Microsoft PowerPoint - SL60 Liquid Level MeasurementExperimental Setup
• Two transparent tanks with a central spillway, one (right) a reservoir the other (left) a transducer chamber in which all the measurements are made
• Each tank has a variable speed pump which may be used to transfer the fluid in that tank to the other, thereby controlling the actual level of liquid
• A calibrated scale mounted on the front of the tanks enables liquid levels to be measured
• For level measurement – capacitance and pressure
• For level sensing and maximum/minimum level control – conductance
Level Detection
• Hydrostatic
– the hydrostatic pressure difference between the top and bottom of a column of liquid is related to the density of the liquid and the height of the column
• Capacitive
– the capacitance changes with a change in fluid level, because all common liquids have a dielectric constant higher than that of air
• Ultrasonic / Optical
– the transit time is proportional to the distance between the liquid surface and the transmitter
Capacitance Probe • The total capacitance of the coaxial sensor is
• If the water is at or below the level h0, the capacitance remains constant
Experiments
– Part B