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.