in an improved electromagnetic induction - type conductivity meter utilizing primary and secondary transformer coils about a liquid sample passageway , a resistance circuit having a conductive lead line extending also through the coils and parallel with the sample passageway is provided . the resistance circuit can be selectively opened and closed , and has the capacity to contribute to the measurement voltage detected on the detector coil when the primary coil is excited . the value of this additional resistance voltage can be used for calibration and monitoring the condition of the conductivity meter .