Module 7 - Pressure & Temp Measurement

Question 1

What are the five types of pressure measurement instruments and what are examples of each?

Answer 1

1. Gravity-fed: manometers, deadweight testers
2. Elastic deformation: Bourdon tube, transducer
3. Gas behaviour: pirani gauge
4. Electric output: magnetic inductance pressure transducer
5. Luminescent coating: PSP

Question 2

What are the different types of pressures and their definitions?

Answer 2

Absolute: pressure relative to a vacuum
Gauge: pressure relative to atmospheric
Stagnation: pressure of fluid brought to rest stoically
Dynamic pressure: component of pressure representing kinetic energy

Question 3

How does a Bourdon tube measure air pressure?

Answer 3

Air travels into the Bourdon tube (flattened hollow tube), which is then deflected outwards. This deflection is proportional to the air pressure, which can be read using a pointer attached to the tube

Question 4

What are common sources of errors in manometers?

Answer 4

• Fluid meniscus: changes in the meniscus, where it’s read from, debris
• Variation of fluid density: temperature changes can result in different fluid density

Question 5

What are different reference standards that can be used to calibrate a device?

Answer 5

• phase change points (ie boiling, melting)
• international reference standards (ie temp-k relationship of platinum)

Question 6

What are some ways of improving the response time of a sensor?

Answer 6

• increase surface area or HT coefficient
• decrease volume or specific heat

Question 7

What is the Seebeck effect?

Answer 7

Phenomenon where any electrical conductor will develop a voltage between two points if there is a temperature difference between the junctions which is proportional to the temperature difference