What’s the resonance frequency of ultrasonic piezoelectric ceramics tube ?

1, resonance frequency of ultrasonic piezoelectric ceramics
The resonance frequency of the ultrasonic piezoelectric ceramic transducer is related to the thickness of the piezo ceramic. After the piezoelectric ceramic is installed in the ultrasonic device, the resonance frequency of the piezo ceramic will decrease. The specific parameters need to be analyzed.

2.Resonant frequency of piezoelectric ceramic tube

Tubular piezoelectric ceramics have at least two resonance frequencies,they are axial and radial resonance frequencies, whose radial resonance frequencies are related to the outer diameter, wall thickness, etc.The resonance frequency in the axial direction (I.e.height direction) can be estimated by the following formula:
Where: n: the frequency constant in the thickness direction depends on the material. For details, seeing the material parameter table, OD: outer diameter [mm], ID: inner diameter  [mm], the calculated value is an estimate value.
For example: N40 piezoelectric tube transducer OD39-ID32-TH13, the axial resonance frequency is calculated as about 550 kHz.

The ultrasonic piezoelectric ceramic chip used for power generation can generate power of 40-50W / cm2 at the resonance frequency, and the high power material generated by the ultrasonic piezoelectric ceramic chip at the resonance frequency is P81 material.

1. How to judge the positive and negative electrodes of piezoelectric ceramics with a multimeter? And are they fixed?

   
   Use a multimeter to judge the positive and negative electrodes of piezoelectric ceramics as follows:
   Lead out the two wires on the two poles of the piezo ceramic cylinder, then connect the wires to the two probes of the multimeter, and use the multimeter's current block. some insulating tools, such as a pencil rubber tip, which were used to lightly press the piezoelectric ceramic to see the direction of the pointer on the multimeter. If the pointer swings to the right, this means that the end connected to the red stylus is positive, while the black one end of the stylus is positive.

   
   The positive and negative electrodes of a piezoelectric ceramic are not fixed, because the positive and negative charges in the piezoelectric ceramic can be separated regardless of the ions. That's why we came to that conclusion.
   

   
   

2. What is a piezoelectric ceramic relay?

   
   Piezo ceramic relays are essentially relays, and which still belong to the category of relays. Specifically, the charging deformation of the piezoelectric ceramic is used to push the reed to move with the contacts, thereby achieving the desiring purpose. Its main advantages are simple structure, low power consumption and large internal impedance. Therefore, it can be used as a control element of a communication device.