By Rich Tallant, Product Manager-Instrumentation Products, TURCK
Instrumentation sensors continue to adapt to changing industry needs. With features such as enhanced connectivity capabilities, durable housing and smaller packages, these sensors can seamlessly integrate with virtually every industrial environment.
Manufacturing and processing industries continue to evolve, requiring smarter, smaller automated components that are capable of gathering and communicating more data. To meet these demands, instrumentation sensors are designed to be more robust with sophisticated features that improve automation, promote productivity, and increase profitability.
Sensors are necessary in virtually every industrial control system to ensure machines operate properly or to monitor production. There are several types and varieties of sensors, which serve a multitude of purposes and measure diverse performance aspects. Today’s sensors are more intelligent and durable, designed to communicate with plant devices and withstand harsh conditions. Three common industrial sensor solutions are temperature, pressure and flow, each delivering accurate and consistent results while ensuring processes run efficiently and effectively.
Instrumentation sensors are crucial for maintaining accurate performance and continuous quality. Delivering precise temperature readings, pressure ratings and flow monitoring, these sensors improve productivity and performance for a range of industries and applications.
Determining accurate temperature readings is one of the most critical components in many processing and manufacturing applications. Temperature sensors must deliver precise, reliable measurements and provide interface flexibility to accommodate diverse and demanding requirements. There are several options available for measuring temperature, including thermocouples, thermistors and one of the most common methods: resistance temperature detectors (RTDs). These devices are highly precise and repeatable with extremely short response times. RTDs offer diverse performance capabilities and can be used alone or in conjunction with a transmitter to condition the output to a common analog signal, such as 4-20 mA. RTDs packaged with a transmitter are commonly referred to as a temperature transmitter or temperature sensor. Standard RTDs may be equipped with a probe and connector, while sensors and transmitters offer more sophisticated features, such as programmability and display capabilities.
RTDs contain a platinum wire that is wrapped around a core or patterned as a thin film on a substrate, minimizing differential expansion or other strains. As the temperature changes, a controller measures the change in the electrical resistance of the platinum wire. These devices offer high resistance, with some up to 1000 Ω, and provide a wide operating temperature range. For example, some RTDs can function between -50 to 500° C. Plus, for enhanced application flexibility, RTDs are available in two-wire, three-wire and four-wire designs. Three- and four-wire are the most common and versatile configurations, containing a lead length compensation wire that allows users to extend the length between the sensor and the input without resistance compensation.
In addition to their performance capabilities, temperature sensors must be user friendly, promoting easy set-up and maintenance. Options available when purchasing temperature sensors vary from simple devices that deliver a resistance output to fully programmable units with visual displays and digital and voltage or current outputs. Simple push-button programming facilitates ease of use and with a recessed button to store selected values, avoids unintentional operational errors. Containing standard M12 connectors, temperature sensors can easily integrate with existing equipment.
Based on their versatile housing options and mounting capabilities, temperature sensors can suit a variety of demanding applications in nearly all automation applications. Housing designs permit sensors to be mounted remotely or in restrictive places. For instance, in applications subject to high temperatures, the RTD probe can be installed in a harsh environment while the visual display remains a safe distance from the heat.
Pressure sensors are used in a range of industries, from hydraulics and pneumatics to food and beverage and oil and gas. With their thermally stable electronics, pressure sensors offer superior reliability and accuracy.
Advances in pressure sensors deliver compact devices that are easy to use. Unlike mechanical controls that require extra lines, hard-wiring and applied pressure to program the device, newer pressure sensors offer offline programming and direct mounting for easy monitoring. Push-button programming options including set points, reset points, output functions and analog ranges, simplify managing these devices.
To satisfy evolving automation requirements and simplify industrial communication, pressure sensors can integrate with plant devices, such as programmable logic controllers (PLCs) and human machine interfaces (HMIs), using I/O Link capabilities—an emerging technology that is gaining popularity among manufacturers—can enhance overall efficiency. Through I/O Link, users can configure measuring parameters, transfer processing data and store information on a remote device for safeguarding—protecting critical process outputs. With the addition of I/O link, user can quickly replace failed sensors and easily download stored parameters into the replacement, simplifying maintenance and ensuring that the parameters within the new sensor are identical.
Given their diverse industry use, pressure sensors are constructed for versatility. Offered in multiple housing options and with protection ratings of IP67, IP68 and IP69K, these sensors withstand harsh and challenging environments.
With advances in instrumentation technology, solid-state flow monitors eliminate moving parts, avoiding performance failures due to broken parts or pieces being lodged in the pipeline. These types of failures are common occurrences when mechanical devices come in contact with the media being sensed. Flow monitors are also equipped with standard connectors to facilitate easy integration with existing equipment. Plus, to accommodate demanding flow applications, they offer high-pressure ratings and can be manufactured with multiple fluid connections—providing a cost-effective solution for diverse flow monitoring needs.
The most common technologies used in solid-state devices are calorimetric and magnetic inductive—indicating the presence or absence of flow. Calorimetric technology measures heat loss in air and liquid based products; the more flow that moves past the sensor, the higher the sensor reads. Calorimetric flow monitors can measure anything from water to the stuffing of a hot dog, including non-homogenous mixtures. Since these sensors will not clog, calorimetric technology minimizes obstruction to the flow stream by eliminating the need to pre-filter through mesh. Magnetic inductive sensors work according to Faraday’s law of induction. To operate, these sensors require a conductive fluid, which creates a potential difference within the sensor that translates to flow.
With a variety of performance levels, from the simplistic to complex fully-featured sensors, flow monitors offer diverse characteristics and operating functions. Models with digital readout are also available for applications that require enhanced performance features. Sensors with digital readouts can easily be programmed to respond to different fluids. In addition, some advanced sensors are capable of producing two separate outputs to accommodate specific application needs. This innovative feature allows a single device to manage both flow and temperature, with one set point to monitor flow while the other point oversees temperature.
Since flow sensors are driven by the application, they are offered in numerous configurations, such as inline, self-contained and remote probe style, to suit specific application needs. Their rugged design and high repeatability provide an unprecedented level of reliability to flow monitoring. Flow sensors offer a variety of outputs, including relay, discrete and analog/discrete, accommodating the most demanding applications, such as coolant flow to weld tips, chemical dispensing and verification and laser cooling.
In the Field
Instrumentation sensors monitor equipment, environments and components to provide measurements that are essential to maintaining consistent, efficient performance. For instance, reliable hydraulic pressure sensing can be difficult. With continuously changing pressure levels straining measuring cells and sealing material and housing, users require a sensor solution designed to withstand this challenging environment. Implementing sensors equipped with innovative ceramic measuring cells provides over-pressure capabilities, drift performance and a rapid reaction time for high resistance to common sensor failures experienced with alternative technologies. Further, pressure sensors featuring IP69k-rated housing are constructed of durable steel, completely sealing the display to prevent moisture and particle ingress.
Instrumentation sensors can also be used together to provide more diverse feedback. A good example of this is on cooling systems. Depending on the complexity, cooling systems can benefit from pressure, flow, and temperature measurements. Flow and temperature feedback enable running at maximum efficiency and pressure measurements can detect clogged filters.
While machines and automated equipment are effective, they are also imperfect, and require the use of monitoring devices to ensure continued performance quality.
Filed Under: Design World articles, Sensors (position + other)