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 (R Ref) for generating a reference voltage, which reference resistor is arranged in the current circuit of said test current, a processing unit (ADC, SO) coupleable to said first and second terminals (F1, F2) and to said reference resistor (R Ref), said circuit being characterized in that the circuit further comprises a switch (W1, W2) which is embodied to direct the test current either through the thermo wires (T1,T2) and the reference resistor (R Ref) in a first stage or in a second stage through the reference resistor (R Ref) only, and in that said processing unit (ADC, SO) 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 (Vt hermo) caused by the thermoelectric effect and a component generated by the resistive component (V RTC) of the thermo wires (T1, T2], and wherein said voltage drop in the second stage consists of said thermo voltage (V RTC) only - to eliminate a contribution of said thermo voltage (V RTC) measured in the second stage to said voltage drop tapped during the first stage, - to determine an ohmic resistance of said first and second thermo wire (T1, T2) based on the resistance of said reference resistor (Rref), and - to determine a defect of said first and second thermo wire (T1, T2). 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 (R Ref) for generating a reference voltage, which reference resistor is arranged in the current circuit of said test current, a processing unit (ADC, SO) coupleable to said first and second terminals (F1, F2) and to said reference resistor (R Ref), said circuit being characterized in that the circuit further comprises a switch (W1, W2) which is embodied to direct the test current either through the thermo wires (T1,T2) and the reference resistor (R Ref) in a first stage or in a second stage through the reference resistor (R Ref) only, and in that said processing unit (ADC, SO) 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 (Vt hermo) caused by the thermoelectric effect and a component generated by the resistive component (V RTC) of the thermo wires (T1, T2], and wherein said voltage drop in the second stage consists of said thermo voltage (V RTC) only - to eliminate a contribution of said thermo voltage (V RTC) measured in the second stage to said voltage drop tapped during the first stage, - to determine an ohmic resistance of said first and second thermo wire (T1, T2) based on the resistance of said reference resistor (Rref), and - to determine a defect of said first and second thermo wire (T1, T2). - 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 (Vt hermo) caused by the thermoelectric effect and a component generated by the resistive component (V RTC) of the thermo wires (T1, T2], and wherein said voltage drop in the second stage consists of said thermo voltage (V RTC) only wherein said voltage drop in the first stage consists of a component generated by a thermo voltage (Vt hermo) caused by the thermoelectric effect and a component generated by the resistive component (V RTC) of the thermo wires (T1, T2], and wherein said voltage drop in the second stage consists of said thermo voltage (V RTC) only - to eliminate a contribution of said thermo voltage (V RTC) measured in the second stage to said voltage drop tapped during the first stage, - to determine an ohmic resistance of said first and second thermo wire (T1, T2) based on the resistance of said reference resistor (Rref), and - to determine a defect of said first and second thermo wire (T1, T2).