L21+L22: EMs and Sensors Flashcards
(25 cards)
What is the equation for efficiency of a DC machine
What are the 5 categories of losses occurring in DC machines
- Copper Losses *
- Brush Losses *
- Core Losses *
- Mechanical Losses
- Stray Losses
(*Electrical Losses)
What would a power flow diagram for a stator and rotor look like
What is are Control Systems (Closed Loop)
What is a measurand
A measurand is a physical quantity that is measured by a system.
It could be:
* Distance
* Temperature
* Velocity
* Acceleration
* Pressure …
What are the two groups of Transducers that exist
- Sensors
- Actuators
How do sensors work
How do actuators work
Range, Span, and Error Definitions
What are three different types of sensors we need to know (and what sensors are which type)
- Resistive Type of Sensors
- Potentiometer
- Thermistor
- Strain Guage
- Inductive Type of Sensors
- Hall effect sensors
- Capacitive Type Sensors
- Piezoelectric
How is a potentiometer operated
It is essentially a variable resistor, which usually has three. It can be translational or rotational
- In a 3 pin configuration, it acts a potential divider, i.e the V at pin 2 depends on the poistion of the slider
- x represents a percentage of the span that can vary from 0% to 100%
- Ohm’s and Kirchoff’s laws are applicable
How is a thermistor operated
- Constructed with sintered metal oxide in a ceramic matrix that changes electrical resistance, R in response to temperature, T
- Its resistance R varies with temperature T in an inverse exponential manner
- Limited range of temperature (-90° to 130°)
- The most common form of the thermistor is a bead with two wires attached
- The most possible failure is for the lead to separate from the body.
How is a strain gauge operated
- Strain gauge is a device made up from metal/wire/foil/ a strip of semiconductor material, which is used to measure strain
- When it is subject to strain, the resistance, R changes, the change in R is in proportion to the strain
Examples of where strain gauges are used
- Pressure sensors
- Rail Roads
- Wind Tunnels
- CT Scan Machine
How do strain gauges work
How do Inductive Sensors operate
Application areas of Inductive Sensors
To measure position of speed, especially in harsh environments
What is a Hall effect sensor
How do Hall effect sensors operate
Application areas of Hall Effect sensors
What are Capacitive Sensors and how do they operate
What is the equation used capacitive sensors
Application areas of Capacitive Sensors
Most common capacitive sensors are piezoelectric sensors, touch screens, and proximity sensors. Precision positioning, position measurement.
