A transducer is essentially a device that converts some form of energy into another form. Common types of transducers used in industrial applications can include sensors used to measure temperature, pressure, force, strain, liquid levels and flow rates, and electrical conductivity among others.
In motion control applications, transducers can refer to any one of a number of sensors such as rotary or linear encoders for position feedback, sensors such as tachometers for speed sensing, and even proximity switches to initiate or halt some machine action.
In applications using hydraulic motion control systems, pressure transducers are a key part of the control. Particularly in applications where pressure changes quickly, the pressure transducers need to respond quickly. Where pressure transducers are mounted can make a big difference in response times. It’s best to mount transducers as close as possible to the points of interest on the cylinder; the fluid flow is less turbulent in the larger areas of the cylinder, and there are no propagation delays as would be caused if pressure were measured in the tubing outside the cylinder.
Another common approach to measuring position in a motion system are magnetostrictive linear displacement transducers (MLDTs), which are typically mounted in the cylinders. MLDTs are best because they use moving magnets that don’t come in contact with the sensor tube, avoiding mechanical wear, and they provide an absolute position readout, requiring no homing step before beginning to work with the position information from the MLDT. Advances in MLDT technology have led to resolutions down to 1 μm, with fast signal processing of up to 1.5 MHz.
There are a few key factors to consider when selecting any transducer including the desired variable to be measured, the accuracy or resolution needed, the type of output, as well as any size or space restrictions, environmental factors, and product lifetime and cost.
For instance, if measuring rotary position, an encoder may be the best choice. A linear motion system may need a linear position transducer, so a rotary encoder may not be the best solution. Next, how accurate does the position data need to be?
Environmental conditions are another important consideration. The sensor/transducer should be able to withstand the environmental conditions of the application. Some of the most common environmental conditions to watch out for are EMI/RFI noise, shock and vibration disturbances, extreme heat or cold, and environmental contaminants such as dirt, dust, moisture, and corrosive chemicals.