RESISTIVE, CAPACITOR, INDUCTIVE, PIEZOELECTRIC SENSOR Tae-eui, Kim
Resistive Sensor ① Strain gage : changes in ② Force sensing resistor : changes in A ③ Thermistor : change in T ④ Potentiometer changes in L
Forcing Sensing Resistive
Thermister ceramicR NTC(Negative Temperature Coefficient) Thermister cf) PTC(Positive Temperature Coefficient)
(A) Voltage Divider (B) Inverting Amplifier
(C) Bridge Circuit (D) Linearization Linear region
Capacitive Sensor Most capacitive sensors are based on changes in
Inductive Sensor ① Self Inductance ② Mutual Inductance ③ Differential Inductance
Inductive Sensor ① Self Inductance
Inductive Sensor ② Mutual Inductance Don’t know where it is
Inductive Sensor ③ Differential Inductance LVDT(Linear variable Differential Transformer) a b c d e f Primary coil
Inductive Sensor (a) When core is at ; cancelled out
Inductive Sensor (b) When core is at
Inductive Sensor (c) When core is at Adventage of LVDT ; You have wide of range of measuring
Problem 13
Rectifier + LPF
Problem 13 Rectifier + LPF
Problem 13 phase – sensitive demodulation
Problem 13 phase – sensitive demodulation
Problem 14
Piezoeletric Sensor ifthen Piezoelectric sensor has no dc response You cannot measure static, but dynamic Microphone, pulse
Piezoeletric Sensor
② Charge Amplifier
Piezoeletric Sensor If you plan to use the piezoelectric sensor for measuring pulse, the lowest frequency of pulse signal is assumed to be 0.1Hz