Direct sensing Flashcards
What is a transducer
Any device that converts energy from one form to another
Principle of use of piezo electric transducer as microphone
Pressure applied to crystal Centers of charge distort Voltage across crystal Electrical connections (silver) Varying voltage Amplified
Structure of metal wire strain gauge
SEALING a length of VERY FINE WIRE in small rectangle of THIN PLASTIC
Metal wire strain gauge principle
plastic stretched Wire also stretched Increase in length Decrease is cross sectional area Both cause increase in resistance Affects output voltage
Displaying output of sensing devices
Potential dividers to give voltage output
Output of operational amplifier formula
V(out) = Ao (v+ - v-)
Where Ao = open loop gain
Ideal op-amp characteristics
Infinite open loop GAIN Infinite INPUT IMPEDANCE infinite BANDWIDTH infinite SLEW RATE ZERO output impedance
Use of op amp as comparator
Lol
Advantages of negative feedback
Increased bandwidth
Less distortion
Greater operating stability
Disadvantages of negative feedback
Reduction is gain
Gain on inverting amplifier
- Rf/Rin
Gain on non - inverting amplifier
1 + Rf/R1
Use of relays in circuits
Electromagnetic switch
Output from op-amp can’t be too high
Small current to turn on/off larger current
Small current energizes electromagnet that operates contacts
Use of LEDS in circuits
Indicate state (polarity) of output
Use of calibration
Output from sensors not always linear
Calibration curve required
To give value of property being measured for given voltage
