Table 2.

Recently developed electrical sensors for SHM.

Sensor Function	Materials/Construction	Measurement Mechanism	Output Parameter(s)	Applications	Ref
Impact Sensor	PZT/standard PZT sensor	LRC	Voltage (amplitude)	Aerospace SHM	[33]
Crack Detector	Dielectric material/Cylinder	Reflection Coefficient and spectrum shift	S11	Surface crack detection on metallic structures	[35]
Strain Sensor	Cu printed on Flexible substrate/Double layer flat coils on a magnetostrictive layer	Guided wave	Voltage (amplitude)	Defect detection in metallic planar structures	[42]
Crack Detector	PZT/standard PZT sensor	LRC	Voltage (amplitude, and phase)	Surface crack detection on metallic structures	[34]
Crack Detector	UHF Antenna	Reflection Coefficient and spectrum shift	S11	Surface crack detection on metallic structures	[36]
Strain Sensor	PDMS/IDT	Capacitance	Capacitance, Frequency	Strain measurement on surfaces	[39]
Strain Sensor	Standard strain gauge	Resistance	Voltage	Strain measurement on surfaces	[40]
Strain Sensor	PVDF/IDT metal deposited on PVDF	Capacitance	Capacitance	strain measurement on surfaces	[41]
Crack Detector	Taconic TLX-0/circular antenna and Meandered transmission line	Reflection Coefficient and spectrum shift, Time domain reflectometry	S11, Voltage amplitude	Surface crack detection on metallic structures	[37]
Crack Detector	PZT/standard PSI-5H4E sensor	Impedance	Magnitude, phase angle	Surface crack detection of structures	[44]
Strain Sensor	FR4/printed rectangular microstrip antenna	Reflection Coefficient and spectrum shift	S11	Strain measurement on surfaces	[38]