Lecture 3 - Sensors II Flashcards
What is a Rotary Potentiometer and how can it be used as a sensor?
A Rotary Potentiometer is “a variable resistance device that can be used to measure angular position”
What is a Strain Gage and how does it work?
a “metal foil strain gage as the most common transducer for experimentally measuring strain”
By elongating the Strain Gage, the resistance changes by both due to both geometry change and piezoresistive effect (“change in the electrical resistivity of a metal when mechanical strain is applied”)
The strain can be directly calculated by knowing the Gage Factor, F, and measuring the resistance, DeltaR and R, through the Gage
How many Strain Gages are needed to predict the principal stresses?
3 Strain Gages.
Potential setups are:
* Rectangular rosette
* T-delta rosette
* Eguiangular (delta) rosette
What is a Wheatstone bridge and what is it used to measure? Could you draw it?
A Wheatstone Bridge is a configuration of 4 resistors in a square where the voltage is meassured in the middle (between A and B). It is used to accurately meassure small changes in one of these 4 resistors.
The 4 resistors are chosen such that the there is no potential difference (V) between A and B. If one of the resistors change, a formula is used to find to calculate said change.
It can be used with a Strain Gage, as this has small changes in resistance.
What is Transvers sensivity of Srain Gages?
Strain Gages are sensitive to transverse sheer. This might be up to 5%.
This means that 10% tranverse sheer results in a 1% x 10% = 0.1% error. If the axial strain then was 5%, you would read 5.1% rather than 5%.
What is an Accelerometer?
“a sensor designed to measure acceleration”
What is
