Sensor for determining gases and method for manufacturing the sensor

Abstract

A sensor for determining the concentration of a gas in gas mixtures, which has a measuring and a reference electrode as well as a polymer layer, which is in contact with the gas mixture and with the measuring electrode. A pH sensitive electrode is provided as the measuring electrode.

1 . A sensor for determining a concentration of a gas in a gas mixture, comprising: 
 a measuring electrode, the measuring electrode being a pH sensitive electrode;    a reference electrode; and    a polymer layer in contact with the gas mixture and the measuring electrode.    
     
     
         2 . The sensor according to  claim 1 , wherein, in addition to measuring a pH value, a conductivity of the polymer layer is measured as well.  
     
     
         3 . The sensor according to  claim 1 , wherein the measuring electrode contains an iridium oxide.  
     
     
         4 . The sensor according to  claim 1 , wherein the measuring electrode is at least substantially shielded from the gas mixture by the polymer layer.  
     
     
         5 . The sensor according to  claim 1 , wherein at least one of the measuring electrode and the reference electrode is an interdigital electrode.  
     
     
         6 . The sensor according to  claim 1 , wherein the polymer layer includes a base.  
     
     
         7 . The sensor according to  claim 6 , wherein the polymer layer contains a quaternary ammonium compound as the base.  
     
     
         8 . The sensor according to  claim 1 , wherein the polymer layer contains an acid.  
     
     
         9 . The sensor according to  claim 8 , wherein the polymer layer contains a sulphonic acid as the acid.  
     
     
         10 . The sensor according to  claim 1 , wherein the polymer layer contains ethylcellulose.  
     
     
         11 . The sensor according to  claim 1 , wherein the sensor is a sensitive element in a fire detector.  
     
     
         12 . The sensor according to  claim 1 , wherein the sensor is a sensitive element in an air-quality sensor.  
     
     
         13 . The sensor according to  claim 1 , wherein the sensor is a sensitive element for detecting ammonia.  
     
     
         14 . A method for manufacturing a sensor for determining a concentration of a gas in a gas mixture having at least two electrodes that are deposited on a ceramic substrate and a polymer layer, the method comprising: 
 in a first step, producing the electrodes on the ceramic substrate by depositing an electrode paste and a subsequent heat treatment; and    in a second step, depositing the polymer layer by applying a polymer solution on at least one of the ceramic substrate and the electrodes and subsequently removing a solvent.    
     
     
         15 . The method according to  claim 14 , wherein the polymer layer has a thickness of 10 to 50 μm.  
     
     
         16 . The method according to  claim 14 , further comprising: 
 in a third step, contacting the electrodes by a hardenable, precious metal-containing polymer.