Someone once said “with a truly smart sensor, you don’t need to know anything about what you’re sensing.” But for many industrial applications, you may not need all that intellect. How about a just-smart-enough sensor?
Magazines are full of visionary articles about magnificently intelligent sensors. Sensors linked in near-sentient networks to monitor flux in nuclear reactors, to watch over growth of mighty redwoods, to track sea currents and warn of tsunamis. And those sensors are wonderfully used in such types of demanding applications.
For the rest of us, smart sensors may mean a well-muscled version of the plain-Jane units we’ve always used. Perhaps with a microprocessor included, or communications capability. Here are some smart sensors that won’t require the technical staff of the Starship Enterprise to get them to work for a living.
Steps toward “smartness”
Your basic vanilla sensor, though useful, is not well adapted to industrial control. For example, a sensor like a common mercury thermometer provides helpful data but requires interfacing before it can be easily used to control a product or process. There are three basic steps toward creating a smart sensor:
1. Digitizing the sensor signal includes converting the analog sensor output into digital signals (analog-to-digital conversion, or ADC), then providing for processing those signals (through digital signal processing, or DSP).
2. Digital signal is usually processed either by wiring with custom hardware, or by using a microprocessor. Microprocessors are used because they offer design flexibility, though sometimes at the expense of speed. A newer type of microprocessor, the digital signal controller, or DSC, is finding favor in low-cost smart sensors that require a high degree of integration.
3. Digital communications are required so that systems using smart sensors can share sensor values and accommodate sensor outputs. This communications interface allows the sensor to share information with the outside world.
Digital sensors, like these from IDEC-DS, typify the new generation of smart sensors. They can look at objects passing by and make intelligent decisions about an empty bottle or marred film passing the sensor.
As Creed Huddleston, author of Intelligent Sensor Design explains, “…it’s the last two elements that really distinguish smart sensors, because they provide the abilities to turn data directly into information, to use that information locally, and to communicate it to other elements in the system.” (See sidebar, Recommended Texts On Smart Sensors.)
Smart vision sensors for manufacturing
”We think of our vision sensors as smart sensors,” explains Carmine Clementelli, Product Mgr. of IDEC-Datasensor at IDEC Corp. He draws a distinction between the lines of standard (universal) sensors, and IDEC’s Application Sensors. “Our Application sensors are microprocessor based, so you can, for example, adjust the threshold of detection, or select different outputs, (which is) very useful when you connect the sensor to other devices.
Clementelli explains that basic photoelectric sensors may be able to see that an object is in the field of view. But Application sensors can go beyond that to detect specifics, as with label-detection sensors, for example, or counter or luminescence sensors.
Many of these sensors require digital communications. Some may need Ethernet connections to take full advantage of their capabilities.
Clementelli explains that IDEC-DS has recently launched two new vision sensors. One works with a PC; the other new model works with a small computer as a configurator.
“With our color sensors,” Clementelli notes, “you can use the color plus intensity function to distinguish very small differences.” For example, in grayscale, you have different intensity of tones. But it is still the same color. When using the color sensors, you can differentiate between colors of less intensity that are basically the same colors to obtain more accuracy for the subtle tones of the color.
Tiny Orientation Sensor from OSRAM uses logic to ensure photo taken by cell phone or digital camera is correctly aligned in landscape or portrait format.
Some of the smart color sensors have up to ten levels of programmable accuracy. Highest accuracy comes with least depth of field. If you need more depth, set the sensor for a bit less accuracy, Clementelli concludes.
Balluff adds capacitive sensor capability
Balluff GmbH recently acquired SIE Sensorik Industrie GmbH, based in Viernheim, Germany. SIE is a leader in capacitive sensors.
Kent Howard, President of Balluff Inc. explained that “Balluff Group is one of the world’s leading providers of sensors for factory automation. With this acquisition, we’ve added increased design expertise and production capability for capacitive sensors to complement our present offering of sensors to help meet the needs of our customers.”
Laser distance sensor from IDEC uses intelligence to determine nature and orientation of passing objects. Similar sensors can measure slots or sense objects passing through light grids.
Managing Director of Balluff GmbH, Rolf Hermle, noted that “SIE offers interesting synergies and will provide the Balluff Group with improved access to its target markets and thereby a significant boost in global sales.”
Sensor resists harsh environments, detect objects
The R-GAG QT50R, from Banner Engineering, is an advanced radar-based sensor for close and long-range presence detection. It works in a broad range of weather conditions. The QT50R features frequency modulated technology to accurately monitor or detect objects while resisting rain, wind, humidity and extreme temperatures.
The QT50R uses Frequency Modulated Continuous Wave (FMCW) radar to reliably detect moving or stationary cars, trains, trucks and cargo. Units detect target objects up to 15 m away and ignore anything beyond the setpoint. The IP67-rated sensor operates at 24 GHz in the Industrial, Scientific and Medical (ISM) telecommunication band, with no special licensing required.
“The cutting-edge QT50R features FMCW true-presence radar paired with exceptional environmental resistance, allowing the sensor to operate in heavy precipitation and temperatures ranging from -40° to 65° C,” said Mike Dean, product manager, Banner Engineering.
Magnetic absolute encoders for harsh duty
New Sendix encoders, from Turck Inc., with 12-bit analog and 14-bit CANopen outputs are designed for tasks requiring rugged, high resolution encoders. These magnetic encoders use protective technology where the electronics are fully encapsulated and the mechanical assembly is separated, providing a high resistance to shock and vibration.
Sendix encoders for CANopen networks may be programmed through the bus for node address, baud rate, and termination for fast, error-free start-up. This also lets you obtain position or speed data in real time. Other parameters, like scale factors, preset values, and limit-switch values that may also be programmed through the bus.
Sendix encoders from Turck allow users to program parameters like scale factors, presets and limit-switch values.
Orientation sensor decides what is up, or sideways
Designed for applications like mobile phones and digital cameras, the SMT Orientation Sensor from OSRAM Opto Semiconductors, reliably detects whether a photo has been taken in portrait or landscape format. It then forwards this information to appropriate software that automatically displays the photo in its correct orientation, eliminating the need to rotate digital pictures.
The orientation sensor has an integrated light barrier comprised of an IR emitter and a detector. In the detection field, an object appears in either portrait or landscape format, depending on the orientation of the mobile terminal. When the terminal is rotated, the object will move out of the detection field of the light barrier. The sensor sends the information indicating whether the object is inside or outside the detection area as a unique signal via a digital output. Appropriate software then processes the signal and rotates the contents of the display to the correct orientation. A photo, for example, will immediately appear in the correct position for viewing. There is no need to flip or rotate the image after downloading.
Balluff Inc.
www.balluff.com
Banner Engineering Inc.
www.bannerengineering.com
IDEC-Datasensor Corp.
www.idec-ds.com
OSRAM Opto Semiconductors
www.osram-os.com
Turck Inc.
www.turck.com
Recommended Texts on Smart Sensors
Intelligent Sensor Design, by Creed Huddleston, sets out to answer the basic question, “What are intelligent sensors, and why should I care about them?”
Conceptually, they’re a new class of electronic sensing device that’s revolutionizing the way we gather data, how we extract useful information, and how we use that newfound information to perform operations faster, more accurately, safer, and less expensively than ever before. Then we can leverage the power of individual intelligent sensors by communicating their information to other intelligent sensors or to other systems, allowing us to accomplish tasks that weren’t possible before and creating advancements in a variety of applications.
The author goes on to discuss signal conditioning (“…our goal … is to turn raw sensor data into meaningful sensor information”), and invests much of the book in showing how to use the microchip dsPIC to design sophisticated smart sensors.
www.elsevierdirect.com/
Signal Conditioning and PC-based Data Acquisition Handbook, by our own John Gyorki, takes a thorough look at signals, sensors, and signal conditioning. Gyorki notes that four factors require close consideration for measurement signals and systems:
* The types of transducers available for converting variables to measurement signals
* Transmission characteristics,
* Data-acquisition system input matching, and
* Transducers available to convert from one type of measurement signals to another.
Key sections of the book focus on the sensors themselves, and on related topics in noise reduction and isolation, and digital and pulse-train signal conditioning.
Filed Under: SENSORS, ELECTRONICS • ELECTRICAL
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