Sensors

Question 1

What are the 4 main classes of sensors?

Answer 1

Resistive, capacitive, voltaic and inductive.

Resistive: change in resistive correlates to the change in the sensor variable (e.g. strain gauge resistive coil will change when it is elongated)

Voltaic: measures the direct voltage across a sensor (e.g. thermocoupler measures the voltage difference due to a temperature gradient across 2 different materials)

Capactive: measures the capacitance across a sensor (e.g. phone touch sensor has an air gap between the screen and the back and when screen is pressed, the capacitance changes)

Inductive: measures the induced EMF from a sensor (e.g. Linear Variable Differential Transformer measures the induced EMF from a moving magnet)

Question 2

Precision vs accuracy in a sensor

Answer 2

High precision means there should be little deviation from the mean. High accuracy means a low bias (bias = measured val - true val)

Question 3

Define linearity in a sensor

Answer 3

How close a graph of actual input vs measured output value corresponds to a straight line

Question 4

Define sensitivity in a sensor

Answer 4

The slope of the line fitted to the input-output relationship over a specified range. High slope means very sensitvity.

Question 5

Define gage factor

Answer 5

Measure of sensitivity. GF > 2 means too sensitive = bad