Meaning
Equivalent electrical circuit models represent the dynamic behavior of piezoelectric resonators. When designing acoustic sensors for inline viscosity measurement, the butterworth-van dyke model provides a way to relate electrical measurements directly to mechanical loading. The system utilizes a parallel combination of static capacitance and a motional branch to represent the transducer.
Electrical Response
The static capacitance represents the dielectric properties of the piezoelectric material held between the electrodes. A motional branch containing series inductance, capacitance and resistance describes the mechanical resonance and energy dissipation of the crystal. This separation of variables allows engineers to isolate the effects of the polymer melt on the sensor.
Melt Loading
Viscous damping of the surrounding fluid increases the effective resistance in the motional branch. Because the polymer melt is highly viscous, the motional resistance rises and the resonant frequency shifts downward during the moulding cycle. The model converts these electrical shifts into viscosity data without interrupting the flow of the material.
This real-time analysis enables the machine to adjust injection pressure dynamically when the melt viscosity drifts from the specified baseline, which prevents underfilled cavities or flashing at the parting line.
Sensor Calibration
Accurate parameter extraction requires measuring the impedance spectrum across the resonance band before exposing the sensor to polymer. If the sensor is not calibrated in air first, the subsequent frequency shifts cannot be converted into absolute viscosity measurements. This initial baseline ensures consistent viscosity tracking throughout long production runs.
