Semester 2

Question 1

How do you calculate Measurement Error?

Answer 1

Measurement Error (E) = Measured value (Xbar) - True value (X)

Question 2

Define accuracy.

Answer 2

How close the measured value is to the true value, usually expressed in percent of full-scale reading

Question 3

Define range

Answer 3

Minimum and maximum values of a quantity that the system is designed to measure

Question 4

What is sensitivity?

Answer 4

Change ΔY in the output for a unit change ΔX in the input

Question 5

Define resolution.

Answer 5

Smallest change in the input that produces an observable change in the output

Question 6

What is the relationship between ΔR/R and ΔL/L?

Answer 6

ΔR/R = Gf ΔL/L = Gf ε

Question 7

WHat is the gauge factor?

Answer 7

Gf = P + 1 + 2v
P is the piezoresistive coefficient and v is the Poisson’s ratio

Question 8

How do temperature changes introduce errors to strain gauge measurements?

Answer 8

• Affecting the strain gauge resistance
• Affecting the connecting wries resistance

Question 9

How can you quantify the resistance change with temperature?

Answer 9

ΔR/R = αΔT
where α is the temp coefficient of resistance

Question 10

What are the two reasons for a gauge resistance change with equations

Answer 10

• An induced mechanical strain which is the true value to be measured, ΔR/R= Gf ε
• A change in temperature, not desirable, so ΔR/R = αΔT, will be a measurement error

Question 11

What can be used to measure ΔV only and therefore ΔR

Answer 11

A wheatstone bridge