Transducer testing

The main parameters of an ultrasonic vibration system are resonance frequency f, free capacitance CT, dynamic resistance R1, and resonance frequency is a commonly used operating frequency for transducers. The driving power supply (also known as the electric box or wave box), the amplitude converter, and the mold must be matched with this frequency.
The free capacitance is the capacitance at both ends of the transducer. Because piezoelectric ceramic components can be regarded as insulators, and transducers actually work through charging and discharging, the size of the electrical capacity has a decisive impact on the matching of the driving power supply.
Dynamic resistance can be seen as the loss of a transducer in an ideal state. It is generally believed that the smaller the dynamic resistance, the better. But one principle to remember is that transducers with low dynamic resistance are not necessarily good, while transducers with high dynamic resistance are definitely not.
Its characteristic is that the equipment requirements are not high, and the testing principle is simple and clear. Manual testing is slow and has poor accuracy.
The resistance value of the voltage divider Ri in the figure matches the output impedance of the signal generator. Generally, RT1=RT2 is taken, and the value of terminal resistance RT2 should correspond to the dynamic resistance R1 of the transducer, with a reference value of 5.1 Ω. The distributed capacitance CAB between A-B is much lower than the free capacitance CT of the transducer. The reactance of the distributed capacitors CT1 and CT2 should meet: 1/ ω CT1>>RT1,1/ ω CT2>>RT2..
Adjust the frequency of the signal generator to make the terminal Voltmeter indicate large, and the frequency at this time is the series resonant frequency fs of the transducer, which is commonly referred to as the transducer frequency. Write down the indication of the terminal Voltmeter, replace the transducer with a variable resistor, and adjust its resistance value so that the terminal voltage indication is the same as the original. At this time, the resistance value of the variable resistor is the dynamic resistance R1 of the transducer..
Its characteristic is that the equipment is expensive and needs to be equipped with a computer. It can automatically test, with fast speed, high accuracy, and complete test data. Generally, as long as the wire is connected and the test frequency range is given, the computer will automatically scan and work to find the resonant frequency, free capacitance, and dynamic resistance. It will also provide the anti resonant frequency, conductivity admittance value, equivalent inductance, mechanical quality factor Qm, etc.