Non-Contact Inductive Couplers Provide Wiring Advantages, Added Flexibility and Cost Savings Over Industrial Multi-Pin Connectors

Today, engineers are adding more and more sensors to in-die sensing packages in stamping applications. They do so to gain more information and diagnostics from their dies as well as reduce downtime. However, the increased number of sensors also increases the number of electric connections required in the automation system. Previously, the most common technique to accommodate large numbers of sensor in these stamping applications was with large, multi-pin connectors. (Figure 1)

Figure 1
Figure 1: A large multi-pin connector has been traditionally used in the past to add more electronics to a die.

The multi-pin connector approach works in these applications but can create issues, causing unplanned downtime. These problems include:

    1. Increased cost to the system, not only in the hardware itself, but in the wiring labor. Each pin of the connector must be individually wired based on the sensor configuration of each particular die. Depending on the sensor layout of the die, potentially each connector could need to be wired differently internally.
    2. A shorter life span for the multi-pin connector due to the tough stamping environment. The oil and lubrication fluids constantly spraying on the die can deteriorate the connectors plastic housings. Figure 1 shows the housing starting to come apart. When the connector is unplugged, these devices are not rated for IP67 and dirt, oil, and/or other debris can build up inside the connector.
    3. Cable damage during typical die change out. Occasionally, users forget to unplug the connectors before pulling the die out and they tear apart the device. If the connector is unplugged and left hanging off the die, it can be run over by a fork truck. Either way, new connectors are required to replace the damaged ones.
    4. Bent or damaged pins. Being mechanical in nature, the pin and contact points will wear out over time by regular plugging and unplugging of these devices.
    5. A lack of flexibility. If an additional sensor for the die is required, additional wiring is needed. The new sensor input needs to be wired to a free pin in the connector and a spare pin may not be available.
Figure 2
Figure 2: Above is a typical set up using these multi-pin connectors hard-wired to junction boxes.

Inductive couplers (non-contact) are another solution for in-die sensors connecting to an automation system. With inductive couplers, power and data are transferred across an air gap contact free. The system is made up of a base (transmitter) and remote (receiver) units. The base unit is typically mounted to the press itself and the remote unit to the die. As the die is set in place, the remote receives power from the base when aligned and exchanges data over a small air gap.

The remote and base units of an inductive coupler pair are fully encapsulated and typically rated IP67 (use like rated cabling). Because of this high ingress protection rating, the couplers are not affected by coolant, die lubricants, and/or debris in a typical stamping application. Being inherently non-contact, there is no mechanical wear and less unplanned downtime.

When selecting an inductive coupler, there are many considerations, including physical form factors (barrel or block styles) and functionality types (power only, input only, analog, configurable I/O, IO-Link, etc…). IO-Link inductive couplers offer the most flexibility as they allow 32 bytes of bi-direction data and power. With the large data size, there is a lot of room for future expansion of additional sensors.

Adding inductive couplers can be an easy way to save on unexpected downtime due to a bad connector.

fig 3
Figure 3: A typical layout of an IO-Link system using inductive couplers in a stamping application.

Capacitive Prox Sensors Offer Versatility for Object and Level Detection

When you think of a proximity sensor, what is the first thing that comes to mind? In most cases it is probably the inductive proximity sensor and justly so because they are the most widely used sensor in automation today. But there are other types of proximity sensors. These include diffuse photoelectric sensors that use the reflectivity of the object to change states and proximity mode of ultrasonic sensors that use high frequency sound waves to detect objects. All of these sensors detect objects that are in close proximity of the sensor without making physical contact.

One of the most overlooked proximity sensors on the market today is the capacitive sensor. Why? For some, they have bad reputation from when they were released years ago as they were more susceptible to noise than most sensors. I have heard people say that they don’t discuss or use capacitive sensors because they had this bad experience in the past, however with the advancements of technology this is no longer the case.

Today capacitive sensors are available in as wide of a variety of housings and configurations as inductive sensors. They are available as small as 4mm in diameter, in hockey puck styles, extended temperature ranges, rectangular, square, with Teflon housings, remote sensing heads, adhesive cut-to-length for level detection and a hybrid technology that is capable of ignoring foaming and filming of liquids. The capability and diversity of this technology is constantly evolving.

Capacitive sensors are versatile in solving numerous 1applications. These sensors can be used to detect objects such as glass, wood, paper, plastic, ceramic, and the list goes on and on. The capacitive sensors used to detect objects are easily identified by the flush mounting or shielded face of the sensor. Shielding causes the electrostatic field to be short conical shaped much like the shielded version of the inductive proximity sensor. Typically, the sensing range for these sensors is up to 20 mm.

Just as there are non-flush or unshielded inductive sensors, there are non-flush capacitive sensors, and the mounting and housing2 looks the same. The non-flush capacitive sensors have a large spherical field which allows them to be used in level detection. Since capacitive sensors can detect virtually anything, they can detect levels of liquids including water, oil, glue and so forth and they can detect levels of solids like plastic granules, soap powder, sand and just about anything else. Levels can be detected either directly with the sensor touching the medium or indirectly where the sensor senses the medium through a non-metallic container wall. The sensing range for these sensors can be up to 30 mm or in the case of the hybrid technology it is dependent on the media.

The sensing distance of a capacitive sensor is determined by several factors including the sensing face area – the larger the better. The next factor is the material property of the object or dielectric constant, the higher the dielectric constant the greater the sensing distance. Lastly the size of the target affects the sensing range. Just like an inductive sensor you want the target to be equal to or larger than the sensor. The maximum sensing distance of a capacitive sensor is based on a metal target thus there is a reduction factor for non-metal targets.

As with most sensors today, the outputs of a capacitive sensor include PNP, NPN, push-pull, analog and the increasing popular IO-Link. IO-Link provides remote configuration, additional diagnostics and a window into what the sensor is “seeing”. This is invaluable when working on an application that is critical such as life sciences.

Most capacitive sensors have a potentiometer to allow adjustment of the sensitivity of the sensor to reliably detect the target. Today there are versions that have teach pushbuttons or a teach wire for remote configuration or even a remote amplifier. Although capacitive sensors can detect metal, inductive sensors should be used for these applications. Capacitive sensors are ideal for detecting non-metallic objects at close ranges, usually less than 30 mm and for detecting hidden or inaccessible materials or features.

Just remember, there is one more proximity sensor. Don’t overlook the capabilities of the capacitive sensor.

Analog Inductive Sensors Enable Easy Double Blank Detection in Stamping

Double sheet detection, also known as double blank detection, is an essential step in stamping quality control processes, as failure to do so can cause costly damage and downtime. Analog inductive sensors can deliver a cost-effective and easy way to add this step to stamping processes.

Most people have experienced on a smaller scale what happens when the office printer accidentally feeds two sheets of paper; the machine jams and the clog must be manually removed. Beyond the annoyance of not getting the printout right away, this typically doesn’t cause any significant issues to the equipment. In the stamping world, two sheets being fed into a machine can severely affect productivity and quality.

When two metal sheets stick together and are fed into a machine together, the additional thickness can damage the stamping dies and other equipment like the robot loaders, which can cause the production line to shut down for repairs. Even if the tool fares better and does not get damaged, the stamped product will likely be defective. In today’s highly competitive and just-in-time market, machine downtime and rejected shipments due to quality can be very costly.

Image 1

A simple solution to detect multiple sheets of metal is analog inductive sensing. This kind of sensor offers non-contact sensing with a 0…10V analog output, which can be used to determine when the thickness of the metallic material changes. As the material gets thicker, or as multiple sheets of metal stack on top of one another, the analog output from the sensor varies proportionally. These sensors can be used with ferrous or non-ferrous metals, but the operating range will be reduced for non-ferrous metals. As shown in the graph (Image 1), as the distance with the metallic target changes, the analog output increases from 0 to 10V.





The pictures above, shows the technology in action. With a single sheet of aluminum, the output from the sensor is 2.946V, and for two sheets, the output is 5.67V. The user can establish these values as a reference for when there is more than one sheet of metal being fed into the machine and stop the equipment from attempting to process the material before it is damaged. These sensors can be placed perpendicular or inline with the target material and are offered in various form factors so they can be integrated into a wide range of applications.




Mobile Equipment Manufacturers: Is It Time to Make the Switch to Inductive Position Sensors?

Manufacturers of mobile equipment are tasked with the never-ending pursuit of making their machines more productive while adhering to the latest safety regulations, and all at less cost. To help achieve these goals, machines today use electronic control modules to process inputs and provide outputs that ultimately control the machine functions. Yet with all the changes in recent years, one component left over from that earlier era remains in regular use — the mechanical switch.  Switches offered a variety of levers, rollers, and wands for actuation, and many were sealed for an IP67 rating for outdoor use, but they came with an array of problems, including damaged levers, contact corrosion, arcing concerns, dirt or grain dust ingress, and other environmental hazards. Still, overall they were an acceptable and inexpensive way to receive position feedback for on/off functions.

Today, mechanical switches can still be found on machines used for boom presence, turret location, and other discrete functions. But are they the right product for today’s machines?

The original design parameters may have required the switch to drive the load directly, and therefore a rating of 10A@240V might be a good design choice for the relay/diode logic circuits of the past. But a newly designed machine may be switching mere milliamps through the switch into the control module. Does the legacy switch have the proper contact plating material for the load today? Switches use rare metals such as rhodium, palladium, platinum, gold, and silver in attempts to keep the contact resistance low and to protect those contacts from corrosion. Consequently, as China pursues Nonroad Stage IV standards, these metals, some also used in catalytic converters, have sharply increased in price, leading to substantial cost increases to switch manufacturers and ultimately switch users.

A better approach to position feedback for today’s mobile machines is the inductive position sensor. Inductive sensors offer a sealed, non-contact alternative to mechanical switches. Sensing ferrous and non-ferrous metals without physical contact, they eliminate many of the field problems of the past, and non-metallic substances such as water, dirt, and grain dust, do not affect the operation. These qualities make the sensor very suitable for the harsh conditions found in agricultural and construction environments.

Inductive proximity sensors come in a variety of form factors:

Threaded cylindrical – With zinc-plated brass or stainless-steel housings, the threaded barrel styles are popular for their ease of mounting and gap adjustment.  


Low profile rectangular – These “flatpack” style sensors are great under seats for operator presence.


Block designs – The compact, cubed package is ideal for larger sensing ranges.


Large cylindrical – These large “pancake” style sensors are great for detecting suspension movements and other applications requiring extreme ranges.


Inductive position sensors are more than just a discrete product used for detecting linkage, operator presence, or turret stops; They can also perform the duties of a speed sensor by counting teeth (or holes) to determine the RPM of a rotating shaft. Other models offer analog outputs to provide a continuous feedback signal based on the linear location of a metal linkage or lever. Safety rated outputs, high temperatures, and hazardous area options are some of the many product variants available with this electromagnetic technology.
So, perhaps it’s time to review that legacy switch and consider an inductive sensor?
To learn how an inductive position sensor performs its magic, please take a look at an earlier blog:

Basic Operating Principle of an Inductive Proximity Sensor

Palletized Automation with Inductive Coupling

RFID is an excellent way to track material on a pallet through a warehouse. A data tag is placed on the pallet and is read by a read/write head when it comes in range. Commonly used to identify when the pallet goes through the different stages of its scheduled process, RFID provides an easy way to know where material is throughout a process and learn how long it takes for product to go through each stage. But what if you need I/O on the pallet itself or an interchangeable end-of-arm tool?

Inductive Coupling


Inductive coupling delivers reliable transmission of data without contact. It is the same technology used to charge a cell phone wirelessly. There is a base and a remote, and when they are aligned within a certain distance, power and signal can be transferred between them as if it was a standard wire connection.


When a robot is changing end-of-arm tooling, inductive couplers can be used to power the end of arm tool without the worry of the maintenance that comes with a physical connection wearing out over time.

For another example of how inductive couplers can be used in a process like this, let’s say your process requires a robot to place parts on a metal product and weld them together. You want I/O on the pallet to tell the robot that the parts are in the right place before it welds them to the product. This requires the sensors to be powered on the pallet while also communicating back to the robot. Inductive couplers are a great solution because by communicating over an air gap, they do not need to be connected and disconnected when the pallet arrives or leaves the station. When the pallet comes into the station, the base and remote align, and all the I/O on the pallet is powered and can communicate to the robot so it can perform the task.

Additionally, Inductive couplers can act as a unique identifier, much like an RFID system. For example,  when a pallet filled with product A comes within range of the robot, the base and remote align telling the robot to perform action A. Conversely, when a pallet loaded with product B comes into range, the robot communicates with the pallet and knows to perform a different task. This allows multiple products to go down the same line without as much changeover, thereby reducing errors and downtime.

Why Sensor & Cable Standardization is a Must for End-Users

Product standardization makes sense for companies that have many locations and utilize multiple suppliers of production equipment. Without setting standards for the components used on new capital equipment, companies incur higher purchasing, manufacturing, maintenance, and training costs.

Sensors and cables, in particular, need to be considered due to the following:

  • The large number of manufacturers of both sensors and cables
  • Product variations from each manufacturer

For example, inductive proximity sensors all perform the same basic function, but some are more appropriate to certain applications based on their specific features. Cables provide a similar scenario. Let’s look at some of the product features you need to consider.

Inductive Proximity Sensors Cables

·         Style – tubular or block style

·         Size and length

·         Electrical characteristics

·         Shielded or unshielded

·         Sensing Range

·         Housing material

·         Sensing Surface


·         Connector size

·         Length

·         Number of pins & conductors

·         Wire gage

·         Jacket material

·         Single or double ended


Without standards each equipment supplier may use their own preferred supplier, many times without considering the impact to the end customer. This can result in redundancy of sensor and cable spare parts inventory and potentially using items that are not best suited for the manufacturing environment. Over time this impacts operating efficiency and results in high inventory carrying costs.

Once the selection and purchasing of sensors and cables is standardized, the cost of inventory will coincide.  Overhead costs, such as purchasing, stocking, picking and invoicing, will go down as well. There is less overhead in procuring standard parts and materials that are more readily available, and inventory will be reduced. And, more standardization with the right material selection means lower manufacturing down-time.

In addition, companies can then look at their current inventory of cable and sensor spare parts and reduce that footprint by eliminating redundancy while upgrading the performance of their equipment. Done the right way, standardization simplifies supply chain management, can extend the mean time to failure, and reduce the mean time to repair.

Size Matters When Selecting Sensors for Semiconductor Equipment

As an industry account manager focusing on the semiconductor industry, I’ve come to realize that when it comes to sensors used in semiconductor production equipment, size definitely matters. A semiconductor manufacturing facility, better known as a fab or foundry, can cost thousands of dollars per square foot to construct, not to mention the cost to maintain the facility. Therefore, manufacturers of equipment used to produce semiconductors are under pressure to reduce the footprint of their machines. As the equipment becomes more compact, it becomes more difficult to incorporate optical sensors that are needed for precise object detection.

A self-contained optical sensor that includes the optics along with the required electronics is often much too large. There simply isn’t enough space for mounting in the area where the object is to be detected. An alternative method is to use a remote amplifier containing the electronics with a fiber optic cable leading to the point of detection where the light beam is focused on the target. However, there are some drawbacks to this method that can be difficult to overcome. There are instances where the fiber optic cable is too large and not flexible enough to be routed through the equipment. Also, a tighter beam pattern is often required in semiconductor equipment for precise positioning. To provide a tighter beam pattern with fiber optics, it is necessary to add additional lenses. These lenses increase the size, complexity and cost of the sensor.

1The most effective way to overcome the limitations of fiber optic sensors is to use very small sensor heads connected to a remote amplifier by electric cables, as opposed to fiber optic cables. The photoelectric sensor heads are exceptionally small, and because the cables are extremely flexible they can easily accommodate tight bends. Therefore, these micro-optic photoelectric sensors are particularly well suited for use in semiconductor equipment. The extremely small beam angles and sharply defined light spots are ideal for the precise positioning required for producing semiconductors. No supplementary lensing is required.

2An excellent example of how this micro-optic sensor technology is utilized in semiconductor equipment is for precision wafer detection needed for automated wafer handling. At the end of a robot arm used for wafer handling there is a very thin end-effector known as a blade. By utilizing a very tightly controlled and focused light spot, the sensor can detect wafers just a few μm thick with extreme precision.

3The combination of extremely small optical sensor heads with an external processor unit (amplifier) connected via highly flexible cables is a configuration that is ideal for use in semiconductor production equipment.


Photoelectric Methods of Operation

Photoelectric sensors vary in their operating principles and can be used in a variety of ways, depending on the application. They can be used to detect whether an object is present, determine its position, measure level, and more. With so many types, it can be hard to narrow down the right sensor for your application while accounting for any environmental conditions. Below will give a brief overview of the different operating principles used in photoelectric sensors and where they can be best used.


Diffuse sensors are the most basic type of photoelectric sensor as they only require the sensor and the object being detected. The sensor has a built-in emitter and receiver, so as light is sent out from the emitter and reaches an object, the light will then bounce off the object and enter the receiver. This sends a discrete signal that an object is within the sensing range. Due to the reflectivity being target-dependent, diffuse sensors have the shortest range of the three main discrete operating principles. Background suppression sensors work under the same principle but can be taught to ignore objects in the background using triangulation to ensure any light beyond a certain angle does not trigger an output. While diffuse sensors can be affected by the color of the target object,  the use of a background suppression sensor can limit the effect color has on reliability. Foreground suppression sensors work in the same manner as background suppression but will ignore anything in the foreground of the taught distance.



Retro-reflective sensors also have the emitter and receiver in a single housing but require a reflector or reflective tape be mounted opposite the sensor for it to be triggered by the received light. As an object passes in front of the reflector, the sensor no longer receives the light back, thus triggering an output. Due to the nature of the reflector, these sensors can operate over much larger distances than a diffuse sensor. These sensors come with non-polarized or polarizing filters. The polarizing filter allows for the sensor to detect shiny objects and not see it as a reflector and prevents any stray ambient light from triggering the sensor.



Through-beam sensors have a separate body for the emitter and receiver and are placed opposite each other. The output is triggered once the beam has been broken. Due to the separate emitter and receiver, the sensor can operate at the longest range of the aforementioned types. At these long ranges and depending on the light type used, the emitter and receiver can be troublesome to set up compared to the diffuse and retro-reflective.



The previous three types of photoelectric sensors give discrete outputs stating whether an object is present or not. With photoelectric distance sensors, you can get a continuous readout on the position of the object being measured. There are two main ways the distance of the object is measured, time of flight, which calculates how long it takes the light to return to the receiver, and triangulation, which uses the angle of the incoming reflected light to determine distance. Triangulation is the more accurate option, but time of flight can be more cost-effective while still providing good accuracy.

Light type and environment

With each operating principle, there are three light types used in photoelectric sensors: red light, laser red light, and infrared. Depending on the environmental conditions and application, certain light types will fare better than others. Red light is the standard light type and can be used in most applications. Laser red light is used for more precise detection as it has a smaller light spot. Infrared is used in lower-visibility environments as it can pass through more dirt and dust than the other two types. Although infrared can work better in these dirtier environments, photoelectric sensors should mainly be used where build-up is less likely. Mounting should also be considered as these sensors are usually not as heavy duty as some proximity switches and break/fail more easily.

As you can see, photoelectric sensors have many different methods of operation and flexibility with light type to help in a wide range of applications. When considering using these sensors, it is important to account for the environmental conditions surrounding the sensor, as well as mounting restrictions/positioning, when choosing which is right for your application.

For more information on photoelectric sensors, visit this page for more information.

Do Your Capacitive Sensors Ignore Foam & Condensation for True Level Detection?

Capacitive sensors detect any changes in their electrostatic sensing field. This includes not only the target material itself, but also application-induced influences such as condensation, foam, or temporary or permanent material build-up. High viscosity fluids can cause extensive delays in accurate point-level detection or cause complete failure due to the inability of a capacitive sensor to compensate for the material adhering to the container walls. In cases of low conductive fluids such as water or deionized water and relatively thin container walls, the user might be able to compensate for these sources of failure. Potential material build-up or condensation can be compensated for by adjusting the sensitivity of the sensor, cleaning of the container, or employing additional mechanical measures.

However, this strategy works only if the fluid conductivity stays low and no other additional influencing factors like temperature, material buildup, or filming challenge the sensor. Cleaning fluids like sodium hydrochloride, hydrochloric acid, chemical reagents, and saline solutions are very conductive, which cause standard capacitive sensors to false trigger on even the thinnest films or adherence. The same applies for bodily fluids such as blood, or concentrated acids or alkaline.

Challenges of this type of application are not obvious. This is especially true when the sensors performed well in the initial design phase but fail in the field for no obvious reason. An example of this would be when the sensors on the equipment are setup with deionized water however, the final process requires some type of acid  Difficult and time-consuming setup procedures and unstable applications requiring frequent readjustment are the primary reasons why capacitive level sensors have been historically avoided in certain applications.

Today, there are hybrid technologies employed in capacitive sensors for non-invasive level detection applications that would require little or no user adjustment after the initial setup process. They can detect any type conductive water based liquid through any non-metallic type of tank wall while automatically compensating for material build-up, condensation, and foam.

This hybrid sensing technology helps the sensors to distinguish effectively between true liquid levels and possible interferences caused by condensation, material build-up, or foaming fluids. While ignoring these interferences, the sensors still detect the relative change in capacitance caused by the media but use additional factors to evaluate the validity of the measurement taken before changing state. These sensors are fundamentally insensitive to any non-conductive material like plastic or glass, which allows them to be utilized in non-invasive level applications.

These capacitive sensors provide cost-effective, reliable point-level monitoring for a wide array of medical, biotechnology, life sciences, semiconductor processes, and other manufacturing processes and procedures. This technology brings considerable advantages to the area of liquid level detection, not only offering alternative machine designs, but also reduced assembly time for the machine builders.  Machine designers now have the flexibility to non-invasively detect almost any type of liquid through plastic, glass tubes, or other non-metallic container walls, reducing mechanical adaption effort and fabrication costs.

Discrete indication tasks like fluid presence detection in reagent supply lines, reagent bottle level feedback, chemical levels, and waste container overfill prevention are now a distinct competence for capacitive sensors. Reagents and waste liquids are composed of different formulas depending on the application.  The sensing technology has to be versatile enough to compensate automatically for changing environmental or media conditions within high tolerance limits. Applications that require precision and an extraordinary amount of reliability, such as blood presence detection in cardiovascular instruments or hemodialysis instruments, medical, pharmaceutical machine builders, equipment builders for semiconductor processes can rely now on these hybrid capacitive sensors

Top 5 Insights from 2019

With a new year comes new innovation and insights. Before we jump into new topics for 2020, let’s not forget some of the hottest topics from last year. Below are the five most popular blogs from our site in 2019.

1. How to Select the Best Lighting Techniques for Your Machine Vision Application

How to select the best vision_LI.jpgThe key to deploying a robust machine vision application in a factory automation setting is ensuring that you create the necessary environment for a stable image.  The three areas you must focus on to ensure image stability are: lighting, lensing and material handling.  For this blog, I will focus on the seven main lighting techniques that are used in machine vision applications.


2. M12 Connector Coding

blog 7.10_LI.jpgNew automation products hit the market every day and each device requires the correct cable to operate. Even in standard cables sizes, there are a variety of connector types that correspond with different applications.


3. When to use optical filtering in a machine vision application

blog 7.3_LI.jpgIndustrial image processing is essentially a requirement in modern manufacturing. Vision solutions can deliver visual quality control, identification and positioning. While vision systems have gotten easier to install and use, there isn’t a one-size-fits-all solution. Knowing how and when you should use optical filtering in a machine vision application is a vital part of making sure your system delivers everything you need.


4. The Difference Between Intrinsically Safe and Explosion Proof

5.14_LIThe difference between a product being ‘explosion proof’ and ‘intrinsically safe’ can be confusing but it is vital to select the proper one for your application. Both approvals are meant to prevent a potential electrical equipment malfunction from initiating an explosion or ignition through gases that may be present in the surrounding area. This is accomplished in both cases by keeping the potential energy level below what is necessary to start ignition process in an open atmosphere.


5. Smart choices deliver leaner processes in Packaging, Food and Beverage industry

Smart choices deliver leaner processes in PFB_LI.jpgIn all industries, there is a need for more flexible and individualized production as well as increased transparency and documentable processes. Overall equipment efficiency, zero downtime and the demand for shorter production runs have created the need for smart machines and ultimately the smart factory. Now more than ever, this is important in the Packaging, Food and Beverage (PFB) industry to ensure that the products and processes are clean, safe and efficient.


We appreciate your dedication to Automation Insights in 2019 and look forward to growth and innovation in 2020!