Evolution of Magnetic Field Sensors

When I visit customers, often a few minutes into our conversation they indicate to me they “must decrease their manufacturing downtime.” We all know that an assembly line or weld cell that is not running is not making any money or meeting production cycle times. As we have the conversation regarding downtime, the customer always wants to know what new or improved products are available that can increase uptime or improve their current processes.

A major and common problem seen at the plant level is a high amount of magnetic field sensor failures. There are many common reasons for this, for example low-quality sensors being used such as Reed switches that rely on mechanical contact operation. Reed switches typically have a lower price point than a discrete solid state designs with AMR or GMR technologies, however these low-cost options will cost much more in the long run due to inconsistent trigger points and premature failure that results in machine downtime. Another big factor in sensor failure is the operating environment of the pneumatic cylinder. It is not uncommon to see a cylinder located in a very hostile area, resulting in sensor abuse and cable damage. In some cases, the failure is traceable to a cut cable or a cable that has been burned through from weld spatter.

Below are some key tips and questions that can be helpful when selecting a magnetic field sensor.

  • Do I need a T- or C-slot mounting type?
  • Do I need a slide-in or a drop-in style?
  • Do I need an NPN or PNP output?
  • Do I need an offering that has an upgraded cable for harsh environments, such as silicone tubing?
  • Do I need a dual-sensor combination that only has one cable to simplify cable connections?
  • Do I need digital output options like IO-Link that can provide multiple switch points and hysteresis adjustment?
  • Do I need a single teachable sensor that can read both extended and retracted cylinder position?

Magnetic field sensors have evolved over the years with improved internal technology that makes them much more reliable and user-friendly for a wide range of applications. For example, if the customer has magnetic field sensors installed in a weld cell, they would want to select a magnetic field sensor that has upgraded cable materials or perhaps a weld field immune type to avoid false signals caused by welding currents. Another example could be a pick and place application where the customer needs a sensor with multiple switch points or a hysteresis adjustment. In this case the customer could select a single head multiple setpoint teach-in sensor, offering the ability to fine tune the sensing behavior using IO-Link.

If the above tips are put into practice, you will surely have a better experience selecting the correct product for the application.

For more information on all the various types of magnetic field sensors click here.

Basic Sensors for Robot Grippers

Robot gripper with inductive proximity sensors mounted
Robot gripper with inductive proximity sensors mounted

Typically when we talk about end-of-arm tooling we are discussing how to make robot grippers smarter and more efficient. We addressed this topic in a previous blog post, 5 Tips on Making End-of-Arm Tooling Smarter. In this post, though, we are going to get back to the basics and talk about two options for robot grippers: magnetic field sensors, and inductive proximity sensors.

One of the basic differences is that detection method that each solution utilizes. Magnetic field sensors use an indirect method by monitoring the mechanism that moves the jaws, not the jaws themselves. Magnetic field sensors sense magnets internally mounted on the gripper mechanism to indicate the open or closed position. On the other hand, inductive proximity sensors use a direct method that monitors the jaws by detecting targets placed directly in the jaws. Proximity sensors sense tabs on moving the gripper jaw mechanism to indicate a fully open or closed position.

Robot gripper with magnetic field sensors mounted

Additionally, each solution offers its own advantages and disadvantages. Magnetic field sensors, for example, install directly into extruded slots on the outside of the cylinder, can detect an extremely short piston stroke, and offer wear-free position detection. On the other side of the coin, the disadvantages of magnetic field sensors for this application are the necessity of a magnet to be installed in the piston which also requires that the cylinder walls not be magnetic. Inductive proximity sensors allow the cylinder to be made of any material and do not require magnets to be installed. However, proximity sensors do require more installation space, longer setup time, and have other variables to consider.

Magnetic Field Sensors – Not Just For Cylinder Applications

When thinking of magnetic field sensors the first form factors that come to mind are C or T slot style sensors designed to fit into specific cylinders. These popular types of magnetic field sensors are used to sense through the aluminum body of a cylinder and detect a magnet inside the housing (cylinder wall) of the cylinder. This is a very reliable sensor type that simply detects the extended or retracted position of a cylinder.

BMF Application2But did you know you can achieve a wide range of applications when using tubular style magnetic field sensors? These types of magnetic field sensors typically come in tubular sizes that range from 6.5mm – M12x1 and can be used with various size magnets to cover several application specifications. These offerings offer precise reliable switch points, robust housings for harsh applications and they are also short circuit protection. For example, if a target is too far away for a traditional inductive proximity sensor or maybe too reflective for a photoelectric sensor, a tubular magnetic field sensor and a mating magnet can reliably sense that magnetic field from 90 mm away! Great distance, switching frequency at 10k Hz, and with a small mounting footprint!

BMF ApplicationApplications include pallet detection, high speed impeller, gear, cog detection, many more in a wide range of industry disciplines.

To learn more about magnetic field sensors you can visit www.balluff.us.

Let’s Get Small: The Drive Toward Miniaturization

minisensorGoing about our hectic daily lives, we tend to just take the modern cycle of innovation for granted. But when we stop to think about it, the changes we have seen in the products we buy are astonishing. This is especially true with regard to electronics. Not only are today’s products more feature-laden, more reliable, and more functional…they are also unbelievably small.

I remember our family’s first “cell phone” back in the ’90s. It was bolted to the floor of the car, required a rooftop antenna, and was connected to the car’s electrical system for power. All it did was place and receive phone calls. Today we are all carrying around miniature pocket computers we call “smartphones,” where the telephone functionality is – in reality – just another “app”.

Again going back two decades, we had a 32″ CRT analog television that displayed standard definition and weighed over 200 pounds; it took two strong people to move it around the house. Today it’s common to find 55″ LCD high-definition digital televisions that weigh only 50 pounds and can be moved around by one person with relative ease.

LabPhotoThese are just a couple of examples from the consumer world. Similar changes are taking place in the industrial and commercial world. Motors, controllers, actuators, and drives are shrinking. Today’s industrial actuators and motion systems offer either the same speed and power with less size and weight, or are simply more compact and efficient than ever before possible.

The advent of all this product miniaturization is driving a need for equally miniaturized manufacturing and assembly processes. And that means rising demand for miniaturized industrial sensors such as inductive proximity sensors, photoelectric presence sensors, and capacitive proximity sensors.

Another thing about assembling small things: the manufacturing tolerances also get small. The demand for sensor precision increases in direct proportion to manufacturing size reduction. Fortunately, miniature sensors are also inherently precision sensors. As sensors shrink in size, their sensing behavior typically becomes more precise. In absolute terms, things like repeatability, temperature drift, and hysteresis all improve markedly as sensor size diminishes. Miniature sensors can deliver the precise, repeatable, and consistent sensing performance demanded by the field of micro-manufacturing.

For your next compact assembly project, be sure to think about the challenges of your precision sensing applications, and how you plan to deploy miniature sensors to achieve consistent and reliable operation from your process.

For more information on precision sensing visit balluff.us/minis.

When is a Weld Field Immune Sensor Needed?

When the topic of welding comes up we know that our application is going to be more challenging for sensor selection. Today’s weld cells typically found in tier 1 and tier 2 automotive plants are known to have hostile environments that the standard sensor cannot withstand and can fail regularly. There are many sensor offerings that are designed for welding including special features like Weld Field Immune Circuitry, High Temperature Weld Spatter Coatings and SteelFace Housings.

For this SENSORTECH topic I would like to review Weld Field Immune (WFI) sensors. Many welding application areas can generate strong magnetic fields. When this magnetic field is present a typical standard sensor cannot tolerate the magnetic field and is subject to intermittent behavior that can cause unnecessary downtime by providing a false signal when there is no target present. WFI sensors have special filtering properties with robust circuitry that will enable them to withstand the influence of strong magnetic fields.

WFIWFI sensors are typically needed at the weld gun side of the welding procedure when MIG welding is performed. This location is subject to Arc Blow that can cause a strong magnetic field at the weld wire tip location. This is the hottest location in the weld cell and typically there is an Inductive Sensor located at the end of this weld tooling.

So as you can see if a WFI sensor is not selected where there is a magnetic field present it can cause multiple cycle time problems and unnecessary downtime. For more information on WFI sensors click here.

Liquid Level Sensing: Detect or Monitor?

Pages upon pages of information could be devoted to exploring the various products and technologies used for liquid level sensing and monitoring.  But we’re not going to do that in this article.  Instead, as a starting point, we’re going to provide a brief overview of the concepts of discrete (or point) level detection and continuous position sensing.

 Discrete (or Point) Level Detection

Example of discrete sensors used to detect tank level
Example of discrete sensors used to detect tank level

In many applications, the level in a tank or vessel doesn’t need to be absolutely known.  Instead, we just need to be able to determine if the level inside the tank is here or there.  Is it nearly full, or is it nearly empty?  When it’s nearly full, STOP the pump that pumps more liquid into the tank.  When it’s nearly empty, START the pump that pumps liquid into the tank.

This is discrete, or point, level detection.  Products and technologies used for point level detection are varied and diverse, but typical technologies include, capacitive, optical, and magnetic sensors.  These sensors could live inside the tank outside the tank.  Each of these technologies has its own strengths and weaknesses, depending on the specific application requirements.  Again, that’s a topic for another day.

In practice, there may be more than just two (empty and full) detection points.  Additional point detection sensors could be used, for example, to detect ¼ full, ½ full, ¾ full, etc.  But at some point, adding more detection points stops making sense.  This is where continuous level sensing comes into play.

Continuous Level Sensing

Example of in-tank continuous level sensor
Example of in-tank continuous level sensor

If more precise information about level in the tank is needed, sensors that provide precise, continuous feedback – from empty to full, and everywhere in between – can be used.  This is continuous level sensing.

In some cases, not only does the level need to be known continuously, but it needs to be known with extremely high precision, as is the case with many dispensing applications.  In these applications, the changing level in the tank corresponds to the amount of liquid pumped out of the tank, which needs to be precisely measured.

Again, various technologies and form factors are employed for continuous level sensing applications.  Commonly-used continuous position sensing technologies include ultrasonic, sonic, and magnetostrictive.  The correct technology is the one that satisfies the application requirements, including form factor, whether it can be inside the tank, and what level of precision is needed.

At the end of the day, every application is different, but there is most likely a sensor that’s up for the task.

5 Tips on Making End-of-Arm Tooling Smarter

Example of a Flexible EOA Tool with 8 sensors connected with an Inductive Coupling System.

Over the years I’ve interviewed many customers regarding End-Of-Arm (EOA) tooling. Most of the improvements revolve around making the EOA tooling smarter. Smarter tools mean more reliability, faster change out and more in-tool error proofing.

#5: Go Analog…in flexible manufacturing environments, discrete information just does not provide an adequate solution. Analog sensors can change set points based on the product currently being manufactured.

#4: Lose the weight…look at the connectors and cables. M8 and M5 connectorized sensors and cables are readily available. Use field installable connectors to help keep cable runs as short as possible. We see too many long cables simply bundled up.

#3: Go Small…use miniature, precision sensors that do not require separate amplifiers. These miniature sensors not only cut down on size but also have increased precision. With these sensors, you’ll know if a part is not completely seated in the gripper.

#2: Monitor those pneumatic cylinders…monitoring air pressure in one way, but as speeds increase and size is reduced, you really need to know cylinder end of travel position. The best technology for EOA tooling is magnetoresistive such as Balluff’s BMF line. Avoid hall-effects and definitely avoid reed switches. Also, consider dual sensor styles such as Balluff’s V-Twin line.

#1: Go with Couplers…with interchangeable tooling, sensors should be connected with a solid-state, inductive coupling system such as Balluff’s Inductive Coupler (BIC). Avoid the use of pin-based connector systems for low power sensors. They create reliability problems over time.


Plural of Giz-mo.  A noun.  Defined as a gadget, one whose name the speaker does not know.  Customers call us and ask for this or that “gizmo” all the time!  I think we should consider creating a product category simply called “GIZMOS”.

I like to call these things “Enablers” because these devices are very much helping hands that optimize the function of sensors.  A sensor of any brand and manufacturer performs only as well as it’s mounted, matching the fixture to the demands of the application at hand. But how often does this happen in a price-driven world?  They often end up in below-par mounting that fails with regularity, in both pristine environments as well as in hostile environments.  Some examples:

Here’s one example below. These inductive proximity sensors in plastic brackets, showing an exposed coil on one, with corroded mounts on the sensor caused by being beaten to death during parts loading and heat.

gizmo1      gizmo2

With a few “Gizmos” like an application-specific quick change mount, some care in gapping the sensor and guarding the cable/connector system, it could look much different. Check out the examples below.

gizmo4 gizmo5

Photoelectric sensors can suffer the same fate.  In this case, a plastic bodied photoelectric sensor, originally used to replace a fiber optic thru beam pair also suffered abuse. With a little extra beefy mounting, these photoelectric sensors can be expected to last a long time without failure.

gizmo6 gizmo7

There are literally hundreds of these mounting “ENABLERS”, off-the-shelf, cost-effective application specific mounts, guards, actuators and entire systems to help protect your sensor investment.  All categories of products have these “enabling” accessories for Magnetic Field (air cylinder), Inductive Proximity, Capacitive, Ultrasonic, Connectivity, Linear Transducer and Photoelectric product categories.

A 3-Step Plan to Improve Your Design of Pneumatic Systems

I’ve been talking pneumatic systems (valves, cylinders, actuators, etc.) recently with my customers and I’m finding among these engineers some common pains coming out of the system design.  It seems that many people are researching networked valve islands with I/O built-in.  These seem to be a great way to consolidate lots of I/O into one IP address, but there are some new issues cropping up similar to the above photo:

  • When assembling these at a machine builder the routing of cables with piping is more cumbersome  with cables hanging off the valves, larger cable tray installations  and large amounts of piping all running to the same spot.
  • For machine builders, with all of the valves centralized in one place, the pneumatic lines have to be longer.  This causes many issues such as slower responsiveness due to air volume, air inertia, and lower air quality.
  • When trying to perform maintenance at an end-user, it becomes a nightmare to troubleshoot with a cluster of cables and pipes.  The zip-tied and clean runs installed by the machine builder are cut, tangled and re-routed as the machine ages and becomes more difficult to troubleshoot.
  • Also at end users, if the manifold needs to be expanded, updated, retrofitted with new valves or I/O, there are big hurdles to jump when doing this: re-piping the valve due to mounting position shifting or even having to edit and repair code in the PLC to adapt to new bitmaps generated by the new valve manifold configuration.
  • When closing the loop with magnetic field sensors mounted on the cylinders, typically reed switches are used which are prone to failure.  In addition, these switches typically have two sensors & cables per actuator to give extend or retract position, these cables cause larger cable trays and long cable runs back to the centralized manifold and I/O.

Continue reading “A 3-Step Plan to Improve Your Design of Pneumatic Systems”

Visit Automation Tradeshows for Free!

I am experiencing the future of tradeshows; a networking & educational conference without the travel, the expense, and the suit!  I can sit at my desk and make contact with future vendors and customers.  The online database GlobalSpec hosts multiple times per year industry specific virtual tradeshow events.  There are presentations and exhibitors.  A place to sit and drink virtual coffee with your peers and of course the token giveaway raffles.

Today I am working the Balluff booth in the Sensors and Switches Virtual show.  It is a collection of companies and attendees from many different industries.  I really enjoy these events because we can contact quickly with potential customers and potential vendors right from the comfort of our conference room and at a much reduced cost. Here you can see our hard working staff chatting with customers.

Check out the Balluff booth at the  Sensors & Switches Virtual Tradeshow, it will be available to visit for 90 days from today.