Apparatus and method for measuring hydrogen concentration in molten metals

Abstract

The invention concerns a probe for measuring hydrogen comprising a probe body and a hydrogen sensor. The sensor body has a wall within which a sealed cavity is defined. The cavity contains a solid reference material for generating a reference partial pressure of hydrogen within the cavity. At least a portion of the wall of the cavity is formed from a solid electrolyte material carrying a measurement electrode on a surface of the solid electrolyte outside the cavity and a reference electrode on a surface of the solid electrolyte within the cavity, exposed to the reference partial pressure of hydrogen. An electrical conductor extends from the reference electrode through the wall of the cavity to an external surface of the sensor body. The probe body comprises a chamber for receiving the sensor and a reference-signal connection for connecting to the electrical conductor when the sensor is received in the chamber.

1 . A hydrogen sensor comprising;
 a sensor body comprising a tube, a solid electrolyte closing one end of the tube and a sensor cap closing the other end of the tube, so as to define a sealed cavity within the sensor body;   a solid reference material within the cavity for generating a reference partial pressure of hydrogen within the cavity;   a measurement electrode on a surface of the solid electrolyte outside the cavity;   a reference electrode on a surface of the solid electrolyte within the cavity, exposed to the reference partial pressure of hydrogen; and   an electrical conductor extending from the reference electrode to an external surface of the sensor body.   
     
     
         2 . The sensor according to  claim 1 , in which the electrical conductor extends outwardly from the external surface of the sensor body. 
     
     
         3 . The sensor according to  claim 1 , in which the solid electrolyte is substantially planar. 
     
     
         4 . The sensor according to  claim 1 , in which the solid electrolyte is substantially disc-shaped. 
     
     
         5 . The sensor according to  claim 1 , in which a maximum lateral dimension of the solid electrolyte is less than 10 mm. 
     
     
         6 . The sensor according to  claim 1 , in which a maximum lateral dimension of the solid electrolyte is less than 6 mm. 
     
     
         7 . The sensor according to  claim 1 , in which a maximum lateral dimension of the solid electrolyte is less than 4 mm. 
     
     
         8 . The sensor according to  claim 1 , in which a maximum lateral dimension of the solid electrolyte is about 3 mm. 
     
     
         9 . The sensor according to  claim 1 , in which the thermal expansion coefficients of the tube and the solid electrolyte are predetermined either so that they are substantially equal or so that the solid electrolyte is under compressive stress at an operating temperature of the sensor. 
     
     
         10 . The sensor according to  claim 1 , in which the cavity contains a buffer material between the reference material and the sensor cap. 
     
     
         11 . The sensor according to  claim 1 , in which the sensor cap comprises the same material as the tube. 
     
     
         12 . The sensor according to  claim 1 , in which the electrical conductor extends to the external surface of the sensor body through the sensor cap. 
     
     
         13 . The sensor according to  claim 1 , in which the solid electrolyte comprises indium-doped calcium zirconate. 
     
     
         14 . The sensor according to  claim 1 , in which the tube comprises calcium zirconate or magnesia/magnesium aluminate. 
     
     
         15 . The sensor according to  claim 1 , in which the solid electrolyte is secured to the tube by a glass seal. 
     
     
         16 . The sensor according to  claim 15 , in which the glass is silica-free glass. 
     
     
         17 . The sensor according to  claim 1 , in which the reference material comprises a metal/metal hydride reference. 
     
     
         18 . The sensor according to  claim 1 , in which the buffer material comprises yttrium oxide powder.