Admittance plot

Admittance plot

Admittance plot is a graph of admittance (vertical axis) versus frequency (horizontal axis). For a stack that is driven by a piezoelectric ceramic, the admittance for each “resonance” will consist of an admittance peak (corresponding to series resonance) followed by an admittance dip (corresponding to parallel resonance) at a somewhat higher frequency.

What is admittance

The current that flows when one volt is applied. [mho] Admittance is the reciprocal of impedance. A high admittance (low impedance) is one indicator of a properly designed stack at series resonance, whereas a low admittance indicates a lossy accumulation.

Admittance symbol unit definition G B
Y Siemens    S In electrical engineering, admittance is a measure of how easily a circuit or device will allow a current to flow G is the conductance
measured in siemens
B is the susceptance
measured in siemens

Transducer detection admittance plot

After the ultrasonic transducer is produced, it is generally tested with an impedance analyser. After the impedance analyser is pushed, the admittance curve will show various ultrasonic transducer indicators. Several critical indicators of the transducer can be known through the admittance curve.

Admittance plot
Admittance plot

Check the Admittance plot below, and you will get many useful parameters.

  1. Fs[Hz]: is the centre frequency of the transducer. Shown in the figure is 20015.2Hz.
  2. F1[Hz] and F2[Hz]: Indicates the transducer’s bandwidth range, the ultrasonic transducer bandwidth ranges from 20001.8 to 20027.1 Hz.
  3. Qm: Q value for short. The larger the Q value, the higher the transducer’s sensitivity and the longer the after-vibration time. The smaller the Q value, the lower the transducer’s sensitivity and the shorter the after vibration time.
  4. Gmax[ms]: 179.925995
  5. R1[ohm]: minimum impedance, the unit is the ohm.
  6. Fp[Hz]: Anti-resonance frequency, the unit is hertz.
  7. Jeff: Electromechanical coupling coefficient
  8. CT[nF]: The unit is nano farad with Static capacitance value. Used for power ultrasound, such as welding, cleaning, this index is used for matching inductance.
  9. C0[nF] and C1[nF]: Add the two = CT.
  10. C0[nF]: Free capacitance.
  11. C1[nF]: Dynamic capacitance. Used for power ultrasound, such as welding, cleaning, this index is used for matching inductance.
  12. L1[mH]: Inductance value, the unit is millihenry.
  13. Zmax[kohm]: The maximum impedance, in kiloohms.


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