Transducers convert energy from one form to another in order to measure a physical quantity or for information transfer. This broad definition includes microphones, thermometers and position and pressure sensors.

In ultrasonic testing, the transducer converts electrical pulses into sound waves while the ultrasonic test instrument generates the initial electric pulse to the transducer and electronically processes the received pulses from the transducer. The transducer is the ear of the system, with a piezoelectric element that transforms electrical pulses into high-frequency sound and vice versa. The most commonly used resonant frequencies are 1, 2.25, 5, 10 and 15 MHz, and the transducer’s resonant frequency may be between 100 kHz and 100 MHz. In addition to the frequency, damping of a transducer is key to its performance, with narrow-band transducers offering more efficiency, but moderate depth resolution. Conversely, broad-band transducers have optimum depth resolution but lower efficiency, with efficiency referring to its ability to convert electrical energy to mechanical energy and back.

Several different types of transducers are commonly used today, including contact, delay-line, dual, angle beam, immersion and multielement. Transducers can be electrical, electronic or electro-mechanical, as seen with this range of products. This technology review highlights several different types of equipment, allowing quality professionals to consider which product works best for their application.

The Etamic Movomatic (www.etamic.com) TPE99 transducer uses subsonic air flow, through one or more air jets, to acquire pressure variations that are converted into analog signals and displayed as an analog or digital measurement. A single filter/regulator can supply multiple banks of TPE99 converters, providing accurate repeatable measurements even with repeated downtime between cycles. This can represent significant cost savings as well as noise reduction for the customer, as the TPE99 can actually be shut down between measurement cycles. It has noncontact measurement, high resolution-0.00001 millimeter-response times down to 50 milliseconds, measuring range up to 0.24 millimeter. Linearity is 0.5% to 1.25% of the air tooling measurement range and supply voltage is 15 to 24 volts. It also has a 4/20 milliamperes electrical output signal, and temperature operation between 5 and 50 C. Modular construction allows multiple banks of up to 8 converters to operate off a single filter regulator. It is Nema 12 certified, with simultaneous and sequential measurements of multiple features or parts. It is used for static and dynamic measurement of geometric tolerances such as diameters, straightness, flatness, circularity, cylindricity, profile, angularity, squareness, parallelism, position, concentricity, symmetry, roundness, runout, taper, ovality, out of round and match.

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Accurate Technology (www.proscale.com) introduces ProScale Zigbee RF. The ProScale Zigbee RF system is designed to simplify the installation of ProScale linear measuring systems in applications and environments where long encoder-to-readout cables are difficult to use. Instead of a long cable between the encoder and the digital readout, a transmitter at the encoder sends data to a receiver connected to the digital readout at a remote location. The transmitter is powered by a single lithium battery and will provide power for about six months. The ProScale Zigbee system uses the 2.4GHz radio spectrum, and 16 channels are available for operation. Multiple ProScale Zigbee systems can be used on a single RF channel without interference; typical range for the RF system is 75 to 100 feet, depending on the operating environment. The ProScale Zigbee RF system is backward-compatible with all Accurate Technology ProScale measuring systems. It requires no modification to the measuring system and is completely transparent to the operator during normal measuring operations.

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A range of phased array ultrasonic immersion transducers, matched for use with the company’s phased array flaw detection equipment, is available from GE Inspection Technologies (www.ge.com/inspectiontechnologies). The transducers can be supplied in flat and curved configurations and applications throughout the power-generation, oil and gas, aerospace, automotive and general engineering sectors. Phased array transducers are essentially multi-element probes, where groups of elements can be individually computer-controlled. In this way, the small wavefronts created can be time-delayed and synchronized for phase and amplitude such that a focused, steerable beam is produced. As a result, a single phased array probe can perform those inspection tasks normally requiring large numbers of conventional probes or multiple scanning passes. This means that inspections are faster, probability of flaw detection is increased, inspection equipment is more flexible as set-up changeover can be achieved very quickly and there is no need to carry different sets of probes for different inspection tasks. In addition, the real-time, sector scan imaging of phased array provides an integrated, cross-sectional, easy-to-understand visualization of any area or component under inspection. This helps ultrasound to distinguish echoes from acceptable geometry and unacceptable reflections. The phased array immersion probes offer frequencies from 1 MHz to 10 MHz and can have 32, 64 or 128 elements. They complement GE’s existing range of linear angle beam phased array probes, which are available with frequencies up to 7.5 MHz, with 16, 32, 64 or 128 elements.

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Rotating torque transducers from PCB Piezotronics Inc. (www.pcb.com) use noncontact rotary transformers for sending excitation voltage to, and receiving measurement signals from, the strain gage instrumented rotating sensor element. The rotary transformer design eliminates the need for replacing worn brushes, as is the case with conventional slip-ring type rotating torque sensors. Because their flange and splined shaft design conform to AND 10262 and 20002, the units can be used in torque studies on cantilevered aerospace hydraulic motors and pumps. Other applications include dynamometers for combustion engines, drive shafts, transmissions, fans and electric motors. In addition to the torque output signal, an optical pickup provides an output proportional to speed and an optional K type thermal couple to monitor internal bearing temperature. The units have high torsional stiffness and low rotating inertia. Custom designed units are available for alternate measurement ranges and speeds.

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Ono Sokki Technology Inc. (www.onosokki.net) introduces the compact and lightweight GS-7710 linear gage sensor that can be installed in current production equipment and existing fixtures. This compact gage is designed to fit in tight spaces. This gage meets IP-67 protection standards, meaning it is capable of submersion in a tank of water at a depth of 1 meter for 30 minutes. This gage was designed to measure dimensions, thickness, curvature, eccentricity, displacement, height, depth, flatness, variation, runout, roundness, distortion, deflection and position.

This gage sensor uses linear glass scale technology. The main advantage of this principle is that operators can maintain high, consistent accuracy throughout its entire range. The GS-7710 produces measurements to 0.00004 inch, and throughout its 10-millimeter measuring range. Also, a dust bellow is provided for extra protection to enable accurate measurements in a harsher environment. Endurance testing shows this sensor may be used beyond 5 million strokes. The GS-7710 comes equipped with an attached six-foot signal cable that can be directly connected to an array of remote displays with various outputs. The outputs are not only compatible with PCs, but with many SPC data acquisition systems on today’s market. If operators require more than the standard 6-foot cable length, they may easily add on extension cables up to 100 feet.

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