Pressure Measurement

Course Number: 773

This course defines the units of pressure and discusses Boyle�s and Charles� laws to explain relationships among pressure, volume, and temperature. It describes sensor operation of manometers, bourdon tubes, diaphragms, and bellows. It explains the operation of potentiometric, capacitive, reluctive, servo, strain-gauge, and piezoelectric transducers. Devices used in low-pressure control are also covered. The course concludes with proper and safe methods for installing and servicing pressure instruments.

Recommended Contact Hours - 8

Chapter 1: Principles of Pressure in Liquids and Gases

Topics: Properties of matter; Units of pressure; Density; Specific gravity, Gauge, absolute, and atmospheric pressure; Pressure and flow

Learning Objectives:

• Compare the three forms of matter.
• Define pressure and explain the difference between gauge pressure and absolute pressure.
• Discuss the conditions that affect the pressure of a liquid.
• Describe how changes in volume affect the pressure of a gas at a constant temperature.
• Describe how changes in temperature affect the volume of a gas at constant pressure, and the pressure of a gas with a constant volume.
• Discuss the two causes of pressure drop in a pipe carrying liquid from a tank.

Chapter 2: Pressure Sensors

Topics: Manometers; Bourdon tubes; Diaphragm sensor construction and capsule elements; Bellows sensors; Maintaining accuracy; Calibration

Learning Objectives:

• Explain how a manometer works.
• Describe four kinds of bourdon-tube sensors.
• Discuss construction details of bourdon tubes, diaphragms, and bellows.
• Explain how bellows pressure sensors work.
• Describe how calibration may be accomplished and list the steps in calibrating a pressure gauge.
• Explain how normally open and normally closed pressure switches work.

Chapter 3: Pressure Transducers

Topics: Pressure conversion; Potentiometric pressure transducers; P/I, P/P, reluctive, servo, strain-gauge, and piezoelectric transducers; Response

Learning Objectives:

• Discuss the advantages and disadvantages of the potentiometric pressure transducer.
• Explain how a P/I transducer works.
• Describe the operation of capacitive, reluctive, and servo pressure transducers.
• Compare the three kinds of strain gauge pressure transducers.
• Describe the operation and advantages of the piezoelectric pressure transducer.
• Discuss three environmental conditions that can affect transducer operation.

Chapter 4: Low-Pressure Measurement

Topics: Low pressure; Methods of conversion; sP transmitters, Pressure, slack-diaphragm, ionization, McLeod, thermal conductivity, Pirani, and thermocouple gauges

Learning Objectives:

• Define the pressure unit torr and calculate pressure in specified units when given the pressure in other units.
• Explain the operation of a differential-pressure transmitter and a slack-diaphragm gauge.
• Name two kinds of ionization gauges and describe how they work.
• Explain how the McLeod gauge works.
• Describe the capacitance manometer.
• Compare the operation of the Pirani gauge and the thermocouple gauge.

Chapter 5: Installation and Service

Topics: Pressure transmitter components; Piping, connections, and fittings; Wiring; Guidelines for periodic maintenance; Calibration; Safety

Learning Objectives:

• List the components of a pressure-transmitter installation.
• Compare methods of joining pipes and other instrumentation components.
• Describe the procedure for placing a pressure instrument into service.
• Discuss the elements of periodic maintenance.
• Explain how to calibrate pressure instruments with electrical and pneumatic outputs.
• Describe three important techniques used in troubleshooting and repair.
• List five important safety rules.