A measurement and control system for use in performing a medical procedure, employing an energy source, wherein the energy source is connected to an energy delivery device via a transmission line, comprising: a measurement system, configured to sample an output signal generated by the energy source, the sampled output signal having a magnitude and phase; a control system including: a calibration unit configured to receive and store loss information for the transmission line, the calibration unit further configured to generate a calibration signal having a magnitude and phase that are representative of the sampled output signal of the measurement system and of the loss information for the transmission line; and a control unit configured to receive the calibration signal and adjust the energy source in response to a value of the calibration signal; characterised in that: the measurement system includes a directional coupler; the directional coupler is configured to sample the output signal generated by the energy source; the measurement system is configured to measure forward and reflected voltages (51, 52) of the output signal generated by the energy source as sampled by the directional coupler; and the measurement system is configured to calculate the magnitude and the phase of the generated output signal from the measured forward and reflected voltages. a measurement system, configured to sample an output signal generated by the energy source, the sampled output signal having a magnitude and phase; a control system including: a calibration unit configured to receive and store loss information for the transmission line, the calibration unit further configured to generate a calibration signal having a magnitude and phase that are representative of the sampled output signal of the measurement system and of the loss information for the transmission line; and a control unit configured to receive the calibration signal and adjust the energy source in response to a value of the calibration signal; characterised in that: the measurement system includes a directional coupler; the directional coupler is configured to sample the output signal generated by the energy source; the measurement system is configured to measure forward and reflected voltages (51, 52) of the output signal generated by the energy source as sampled by the directional coupler; and the measurement system is configured to calculate the magnitude and the phase of the generated output signal from the measured forward and reflected voltages. a calibration unit configured to receive and store loss information for the transmission line, the calibration unit further configured to generate a calibration signal having a magnitude and phase that are representative of the sampled output signal of the measurement system and of the loss information for the transmission line; and a control unit configured to receive the calibration signal and adjust the energy source in response to a value of the calibration signal; characterised in that: the measurement system includes a directional coupler; the directional coupler is configured to sample the output signal generated by the energy source; the measurement system is configured to measure forward and reflected voltages (51, 52) of the output signal generated by the energy source as sampled by the directional coupler; and the measurement system is configured to calculate the magnitude and the phase of the generated output signal from the measured forward and reflected voltages. the measurement system includes a directional coupler; the directional coupler is configured to sample the output signal generated by the energy source; the measurement system is configured to measure forward and reflected voltages (51, 52) of the output signal generated by the energy source as sampled by the directional coupler; and the measurement system is configured to calculate the magnitude and the phase of the generated output signal from the measured forward and reflected voltages.