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Sensors toughen up for industrial use

Posted: 16 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:image sensors? CMOS? MEMS? FPGA? temperature sensor?

While there has been a lot of discussion recently about the CMOS and CCD image sensors used in mobile devices, there's a plethora of sensor types that are used in other applications, including industrial-based systems such as heating, ventilation and air conditioning (HVAC), motion control, hydraulic systems and robotics.

These sensors perform any number of measurements, including acceleration, pressure, torque, temperature, position, flow and level. Precision measurements are often a key requirement for industrial-type applications, as are a device's size and its ability to withstand harsh environments.

It's interesting to note that the devices being used in industrial applications are designed and manufactured not only by sensor specialists such as American Sensor Technologies Inc. (AST), Macro Sensors and MTS Sensors, but also by semiconductor companies such as Analog Devices Inc., Dallas Semiconductor, Maxim Integrated Products and Texas Instruments Inc.

The U.S. market for industrial sensors is expected to reach $2.6 billion in 2010, up from $2.2 billion in 2005, according to market researcher Freedonia Group Inc. Industrial sensors account for about 21 percent of the total U.S. sensor market.

Key growth areas, according to Freedonia, will be advanced proximity and positioning sensors, optical chemical sensors, CMOS devices and thermal imaging sensors, as well as those using advanced technologies such as MEMS.

MEMS advances
Omron Electronics has developed a cyclone-type MEMS flow sensor that detects minute flow rates with high sensitivity even in dusty environments, thanks to its dust segregation system (DSS).

Though aimed at flow-rate control in air conditioners for homes and offices, the bidirectional flow-sensing device can also be used in measuring devices, medical products and semiconductor equipment. The D6F-P is about 50 percent smaller than its predecessor in the Omron line.

Another MEMS-based sensor comes from ADI. The company has leveraged its iMEMS motion signal-processing technology to develop an industrial device for motion analysis and navigational dead-reckoning functions that were previously reserved for defense, aerospace and other high-end applications.

The ADIS16355 inertial measurement unit (IMU) detects tiny shifts in linear acceleration and angular movement, according to ADI.

In addition to navigation, the ADIS16355 multiple-axis motion sensor can be used in highly sensitive robotic and other motion-control devices, where the IMU helps ensure that precision movements can be accurately repeated thousands of times, according to the company.

Meanwhile, TI says that its TMP421 and TMP422 temperature sensors are the industry's smallest remote junction temperature sensors with a built-in local temperature sensor. The single-remote channel TMP421 and dual-remote channel TMP422 both deliver remote sensor accuracy of 1C (maximum) and a local temperature sensor range of 1.5C (maximum).

Other benefits of the TMP421 and TMP422 include a two-wire/SMBus serial interface and multiple addresses. The devices are said to be suitable for a range of applications such as telecommunications equipment, industrial controllers, processor and FPGA temperature monitoring, and SANs.

Similarly, Maxim has introduced a low-voltage digital temperature sensor that allows up to 27 addresses on one I?C communication bus. Maxim's DS75LX, which operates from a low 1.7V to 3.7V supply voltage, is factory calibrated to an accuracy of 2C maximum over its entire supply voltage range and its wide temperature range of -25C to 100C. It is accurate to 3C (max.) over its full operating temperature range of -55C to 125C.

Dallas Semi, for its part, offers the DS28EA00, a one-wire digital temperature sensor with 0.5C accuracy and a chain-mode signaling and protocol feature that automatically determines the physical location of individual sensors in an environment where multiple sensors are connected to a common one-wire line.

MTS Systems' modular ML sensor is available in a range of housing materials to accommodate applications in a variety of fluids used in heavy production equipment.

Typical applications for the Dallas Semi sensor include rack-based equipment such as wireless base stations, central-office switches, enterprise servers and HVAC and process monitoring. The device is available in an 8-pin microSOP package.

Locking out contaminants
For heavy-duty applications, MTS Systems Corp.'s Sensors Division has released the GT and ML sensors. Offering maximum safety in critical applications, the GT sensora redundant version of the G-Series Temposonics sensorsmeasures critical variables with two or three independent and identical measurement systems that can be switched on individually in a single sensor housing.

The GT sensor is said to be suitable for measurement of linear movements in drives and fluid cylinders or in machine operation. Earlier this year, MTS announced a heavy-duty liquid-level sensor for production equipment. The ML sensors are available with stainless steel or plastic housings, or as an embeddable core sensor to accommodate applications in a variety of fluids that are part of heavy production equipment, including hydraulic oil and cooling water, according to the company.

For pressure measurement, AST has enhanced its line of HVAC/R pressure products with thermal flash protection. The feature lets the devices operate in HVAC and refrigeration environments that contain ammonia, according to the company.

The AST HVAC/R pressure sensors feature one-piece stainless-steel construction that contains no internal seals or gaskets, eliminating the chance of permeation, system contamination or freezing in HVAC and refrigeration applications, the company said.

AST also introduced a miniature stainless-steel pressure sensor for pressure measurement in confined areas. The pressure sensor may be used in a range of applications, including hydraulic systems, test stands, HVAC/R, panel builders and automotive systems, as well as in industrial and agricultural equipment.

ADI's ADIS16355 is a multi-axis motion sensor that combines gyroscopes and accelerometers to measure all six degrees of mechanical freedom--linear motion in the X, Y and Z axes, and rotation around the three axes.

The Model AST4800 features a one-piece stainless-steel sensing element that is free of silicone oil, welds or O-rings, thus eliminating the chance of contamination from outside media, AST said. The pressure sensor features high-strength stainless-steel construction that is said to be highly compatible with a range of liquids and gases.

The GHSE/GHSER 750 Series 24V spring-loaded position sensor from Macro Sensors comes in a ready-to-use package for position measurement in gauging applications. Constructed entirely of stainless steel, the hermetically sealed, 19mm-diameter sensors have a spring-loaded sleeve bearing and are designed for use in hostile environments.

The output from the GHSE 750 series is designed to operate with most PLCs, digital indicators and DAQ systems, the company said.

Macro Sensors also introduced several LVDT sensor series that can operate in extremely harsh environments. The rugged, hermetically sealed LVDT sensors provide 4-20mA I/O for easy field integration with PLCs, digital indicators, host-computer-based data processing and quality-control data collection systems.

In image sensors, Eastman Kodak Co. released three CCD sensors earlier this year for applied markets, including industrial and scientific imaging.

Panchromatic support
The Kodak KAI-10100 image sensor is a new, high-resolution color device, while the existing Kodak KAF-39000 and Kodak KAF-8300 image sensors are now available in monochrome versions, making them suitable for panchromatic imaging applications.

The Kodak KAI-10100 is a 10Mpixel, 22.5mm optical diagonal, interline CCD image sensor. A newly designed, 4.75?m interlaced pixel architecture is said to provide low noise and electronic shutter capabilities, according to Kodak, and hardware color binning is said to support progressive-scan readout at several subsampled resolutions for improved sensitivity and faster readout rates.

- Gina Roos

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