Patent ID: 7427347

Claim:
A method for operating a measurement probe for measuring a gas concentration in a measuring gas using a solid electrolyte which conducts oxygen ions and has a measurement cavity for holding the measuring gas, a measuring electrode and an external electrode, a pumping current flowing between the measuring electrode and external electrode transporting oxygen ions from the measuring electrode to the external electrode, comprising: checking the measuring electrode by determining the electrode area effectively available for oxygen diffusion, or a value dependent thereon wherein the measuring electrode is checked by: setting a predetermined oxygen concentration in the measurement cavity, impressing a predetermined constant pumping current between the measuring electrode and external electrode, and measuring the resulting Nernst potential at the measuring electrode, measuring the period of time until the measured Nernst potential jumps from small to large values, comparing the measured period of time with a predetermined threshold value, and establishing a defect in the measuring electrode when the measured period of time falls below the predetermined threshold value.