 3, wherein said metal oxide is Fe2O3.
Claim 6
Dependent Claim
18 words
A moisture sensitive element as claimed in claim 1, wherein said humectant material is a stable hygroscopic polymer.
Claim 7
Dependent Claim
15 words
A moisture sensitive element as claimed in claim 5, wherein said humectant is polyethylene glycol.
Claim 8
Dependent Claim
17 words
A moisture sensitive element as claimed in claim 1, including a moisture-permeable membrane superimposed over said coating.
Claim 9
Dependent Claim
17 words
A moisture sensitive element as claimed in claim 7, wherein said moisture-permeable membrane is polyvinyl alcohol sheet.