How to Size and Select a Transducer for Motion Control

A transducer is any device that converts one form of energy into another. It’s also defined as a device that converts a non-electrical quantity into a proportional electrical quantity. Transducers can be used to sense a wide range of different energy forms such as movement, electrical signals, radiant energy, thermal or magnetic energy etc, and there are many different types of both analog and digital input and output devices available.

Transducers for motion control applications come in various types and the choices available depend upon the quantity being measured or controlled. For motion control applications, typically the measured variable is position. Depending on a number of factors, the right transducer may be an encoder or a resolver or a simple potentiometer.

Before deciding on which type of transducer to select, here are some of the most important questions to ask.

For starters, what kind of motion is involved, rotary or linear? Specific transducer types exist for each kind of motion. For instance, there are rotary and linear encoders as well as highly accurate non-contact magnetic encoders for linear motion.

Next, determine the desired accuracy needed. This includes factors such as linearity, resolution, and repeatability. Generally speaking, the greater the accuracy, the more expensive the transducer. This is why knowing the needed accuracy can help you select the best type of transducer and lower the design costs by not paying for more resolution than the application needs.

Along those lines, what range must the transducer measure? For linear applications, is the range a few millimeters or inches or several feet? For rotary applications, if measured in degrees, is the angular distance more or less than 360 degrees? In other words, is the type of encoder needed a single turn or multi-turn device? Also, if selecting an encoder, does it need to be absolute or incremental?

Consider the type of output. Is it voltage or current? Digital or analog? This might also depend on the type of input the controller or drive accepts, or the type of network connection available.

Other considerations may include any physical size or weight restrictions or special installation or mounting requirements. Also, there may be special environmental protection needed depending on conditions such as temperature, humidity, moisture, vibration, or the presence of any corrosive substances.