Sensing & Measurement Resource Center

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Controls engineers need a variety of information on topics such as presence sensing, process variables, transmitters, transducers, encoders and RFID. Timely news, back-to-basics primers, feature articles, technical white papers and descriptions of the latest products all provide valuable insights that can be used in designing and building machine controls.

Focus On: Retaining Automation Know-How
ControlDesign.com
This insightful look at our February 2010 cover story, "Stick to the Playbook" (www.ControlDesign.com/reuseknowhow) examines how machine builders are creating standards and reusable modular design to retain the work and the knowledge of their engineers. Control Design's editorial staff interviews Pat Phillips, engineering manager at Haumiller, which builds high-speed, automated assembly machines, and Chris Lovendahl, sales manager at Concep Machine, makers of special-purpose machine and factory-automation systems, to get a closer look at how those two companies are retaining their automation know-how.

Web Poll
ControlDesign.com
How Do You Rate the Safety at Your Plant?

Market Intelligence Report: Sensors & Vision
ControlDesign.com
Control Design's Managing Editor Mike Bacidore and Rixan Associates' Director of Egineering, Mark Battisti, go over Control Design's results of its latest survey on machine sensors and vision systems. The survey asked its participants about the type of sensing they currently used in their machines including vision systems, how end-users are connecting to I/O, what they use machine vision for and whether wireless sensing is a viable option. Watch this video report to learn about the results of this survey.

Conditioners' Smaller Size and Digital Signal Processing Change the Landscape for Signal Conditioners and Noise Control
Data Vista Looks Smaller, More Digital: Signal Conditioners Have Changed Slightly Over the Past Decade

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White Papers: In Depth Research

Laser Displacement Sensor Technology Book
Author: KEYENCE
Posted: 02/08/2010
Innovative Measurement Accuracy and Stability

A laser beam emitted from the semiconductor laser is applied to the target. The light reflected from the target is collected by the receiver lens and focused on the light-receiving element. When the distance to the target changes, the angle of the reflected light passing through the receiver lens changes, and the light is focused at a different position on the light-receiving element.

The measurement accuracy of the laser sensor utilizing triangulation is greatly affected by the following two factors:
Optical design and Stability of received light intensity and waveform.

With a single receiver lens, the spot diameter formed on the light-receiving element becomes larger when the measuring distance is shorter or longer than the reference distance, due to the lens aberration. When the spot diameter on the light-receiving element becomes larger, the measurement accuracy factors, such as "resolution", "linearity", and "scan resolution", become poorer than those obtained at the reference distance. Consequently, it is necessary to develop an optical design which ensures a constant spot size regardless of the measuring distance.

As described in "1. Basic principle of triangulation", a laser displacement sensor calculates the distance to a target by focusing the light reflected from the target on the light-receiving element. If the light reflected from the target changes due to the color, gloss, surface condition (roughness, tilt) of the target surface, the condition of the beam spot formed on the light-receiving element (received light waveform) also changes. Such a change in the beam spot condition (received light waveform) affects the measurement accuracy of laser displacement sensors.

Semiconductor Manufacturing Processes and Laser Displacement Sensors
Author: Michael Montgomery, EE, Assistant Technical Marketing Manager, Keyence Corporation of America
Posted: 01/28/2010
One of the driving forces in the semiconductor manufacturing industry today is to reduce manufacturing cost and increase efficiency. In the past, laser displacement sensors have been used infrequently due to lack of speed, accuracy and flexibility. Recently, laser displacement sensors have become more accurate (0.02 μm repeatability), faster (392 kHz sampling rate) and more flexible. Because of their greater speed, accuracy and flexibility, these sensors can be used in a wider variety of applications ranging from wafer production and handling all the way to wire bonding and final packaging. Some common applications of laser displacement sensor, specifically when producing semiconductor wafers are noncontact thickness, flatness, perpendicularity, and warpage.

Speed can be explained as a measure of how often a sensor takes measurements on a target (sampling rate). The advantage of high speed is the more measurement samples the sensor makes on a target, the more averaging of these measurements can occur, giving a more stable reading.

Accuracy can be thought of as if you take a measurement anywhere in the measuring range of the sensor, how much error there can be. This number is the total error, including the error caused by the sensor (linearity), caused by temperature fluctuations, sensor mounting errors, etc. By understanding and limiting these sources of error, more accurate measurements can be made. When gauging the accuracy of a measurement, the accuracy of the sensor itself is only one component. Depending on the required tolerances, this may or may not be significant. In many cases, full scale linearity may not be as important as resolution and repeatability. Resolution is the smallest amount of change the sensor will register. Repeatability of the sensor is a measurement of differences seen when a target is measured over and over again in the same position under the same conditions. If the part is placed in the same spot in the sensors measuring range over and over again, this is a measure of the sensor repeatability and what ever method of placing the parts’ repeatability. To make a long story short, by increasing the resolution and repeatability, the sensors accuracy can be improved.

Membrane Potentiometers Simplify Position Sensing
Author: Guido Woska
Posted: 10/20/2009
Ultra-flat design enables smart engineering and cost-saving applications.

Membrane potentiometers have c hanged the way engineers think about sensing. With some measuring only 0.5mm [.05cm]thick, ultra-flat membrane potentiometers feature comparable product characteristics to conventional potentiometers, but are liberal with design freedom at significantly lower costs.

Today's membrane potentiometers can be used in the same applications as conventional potentiometers, but can also fit into space-constrained areas. In this case, function can follow form an uncommon feature of mechanical potentiometers.

Because most producers of membrane potentiometers offer customized products with only small tooling efforts, costs are very competitive, even for small prototype quantities. Three additional advantages are found in the basic construction of the membrane potentiometer: its ability to be fully sealed; the possibility of a hollow shaft design; and numerous wiper options, including operation by hand.

Most membrane potentiometers, like the Sensofoil products, c an be sealed at up to an IP65 (NEMA4x) rating and beyond. Conventional potentiometers require a difficult assembly of the wiper, particularly in a hollow shaft assembly. The hollow shaft design of membrane potentiometers, as with Sensofoil , is more reliable and cost efficient. Because of the simple nature of the membrane potentiometer, such technical adjustments are not required. The wiper for the membrane potentiometer c an be as simple as a small plastic knob sliding across the surface; it requires no external electric al contact. Most membrane potentiometers c an also be operated by sliding a finger over its surface, and Sensofoil is even available in a contactless magnetic version.

New Touch Sensors
Author: ITW ActiveTouch
Posted: 10/09/2009
Touch sensitive devices have become increasingly common – from cell phones to industrial touch panels to appliances. These devices typically use capacitive sensors to create the 'touch' surface. In reality capacitive does not require touch, but merely close proximity of an object capable of changing the capacitance of the system. Capacitive systems are typically limited to non-metallic materials, may not work well with gloves and can be susceptible to false activations caused by water. Even with these limitation capacitive works well for many consumer applications.
For situations with more stringent requirements – requiring a definitive touch, wet/underwater applications or high vandalism potential – another technology is possible. Trapped Acoustic Resonance technology expands touch-sensitive capabilities into metallic substrates. The technology, referred to simply as ActiveTouch, was developed by ITW (Illinois Tools Works) over the past seven years, and can turn a solid steel plate up to 0.5" thick into a touch sensitive surface with multiple switch points. The technology even works with ballistic steel, creating the potential for putting a switch in a bullet proof steel plate with no seams.

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