Thermo wire testing circuit

A thermo wire testing circuit for testing a first and a second thermo wire of a thermocouple, comprising:

• a current source terminal for supplying a test current to a first thermo wire via a first terminal during a test mode;
• a current drain terminal for receiving said test current from a second thermo wire via a second terminal during said test mode;
• a reference resistor for generating a reference voltage, which reference resistor is arranged in the current circuit of said test current;
• a processing unit coupleable to said first and said second terminals and to said reference resistor, and
• a switch which is embodied to direct the test current either through the thermos wires and the reference resistor in a first stage or in a second stage through the reference resistor, wherein
• said processing unit is configured to tap a voltage drop caused by said test current between the first and second terminal and to compare said voltage drop with said reference voltage in the first and second stage, wherein said voltage drop in the first stage consists of a component generated by a thermo voltage caused by the thermoelectric effect and a component generated by the resistive component of the thermos wires;
• and
• said voltage drop in the second stage consists of said thermo voltage only to eliminate a contribution of said thermo voltage measured in the second stage to said voltage drop tapped during the first stage to determine an ohmic resistance of the said first and second thermo wire based on the resistance of a reference resistor, and to determine a defect of said first and second thermo wire.