Abstract: Apparatus for generating an output dependent upon the impedance or at least one component of the impedance of a device includes a load component having a known impedance or component thereof for connection in series with the device; a measurement channel for measuring voltages; a switch arrangement connected to the measurement channel for switching the measurement channel to sequentially measure a first voltage on a first side of the load component and a second voltage on a second side of the load component or a voltage difference across the load component; a processing arrangement connected to the measurement channel for processing the sequentially measured voltages to generate an output dependent upon the impedance or at least one component of the impedance of the device; and a signal generating arrangement for generating an electrical signal for application to the series connected load component and device.

Abstract: Apparatus for generating an output dependent upon the impedance or at least one component of the impedance of a device comprises a load component having a known impedance or component thereof for connection in series with said device; a measurement channel for measuring voltages; a switch arrangement connected to said measurement channel for switching the measurement channel to sequentially measure a first voltage on a first side of said load component and a second voltage on a second side of said load component or a voltage difference across said load component; a processing arrangement connected to said measurement channel for processing the sequentially measured voltages to generate an output dependent upon said impedance or at least one component of the impedance of said device; and a signal generating arrangement for generating an electrical signal for application to the series connected load component and device.