Lesson 1 - Principles of Level Measurement


Surface-sensing and storage tank gauges; Sight glasses; Magnetic and displacer gauges; Buoyancy; Level, mercury, and magnetic reed switches; Switches with multiple displacers

Learning Objectives:
– Define datum point, and contrast direct and indirect level measurement.
– Describe the main kinds of surface-sensing gauges.
– Define buoyant force and explain how it is used in displacer gauges to measure liquid level.
– Describe maintenance procedures for float devices, displacer gauges, and sight glasses.
– Compare the use of sight glasses, mercury level switches, and magnetic reed switches.

Lesson 2 - Electrical Instruments


Conductivity and liquid level; Capacitance probes; Zero and span adjustments; Ultrasonic, resistance, and photoelectric level detectors

Learning Objectives:
– Differentiate between continuous and point level measurements, and between direct and indirect level measurement.
– Describe the operation of a conductance probe in a conducting liquid.
– Describe the operation of a capacitance probe in a dielectric liquid.
– Explain the operation of ultrasonic, resistance, and photoelectric level sensors.
– Describe conductance point level probes, capacitance point level probes, and ultrasonic point level detectors.

Lesson 3 - Pressure Head Instruments


Hydrostatic pressure; Relative density; Pressurized fluids; Air bellows; Air/liquid purge systems; Force-balance diaphragm system

Learning Objectives:
– Define hydrostatic pressure and explain how it is calculated by means of the relative density (specific gravity) of a liquid in a tank.
– Discuss the relationship between pressure head and the location of the pressure (level) indicator.
– Compare the air bellows and air purge systems and discuss advantages for each.
– Explain how a force-balance diaphragm system works.
– Describe the operation of a differential pressure transmitter and explain how it is used to measure level and density.

Lesson 4 - Solid Level Measurement


Weight method; Ultrasonic, microwave, and radiation level detectors; Capacitance and resistance probes; Bob-and-cable tension method

Learning Objectives:
– List the data needed to compute the level of a bulk solid in a bin.
– Describe and compare the operation of wire strain gauges and semiconductor strain gauges.
– Compare the advantages and disadvantages of ultrasonic and microwave level measuring methods.
– Discuss the operation of capacitance probes, resistance probes, and bob-and-cable units in measuring bulk solids.
– Describe how diaphragm switches and tilt switches are used for point level detection in automatic bin fillers.
– Discuss the use of rotating paddle detectors in controlling level within a band.

Lesson 5 - Other Level Measurement Instruments


Radiation level detectors; Ionization, semiconductor, and photoelectric radiation sensors; Infrared detectors; Interface levels

Learning Objectives:
– Explain how radiation level detectors are used for both continuous and point level measurement.
– Describe the operation of ionization radiation sensors, semiconductor radiation sensors, and scintillation counters.
– Discuss the operation of an infrared point level detector.
– Describe several methods of measuring interface levels.
– Explain how range suppression and range elevation are used.
– Discuss the important considerations in equipment selection.