1.
Sensors - Kinds of sensors - Ways to categorize
sensors
-
Sensors can be categorized
by the physical quantity they sense.
Sensors can be used to measure many, many physical quantities.
-
Temperature (the most
common measurement)
-
pH
-
Rotational rate (tachometer,
like in a car)
-
Linear velocity (speedometer
in a car, and others)
-
Flow rate
-
Pressure
-
Strain
-
etc,
2.
Sensors - Kinds of sensors - Ways to categorize
sensors - restricting ourselves to electrical sensors.
-
Sensors can be categorized
by the electrical quantity which changes.
-
Voltage sensors
- where the sensor produces a voltage change
-
LM35 Temperature Sensor
-
Pressure Sensors
-
DC tachometers
-
Photocells
-
Resistive sensors
- where the resistance of the sensor produces changes
-
Strain gages
-
Thermistors
-
Photoresistors
-
Frequency sensors
- where the sensor produces an voltage signal with a changing frequency
-
AC tachometers
-
Some flow meters
Note: The
categories above are anything but exhaustive. Some sensors require
circuits to convert their electrical changes into useful signals - usually
voltage signals.
4.
Understand Voltage Dividers and Their Use
in Sensor Circuits
5.
Time Constants
-
Where are we going to
find time constants? (You will encounter them in lab!)
-
Actually, they are found
in numerous systems including:
-
Thermal systems
-
Rotational systems (motors
starting up)
-
etc.
-
What is a time constant?
-
A way of describing how
quickly a system responds to changing inputs, and a fundamental parameter
in many systems.
-
Where do they come from?
Link
to material on thermal time constants
-
How do you calculate them
once you have lab data? Link
to material on ways to calculate a time constant
-
An
example - finding time responses in a time constant system.Where are
we going to find time constants? (Hint, check the next lab.)
Readings:
-
Links to material in the
electronic lessons.
Problems: