Sensors & transducers

Sensors & transducers

This past June saw both the opening of Sensors Expo and the market launch of the sensor-laden Apple iPhone. So it’s not surprising that there’s recently been a flood of sensor product announcements. The newly introduced sensors target a broad range of applications, but most prominent are those for use in consumer/automotive products and heavy industrial applications.

Motion and acceleration

Accelerometers are one type of sensor attracting a lot of attention in the consumer realm. Melexis USA (Concord, NH) introduced the MLX90333 3D Triaxis sensor to over come past problems with joystick operation. The Hall-effect IC can triangulate the location of a common magnet within 15 mm of the chip to give highly accurate and repeatable position information

The ADIS1635 Inertial Measurement Unit developed by Analog Devices (Norwood, MA) combines three axes of angular-rate sensing with three axes of acceleration sensing in a space of less than 0.75 in.3 . With dynamic ranges of ±300°/s and ±10 g, it has 50 times greater sensor accuracy than other off-the-shelf parts and 1/10 the cost of previous solutions.

Said to be the thinnest such devicethe MEMS-based MMA7450L tri-axial accelerometer from Freescale Semiconductor (Austin, TX) is packaged in an 0.8-mm-thick plastic LGA. With a digital output for easy interface to an MCU, the sensor targets handheld controls and appliances requiring motion, acceleration, or inclination sensing.

The MEMS-based model 40366 surface-mount accelerometer from Endevco (San Juan Capistrano, CA) is intended for implantable medical devices such as rate-responsive heart pacemakers and defibrillators. Hermetically sealed with a shear bond strength of 1 kg, it delivers repeatability of less than 0.035 pF in an SMT footprint of only 2.05 x 2.90 mm configured as a three-terminal half-bridge.

Endevco’s model 71 accelerometer

Kionix (Ithaca, NY) announced the availability of its highest-performing MEMS accelerometer, the KXR94 . It has appreciably less drift over temperature, low noise density of 50 µg/√Hz on all three axes, and can be programmed to a +/- 1-g range on all three axes for electronic compass tilt correction. Parts come in an industry-standard DFN plastic package measuring 5 x 5 x 1.2 mm with a digital SPI or multiplexed analog interface and an internal low pass filter on all three outputs.

The subminiature, high-shock, model 71 SMT piezoresistive accelerometer from Endevco (San Juan Capistrano, CA) has a small size and low mass that let it survive high-frequency shock pulses that can shatter other accelerometers. It is available in 6,000, 20,000 and 60,000-g measurement ranges with sensitivities of 30, 10 and 3 μV/g respectively.

The Inertial Measurement Unit (IMU) from Systron Donner Automotive (Moorpark, CA) can simultaneously detect both angular-rate and acceleration along multiple axes. It includes solid-state MEMS gyroscopes, accelerometers, a CAN interface, power conditioning, and microcontroller, configured to meet the sensing and packaging requirements of OEMs or Tier 1 suppliers.

Systron Donner’s Inertial Measurement Unit

The LIS244AL accelerometer is an ultra-compact ‘low-g’ dual-axis motion-sensing linear device from STMicroelectronics (Lexington, MA). The 4 x 4 x 1.5-mm device’s ultra-compact square footprint and low power consumption suit it for battery-powered portable applications, such as mobile phones, portable multimedia players or remote controls. The device incorporates both the dual-axis MEMS sensor and a CMOS interface chip to provide two simultaneous, real-time, low-noise analog outputs: one for lateral and one for longitudinal motion detection.

STMicroelectronics’ LIS244AL accelerometer

Bosch Sensortec (Reutlingen, Germany) and Nemerix (Manno, Switzerland) announced the integration of their technologies in a multi-sensing GPS solution . The system, which offers significantly enhanced results for navigating urban stacked road systems, multi-level bridges, and tunnels, integrates the high-resolution SMD500 pressure sensor with Nemerix’s high-accuracy navigation solution, offering the ability to identify if, say, a car is travelling on the upper or lower level of a stacked road.

Pressure, strain, and flow

The model 175A01 dynamic pressure sensor from PCB Piezotronics (Depew, NY) is designed for measuring dynamic combustion pressure in gasoline or diesel engines at high temperatures (to +600 °F/+315 °C) without cooling. It is available with a dynamic range to 4,000 psi, and sensitivity of 1.5 pC/psi with mounting adaptors for various engine types.

PCB Piezotronics’ model 175A01 dynamic pressure sensor

The miniature D6F-03 unidirectional MEMS mass flow sensor from Omron Electronic Components (Schaumburg, IL) is capable of measuring mass airflow to 3 lpm with a repeatable ±5% full-scale accuracy. The 16.8 x 8 x 36.6-mm, 5.27-g device uses a thermopile element to convert thermal energy into electrical energy, and suit pick-and-place systems, leak detector, mass flow controllers, test equipment, and fuel cells.

Omron Electronic Components’ D6F-03 unidirectional MEMS mass flow sensor

The AccuGauge AG200 series digital pressure gauges from American Sensor Technologies (Mt. Olive, NJ) is media-isolated and offers a 4 to 20-mA output and large LCD display able to give readouts in psi, bar, kg/cm, ATM, inches H2 0 and Hg. A Test button lets users evaluate the loop current to ensure the correct system setup and adjust the current in 2 mA. Factory set calibration points and output can be adjusted and the factory settings restored at any time.

American Sensor Technologies’ AccuGauge AG200 series digital pressure gauge

The digital RCE series pressure sensors from Sensortechnics (Walpole, MA) offer precision absolute, gage or differential measurement from ±10 mbar to 5 bar with accuracies up to ±1.0 %FS. The PCB-mountable devices comply with the SPI bus protocol, and specific custom outputs, I2C bus, analog or switching outputs can also be provided on request.

Fully compensated Sensilica AST pressure sensors use a 0.8 x 0.8 x 0.4-mm silicon MEMS piezoresistive pressure sensing die coupled with a compensation ASIC for interface and device calibration mounted in a TO-5 style package. Pre-calibrated for offset, sensitivity, temperature drift, and non-linearity, the devices can also be reconfigured by users for device calibration and output formats; options include either analog or pressure-only or pressure-and-temperature digital output formats.

The MEMS-based P992/P993 low-range differential pressure sensors made by Kavlico (Moorpark, CA) are suited for such HVAC energy-control applications as variable-air-volume systems, gaseous leak detection, pneumatic controls, and filter-pressure, duct-airflow, and static-pressure monitoring, as well as medical equipment. Available in pressure ranges of ±1 to 10 in. H2 0, the RoHS-compliant sensors have low power consumption, high output signal stability, and absolutely no position sensitivity.

Kavilco also released its Silicon- MEMS-based SmartSense sCAP3 ultra-low-power pressure sensors which allow continuous monitoring of tire pressure with up to a 5x faster response than previous devices. With an unpackaged footprint of just 1.2 x 1.5 mm, the sensor has 2.2 to 5-Vdc, 20-µA power needs compatible with wireless and battery applications.

The Bend Sensor developed by Flexpoint Sensor Systems (Draper, UT) reduces the dimensions of a typical deflection sensor systems by up to 90%. The resistance-based sensor has a life greater than 1 million cycles, a −35 to 85C range, and can provide resistance changes of more than 500% and resolution better than 1° change in angle.

Temperature and moisture

Suited for measurement of moisture in ultra-high purity gases used in a variety of semiconductor, LCD and other manufacturing processes, HygroTrace from GE Sensing (Billerica, MA) accurately and reliably measures 0 to 100-ppb moisture levels using an aluminum oxide technology with a newly patented technique that provides PPB moisture measurement in minutes. The UL508 certified device is 80-90% smaller than competitive analyzers by and costs 50-70% less.

The Foresight Series fiber-optic distributed strain and temperature sensors from OZ Optics (Ottawa, Canada) uses Brillouin scattering in optical fibers to measure changes simultaneously in both temperature and strain along the length of a standard, low-cost optical fiber. By wrapping or embedding a fiber inside a structure such as an oil pipeline dam, power lines, or security fence users can detect when the structure is being strained or heated/cooled use.

The DS75LX digital temperature sensor from Maxim Integrated Products (Sunnyvale, CA) allows up to 27 addresses on one I2C communication bus introduces. To enable 27 address combinations, the sensor provides three dedicated address pins that can be placed in one of three states: tied to GND, tied to VDD, or left floating.

The TC-LINK -6CH wireless thermocouple node from MicroStrain (Williston, VT) features six thermocouple channels, an embedded cold junction compensation sensor, a real-time clock, and, optionally, a relative humidity sensor. Its uses a 24 bit delta-sigma ADC, stores up to 300,000 data points, runs at a rate of 1 sample/min. monitoring all six channels, and can operate for more than ten years between battery changes.

Location and position

The Visi-Trak high resolution sensor from Visi-Trak Sensors (Charlottesville, VA) is based on a new technology that uses an encoded piston rod and non-contacting magnetic transducer that user design into hydraulic or pneumatic actuator. The sensor can sense linear position/motion in rugged environments at position resolutions better than 0.001 in. at speeds in excess of 200 in./s.

VisiTrak Sensors’ Visi-Trak high linear motion sensor

Designed to be embedded in welded and tie-rod style or any space-limited cylinder, the Temposonics MT magnetostrictive position sensor from MTS Sensors Division (Cary, NC) offers an additional level of inherent safety by providing full redundancy while eliminating signal crosstalk. Each of the dual measurement systems consists of a sensor element and evaluation electronics with separate output signal and supply voltage, and both sensor elements are housed in a standard-size, pressure-resistant, stainless steel pipe for direct stroke measurement in the cylinders.

MTS Sensors Division’s Temposonics MT magnetostrictive position sensor

For use in oil and gas exploration and production, as well as transportation, heavy equipment, and factory automation applications, the Positek X111 intrinsically safe linear variable inductive transducer position sensor is said to be most robust device of its kind in the 50 to 800-mm measurement range. Highly linear and offered in various mounting configurations, it is ATEX certified to EEX ia IIC TA standards (TA = -40º to +80 ºC), equivalent to US Class 1, Div 1, Groups B, C, D, and is available in the U.S. through Everight Precision Technologies (Penn Valley, PA)

Optics, acoustics, and force

The IM103 CMOS image sensor from Sensata Technologies (Attleboro, MA) is an automotive-grade device with a 120 db dynamic range that produces clear video in both visible and near-IR lighting, allowing automotive camera systems to see in both day and night driving conditions. The sensor is also available in the ACM100 automatic camera module with lens and on-board electronics for image processing, and the Vision Platform vision support software library is also offered.

Also aimed at automotive applications, the TCPT1300X01 and TCUT1300X01 950-nm SMT transmissive optical sensors from Vishay Intertechnology (Malvern, PA) have an AEC Q101 Moisture Sensitivity Level rating of 1 (MSL1), giving them an unlimited floor life. With a 3.0-mm gap width, the sensors can be used with a wide variety of materials and allow for looser mechanical tolerances than smaller-gap sensors.

Vishay Intertechnology’s automotive 950-nm optical sensors

The AKU2103 CMOS MEMS microphone from Akustica (Pittsburgh, PA) provides wider bandwidth capability than previous, standard-definition devices, and thus opens the door for high-definition (HD) voice quality in laptops and other broadband mobile devices. The digital device is the first to guarantee compliance with the latest voice-quality requirement for applications such as VoIP.

The RoHS-compliant, Microsoft Windows-compatible TSM9915 capacitive touchpad. from Cirque (Salt Lake City, UT) offers a compact, 48 x 32.5-mm design with a PS2-compliant interface suiting applications in point-of-sale keyboards and remote controls. The unit employs the patented GlidePoint technology.

The ML17 Tru-Vue series photoelectric sensors from Pepperl+Fuchs (Twinsburg, OH) are compact (29-mm deep) with a typical sensing range of over 100 mm for diffuse fiber optic cables and 400 mm for thru-beam fiber optic cables. They offer 360° visibility LEDs, five connection options, and 4-in-1 outputs, which enable a single sensor to operate in NPN normally open, NPN normally closed, PNP normally open, or PNP normally closed configurations to ease sensor selection and stocking.

Pepperl+Fuchs’ ML17 Tru-Vue series photoelectric sensor

The AMRS-2325 mobile navigation pad module and AMRI-1000 mobile navigation sense and interface IC have been combined by Avago Technologies (San Jose, CA) to provide a mouse-like pointing solution for use in a wide range of handheld and gaming devices, computer peripherals, and remote controls for set-top box and multi-media PC applications. Based on embedded capacitive sense technology, the input device incorporates a five-way rocker switch with scrollwheel emulation, mouse, and joystick (2D) navigation.

Avago Technologies’ mobile navigation pad/sense/interface module

The iLoad digital load sensor from Loadstar Sensors (Mountainview, CA) uses capacitive sensing to provide measurements up to 10, 50, 100, 250, or 500 lb directly into the USB port of a PC without need for any additional signal conditioning, data acquisition, or special software. Accuracies range from 0.25% to 0.025% FS, temperature compensation schemes are built-in, and models with higher capacitiesup to 15,000 lbare expected to be released in the coming months.

Able to detect presence, proximity, level, volume, and distance in ranges from 4 in. to 18 ft depending on model, the RPS-409A-IS intrinsically safe ultrasonic sensors are UL listed for use in Class I to III, Division I, hazardous locations. They need no setup adjustments or calibration.

The 16-key QT60160 and 24-key QT60240 touch sensor chips from Quantum Research Group (Southhampton U.K.) sense the touch of a finger through panels of any electrically insulating material up to about 50 mm thick. Each sensor can be tuned for sensitivity, response time, and other parameters via its I2C interface.

The MPR081 16-position rotary touch-wheel and MPR082 20-touchpad proximity capacitive sensor controllers from Freescale Semiconductor (Austin, TX) have proprietary false-touch-rejection technology to provide consumers with high reliability. They provide digital output in the form of I2C with custom addressing.

Sensor enhancement

The Atlas model 00ACMZB generic hardware/software interface from Pervasa (Gainesville, FL) simplifies sensor-enterprise integration by providing a complete software representation of any kind of sensor hardware’s capability. This capability lets engineers use software to access and implement the sensor’s functionality in existing and new applications.

Used for packaging sensors, Vectra liquid-crystal polymer from Ticona (Florence, KY) withstands short-term exposure to 340ºC during surface-mount and Pb-free soldering, and can withstand continuous temperatures as high as 240ºC. It is said to absorb no moisture, have excellent chemical resistance, undergoes little thermal expansion, like FR4 and silicon, and serves well as an encapsulation material.

Microchip Technology’s dsPIC33FJ12GP smart sensor controller chip

The dsPIC33FJ12GP family of digital signal controllers from Microchip Technology (Chandler, AZ) were developed for smart sensor applications. The controller’s 6 x6-mm footprint allows it to be located close to the sensor to reduce communication-induced noise while offloading the system’s CPU and the unit’s price of $1.99 ea/10,000 makes it easily affordable in many applications. ■

Richard Comerford