Mechanical level switches are distinct from non-mechanical utilities like ultrasonic level sensors, optical level switches and capacitance level sensors in that they are always meant to make direct, physical contact with the materials they are used to measure.
There are many different mechanical level switch varieties. For example, float level switches, which are used primarily to measure liquid levels in storage enclosures, involve buoyant bulbs that raise and lower based on material levels. Paddle or rotary level switches transmit information about material levels when their rotation is interrupted by contact with the materials they measure.
Such systems are simple, accurate tools that can be used in all kinds of contexts. Float level switches are widely used in wastewater treatment plants, agricultural settings, in fuel and other chemical storage systems in many other settings. Rotary and paddle level switches are employed in grain silos, road salt storage systems and in many other contexts in which bulk granular solids are stored. Displacer level switches are also mechanical, and they can be applied in a wide range of contexts.
All level control utilities, mechanical and non-mechanical, can be used for level sensing or for both sensing and control. The simplest level sensors only detect and report levels in an enclosure or transmission system. For example, a simple float level switch may involve only a moving part that changes position as it comes into contact with rising materials; if sufficiently displaced, the circuit in the switch closes, indicating that the material level has reached a certain point.
The same can be true of other simple mechanical level switches like paddle and rotary switches. More complicated systems involve both reporting equipment and control equipment. Once a level is measured in such systems, a signal can be sent to control equipment that prevents the level from rising further. Such systems are very valuable in liquid enclosures, because they can prevent overfilling or other problems. Mechanical level switches offer a few advantages over non-mechanical switches.
In terms of design and construction, they are often much simpler, which means that they can be less expensive and easier to replace. That said, non-mechanical level switches, which are usually not intended to come into direct contact with the materials they measure, are less likely to become damaged or degraded by the materials they measure precisely because they are isolated from them.