Moisture sensing element and method of making same

Claim 3

The mEthod defined in claim 3, wherein said compounds Cr2O3 and V2O5 are mixed in a ratio of approximately one to one by weight.

Claim 4

The method defined in claim 3, wherein said sensing element is baked at a temperature within the range of 1,100* C up to the melting point of the crystal lattice being formed therein for a period of time in the range of 10 minutes to 2 hours.

Claim 5

The method defined in claim 3, wherein said sensing element is cooled to ambient temperature by first lowering its temperature to approximately 860* C and then quenching it.

Claim 6

The method defined in claim 3, wherein said electrodes are measured lengths of platinium-iridium wire.

Claim 7

The method defined in claim 3, wherein said sensing elements are baked in the presence of Al2O3 doping chips.

Claim 8

The method defined in claim 7 wherein the electrodes are spaced apart approximately 5 mils.

Claim 10

The method defined in claim 10, wherein: said platinium-iridium wires are measured lengths of annealed platinium-10 percent iridium 4 mil wire, are embedded in said mixture approximately 5 mils apart and are positioned to have a side by side length alongside each other of approximately 75 mils; and said sensing element is baked in the presence of Al2O3 doping chips for 30 minutes at a temperature of 1,550* C.

Claim 11

The method defined in claim 11, wherein: the compounds Cr2O3 and V2O5 are ground into powders and are mixed by grinding; said sensing element is baked in a furnace, said sensing element being placed in said furnace when said furnace is at ambient temperature and the temperature of said furnace being increased to 1,550* C by injecting nitrogen gas under pressure into said furnace and supplying heat to increase the temperature of said furnace at the rate of 10* C per minute for forty minutes, exhausting said nitrogen gas, pumping dry air into said furnace and supplying heat to continue increasing the temperature of said furnace at the rate of 10* C per minute until the temperature of 860* C is reached, and then supplying heat to increase the temperature of said furnace at the rate of 20* C per minute until the baking temperature of 1,550* C is reached; and said sensing elements are cooled after baking to approximately 860* C by stopping the supply of heat to said furnace and cooling said furnace.

Claim 12

A moisture sensing element comprising a pair of electrodes held spaced apart by a crystal lattice formed by baking a mixture of V2O5 and Cr2O3, said crystal lattice being made of a subsTantially electrically neutral material and having interstitial spaces formed therein between said electrodes, said interstitial spaces being formed in said crystal lattice so that the molecules of atmosphere being monitored may randomly drift in and out of said crystal interstices whereby the volumetric resistance of said sensing element between said electrodes varies as a function of the percent of water vapor present in the molecules of atmosphere within said crystal interstices.

Claim 13

The invention defined in claim 13, wherein said mixture of V2O5 and Cr2O3 is baked in the presence of Al2O3 doping chips.

Claim 14

The invention defined in claim 13, wherein said electrodes are platinium-iridium wires.

Claim 15

A moisture sensing element comprising a pair of electrodes held spaced apart by a crystal lattice formed by baking a mixture of V2O5 and Cr2O3 in the presence of Al2O3 doping chips, said electrodes being annealed platinum - 10 percent iridium 4 mil wires which are positioned a predetermined distance apart alongside each other in a substantially mutually parallel realtionship to extend away from each other and have a side by side length alongside each other of approximately 75 mils, said electrodes being held spaced apart by approximately one layer of the crystals forming said crystal lattice, said crystal lattice being made of a substantially electrically neutral material and having interstitial spaces formed therein between said electrodes, said interstitial spaces being formed in said crystal lattice so that the molecules of atmosphere being monitored may randomly drift in and out said crystal interstices whereby the volumetric resistance of said sensing element between said electrodes varies as a function of the percent of water vapor present in the molecules of atmosphere within said crystal interstices.

Claim 16

The invention defined in claim 16 including a coating of glass frit formed around the body portion of said sensing element.

Claim 17

A moisture sensing element comprising a pair of electrodes held spaced apart by a crystal lattice, said crystal lattice having interstitial spaces formed therein between said electrodes and being made of a substantially electrically neutral semi-conducting solid state type material having a Fermi level approximately neutral so that water ions in the atmosphere are not attracted into nor repelled from said crystal interstices, said interstitial spaces being formed in said crystal lattice so that the molecules of atmosphere being monitored may randomly drift in and out said crystal interstices whereby the volumetric resistance of said sensing element between said electrodes varies as a function of the percent of water vapor present in the molecules of atmosphere within said crystal interstices.