Originally Published MPMN October 2005
Originally Published MPMN October 2005
SPOTLIGHTSpotlight on Sensors and Transducers
A transducer incorporates a flexible cable, a spring-loaded spool, and a potentiometer to detect and measure linear position. With a measurement range of 4.75, 12.5, 25, or 50 in., the SP1 string pot is suited for restricted space installations. Most common usages of this model are on medical beds, surgical tables, and robotic surgical machines. The cable-extension transducer features a polycarbonate enclosure, an operating temperature range of -40° to 200°F, a vibration specification of up to 10 G to 2000 Hz maximum, and a voltage divider output signal.
Celesco Transducer Products, Chatsworth, CA
Magnetic position sensor
An omnipolar, magnetic position sensor detects position displacements to tenths of a millimeter. The sensor measures very weak magnetic fields of typically 15 gauss, allowing for longer sensing distances. The sensor operates with a supply voltage of 3.8 to 30 V dc, a supply current of 11 mA, and a maximum output current of 20 mA. The housing has been designed to provide high resistance to mechanical stress.
Gentech, Ayrshire, Scotland, UK
A series of miniature linear variable differential transformers (LVDTs) for position measurement is designed for tight space restrictions and for applications having high dynamic response requirements. The CD375 series offers a 50% larger core-to-bore radial clearance than similar-sized competitor's units, and features good repeatability, high resolution, and high sensitivity with a maximum linearity error of ±0.25% FRO. The units are protected from environmentally hostile conditions by stainless-steel housings and epoxy encapsulation, and can withstand extreme temperatures of -65° to 225°F.
Macro Sensors, Pennsauken, NJ
A glass-encapsulated thermistor provides an extensive temperature range, a hermetic seal, and long-term stability. The nonthermal coupling thermistor is designed for interchangeable tolerances and operates from -55° to 300°C. The glass beads can withstand harsh environmental conditions and virtually eliminate the issue of moisture-related failure.
Quality Thermistor Inc., Boise, ID
Rotary position sensors
Noncontacting rotary position sensors provide analog, pulse-width modulation, and control outputs. The company's RSC2200 line provides 360° absolute angle measurements with 12-bit resolution. Owing to a microprocessor incorporated into the sensor, the output characteristic curve can be preprogrammed to a customer's specifications. Outputs are proportional to the rotary position of the shaft and include 4 to 20 mA, 0 to 10 V, or 0.5 to 4.5 V analog, as well as digital pulse-width modulation. Key specifications include resolution to ±0.09°C, accuracy to ±0.35°, and a service lifetime of more than 350 million operations.
Novotechnik, Southborough, MA
A three-axis, low-gravity microelectromechanical systems-based sensor is a single-chip device that detects in three dimensions. This capability enables portable devices to intelligently respond to alterations in position, orientation, and movement. The MMA7260Q is also equipped with a g-select feature that ranges from 1.5 to 6 g. This option gives designers the flexibility to select the g-force detection for specific application needs.
Freescale, Phoenix, AZ
Miniature pressure sensors
A line of industrial miniature pressure sensors services medical devices and regulating systems. Available in sizes 0.5 mm and larger, the sensors measure the kinematical behavior of both solids and fluids in miniature medical applications. Custom applications include multiple arrays of single pressure sensors and miniature probes with sensor tips.
RL Instruments, Manchaug, MA
A company offers pulse-type ultrasonic sensors for the noninvasive monitoring of fluids flowing through tubing to determine if air or air bubbles have entered the line. Pre-engineered or custom-designed sensors are available for a range of tubing sizes, fluid types, and applications. Use of these sensors does not contaminate the fluids being monitored. Air bubble sensors are designed with microprocessor-based circuitry and mounted internally within the sensor assembly.
Introtek International, Edgewood, NY
Fiber-optic pressure sensor
A miniature fiber-optic pressure sensor and a temperature sensor are suitable for applications requiring high accuracy and small size. The OPP-M pressure sensor can be used for in vivo blood, intrauterine, and intracranial pressure measurement applications, while the OTP-M temperature sensor is designed for the MRI and electrosurgery environment. The temperature sensor has a resolution of 0.01°C and an accuracy of ±0.1°C. These products are tolerant to cable bending and deliver high-fidelity and artifact-free measurements in high-level EMI and RFI environments.
Opsens, Sainte Foy, QC, Canada
Bidirectional current transducers
A series of bidirectional current transducers follow ac and dc waveforms in the range of dc to 350 kHz. The transducers are compact and lightweight, and can be powered by any dc voltage within the range of 10 to 34 V, eliminating the need for a negative power source. In addition, the units consume 80 to 270 mW during operation and their input power connections can withstand a ±60-V transient power surge.
American Aerospace Controls, Farmingdale, NY
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