is it possible to make a DIY impedance analyzer for checking the resonance frequency of high power ultrasonic transducers? for example a face mask welding ultrasonic transducer
The most straightforward way is through Ohm’s Law. By using a voltage sensor to measure the test signal's voltage across the transducer and using a current sensor to measure the test signal's current flowing through the transducer, together with various signal processing algorithms, the impedance over the frequency range of interest can be obtained. The test signal can be produced by a signal generator. As an alternative, you also can use the Inductive Coupling Method for the measurement of the impedance of the transducer. More information about these methods have been detailed in my following papers/monograph:
[1] Z. Zhao, "Measurement setup consideration and implementation for inductively coupled online impedance extraction," Ph.D. thesis, Nanyang Technological University, Mar. 2021, doi: 10.32657/10356/146738.
[2] Z. Zhao, A. Weerasinghe, Q. Sun, F. Fan, K. Y. See, "Improved calibration technique for two-probe setup to enhance its in-circuit impedance measurement accuracy," Measurement, 2021, vol. 185, Art no. 110007.
[3] A. Weerasinghe, Z. Zhao, N. Narampanawe, Z. Yang, T. Svimonishvili, K. Y. See, "Single-probe inductively coupled in-circuit impedance measurement," IEEE Trans. Electromagn. Compat., 2021, doi: 10.1109/TEMC.2021.3091761.