Solid state sensor element

Claim 2

A solid state sensor element comprising a planar substrate of a material selected from the group consisting of electrically insulating material and material having electrically insulating faces, the substrate having, on one face thereof, a first pair of electrical connection points and a temperature responsive electrically conducting path extending between forming a resistance thermometer element, and, on the opposite face of the substrate, a second pair of connection points and a pair of physically separate electrical conductors connected respectively to said second pair of connection points, the electrical conductors having between them an elongate gap of substantially constant width.

Claim 3

A sensor element as claimed in claim 1, including at least one coating over said pair of conductors, the coating being of a material which is electrically responsive to variations in a selected parameter of the ambient atmosphere.

Claim 4

A sensor element as claimed in claim 2, wherein the coating is a layer of a refractory oxide material having an electrical conductivity which is dependent on the presence of a gas or gases in the ambient atmosphere.

Claim 5

A sensor element as claimed in claim 3, wherein refractory oxide layer is of zirconia doped with one of the materials from the group consisting of yttria, and the following oxides: ______________________________________ Simple oxides Complex oxides ______________________________________ Cobalt oxide Co.sub.3 O.sub.4 Bismuth molybdenum oxide Nickel oxide Ni O Vanadium molybdenum oxide Copper oxide Cu O Uranium antimony oxide Chromium oxide Cr.sub.2 O.sub.3 Strontium iron oxide Uranium oxide U O.sub.2 ______________________________________

Claim 6

A sensor element as claimed in claim 4, wherein the layer includes between 10 and 30% by volume of sodium silicate.

Claim 7

A sensor element as claimed in claim 2, wherein the coating is of a semi-conductor material.

Claim 8

A sensor element as claimed in claim 6, wherein the semi-conductor material is zinc oxide.

Claim 9

A sensor element as claimed in claim 2, wherein the coating is of a porous material.

Claim 10

A sensor element as claimed in claim 8, wherein the porous material is aluminum oxide.

Claim 11

A sensor element as claimed in claim 8, wherein the porous material is impregnated with a solution of a hygroscopic material.

Claim 12

A sensor element as claimed in claim 10, wherein the hygroscopic material is lithium chloride.

Claim 13

A sensor element as claimed in claim 2, wherein the coating is a mixture of a hygroscopic material and a gelling agent.

Claim 14

A sensor element as claimed in claim 12, wherein the coating is a mixture of lithium chloride and polyvinyl alcohol.

Claim 15

A sensor element as claimed in claim 1, wherein the temperature responsive electrically conducting path has an impervious coating of an inert material.

Claim 16

A sensor element as claimed in claim 1, wherein the temperature responsive electronically conducting path is formed of a fused vitreous film containing platinum particles.

Claim 17

A sensor element as claimed in claim 1 wherein said electrical conductors are films of noble metal.

Claim 18

A sensor element as claimed in claim 1, wherein said electrical conductors are interdigitated one with the other.