Flush, Non-Flush, or Factor 1? Which Inductive is Best for Your Application?

Ever feel like your proximity application isn’t working just right? Maybe it’s the inductive sensor selection.

Understanding the following three inductive mounting principles is key to selecting the ideal sensor for your application and/or figuring out why the one you have isn’t working correctly. So which inductive is best for your application?

Flush (shielded) sensor

Typically having the shortest sensing range, a flush (shielded) sensor has a flush mount sensor illustration sensing field that will only sense objects that approach it from the face of the sensor. The entire face of the sensor can be surrounded by metal and the sensor face sits flush with the mounting surface. It is designed specifically to send the sensing field out the front of the sensor. We see this a lot in metal stamping dies because the flush mounting protects the sensor from the often-destructive atmosphere of the press.

Non-Flush (non-shielded) sensornon-flush sensor illustration

A non-flush (non-shielded) sensor has a sensing field that comes out the side of the front of the sensor, allowing it to sense objects from the side and giving it a greater or longer sensing range. But you can’t have metal around the face of the sensor. Otherwise it might accidentally detect the environment rather than a specific target.

Factor 1 or multi-metal sensor

A Factor 1 or multi-metal sensor adjusts the sensing range for all types of metals, most importantly those that are not steel. An inductive sensor has a correction factor. Based upon the type of metal, the sensing range is reduced. They are specially designed to trigger for most any metal target at the same sensing distance. This is important as many hybrid/electric automotive and consumer goods applications are using more aluminum and custom metals today.

More to consider

When choosing an inductive sensor, think about what you’re trying to detect. For example, if it’s not steel or is iron-based, a factor 1 or a multi-metal inductive sensor that is a special inductive technology will allow you to see all metals, basically at the same distance.

Traditional inductive proxes are designed for steel/ferrous targets. When presented with a metal like aluminum or copper there is a correction factor to reduce the sensing distance. This can cause problems in sensing applications.

Virtually every inductive proximity sensor vendor offers these three modes to allow for adaption to your specific application and target.

Each metal that you’re trying to detect has a different correction factor for an inductive sensor. So if you’re working with aluminum, for example, you’ll want to look for something that has Factor 1 or multi-metal sensing. If you’re trying to detect copper, Factor 1 has the most value.

Many industries – traditional automotive and electric vehicles, appliance, metalworking, forming, bending and even food and beverage industries – rely on inductive sensors in their automation applications. They sense objects without any physical contact with the target or the object being sensed.

https://www.youtube.com/watch?v=ORQ2n0_CPAo

What is IO-Link? A Simple Explanation of the Universal Networking Standard

Famed physicist Albert Einstein once said, “If you can’t explain it simply, you don’t understand it well enough.” When the topic of IO-Link comes up, whether a salesperson or technical expert is doing the explaining, I always find it’s too much for the layman without a technical background to understand. To simplify this complex idea, I’ve created an analogy to something we use in our everyday lives: highways.  

Prior to the Federal Highway Act of 1956, each individual state, determined the rules of its state highway routes. This included everything from the width of the roads to the speed limits and the height of bridge underpasses — every aspect of the highways that were around at the time. This made long-distance travel and interstate commerce very difficult. It wasn’t until 1956 and the passage of President Eisenhower’s Federal Highway Act, that the rules became standard across the entire United States. Today, whether you’re in Houston, Boston or St. Louis, everything from the signage on the road to the speed limits and road markings are all the same. 

Like the standardization of national highway system, the IO-Link Consortium standardized the rules by which devices in automation communicate. Imagine your home as a controller, for example, the roads are cables, and your destination is a sensor. Driving your car to the store is analogous to a data packet traveling between the sensor and the controller.  

You follow the rules of the road, driving with a license and abiding by the speed limits, etc. Whether you’re driving a sedan, an SUV or a semitruck, you know you can reach your destination regardless of the state it’s in. IO-Link allows you to have different automation components from different suppliers, all communicating in sync unlike before, following a standard set of rules. This empowers the end user to craft a solution that fits his or her needs using sensors that communicate using the protocols set by the IO-Link Consortium. 

How Industrial RFID Can Reduce Downtime in Your Stamping Department

The appliance industry is growing at record rates. The increase in consumer demand for new appliances is at an all-time high and is outpacing current supply. Appliance manufacturers are increasing production to catch up with this demand. This makes the costs associated with downtime even higher than normal. But using industrial RFID can allow you to reduce downtime in your stamping departments and keep production moving.

Most major household appliance manufacturers have large stamping departments as part of their manufacturing process. I like to think of the stamping department as the heart of the manufacturing plant. If you have ever been in a stamping department while they are stamping out metal parts, then you understand. The thumping and vibration of the press at work is what feeds the rest of the plant.  I was in a plant a few weeks ago meeting with an engineer in the final assembly area. It was oddly quiet in that area, so I asked what was going on. He said they’d sent everyone home early because one of their major press lines went down unexpectedly. Every department got sent home because they did not have the pieces and parts needed to make the final product. That is how critical the stamping departments are at these facilities.

In past years, this wasn’t as critical, because they had an inventory of parts and finished product. But the increase in demand over the last two years depleted that inventory. They need ways to modernize the press shop, including implementing smarter products like devices with Industry 4.0 capabilities to get real-time data on the equipment for things like analytics, OEE (Overall Equipment Effectiveness), preventative maintenance, downtime, and more error proofing applications.

Implementing Industrial RFID

One of the first solutions many appliance manufacturers implement in the press department is traceability using industrial RFID technology. Traceability is typically used to document and track different steps in a process chain to help reduce the costs associated with non-conformance issues. This information is critical when a company needs to provide information for proactive product recalls, regulatory compliance, and quality standards. In stamping departments, industrial RFID is often used for applications like asset tracking, machine access control, and die identification. Die ID is not only used to identify which die is present, but it can also be tied back to the main press control system to make sure the correct job is loaded.

need for RFID in appliance stamping
This shows an outdated manual method using papers that are easily lost or destroyed.
appliance stamping can be improved by RFID
This image shows an identification painted on a die, which can be easily destroyed.

Traditionally, most companies have a die number either painted on the die or they have a piece of paper with the job set up attached to the die. I cannot tell you how many times I have seen these pieces of paper on the floor. Press departments are pretty nasty environments, so these pieces of paper get messed up pretty quickly. And the dies take a beating, so painted numbers can easily get rubbed or scratched off.

Implementing RFID for die ID is a simple and affordable solution to this problem. First, you would attach an RFID tag with all of the information about the job to each die. You could also write maintenance information about the die to this tag, such as when the die was last worked on, who last worked on it, or process information like how many parts have been made on this die.
Next, you need to place an antenna. Most people mount the antenna to one of the columns of the press where the tag would pass in front of it as it is getting loaded into the die. The antenna would be tied back to a processor or IO-Link master if using IO-Link. The processor or IO-Link master would communicate with the main press control system. As the die is set in the press, the antenna reads the tag and tells the main control system which die is in place and what job to load.

In a stamping department you might find several large presses. Each press will have multiple dies that are associated with each press. Each die is set up to form a particular part. It is unique to the part it is forming and has its own job, or recipe, programmed in the main press control system. Many major stamping departments still use manual operator entry for set up and to identify which tools are in the press. But operators are human, so it is very easy to punch in the wrong number, which is why RFID is a good, automated solution.

In conclusion

When I talk with people in stamping departments, they tell me one of the main reasons a crash occurs is because information was entered incorrectly by the operator during set up. Crashes can be expensive to repair because of the damage to the tooling or press, but also because of the downtime associated. Establishing a good die setup process is critical to a stamping department’s success and implementing RFID can eliminate many of these issues.

UHF RFID: Driving Efficiency in Automotive Production

Manufactured in batch size 1, bumper to bumper on modular production lines, with the support of collaborative robots –  this is the reality in modern automotive production. Without transparent and continuous processes, production would come to a standstill. Therefore, it is important to have reliable technology in use. For many car manufacturers, UHF RFID is not only used to control manufacturing within a plant but recently more and more also to track new vehicles in the finishing and even shipping processes. And many manufacturers have already started using UHF across production plants and even across companies with their suppliers because it makes just-in-time and just-in-sequence production a lot easier. This blog post gives an insight into why UHF could be the technology of the future for automotive production.

What is UHF?

UHF stands for ultra-high frequency and is the frequency band of RFID (Radio Frequency Identification) from 300 MHz to 3 GHz. UHF with the EPC global Gen2 UHF standard typically in the frequency range of 860 – 960 MHz, with regional differences. Besides UHF other popular RFID frequency bands used in production are LF (low frequency) – operating typically at 125 kHz – and HF (high frequency) – operating typically at 13.56 MHz worldwide. LF is used mainly for Tool ID and HF for ticketing, payment, and production and access control.

UHF RFID used to ensure the proper headrest is placed on automotive seats.
An RFID sensor scans a tag on a car headset during production

UHF systems have the longest read range with up to a few meters and a faster data transfer rate than LF or HF. Therefore, it’s used in a wide variety of applications and the fastest growing segment of the RFID market. Tracking goods or car parts in the supply chain, inventorying assets, and authenticating car parts are just some examples for the automotive industry.

And this is how it works: A UHF reader emits a signal and energy to its environment via an antenna. If a UHF data carrier can be activated by this energy, a data exchange can take place. The data carrier or tag backscatters the reader signal and modulates it according to its specific data content.

UHF vs. Optical systems

Intelligent data generated by intelligent RFID solutions is a crucial part of efficient and transparent processes. To achieve this, the use of innovative UHF technology is essential. Because in the long-term UHF could replace existing HF or LF RFID applications as well as optical systems. Due to its wider range of functions and performance, UHF has the potential to enable a cross-enterprise data flow.

This table shows that UHF can offer a performance and interaction that optical formats can’t:

 

  UHF Systems Optical Systems
Automation Automated process reduces or eliminates manual scanning Manual scanning or low-level automation
Speed 20,000 units per hour (ms/read) 450 units per hour (s/read)
Convenience Can scan items even when they are hidden from view or inside a package Can scan only what it can see
Efficiency Scanning many at once is possible Scans one at a time
Intelligence Chip memory, which can be updated or rewritten to create a more dynamic and responsive process Static data on the label
Security Security features, such as authentication, can be offered on the item level Security features not available or even possible

Sometimes short range is required

Although the UHF technology can read up to a few meters – which is perfect and even required for (intra)logistic processes – this can also be a challenge, especially in some manufacturing areas. Within part production it is often necessary that the detection range is limited and only one part is detected at a time. In these cases, it’s important that the power is either turned down so far that only one part is detected at a time or a special short-range UHF reader resp. special short-range antenna are used.

The technology’s potential can only be fully exploited if every stage of production is supported by UHF. The use of UHF is versatile and can either be used as closed-loop where the UHF tag stays in the production process or as open-loop with UHF labels that are glued onto or into parts like car bodies, bumpers, head rests, tires etc. where they will remain and possibly be used during the subsequent logistics applications.

Besides eliminating manual processes, UHF RFID delivers full visibility of your inventory (automated!) at any time which helps you to reduce shrinkage and prevent stock losses. This improves your overall business operations. Additionally, you can secure access to certain areas.

Another reason to rely up on UHF is the consistently high standard of data quality. When you acquire the same data type from all areas you can generate trend analysis as the readings can be compared with one another. So, you can obtain extensive information on the entire production process – something that isn’t possible when mixing different technologies. This gives you the opportunity to utilize preventive measures.

 

5 Manufacturing Trends to Consider as You Plan for 2022

It’s that time of year again where we all start to forget the current year (maybe that’s OK) and start thinking of plans for the next — strategy and budget season! 2022 is only a few weeks away!

I thought I’d share 5 insights I’ve had about 2022 that you might benefit from as you start planning for next year.

    1. Electric Vehicles

      The electric vehicles manufacturing market is receiving major investments, machine builders are building up expertise, and consumers are trending towards more electric vehicles. According to PEW research, 7% of US adults say they currently own a hybrid or electric vehicle, but 39% say the next time they purchase a vehicle they are at least somewhat likely to seriously consider electric. Traditional automotive won’t go away any time soon, but I see this as a growth generator.

    1. Automation in Agriculture & Food

      Automation in the agriculture, food, beverage and packaging markets is also growing strong with more demand for packaged goods and more SKUs than ever before. Urbanization and shortages in agriculture labor markets are driving investments in automation technologies in manufacturing and on the farm. Robotic agriculture startups seem to be growing faster than weeds and are providing real value for those who are struggling to get product from the field to the factory.

    1. Supply Chain Disruption

      Several economists have said the chip shortage will be with us well into 2023, and now I hear rumors of plastics or other materials having disruptions. Disruption might be the new normal for the short to mid-term. I flew out of LAX a few weeks ago and there were dozens of container ships parked outside the port. We are also seeing a major breakdown of our “over-land” logistics infrastructure. Investment in automation and labor for this market will be vital to a strong recovery. Plan for these things and be willing to have open and honest discussions with your vendors and your customers. Untruths might get you by in the short term but could permanently damage your business relationships for years.

    1. Real not Hyped Sustainability

      As Generation Z (18-24year old) workers increasingly enter our economy, they are pushing us to truly work towards sustainability much more than Millennials did before them. What this means is other markets that I see as growth opportunities are ones where we can have major impact on this, like mining, waste/recycling, and agriculture.

    1. Technology as an HR tool

      All manufacturers will be impacted by the skills-gap and labor shortage if you aren’t already. Part of your strategy for 2022 must include automation and robotics as part of your labor strategy. We need to consider how can we use automation and robotics to do our dull, dirty, dangerous jobs or how can we use automation and robotics to extend the careers of our long-term experienced workers. What disruptive technology could you be investing in to make a real difference in your work processes — 3D printing, machine vision, AR/VR, exoskeletons, drones, virtual twin, AI, predictive maintenance, condition monitoring, smart sensors? Pick something you will do different in 2022. You have to.

What do you see for 2022 that will have a major impact on our businesses?

How to Choose the Best 4K Camera for Your Application

I need 4K resolution USB camera, what would you recommend me?

This is a common question that I am asked by customers, unfortunately the answer is not simple.

First, a quick review on the criteria to be a 4K camera. The term “4K” comes from TV terminology and is derived from full HD resolution.

Full HD is 1920 x 1080 = 2,073,600 total pixels
4K is 3840 x 2160 = 8,294,400 total pixels.

This assumes that the minimum camera resolution must be 8.3 Mpix. It is not guaranteed that the camera reaches 4K resolution, however, it is a basic recognition. For example, a camera with an IMX546 sensor has a resolution of 2856 x 2848 pixels. While the height of the sensor richly meets the conditions of 4K, the width does not. Even so, for our comparison I will use this camera because for certain types of projects (e.g. square object observation), it is more efficient than a 10.7 Mpix camera with a resolution 3856 x 2764 pixels.

Of course, 4K resolution isn’t the only parameter to consider when you are choosing a camera. Shutter type, frame rate and sensor size are also incredibly important and dictated by your application. And, of course, you must factor price into your decision.

Basic comparison

Sensor Mpixel Shutter Size Width Height Framerate Pricing
MT9J003 10.7 Rolling Shutter / Global Reset 1/2.35 3856 2764  

7.3

 

$
IMX267 8.9 Global 1 4112 2176 31.9 $$
IMX255 8.9 Global 1 4112 2176 42.4 $$$
IMX226 12.4 Rolling Shutter / Global Reset 1/1.7

 

4064 3044 30.7 $
IMX546 8.1 Global 2/3 2856 2848 46.7 $$$
IMX545 12.4 Global 1/1.1 4128 3008 30.6 $$$$

 

Shutter
Rolling shutter and global shutter are common shutter types in CMOS cameras. A rolling shutter sensor has simpler design and can offer smaller pixel size. It means that you can use lower cost lenses, but you must have in mind that you have limited usage with moving objects. A workaround for moving objects is a rolling shutter with global reset functionality which helps eliminating the image distortion.

Frames Per Second
The newest sensors offer a higher frame rate than the USB interface can handle. Check with the manufacturer; not everyone is able to get the listed framerate because of technical limitations caused by the camera.

Sensor Size
Very important information. Other qualitative information should also be considered, not only of the camera but also of the lens used.

Price
Global shutter image sensors are more expensive than rolling shutter ones. For this reason, the prices of global shutter cameras are higher than the rolling shutter cameras. It is also no secret that the image sensor is the most expensive component, so it is understandable that the customer very often bases the decision on the sensor requirements.

Advanced comparison

Sensor Pixel size EMVA report Dynamic range SNR Preprocessing features
MT9J003 1.67 link 56.0 37.2 *
IMX267 3.45 link 71.0 40.2 **
IMX255 3.45 link 71.1 40.2 ***
IMX226 1.85 link 69.2 40.3 **
IMX546 2.74 link 70.2 40.6 ****
IMX545 2.74 link 70.1 40.3 ****

 

There are many other advanced features you can also consider based on your project, external conditions, complexity of the scene and so on. These include:

Pixel Size
Sensor size from the basic comparison is in direct correlation with the size of the pixel because the size of the pixel multiplied by the width and height gives you the size of the sensor itself.

EMVA Report
EMVA 1288 is great document comparing individual sensors and cameras. In case you want the best possible image quality and functionality of the whole system, comparison is an important component in deciding which image sensor will be in your chosen camera. EMVA 1288 is the standard for measurement and presentation of specifications for machine vision sensors and cameras. This standard determines properties like signal-to-noise ratio, dark current, quantum efficiency, etc.

Dynamic Range
Dynamic range is one of the basic features and part of EMVA 1288 report as well. It is expressed in decibels (dB). Dynamic range is the ratio between the maximum output signal level and the noise floor at minimum signal amplification. Simply, dynamic range indicates the ability of a camera to reproduce the brightest and darkest portions of an image.

SNR
Signal-to-noise ratio (SNR) is a linear ratio between recorded signal and total root mean squared noise. SNR describes the data found in an image. It establishes an indication as to the signal quality found in the image indicating with what amount of precision machine vision algorithms will be able to detect objects in an image.

 

Preprocessing Features

Do you build high-end product? Is the speed important for you?
You need to rely on the camera/image sensor features. Every update of an image sensor comes with more and more built-in features. For example:

  • Dual trigger, where you set two different levels of exposure and gain and each can be triggered separately.
  • Self-trigger – you set 2 AOI, the first one triggers image and second detects difference in the AOI.
  • Short exposure modes – you can set as fast as 2us between shutters.

Machine vision components continue to be improved upon and new features are added regularly. So, when you are selecting a camera for your application, first determine what features are required to meet your application needs. Filter to only the cameras that can meet those needs and use their additional features to determine what more you can do.

How Vibration Measurement Saves Manufacturers Time and Money

Vibration is all around us. We can feel it and we can hear it. Some vibrations we find pleasant, such as music that we like to listen to, and some vibrations we find unpleasant such as scratching fingernails across the chalkboard. Humans also can predict when something is about to fail or determine when something needs our attention based on the vibrations we can feel or hear in our surroundings. An example almost anyone can relate to is when you are driving or riding in a car and the tires are out of balance or are damaged. In addition to the audible noise, you can feel the vibration through the steering wheel and the chassis of the car. Frequency and amplitude of the vibration typically increase as you speed up, and often amplify your worry as well. This can push you to find the cause of the vibration and fix it.

This same principle can be used in a manufacturing plant environment, which is what makes monitoring vibration so important. Without it, machines break down and stop, costing you time, and money. We all know that one maintenance guru that has a special gift of being able to determine what is happening with a machine based on its vibration feedback, the one who can place his hand on a machine, or hear the machine speak to him, and determine what is wrong with it.

However, using this institutional knowledge isn’t full-proof and it can introduce additional variables in the mix; sometimes resulting in wasted parts, labor, unplanned machine downtime, loss of production, etc. And as tenured staff retires and is replaced with less experienced staff, it has become even more important to remove the human element from the equation and properly capture the data to determine the root cause of mechanical issues. But how? By equipping machines with a monitoring system, the machine can then continuously monitor itself. And when the variables exceed the preset acceptable thresholds, the machine can act based on predetermined actions set by the OEM manufacturer or the maintenance team.

There are many monitoring systems on the market today that vary in complexity and cost. More complex systems include sensors, cables, data acquisition cards, computers, analysis software, data base, cloud subscription, and paid service contracts to pinpoint exact condition of the equipment or asset that is being monitored. This type of system or service is very costly, and in most cases, it is cost prohibitive to be used on non-critical equipment or assets. However, there are lower cost solutions that may not be able to pinpoint what has failed but can tell you when something wrong with the machine that needs to be examined by the maintenance technician. Such devices can be easily integrated into an existing controls architecture and can provide continuous condition monitoring of the machine or asset. Practice of continuous condition monitoring of machines can save the company valuable time and money by reducing unscheduled machine downtime, eliminating wasted parts and time for unnecessary scheduled maintenance, improving total OEE (Overall Equipment Effectiveness) of the machine, and increasing production. This all leads to increased profits.

Because there are more and more solutions available in the market today, there are few things you need to consider when choosing the right solution for your application:

  • Overall cost of implementation – hardware, software, and any installation costs?
  • Is the solution proprietary? Hardware, software, or communications?
  • Is there an annual service contract(s)? Subscriptions?
  • Does the machine/asset require periodic or continuous monitoring?
  • Quality of data? Do you need to know the exact failure point or is knowing that the machine is operating outside of its specified parameters good enough?
  • Can the system be easily expanded for the future state?
  • Are there any additional features that can aid in analyzing the condition of the machine such as pressure, temperature, humidity?

Knowing what you need and want ahead of time will help you better choose the correct solution for your application without wasting money and time on unnecessary features and functions.

 

5 Steps to Make Troubleshooting Less Troublesome

There’s an old, not so funny joke about troubleshooting electrical devices with a punch line that ends with “is it plugged in?”

The reality is that it is easy to overlook basic or simple issues, especially when troubleshooting mechanical, electrical or software problems isn’t part of your regular routine. But following the basic troubleshooting steps listed below can prevent much frustration and lost time. (To be suggestive, many of these steps can be applied to our everyday lives, not just at work.)

There is a scientific and philosophical rule known more commonly as Occam’s razor that states that entities should not be multiplied unnecessarily. In layman’s terms, the simplest explanation is usually the best one. Occam’s razor is often stated as an injunction not to make more assumptions than you absolutely need to. In other words, do not over complicate things. This is especially important when beginning the troubleshooting process.

Here are five general steps to consider when troubleshooting in manufacturing (and in general):

  1. Identify the problem
    • Take the time to understand the malfunction. Look at the problem from where you believe it starts, not necessarily from the end effect you may be witnessing. Sometimes what you observe is a symptom of the problem but not the problem itself. This is the first critical step and usually dramatically reduces the steps required to diagnose the culprit causing the problem. This may also require checking even the simplest things like whether you have power. (Sorry, couldn’t resist.)
  2. Establish a theory of probable cause
    • This is where Occam’s razor should come in. Start by considering the most obvious things first, whether it be a power supply, a sensor, a cable(s) or even a connector, (especially field attachables). Then work your way to the more complex if needed, from network wiring in networks like Ethernet/IP or Profinet, to network traffic or ladder code sequencing. You shouldn’t start examining the more complex until you have eliminated the most obvious. Sometimes a poor performing sensor cable can mimic code problems. Be sure to make a list so you can easily remember your thoughts and probable causes to prevent covering things twice; that is a huge time waster.
  3. Establish an action plan and execute the plan
    • Start testing probable cause theories to try to determine the actual cause or root cause of the problem. Remember to always consider what you understand as the problem and your theories, then start executing your testing from the simplest possible cause to the more complex (if needed). Be careful not to get distracted by issues you find along the way, like something unrelated you remembered you wanted to take care of but is not related to the current problem. (This is where your written list really comes in handy.) Start examining methodically, don’t jump around and don’t repeat steps you’ve already eliminated.
      Hints: Try swapping components when possible and see if the problem corrects itself. And check that someone didn’t change something recently from the original design. This can many times manifest itself as the proverbial “ghost in the machine” syndrome. Consider this process a ladder you are climbing from the simple lower steps to the higher more complex steps. Using this analogy, why climb higher if you don’t need too.
  4. Verify full system functionality
    • Once you have found what you think may be the problem and corrected it, be sure to validate the system after the repair or replacement and make sure it is functioning as it should. In some rare cases, one root cause can cause other problems or damage, so it is important to ensure the system is functioning as it should before returning it back to service. This may lead to some pushback because of the additional time needed, but it could take the system off-line again even longer if unresolved problems are overlooked.
  5. Document the process.
    • Finally, be sure to document what you found and maybe even how you found it in a log or service documentation system. This is especially important if the problem was caused by a part wearing out from normal wear, as it is likely to happen again. If you can categorize the problem, this will make it easier for you and other staff to detect and remedy if it arises again. You may want to consider reviewing your findings at intervals to see if there are possible improvements or changes, like routine maintenance or more reliable components, that could minimize these problems in the future.

Establishing a good process like this will help you more quickly troubleshoot your application or machine, and even help with home projects. Critical thinking like this helps eliminated wasted time, frustration and most importantly, unplanned down time.

 

Today’s Pressure Sensors: More Options to Meet Your Application Needs

Pressure sensing devices are prevalent in industrial machinery.  

 

There are three types of pressure measurements, each with their advantages and disadvantages. 

Absolute pressure (psia) is referenced to a perfect vacuum. This pressure measurement is always positive and is used in measuring barometric pressure or in altimeters.  

 

Gauge pressure (psig) measurement is measured relative to ambient pressure. Examples of gauge pressure include blood pressure and intake manifold vacuum in an engine. Typically, these types of sensors have an atmospheric vent hole located somewhere in the housing. An advantage to this type of sensor is it can measure both positive and negative, thus it can be used in vacuum applications such as robots picking up glass or other products with suction cups.  

 

Differential pressure (psid) measurement is the difference between two pressure sources. The gauge pressure measurement is really a differential measurement as one side is open to the ambient pressure and the other side is connected to the process pressure. However, for most differential pressure sensors the second pressure source is not the ambient air. 

In the past, pressure sensing was accomplished by mechanical switches that typically used Bourdon tubes, diaphragms or bellows. These devices caused a mechanical movement in the switch as the pressure increased or decreased. A course adjustment screw was used to set the desired set point to actuate the various controls. In addition to the switch, some sort of indication was needed so an analog gauge was also typically required. While these devices solved the control requirement, accuracy was not as reliable as the controls required or what was preferred. 

To convert pressure into an electrical output, several different technologies are used in electronic pressure sensors. The first type of strain gauge technology — Piezoresistive technology — is based on measuring the resistance of a deforming silicon semiconductor. stainless steel housing protects the silicon chip as pressure is indirectly transferred to the membrane with a liquid that is usually silicon oil. This type of measurement is most often used in high dynamic pressures.

Thin film technology utilizes a stainless steel carrier. The resistors and other circuitry are placed on the membrane, and measurement is based on the strain gauge technology. The advantage of the thin stainless steel film is its ability to withstand high peak pressures and burst pressures.  

Thick film technology, which also utilizes strain gauge concepts, uses a ceramic carrier. The resistors and other associated circuitry are placed on a membrane using a thick film process. Ceramic cells offer long-term stability and good corrosion resistance. 

In capacitive measuring cells, one electrode is fitted to an elastic membrane and the other electrode is on the support or housing surface on the opposite side. This forms a capacitor in which one electrode follows the movement of the membrane. As the pressure increases or decreases the distance between the electrodes change causing a change in capacitance. 

 

Today’s pressure sensors incorporate both the switching functions and the display of the current pressure. Since these devices are electronic, there are a multitude of output functions available as opposed to the simple on-off functionality of the mechanical pressure switch. These include multiple discrete PNP or NPN outputs from one sensor with multiple functionalities. In many cases a sensor will provide a single discrete output plus a continuous analog output proportional to the pressure value. The discrete output can provide an alarm function while the analog output provides a dynamic value of the process.

The discrete outputs can be programmed for various operations. First and most important are the set points, sometimes referred to as hysteresis, of when the output should activate (SP) and when the output should reset or turn off (RP). Hysteresis keeps the switching outputs stable even if the system pressure fluctuates around the set point.

In some applications it is desirable to know if the pressure is within operating range for machine functions to continue. The output or outputcan be programmed with a window function. The output will be active as long as the measured values fall between the defined low pressure and the defined upper pressure.

Pressure spikes can cause problems not only with the mechanics of the system but with the logic of electrical controls including outputs changing states quickly or chattering. The electronic sensors offered today include the ability to delay the switching outputs of the sensor. Typically, the delays are programmable up to 50 seconds. 

Pressure is usually measured in PSI or bar with one bar of pressure being equal to 14.5 PSI. When applying pressure sensors various pressures should be taken into consideration. First is the nominal operating pressure of the system. The pressure sensor applied to the system should in the 50 – 60% maximum rating of the sensor as this will provide a safety margin.  

 

Overload pressure can be caused by pressure spikes in the system from valves opening or closing or pump cavitation. These spikes can exceed the specified sensor limit, however, no permanent damage or change will occur. Burst pressure is the pressure that can cause permanent damage to the sensing device or mechanical damage to the sensor.   

 

What if the application involves a paste or thick substance that could potentially clog the orifice or dead space of the sensor? Some pressure sensor manufacturers offer flush mounted pressure sensors. These devices are perfect for detecting pastes, greases or thick substances as the bottom of the sensor has a protective membrane, typically stainless steel.  

 

Today’s display is multifunctional as not only does it display dynamic values but it is also used for programming or configuring the sensor. Included on the display is the pressure, parameters, parameter values, scaling of the device, and output(s) status. Also included are programming keys and, in some cases, keypad lock out functionality. 

The true epitome of a pressure sensor is one that can have all of capabilities I’ve mentioned as well as the ability to provide additional functionality and parameterization. Pressure sensors that connect to networks such as IO-Link can optimize processes allowing process monitoring, configuration and error analysis to take place through the system controller. Digital transmission of analog values ensures high signal quality over longer distances and signal delays and distortions are eliminated.  

 

Networkable sensors, such as IO-Link, reduce downtimes and possible configuration errors with plug-and-play functionality. Maximum system flexibility can be achieved during operation as parameters can be modified quickly and remotely. In addition, process diagnostics, data, and errors are reported directly to the controller and displayed on man-machine interfaces. 

 

Pressure sensors have come a long way from the multiple mechanical based components used in the past in both functionality and capabilities. 

 

Choosing the Right Sensor for Your Welding Application

Automotive structural welding at tier suppliers can destroy thousands of sensors a year in just one factory. Costs from downtime, lost production, overtime, replacement time, and material costs  eat into profitability and add up to a big source of frustration for automated and robotic welders. When talking with customers, they often list inductive proximity sensor failure as a major concern. Thousands and thousands of proxes are being replaced and installations are being repaired every day. It isn’t particularly unusual for a company to lose a sensor on every shirt in a single application. That is three sensors a day  — 21 sensors a week — 1,100 sensors a year failing in a single application! And there could be thousands of sensor installations in an  automotive structural assembly line. When looking at the big picture, it is easy to see how this impacts the bottom line.

When I work with customers to improve this, I start with three parts of a big equation:

  • Sensor Housing
    Are you using the right sensor for your application? Is it the right form factor? Should you be using something with a coating on the housing? Or should you be using one with a coating on the face? Because sensors can fail from weld spatter hitting the sensor, a sensor with a coating designed for welding conditions can greatly extend the sensor life. Or maybe you need loading impact protection, so a steel face sensor may be the best choice. There are more housing styles available now than ever. Look at your conditions and choose accordingly.
  • Bunkering
    Are you using the best mounting type? Is your sensor protected from loading impact? Using a protective block can buffer the sensor from the bumps that can happen during the application.
  • Connectivity
    How is the sensor connected to the control and how does that cable survive? The cable is often the problem but there are high durability cable solutions, including TPE jacketed cables, or sacrificial cables to make replacement easier and faster.

When choosing a sensor, you can’t only focus on whether it can fulfill the task at hand, but whether it can fulfill it in the environment of the application.

For more information, visit Balluff.com