by Randy Frank, Contributing Editor
Manufacturers are tackling more difficult—and unique—design problems with the newest generation of sensors.
Getting serious consideration for a design-in involves meeting all of the required specifications. This is true for all applications. However, industrial is one marketplace where the specifications can be classified into usual (or typical or standard) and unusual or tough (or unique) requirements. The usual specs are satisfied by many suppliers and many products. The tough ones require special design considerations by the supplier to satisfy specific application issues and/or survive in a harsh application environment.
Recognizing and addressing tough requirements
For All Sensors, a supplier of pressure sensors, unusual application requirements were historically addressed with unique electronic performance. This changed with the introduction of the SPM 401 series of stainless-steel media-isolated and CPM 602 series of ceramic sensors.
The sensor families address similar markets but have different strengths. Both are radical departures from the design capabilities of the company’s previous pressure sensors. The need for the media-isolated families came from an annual customer satisfaction survey.
“In the past few years, customers have indicated that they would like All Sensors to offer media-isolated pressure sensors and we decided to take on this challenge,” said Han Mai of the All Sensors marketing department.
Complementing the electrical capability of its existing microelectromechanical system (MEMS) sensors, the media-isolated SPM 401 series can address pressure ratings as low as 1.5 psi and typically require half of the current of competitive products for high output.
The pressure spikes that can occur in applications involving pumps require high burst pressure capabilities. For this reason, All Sensors’ design has a rating that is typically twice the capability of comparable units.
With stainless steel providing the media isolation and oil providing a transfer media to apply pressure to the MEMS sensor, these three differentiating capabilities are still available in the SPM 401 products. The stainless-steel design does add cost to the sensor.
Ceramics sensors address media compatibly with a lower cost approach and can handle much higher pressures. In some environments, a ceramic design has a significant advantage, providing higher mechanical stress capability compared to the thin stainless-steel membrane that can be destroyed or deformed by poking it with an object, such as a screwdriver. So processes that require a high mechanical stability typically dictate a ceramic sensor design.
“The SPM 401 series specifically allows All Sensors to address medical devices, HVAC controls, ship and marine systems and environmental engineering in the lower pressure range from 1.5 to 100 psi,” said Jason Paiva, product manager for media-isolated sensors at All Sensors. “The CPM 602 series covers applications for automotive, medical devices, marine systems, and plant and mechanical engineering and allows us to have a higher pressure range of 30 to 6,000 psi.”
All Sensors plans on introducing more products for both series later this year.
Environment issues
Other types of sensors also need to survive harsh environments. For example, the new IMB inductive sensor from SICK was made specifically for two extremely harsh environments: machine tooling and outdoor applications.
“A long life expectancy with a reliable output is required in these working conditions and can be achieved with the IMB’s IP69K stainless-steel housing, −40 to 100° C extended temperature range, and 150 g shock and vibration rating,” said Jill Oertel, product manager at SICK.
The durability that results from the design of the IMB inductive sensor saves costs and time by reducing the risk of machine downtime.
Avoiding downtime is an important consideration in any manufacturing environment. This can lead users to specify the type of packaging they require.
According to Dennis Smith, senior technical marketing manager, Banner Engineering, “Some production environments damage low-cost plastic sensors leading to machine downtime. Banner’s M18-4 photoelectric sensors are designed to provide long term and reliable sensing performance in harsh industrial applications with enhanced chemical and washdown resistance.”
For harsh industrial environments where abrasive chemicals and ingress fluid are present, the M18-4 self-contained photoelectric sensors have an IP69K-rated, 316 stainless steel housing. In addition to their mechanical ruggedness, the sensors have circuitry that provides resistance to fluorescent light and a high level of crosstalk avoidance.
Some applications require an intrinsically safe sensor. For example, TE Connectivity’s recently introduced HLIR 750 series Intrinsically Safe, 4-to-20-mA LVDT Position Sensors provide reliable contact-less position measurement for critical applications in gas turbines for fuel valve position feedback, vane pitch servo controls, governor controls and generator shell expansion measurements.
The HLIR 750 series sensors have built-in electronics that allow them to operate without the need for external signal conditioning. This simplifies the installation and flexibility in connections with the outside world. But the key parameter is the safety rating.
“Units are Class I Division 1 Intrinsically Safe, Exia approved for use in areas where an intrinsically safe sensor is required,” said Karmjit Sidhu, TE Connectivity, director of Business Development, Oil & Gas, Power Generation and Marine Applications.
Difficult specifications
Not all tough requirements are harsh. Low operating current and low power supply voltage levels are critical in some applications such as portable robotics, motor controls and automation. To meet these demanding requirements, Micro Oscillator Inc. designed its LPS series of inductive proximity sensors.
“We are currently working with several utility meter suppliers to provide longer battery life in wireless connectivity applications,” said Fred Mirow, CEO of Micro Oscillator Inc. “The ability of our product to operate directly at the battery voltage while consuming just a few micro amps of current in these applications is paramount.”
The LPS series uses the company’s patented LS1500 IC to perform at the industry’s lowest operating current (4 µA) level and lowest power supply voltage levels (2.5 to 27 V).
Some applications involve tough specifications in harsh environments. For example, Autodesk’s SeeControl offers a cloud service for collecting data from sensors and microcontrollers designed into industrial products.
“We do everything in the cloud that’s required to connect to the machine, gather the data, analyze it and then present that information to the person that is using the machine,” said Bryan Kester, head of IoT at Autodesk.
In addition to collecting data from the machine, Autodesk has accumulated data about both the sensors and the communication modules themselves.
“Over time we are going to be gathering a lot of data about how various sensors and devices that collect all the data and how they actually perform in different environments,” said Kester.
With this knowledge, Autodesk can recommend sensors to match the data collecting and communicating board.
“We have a customer now who is designing a private, commercial fuel pumping station,” said Kester. “They are designing a fleet of sensors to gather the data from the fuel pumps.”
Instead of searching for and experimenting with combinations of products that can be intrinsically safe, Autodesk has a curated library for harsh or dangerous environments.
“We have a list of pre-approved devices and sensors that can talk to those devices that work with our platform that the customer can pick right off the shelf,” said Kester.
Extreme environments
For tough requirements it is hard to beat a sensing application that has to cope with remotely measuring water level and withstand lightning strikes.
“Senix customers are installing remote water level sensors where thousands of lightning strikes a year are common. Nothing stops a direct strike, but 7-kV surge protection allows sensors to survive transients from nearby strikes,” said Doug Boehm, who has been designing industrial sensors for more than 30 years and is Senix’s founder and CTO.
The ToughSonic Remote 14 sensors use ultrasonic sound waves to provide high reliability and fast, non-contact measurements at distances up to
14 ft (4.3 m). Longer range ToughSonic Remote 30 and 50 sensors that can handle distances up to 50 ft (15.2 m) will be available this year.
Tackling unusual requirements
While the unusual application requirements can vary extensively, meeting them not only provides the company who is willing to go outside of the industry comfort zone of usual specifications the potential of a greater market share, it also means bringing advanced technology, safety and durability to more users.
All Sensors
www.allSensors.com
Autodesk SeeControl
www.seecontrol.com
Banner Engineering
www.bannerengineering.com
Micro Oscillator, Inc.
www.micro-oscillator.com
Senix
www.senix.com
SICK
www.sick.com
TE Connectivity Macro Sensors
www.macrosensors.com