An electromagnetic method for measuring AC losses in HTS tapes without lock-in amplifier

The measurement of AC losses in high temperature superconducting tapes is a complex task due to the small magnitude of the quantities to detect, and to the difficulty to separate the inductive and resistive parts of the measured voltage. This work describes a different approach to the electrical measurement of AC losses, not requiring lock-in amplifiers for the signal processing. The system is based on the acquisition of the voltage and current signals from the sample and their projection on a reference signal, performing a Hilbert transform based treatment procedure. This method allows one to retrieve the harmonic components of the signals with a significant noise reduction, thus improving the quality of the results. The experimental set-up is applied to measure AC losses in different HTS tapes, using sinusoidal currents of different amplitude and frequency. The results are compared with those obtained on the same tapes at other laboratories.