inductive sensors Archives - AUTOMATION INSIGHTS

Overcoming Challenges in Metal Detection: The Power of Factor 1 Sensors

Standard inductive proximity sensors are used across the automation industry for metal detection applications and are generally reliable in these operations. But issues arise when switching from steel to other metals like copper, brass, or aluminum. A standard inductive sensor may encounter problems in such scenarios. Due to the reduction factor, the standard inductive sensor detects these different metals at different distances. If you had a sensor mounted and set up to sense a steel material but switched to copper, for example, the copper material might be out of the sensor’s range due to this difference in reduction factor, resulting in a missed reading. Factor 1 sensors were created to eliminate this problem.

Reduction factor

The reduction factor is the root cause of variable distance readings with a standard inductive sensor. But what exactly is it? The standard operating range of an inductive proximity sensor is determined by its response to a one-millimeter-thick square piece of mild steel. Other metals like copper and aluminum deviate from this standard range due to differences in material properties. For example, copper has a reduction factor of around 0.4, so it can only be detected at 0.4 times the standard operating range of an inductive proximity sensor.

We can save for later the details of why this occurs, but the key point here is that different material properties cause different reduction factors, which result in different switching distances. The table below shows these different reduction factors and switching distances. Factor 1 sensors take all these variable reduction factors and equalize them to a standard operating distance. This means that you can read anything from copper to steel at the same range, reducing the possibility of missed readings and eliminating the need for repositioning sensors whenever a material change occurs.

When to use Factor 1 sensors

Factor 1 sensors are well-suited for any process that involves different metals. Whether it is automated welding or a packaging conveyor, the factor 1 sensor will keep the material switching ranges uniform. But why is this such a big advantage?

Think about the time spent having to adjust sensor distances. Not only is the task annoying, it also takes up time. Having factor 1 sensors in place will increase the uptime of these processes and eliminate the need for sensor adjustments.

One last benefit to note about factor 1 sensors is that they are inherently weld field immune. The internal construction of the sensor prevents it from being affected by the electromagnetic field generated during welding. This additional immunity allows the sensor to survive in these welding conditions where a typical sensor might fail if it comes in proximity to the weld field.

In the end, you know your application best, but if any of the above benefits resonate with you, it’s time to start thinking about factor 1.

Choosing Between M18 and Flatpack Proxes

Both M18s and flatpacks are inductive or proximity sensors that are widely used in mechanical engineering and industrial automation applications. Generally, they are similar in that they produce an electromagnetic field that reacts to a metal target when it approaches the sensor head. And the coil in both sensors is roughly the same size, so they have the same sensing range – between 5 to 8 millimeters. They also both work well in harsh environments, such as welding.

There are, however, some specific differences between the M18 and flatpack sensors that are worth consideration when setting up production.

M18

One benefit of the M18 sensor is that it’s adjustable. It has threads around it that allow you to adjust it up or down one millimeter every time you turn it 360 degrees. The M18 can take up a lot of space in a fixture, however. It has a standard length of around two inches long and, when you add a connector, it can be a problem when space is an issue.

Flatpack

A flatpack, on the other hand, has a more compact style and format while offering the same sensing range. The mounting of the flatpack provides a fixed distance so it offers less adjustability of the M18, but its small size delivers flexibility in installation and allows use in much tighter fixes and positions.

The flatpack also comes with a ceramic face and a welding cable, especially suited for harsh and demanding applications. You can also get it with a special glass composite protective face, a stainless-steel face, or a steel face with special coatings on it.

Each housing has its place, based on your detection application, of course. But having them both in your portfolio can expand your ability to solve your applications with sensor specificity.

Check out this previous blog for more information on inductive sensors and their unlimited uses in automation.

Pressure-Rated Inductive Sensors Add Security in Mobile Equipment

Manufacturers of mobile equipment have long understood the benefits of replacing mechanical switches with the non-contacting technology of inductive sensors. Inductive sensors provide wear-free position feedback in a sealed housing suitable for demanding environments. But some applications may require a different approach if potential mounting issues or sensing ranges are a concern. For instance, as the mobile machine ages and bushings wear due to typical daily operations, the sensing air gap between the linkage to be sensed and the sensor face may increase beyond the sensor’s optimum working range. If this scenario is possible, periodic maintenance will be required to adjust the sensor mounting to compensate for the increasing wear. Another consideration is the mounting bracket itself, and the likelihood of misalignment due to physical contact.

Many off road applications requiring sensor feedback involve hydraulic cylinders. If these cases, a pressure-rated inductive sensor installed inside a cylinder or valve may be the better design choice. Pressure-rated inductive sensors are offered with a variety of discrete outputs with numerous housing styles and connections. Utilizing non-contact switching, stainless steel housings, and sealed to pressures up to 500 Bar, the sensors are designed to provide reliable feedback under the harsh conditions of off highway applications.

Mounting a pressure-rated inductive sensor into a cylinder or valve is straightforward, and very similar to the preparation of a hydraulic port:

1. 1. the sensor is threaded into the cylinder wall
  2. the sensing air gap is set
  3. the provided nut locks down the sensor
  4. a cable or connector is attached.

Day-to-day wear of the machine no longer affects the sensing gap and the sensor benefits from the additional protection of being installed into the cylinder, avoiding mounting mishaps and is better protected from external damage.

An outrigger application is a good example of the added benefits of using a pressure-rated inductive sensor. Outriggers are used in cranes, firetrucks, aerial devices, and other mobile machines to provide lateral stability. Mechanical switches and standard inductive sensors are used to denote when the outrigger is fully raised, lowered, etc. A standard external sensor will do a good job as long as the mounting is intact and the sensing gap is within the proper range. But a pressure-rated inductive sensor mounted internally into the hydraulic cylinder takes the worry out of those potential failure scenarios.

Applications with locking cylinders should also be considered. Many locking cylinder applications are associated with a safety feature, where feedback that the cylinder is locked is critical. An example would be the rear hatch of a refuse truck. Occasionally, a worker may need to get inside the rear of a refuse truck. With the rear hatch raised hydraulically, there’s a possibility that the rear hatch closes with gravity. Positive feedback that the cylinder is locked is reassuring.

Therefore to reduce downtime caused by wear, to eliminate the misalignment of a mounting bracket, or to ensure your locking cylinder is absolutely locked, consider going “internal” to increase the quality and security of your application.

Industrial sensors with diagnostic functionality

Self-Awareness
For monitoring functionality in industrial processes two aspects are relevant: Environmental awareness and self-awareness. Environmental awareness analyzes impacts which are provided by the environment (e.g. ambient temperature). Self-awareness collects information about the internal statuses of (sub)systems. The diagnostic monitoring of industrial processes, which are typically dynamic, is not as critical as the monitoring of static situations. If you have many signal changes of sensors due to the activity of actuators, with each plausible sensor signal change you can be confident that the sensor is still alive and acts properly. A good example of this is rotation speed measurement of a wheel with an inductive sensor having many signal changes per second. If the actuator drove the wheel to turn but the sensor would not provide signal changes at its output, something would be wrong. The machine control would recognize this and would trigger a stop of the machine and inspection of the situation.

Inductive Sensors with self-awareness

DESINA
For level sensing applications in cooling liquid tanks of metalworking applications inductive sensors with self-diagnostics are often used. The inductive sensors detect a metal flag which is mounted to a float with rod fixation.

Additionally, to the switching output these sensors have a monitor output which is a “high” signal when the sensor status is OK. In situations where the sensor is not OK, for example when there has been a short circuit or sensor coil damage, the monitor output will be a “low” signal. This type of so called DESINA sensors is standardized according to ISO 23570-1 (Industrial automation systems and integration – Distributed installation in industrial applications – part 1: Sensors and actuators).

Dynamic Sensor control
Another approach is the Dynamic Sensor Control (DSC). Rather than using an additional monitoring output, this type of sensors provides impulses while it is “alive.”

The sensor output provides information about the position of the target with reference to the sensor as well as status diagnostic of the sensor itself.

IO-Link
With IO-Link communication even teaching of defined switching distance can be realized. The IO-Link concept allows you to distinguish between real-time process data (like target in/out of sensing range) and service data which may be transferred with a lower update rate (in the background of the real process).

For more information, visit www.balluff.com.

This blog post was originally published on the innovating-automation.blog.

Inductive Sensors for Washdown Conditions

WashdownSensors When selecting the proper Inductive sensor it is very important to understand the type of application environment the sensor will be installed in. In previous posts, I have blogged about various types of sensors and how they fit into the application mix. For example, a welding application will need specific sensor features that will help combat the normal hostilities that are common to heat, weld spatter and impact due to tight tolerances within the fixture areas.

Inductive sensors are also used more and more in aggressive environments including machine tools, stamp and die, and food and beverage applications. Many times within these types of applications there are aggressive chemicals and cleaners that are part of the application process or simply part of the cleanup procedure that also
mandates high pressure wash down procedures.

So, when we have a stamping or food and beverage application that uses special oils or coolants we know a standard sensor is on borrowed time. This is where harsh environment sensors come in as they offer higher IP ratings with no LED function indicators that seals the sensor to withstand the harshest processes. They also will have high grade stainless steel housings special plated electronics along with additional O-rings making them ideal for the most hostile environment.

InductiveWashdown Features: