above or below the sensing point. Generally the latter detect levels that are excessively high or low.
There are many physical and application variables that affect the selection of the optimal level monitoring method
for industrial and commercial processes. The selection criteria include the physical: phase (liquid, solid or slurry),
temperature, pressure or vacuum, chemistry, dielectric constant of medium, density (specific gravity) of medium,
agitation (action), acoustical or electrical noise, vibration, mechanical shock, tank or bin size and shape. Also
important are the application constraints: price, accuracy, appearance, response rate, ease of calibration or
programming, physical size and mounting of the instrument, monitoring or control of continuous or discrete (point) levels.