Piezoelectric Transducer Concepts
1. Permittivity (ฮต)
Definition: Ability of a material to store electrical charge when an electric field is applied.
Unit: Farad/meter (F/m)
Formula: C = ฮต × (A / t)
Key Insight:
- High permittivity → High capacitance → Low voltage
- Low permittivity → Low capacitance → High voltage
Trick: Permittivity ↑ ⇒ Voltage ↓
2. Charge Sensitivity
Definition: Charge generated per unit force.
Formula: Q / F
Unit: Coulomb/Newton (C/N)
Important Point:
- Independent of external circuit
- Depends only on material
3. Voltage Sensitivity
Definition: Voltage generated per unit force.
Formula: V / F
Unit: Volt/Newton (V/N)
Important Point:
- Depends on capacitance
- Affected by external circuit
4. Relationship
V = Q / C
Voltage Sensitivity = Charge Sensitivity / Capacitance
5. Comparison Table
| Feature | Charge Sensitivity | Voltage Sensitivity |
|---|---|---|
| Definition | Q / F | V / F |
| Unit | C/N | V/N |
| Dependency | Material only | Material + Capacitance |
| Stability | More stable | Less stable |
6. Summary
- Charge sensitivity = constant (material property)
- Voltage sensitivity = varies with capacitance
- Permittivity ↑ ⇒ Voltage ↓