Lecture 2 Info

Question 1

Temperature dependence of resistance

Answer 1

• R20 is the resistance at 20 Celsius
• a20 is the temp coefieencet of resistance at 20 celsius

Question 2

What is equation for temperature sensing

Answer 2

Question 3

Wheatstone Bridge

Answer 3

Divided “bridge” circuit used to measure static or dynamic electrical resistance
Can be used to accurately measure unknown resistance -> very low values down to m(Ω) range
Produces zero voltage difference between the two parallel branches (nodes C - D) when balanced

Question 4

Wheatstone Bridge for strain gauges

Answer 4

• Single-strain-gauge configuration
• • > variable strain sensor resistance R4 = Rg
• • > other arms are fixed value resistors
• Output voltage of the circuit (Vout)
• • > equivalent to total strain
• • > voltage drop across R2 and Rg

Question 5

Wheatstone Bridge for strain gauges. Why do we use Wheatstone to measure strain?

Answer 5

• capable of measuring the minute changes in resistance corresponding to strain
• Small delta R will throw the bridge out of balance, making it good for detection of strain
• When Rg is the only active strain gauge, the strain measurement is related to the change in Rg

equation:

Question 6

Hw review:

Answer 6

With the strain gauge, it being set to a 100, and having the gauge factor being 2, is what creates that unbalance, as the top voltage display has a slightly less value than 5 while the bottom voltage display has a slightly higher value than 5. It is trying to have the balance, but because of the uniform random number and the gauge factor difference

It is interesting to see the concept of this wheatstone bridge, and how there is this slight imbalance, and what makes this imbalance being the strain gauge.

The inverse relation of graphs was due to the orientation of the Vout voltage sensor, which can be seen in the images and even though in the second graph image, the Vout and Rg are similar graphing, the difference in the vertical axis demonstrates the fact that Vout will be smaller due to the slight difference between the resistors.

Question 7

What is Wheatstone bridge like actually

Answer 7

A simple circuit used to measure an unknown resistance by comparing it to known resistances.