me 361 l1 basics
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7/25/2019 ME 361 L1 Basics
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Basic Input Circuits
Most common input circuits used in transducerwork:
1. Current-sensitive Circuit
2. Voltage-sensitive (ballast) Circuit
3. Voltage-divider Circuit
4. Voltage-balancing Potentiometer Circuit
5. Bridge Circuit
6. Amplifier CircuitCurrent-sensitive Input Circuit
• Current flow through the circuit indicates sensor’s resistance R.
• Current flow varies linearly with R for some ranges of operation.
Voltage-sensitive (ballast) Circuit
• Voltmeter impedance is very high & draws negligible current.
• Change in R is indicated by voltage change.
• Sensitivity, S = dEo/dR
• For maximum sensitivity, dS/dRi = 0, gives R=Ri
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
• Anode : +ve side of source where electrons are attracted.• Cathode : -ve side from where electrons are released.
• Ground : a reference point where voltage is assumed zero.
• Load : network of circuit elements that dissipate or store electrical energy.
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
• Ground indicates a reference point in the
circuit where the voltage is assumed to be
zero.
• There are three basic passive elements: the
resistor (R), capacitor (C) and inductor (L).
• Passive elements require no additional
power supply, as active elements such as
integrated circuits.
• There are two types of ideal energy sources:
a voltage source (V) and a current source (I).• Ideal sources contain no internal resistance,
inductance or capacitance.
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Resistor
• Capacitance is a property of the dielectric material, the
plate geometry and separation.
• Capacitors block DC voltage and pass the AC voltage. DC
voltage will build a potential difference in the capacitor
until they are equal. AC voltage simply alternates the
charge and discharge of the capacitor and is passed, not
blocked, in a circuit.
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
• Current through an inductor cannot change
instantaneously because it is an integral of the voltage.
Motor, electromagnetic relays or solenoids have large
inductance, so it is difficult to turn these ON or OFF very
fast.
• The inductor is made by a coil of conductor around a
core like a solenoid.
• What happens if you open a switch that is providing
current to an inductor?
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Ohm's Law: E = IR
Kirchhoff's Laws (V,I)
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
KVL…..
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Voltage Divider…..
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Voltage Divider…..Example
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Diodes…..
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Diodes Homework…..
Diode: some important factors…
• Forward voltages of silicon diodes are really small ( ̴0.6-0.7 volts)
• Diodes don’t have resistance. If the voltage is below a diode’s forward voltage,
then the element looks like an open circuit. If the voltage is below the forward
voltage, the element behaves as a short circuit
Assignment……
Q. Write a short note on Zener Diodes
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Diodes Homework 2…..
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ME 361: Instrumentation and Measurement
aminul islam khan
Electronics : Basics
Relays…