What are linear displacement transducers?

"Transducers" are devices that convert one form of energy into another. There are many different transducer types, converting many different forms of energy. One common example would be a microphone, which converts sound waves into an electrical signal for transmission to some type of signal amplifier. (Conversely, another example could be the speaker that receives that amplified signal, and converts it back into sound waves again.) Heat, strain, vibration, and pressure are other examples of energy that can be converted into various output signals.

"Displacement" refers to how the transducer receives or measures "input information" through various forms of motion. Stretching, flexing, shaking, and pressures are examples of these motions.

"Linear" refers to the design of a transducer, in that it receives information from a source in a linear, or straight, direction.

So, a Linear Displacement Transducer is a device that takes some form of input energy fed to it in a straight line, and outputs a converted signal relative to the range of displacement that has taken place. (If you know what a "potentiometer" is, think of a Linear Displacement Transducer as a potentiometer that moves in and out rather than rotates left and right.)