Level Detection Basics – Where to begin?

Initially I started to write this blog to compare photoelectric sensors to ultrasonic sensors for level detection. This came to mind after traveling around and visiting customers that had some very interesting applications. However, as I started to shed some light on this with photoelectrics, sorry for the pun but it was intended, I thought it might be better to begin with some application questions and considerations so that we have a better understanding of the advantages and disadvantages of solutions that are available. That being said I guess we will have to wait to hear about ultrasonic sensors until later…get it, another pun. Sorry.

Level detection can present a wide variety of challenges some easier to overcome than others. Some of the questions to consider include the following with some explanation for each:

  • What is the material of the container or vessel?
    • Metallic containers will typically require the sensor to look down to see the media. This application may be able to be solved with photoelectrics, ultrasonics, and linear transducers or capacitive (mounted in a tube and lowered into the media.
    • SmartLevelNon-metallic containers may provide the ability for the sensors look down to see the media with the same technologies mentioned above or by sensing through the walls of the container. Capacitive sensors can sense through the walls of a container up to 4mm thick with standard technology or up to 10mm thick using a hybrid capacitive technology offered by Balluff when detecting water based conductive materials. If the container is clear or translucent we have photoelectric sensors that can look through the side walls to detect the media. You can get more information in our white paper, SMARTLEVEL Technology Accurate point level detection.
  • What type of sensing is required? The short answer to this is level right? However, there are basically two different types of level detection. For more information on this refer to the Balluff Basics on Level Sensing – Discrete vs. Continuous.
    • Single point level or point level sensing. This is typically accomplished with a single sensor that allows for a discrete or an on-off signal when the level actuates the sensor. The sensor is mounted at the specific level to be monitored, for instance low-low, low, half full (the optimistic view), high, or high-high. These sensors are typically lower cost and easier to implement or integrate into the level controls.
    • Example of in-tank continuous level sensor

      Example of in-tank continuous level sensor

      Continuous or dynamic level detection. These sensors provide an analog or continuous output based on the level of the media. This level detection is used primarily in applications that require precise level or precision dispensing. The output signals are usually a voltage 0-10V or current output 4-20mA.  These sensors are typically higher cost and require more work in integrating them into system controls.  That being said, they also offer several advantages such as the ability to program in unlimited point levels and in the case of the current output the ability to determine if the sensor is malfunctioning or the wire is broken.

Because of the amount of information on level detection this will be the first in a series on this topic. In my next blog I will discuss invasive vs non-invasive mounting and some other topics. For more information visit www.balluff.us.

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Predictive Maintenance for Zen State of Manufacturing

Industry4.0In a previous entry, Mission Industry 4.0 @ Balluff, I explained that the two primary objectives for Balluff’s work in the area of Industry 4.0 are to help customers achieve high production efficiencies in their  automation and achieve  ‘batch size one’ production.

There are several levers that can be adjusted to achieve high levels of manufacturing efficiencies in the realm of IIoT (Industrial Internet of Things). These levers may include selecting quality of production equipment, lean production processes, connectivity and interoperability of devices, and so on. Production efficiency in the short term can be measured by how fast row materials can be processed into the final product – or how fast we deliver goods from the time the order comes in. The later portion depends more on the entire value-chain of the organization. Let’s focus today’s discussion on manufacturing – inside the plant itself.  The long-term definition of production efficiency in the context of manufacturing incorporates the effectiveness of the production system or the automation at hand. What that means is the long-term production efficiency involves the health of the system and its components in harmony with the other levers mentioned above.

The Zen state of manufacturing – nothing important will come up on Google for this as I made this phrase up. It is the perfect state of the entire manufacturing plant that continues production without hiccups all days, all shifts, every day. Does it mean zero-maintenance? Absolutely not, regular maintenance is necessary. It is one of those ‘non-value added but necessary’ steps in the lean philosophy.  Everyone knows the benefits of maintenance, so what’s new?

Well, all manufacturing facilities have a good, in some cases very strictly followed maintenance schedule, but these plants still face unplanned downtimes ranging from minutes to hours. Of course I don’t need to dwell on the cost associated with unplanned downtime. In most cases, there are minor reasons for the downtime such as a bad sensor connection, or cloudy lens on the vision sensor, etc. What if these components could alert you well in advance so that you could fix it before they go down? This is where Predictive Maintenance (PdM) comes in. In a nutshell, PdM uses actual equipment-performance data to determine the condition of the equipment so that the maintenance can be scheduled, based on the state of the equipment. This approach promises cost savings over “time-based” preventive maintenance.

PowerSuppliesIt is not about choosing predictive maintenance over preventive maintenance. I doubt you could achieve the Zen state with just one or the other. Preventive and predictive maintenance are both important – like diet and exercise. While preventive maintenance focuses on eliminating common scenarios that could have dramatic impact on the production for long time, predictive maintenance focuses on prolonging the life of the system by reducing costs associated with unnecessary maintenance.  For example, it is common practice in manufacturing plants to routinely change power supplies every 10 years, even though the rated life of a power supply under prescribed conditions is 15 years. That means as a preventive measure the plants are throwing away 30% life left on the power supply. In other words, they are throwing away 30% of the money they spent on purchasing these power supplies. If the power supplies can talk, they could probably save you that money indicating that “Hey, I still have 30% life left, I can go until next time you stop the machine for changing oil/grease in that robot!”

In summary, to achieve the zen state of manufacturing, it is important to understand the virtues of predictive maintenance and condition monitoring of your equipment. To learn more visit www.balluff.us.

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Enhancing Stepper Motor Systems with Linear Encoders

Tabletop automation is a trend that is gaining momentum, especially in the fields of medical laboratory automation and 3D printing. Both of these applications demand a level of linear positioning accuracy and speed that might suggest a servomotor as a solution, but market-driven cost constraints put most servos out of financial consideration. New advances in stepper motor design, including higher torque, higher power ratings, and the availability of closed-loop operation via integrated motor encoder feedback are enabling steppers to expand their application envelope to include many tasks that formerly demanded a servo system.

Meeting the Demand for Even More Accurate, More Reliable Positioning

As tabletop automation development progresses, performance demands are increasing to the point that steppers systems may struggle to meet requirements. Fortunately, the addition of an external linear encoder for direct position feedback can enhance a stepper system to enable the expected level of reliable accuracy. An external linear encoder puts drive-mechanism non-linearity inside the control loop, meaning any deviations caused by drive component inaccuracy are automatically corrected and compensated by the overall closed-loop positioning system. In addition, the external linear encoder provides another level of assurance that the driven element has actually moved to the position indicated by the number of stepper pulses and/or the movement reported by the motor encoder. This prevents position errors due to stepper motor stalling, lost counts on the motor encoder, someone manually moving the mechanism against motor torque, or drive mechanism malfunction, i.e. broken drive belt or sheared/skipped gearing.

Incremental, Absolute, or Hybrid Encoder Signals

bmlThe position signals from the external encoder are typically incremental, meaning a digital quadrature square wave train of pulses that are counted by the controller. To find a position, the system must be “homed” to a reference position and then moved the required number of counts to reach the command position. The next move requires starting with the position at the last move and computing the differential move to the next command position. Absolute position signals, typically SSI (synchronous serial interface) provide a unique data value for each position. This position is available upon power-up…no homing movement is required and there is no need for a pulse counter. A recent innovation is the hybrid encoder, where the encoder reads absolute position from the scale, but outputs a quadrature incremental pulse train in response to position moves. The hybrid encoder (sometimes referred to as “absolute quadrature”) can be programmed to deliver a continuous burst of pulses corresponding to absolute position at power up, upon request from the controller, or both.

For more information about magnetic linear encoder systems, visit www.balluff.us.

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Simplifying wiring with sensors and Multiple Interface Blocks

When machine builders build assembly machines for their customers they want to keep the wiring as clean and clear as possible for an attractive machine but more importantly the ease of troubleshooting in the event of a failure. Simplifying connections with unnecessary cables and splitters not only makes it easier for the maintenance technicians to trouble shoot but it also saves the company money with unneeded product and components to inventory and maintain.

V-Twin sensor with one cable

V-Twin sensor with one cable

In the past it was common practice to wire sensors and cables all the way back into a terminal box located in sections of an assembly line. This could be very difficult to track down the exact sensor cable for repair and furthermore in some cases five meter cables or longer would be used to make the longer runs back to the terminal box. The terminal boxes would also get very crowded further complicating trouble shooting methods to get the assembly lines back up and running production. This is where Interface Blocks come in and can provide a much cleaner, effective way to manage sensor connections with significantly decreasing downtime.

For example: If our customer has a pneumatic cylinder that requires two sensors, one for the extended position and one for the retracted positon. The customer could run the sensor cables back to the Interface Block. This sometimes is used with a splitter to go into one port to provide the outputs for both sensors only using one port. Now we can take this a step further by using twin magnetic field sensors (V-Twin) with one connection cable. This example eliminates the splitter again eliminating an unneeded component. As you can see in the reference examples below this is a much cleaner and effective way to manage sensors and connections.

BMFvsVTwin

For more information visit www.balluff.us.

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How do I see PLC data from my smartphone?

From my smartphone, I can do anything from making coffee to adjusting my home thermostat. This wave of appliances and other physical devices connecting and communicating through a network is known as the Internet of Things and it’s playing a crucial role in industry. With the Industrial Internet of Things (IIoT) we can now monitor PLC data without ever intruding on the PLC. Let’s take a look at how I implemented PLC tags on a web application.

IIoT_computer The first step is to download OPC UA historian software. OPC UA stands for Open Platform Communications Unified Architecture. OPC is a client/server communication standard that was made as a gateway between the PLC and a Windows PC. The UA was added as an upgrade that allowed communication across other operating systems such as Linux and iOS along with other added functionality improvements. Once this software is running and the PLC and PC are communicating, we can work on hosting that data.

IIoT_StructureHosting the controller data can seem like a daunting task at first due to the many different options in software and programming languages to use. For example: Ruby, PHP, ASP, ASP.NET and much more are available for back-end development. For my web app, I used SQL to host the data from the OPC UA software. As for the back-end, I went with node.js because it has great packages for working with SQL; in addition to the fact that node.js uses JavaScript syntax which I’m familiar with. The front end of the app was written with HTML and CSS with JavaScript for interactivity. With all these elements in place, I was ready to host the server on the PC to host PLC data.

With smart IO-Link sensors on our conveyor I was able to look at diagnostic and functional data in the PLC and setup an interactive screen at the conveyor for viewing production and maintenance information.

And now I can even check my sensor outputs with the same smartphone that just made my coffee and adjusted my office’s temperature.

IIoT_warehouse

You can learn more about the Industrial Internet of Things at www.balluff.us.

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QR Codes for Business vs Industry

QRCode

Example of a QR code for business use

In a previous post I discussed the different types of bar codes. Aside from the 1D bar codes that we see in the grocery store, the most common type of bar code today is the QR code.

The QR code was 1st designed for the automotive industry to track vehicles in the assembly process. The QR code system became popular outside the automotive industry due to its greater storage capacity compared to standard UPC bar codes. A QR code can have up to 7,089 ASCII characters and can read numeric, alphanumeric, byte/binary, and kanji. Businesses often use this type of QR code on vehicles and products for advertising. When a picture is taken with a cell phone, typically in a QR code reader app, the user will be taken to a website for more information.

Sharpshooter vision sensor for reading micro & QR codes

Sharpshooter vision sensor for reading micro & QR codes

Micro QR codes, on the other hand, have a limitation of 35 digits of numeric characters. These are usually seen in industrial applications. For example, they are seen on cam shafts, crankshafts, pistons, and circuit boards. An example of data that is often written to a micro QR code would be a serial number to track and trace through an assembly plant. An industrial vision sensor is typically needed to decipher micro QR codes.

ILoveBalluffQRCodes

An example of a QR code (left) vs a micro QR code (right)

For more information visit www.balluff.us/vision.

 

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Acids Can Put Your Sensors in a Pickle

In many types of metals production, pickling is a process that is essential to removing impurities and contaminants from the surface of the material prior to further processing, such as the application of anti-corrosion coatings.

In steel production, two common pickling solutions or pickle liquors are hydrochloric acid (HCl) and sulfuric acid (H2SO4). Both of these acids are very effective at removing rust and iron oxide scale from the steel prior to additional processing, for example galvanizing or rolling. The choice of acid depends on the processing temperature, the type of steel being processed, and environmental containment and recovery considerations. Hydrochloric acid creates corrosive fumes when heated, so it typically must be used at lower temperatures where processing times are longer. It is also more expensive to recover when spent. Sulfuric acid can be used at higher temperatures for faster processing, but it can attack the base metal more aggressively and create embrittlement due to hydrogen diffusion into the metal.

Acids can be just as tough on all of the equipment involved in the pickling lines, including sensors. When selecting sensors for use in areas involving liquid acid solutions and gaseous fumes and vapors, care must be given to the types of acids involved and to the materials used in the construction of the sensor, particularly the materials that may be in direct contact with the media.

PressureSensor

A pressure sensor specifically designed for use with acidic media, at temperatures up to 125° C.

A manufacturer of silicon steel was having issues with frequent failure of mechanical pressure sensors on the pickling line, due to the effects of severe corrosion from hydrochloric acid at 25% concentration. After determination of the root cause of these failures and evaluation of alternatives, the maintenance team selected an electronic pressure sensor with a process connection custom-made from PVDF (polyvinylidene fluoride), a VitonTM O-ring, and a ceramic (rather than standard stainless steel) pressure diaphragm. This changeover eliminated the corroded mechanical pressure sensors as an ongoing maintenance problem, increasing equipment availability and freeing up maintenance personnel to address other issues on the line.

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Connectivity in Welding Environments

PrintWhen working in harsh environments and in heavy duty applications like welding, it is important to take a multi-angle approach to designing the application. When you are working with existing sensor installations, it is important to consider all the reasons for the sensor’s failure before determining a winning solution. An important step in any application is to protect the connection between the controller and the sensor. In a welding environment, whether the sensor cable fails from weld slag buildup or from physical damage from contact with a part, the cable can be the key to a successful weld-sensing application.

siliconecables

Silicone Cable vs Silicone Jacket Cable

That being said, the number of options available to protect the connection can be overwhelming and at times even confusing. For example, silicone cables vs silicone tube cables. Silicone cables have a jacket that is made out of silicone material over the conductors.  This usually allows for a smaller diameter and more variety with the cordsets i.e. length and connector types. On the other hand, a silicone tube cable is a standard sensor cable with a silicone pulled over the cable then over-molded.  The silicone tube is a second jacket and the air is a good insulator, prolonging the life of the sensor cable.

CableOutvsQuickDisconnect

Sensor with Connector vs Sensor with Cable Out

Another important consideration is how to even connect your sensor. One option is to install a sensor with a connector. This allows for a quick disconnect from the cable. In this case, it may be better to use a right angle connector, so the bend radius of the cable is not hanging loose. A second option is to install a sensor with cable out. This can have flying leads or a connector added to the end.  At times, when there is not enough room to add a cordset, the cable out gives extra space.

To learn more about welding best practices visit www.balluff.us.

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IP Ratings and ECOLAB Basics

WashdownSensorsIntegrating sensors in washdown applications can be confusing when considering the various approvals.  So what do they all mean?  If a sensor is an IP69K rated sensor does that mean it will survive everything?  In the world of sensors there is IP54, IP67, IP68 and IP69 so if my sensor is IP69K that means it is the best right?  The short answer is no.  Let’s take a brief look at the differences.

IP ratings will generally have two digits with the first digit referring to the solid particle protection.  The second digit indicates the level of protection against the ingress of water.

Sensors rated for IP54 indicates they are dust protected, meaning that dust can get inside the sensor, however, it cannot be enough to interfere with the operation of the equipment –  this is designated by the 5.  The 4 indicates that the sensor withstands splashing water on the housing from any direction with no detrimental effect.  The test for the splashing of water lasts at least five minutes with a water volume of 2.64 gallons per minute with a pressure of 7.25 to 21.76 PSI.

IP67 rated sensors are the most commonly used sensors on the market.  Even most electrical enclosures used in automation are IP67 rated.  The 6 indicates these devices will not allow the entry of dust.  The 7 indicates that the sensor can be immersed in water to a depth of 1 meter for 30 minutes.

IP68 rated sensors are dust tight sensors that can be immersed in water continuously under conditions specified by the manufacturer.  Typically the depth of the immersion is 3 meters.

The IP69K rating is based on a dust tight sensor that can withstand high pressure sprays.  The devices are sprayed with a pressure of 1,160 to 1,450 PSI.  The water temperature can be as high as 176°F with a flow rate of 3.7 to 4.2 gallons per minute.  The distance from the nozzle to the device is 4 to 6 inches.  The sensor is placed on a rotary table that rotates at 5 revolutions per minute and the sensor is sprayed for 30 seconds at four angles 0°, 30°, 60°, and 90°.

The ultimate sensor would have a rating of IP67/IP68/IP69 indicating that it will survive submersion and high pressure washdown.  Also, some of these sensors are 316L stainless meaning they have low carbon content and are more corrosion resistant than other stainless steel grades.  Are all IP69K sensors stainless steel?  No, some sensors utilize polycarbonate-ABS thermoplastic.

Usually during washdown applications in the food and beverage industry the spray is not just water but some sort of cleaning chemical or disinfectant.  These aggressive cleaning and disinfecting agents can attack different housing materials.  This is addressed by the ECOLAB certification.

The ECOLAB test consists of testing the housing and sensor materials to exposure to these aggressive cleaning and disinfecting agents.  The devices are tested for 14 to 28 days at a room temperature of 68° F.  During this time the sensor is visually inspected for swelling, embrittlement, or changes in color.

Don’t forget that even though the sensor has the correct IP rating for your application that the mating connector has to meet the same specifications.  For example, if the sensor is IP69K rated and a IP67 mating cable is used then the lower IP rating has precedence.

If you are interested in what sensors and cables meet washdown requirements, please visit www.balluff.us.

Posted in All posts, Capacitive Sensors, Inductive Proximity Sensors, Object Detection Sensors, Photoelectric Sensors, Ultrasonic Sensors | Tagged , , , , , , , , , | Leave a comment

UHF making a big impact on manufacturing

RFIDUltra-High Frequency (UHF) RFID is quickly becoming the go-to identification system for flexible manufacturing lines around the world. While it was once considered to be a system designed primarily for distribution centers and retail stores, UHF technology has evolved to meet the rigors of the manufacturing environment.

Not long ago I was in a discussion with one of my customers who had been using RFID for almost 25 years. He was caught in a tough spot because he had an application which required reading tags from as little as six inches away to as far as two feet away. The HF system he had could easily meet his needs for the six inch read range, but reading at two feet away limited him to using UHF. When I explained that, his bewildered look indicated to me he was reluctant to consider UHF as a real option. He went on to explain that about ten years prior he conducted tests in his plant with UHF and found a host of limitations with the technology. His main concern was how the operators’ two-way radios interfered with the UHF operating frequency of 902-928MHz. Having heard this from other manufacturing organizations who were early adopters I knew right away that he wasn’t aware of how the technology has evolved over the last decade.

Frequency hopping has pretty much eliminated interference with other radio signals. In addition to overcoming radio interference, being able to read and write to tags which are mounted on or near metal and liquids has become a reality with recent advancements. These improvements have led to more flexible read ranges which are a requirement in today’s flexible manufacturing applications.

In a nutshell, the demands of flexible manufacturing have spurred advancements in the process as well as the supporting technology. As it applies to identification of parts or pallets in the manufacturing process, the flexibility of UHF RFID enables manufacturers to gain visibility in their process and provides actionable data that is used to make complex business decisions.

You can learn more about the technology in Balluff’s white paper, What Makes RFID Systems Industrial Strength? or by visiting our website at www.balluff.us/rfid

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