Apparatus for monitoring moisture in a gas stream

Abstract

A device is provided comprising a piezoelectric material and at least one non-crystalline .[.non-crystalline.]. metal oxide.[.,.]..Iadd.; .Iaddend.crystalline.[.-.]..Iadd.,.Iaddend.non-zeolite metal oxide and mixtures thereof coating chemically reactive with trace quantities of water in chemically reactive and inert gases. The piezoelectric material is bonded to a conductor for delivering an alternating electric current and to a conductor for transmitting resonant vibration frequency of the crystal. The reactive metal oxide coating has an effective thickness which provides a serviceable life for the coating while not being so thick as to prevent vibration of the piezoelectric material.

I claim: 
     
       1. A sensing device for measuring water content in a stream of purified gases which comprises: a piezoelectric material having an effective mass of a coating .[.non-crystalline metal oxide.]. on at least one surface of said sensing device, with said coating formed of a composition .Iadd.selected from the group consisting of a non-crystalline metal oxide, a crystalline, non-zeolite metal oxide and mixtures thereof, said coating being .Iaddend.chemically reactive with water to form a metal hydroxide product, said coating having a mass which permits said material to vibrate in response to applied alternating electrical current,   means for applying an alternating electrical current to said piezoelectric material and means for measuring frequency of vibration of said piezoelectric material.   
     
     
       2. The device of claim 1 wherein said material has said coating on two opposing surfaces. 
     
     
       3. The device of claim 1 wherein said piezoelectric material is quartz. 
     
     
       4. The device of claim 2 wherein said piezoelectric material is quartz. 
     
     
       5. The device of claim 1 wherein said coating is barium oxide. 
     
     
       6. The device of claim 2 wherein said coating is barium oxide. 
     
     
       7. The device of claim 3 wherein said coating is barium oxide. 
     
     
       8. The device of claim 4 wherein said coating is barium oxide. 
     
     
       9. The device of claim 1 wherein said piezoelectric material is poly(vinylidene fluoride). 
     
     
       10. The device of claim 2 wherein said piezoelectric material is poly (vinylidene fluoride). 
     
     
       11. The device of claim 1 wherein said coating includes a layer of protective material between said metal oxide coating and said piezoelectric material comprising poly(vinylidene fluoride). 
     
     
       12. The device of claim .[.I.]. .Iadd.1 .Iaddend.wherein said coating includes a layer of protective material between said metal oxide coating and said piezoelectric material comprising polytetrafluoroethylene. 
     
     
       13. The device of claim 2 wherein said coating includes a layer of protective material between said metal oxide coating and said piezoelectric material comprising poly(vinylidene fluoride). 
     
     
       14. The device of claim 2 wherein said coating includes a layer of protective material between said-metal oxide coating and said piezoelectric material comprising polytetrafluoroethylene.