Sensing & Measurement Resource Center

• › Articles (115)
• › White Papers (48)
• › News (68)
• › Products (377)

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.

Encoder Resolution for the Taking
Encoders Today Can Do Everything a Resolver Can Do

Sensing Without Wires
Wireless Sensors Can Streamline Production and Improve Reliability and Safety, but Still Need a Few Improvements

Machine-Mount I/O Go Everywhere
Technical Advances, Regulatory Reforms Allow I/O Components to Do the Same Jobs Outside of Their Former Enclosures

Green Is No Gamble
It Can Be a Sure Thing to Develop Sustainable Machines and Production Lines That Will Improve Your Bottom Line

More Articles »

White Papers: In Depth Research

Signal Conditioning and PC-Based Data Acquisition Handbook
Author: Measurement Computing
Posted: 04/17/2012

The third edition of this handbook has been totally revised to include new chapters on Electrical Measurements, Vibration and Sound, Displacement and Position Sensing, and Transducer Electronic Data Sheets (TEDS). It also includes several new subjects and expands on selected items including Fundamental Signal Conditioning.

All chapters have been enhanced to address more practical applications than theoretical measurement issues. They cover a major topic with sufficient detail to help readers understand the basic principles of sensor operation and the need for careful system interconnections. The handbook also discusses key issues concerning the data acquisition system's multiplexing and signal conditioning circuits, and analog-to-digital converters. These three functions establish the overall accuracy, resolution, speed, and sensitivity of data acquisition systems and determine how well the systems perform.

Data acquisition systems measure, store, display, and analyze information collected from a variety of devices. Most measurements require a transducer or a sensor, a device that converts a measurable physical quantity into an electrical signal. Examples include temperature, strain, acceleration, pressure, vibration, and sound. Yet others are humidity, flow, level, velocity, charge, pH, and chemical composition.

Probability and Redundancy
Author: Kristen Barbour, Pepperl+Fuchs
Posted: 03/30/2012

Process plants are striving now more than ever to reduce operational expenditures while increasing productivity and efficiency. Today's process engineers place a tremendous amount of emphasis on system integrity requirements. Why? Because it's a variable that can be controlled when the right equipment is in place.

System Integrity Requirements
System integrity: State of a system where it is performing its intended functions without being degraded or impaired by changes or disruptions in its internal or external environments.

System reliability is a calculation based on estimates. Certain procedures and component evaluations are used to predict the integrity of a given system or individual component. Each component of a system is evaluated individually and its probability of failure is estimated. The manner in which components are connected will influence the integrity of the system. For example a system component connected in series will have more probable impact on the system integrity than a more reliable parallel connection. Each component estimates are combined to provide an over all estimate to the probability of failure for a given system. Redundancy is used to add to the systems overall availability and reduce a given systems probability of failure.

Parallel Redundancy
Two or more system components are operating simultaneously. Only one component is required to be working for the system to operate, and it should continue to function at acceptable performance levels after the loss of any component. Both components must fail in order for a system failure.

Download the entire white paper to learn more.

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, 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.

More White Papers »