What is a Transducer?

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.

Linear Cable Transducer from BEI Industrial Encoders

BEI Industrial Encoders’ new linear cable transducer provides digital position and speed feedback information in a rugged, easy-to-install package. Model LT25 cable transducer utilizes a flexible measuring cable mounted to an internal spring-loaded spool and a quadrature encoder output to precisely measure linear motion applications. The sturdy cable is made of nylon coated stainless steel for ultimate strength and has a measurement range up to 125 inches.

Easy to install, simply connect the LT25 cable to your moving equipment and secure the base to a fixed object. Hard to reach areas or worries about shaft misalignment are now not a problem. The LT25 cable transducer allows for easy reorientation of the mounting bracket or encoder connector position, giving users added adaptability to their installation. With an IP66 rating, the LT25 is a perfect solution for a variety of industrial measurement challenges including wet, dirty, or outdoor environments or applications where your measuring range travels over a harsh environment.

BEI Industrial Encoders
www.beiied.com/cable-transducer

Curtiss-Wright Awarded Contract for Helicopter Programs

PARSIPPANY, N.J. — Curtiss-Wright Corporation (NYSE: CW) announced that it has received a contract from Claverham Limited to provide transducers for use in the fly-by-wire systems that control the main rotor and tail rotor on the Sikorsky UH-60M Upgrade and CH-53K helicopters. The contract has a potential value in excess of $20 million over a 15-year period with shipments expected to begin in 2009. The company will supply these products from its Motion Control facility in Christchurch, UK.

Curtiss-Wright is a leading supplier of linear displacement transducers, rotary displacement transducers and solenoids for fixed and rotary wing aircraft operating in commercial and defense applications. Under the terms of this award, Curtiss-Wright will supply multi-channel and pressure sealed linear variable displacement transducers (LVDTs) for use on the U.S. Army’s helicopter programs. The LVDTs are embedded in the primary flight control actuators manufactured by Claverham Limited, a Hamilton Sundstrand Flight Systems business unit. The transducers provide electrical signals that are proportional to the position of the hydraulic actuator rod. The actuators form part of the fly-by-wire control system, which changes the rotor pitch angles on the main and tail rotors in response to the pilot’s commands during flight.

The UH-60M BLACK HAWK helicopter has become an integral part of the U.S. Army’s command and control system, providing brigade commanders with real time digital situational awareness and command and control options. The CH-53K helicopter is expected to replace the Sikorsky CH-53E, which is the largest and heaviest helicopter in the United States military. The Marine Corps currently deploys the CH-53E from amphibious assault ships to transport personnel and equipment, and to carry external cargo loads.

www.curtisswright.com