Pepperl+Fuchs Blog

10 Obstacles You Can Overcome with the Right Inductive Sensor

Posted by Zach Steck on Wed, Aug 27, 2014

Let’s take a look at ten scenarios below and determine what would be the best inductive sensing solution.

10 Questions about Inductive SensorsQ1: I have a sensor installed where the target makes physical contact with the sensor face. Over time, it wears out the sensing face and stops working. Do you have anything that would be more durable?

A: For this application, we would turn to our Pile Driver series, which is our metal face inductive sensors. Pile Driver sensors feature a completely stainless steel housing. When tested against a standard plastic face sensor, it lasted 20X longer!
Example model: NMB5-18GM65-E2-FE-V1

Q2: We use an inductive proximity sensor to detect both steel and aluminum targets. It works fine for the steel but does not see the aluminum unless it is actually touching the metal. What’s going on?

A: Nonferrous targets such as aluminum create a reduction factor in standard inductive sensors. The sensors are less sensitive to these targets, which reduces the overall detection range. You can combat this with a Reduction Factor 1 inductive prox. Proximity sensors detect both ferrous and nonferrous targets at the same sensing range.
Example model: NRB8-18GS40-E2-V1

Q3: I am trying to select an inductive sensor to use on a snow plow. It needs to be able to withstand very cold temperatures and most of the options I found are only rated to -13 ºF. Do you have anything that goes colder?

A: The best option for this application is a mobile equipment / harsh duty sensor. These are identified with a –M at the end of the model number. Mobile equipment sensors have an extended temperature range from 85 ºC all the way down to -40 ºC (-40 ºF … 185 ºF). They also have high shock/vibration immunity and an IP69K protection rating.
Example model: NBB8-18GM50-E2-M

Q4: Looking for an inductive sensor that can be paired with an isolated barrier in order to meet Class I, Division 1 requirements. The barrier accepts NAMUR outputs. What does this mean?

A: NAMUR sensors have voltage and current values which are kept at very low levels so that they can be used in potentially explosive environments. This product series is identified by an –N at the end of the model number and is sometimes combined with a number. NAMUR proximity sensors are intrinsically safe when used with an appropriate isolation amplifier.
Example model: NCB5-18GM40-N0

Q5: We have an inductive sensor that is being used in a welding application and are experiencing some issues with its performance. The biggest problem is false tripping. I read that the strong magnetic fields can affect the sensor output. Is this true? Are there any other concerns that I should be aware of?

A: There are sensors specifically designed for use in welding environments and they are referred to as “weld-field immune.” These sensors have a couple of unique characteristics, including: magnetic-field-immune electronics, high-temperature sensing face materials, and a weld-slag-resistant coating. Weld slag is the other major concern in welding applications. These are small beads of molten metal that fly through the air and can settle on or adhere to metal surfaces, including sensor housings. The coating prevents the slag from sticking, so it can be removed quickly and easily.
Example model: NBB5-18GM50-E2-C-V1

Q6: I have an application need for an inductive sensor that can withstand temperatures as high as 200 ºF. Do you have an option for me?

A: Our inductive sensors with extended temperature have an operating range of -25 ºC …100 ºC (-13 ºF …212 ºF) so this would be a suitable option for your application. These are available in a variety of housing options including cylindrical, cube, limit switch, and flat packs!
Example model: NBB5-18GM50-E2-T-V1

Q7: We are in need of an inductive sensor to monitor a rotating shaft for over speed detection. Do you have a sensor we can use that does not require any additional hardware?

A: There are some options of speed monitoring inductive sensors available for this purpose. These include limit switch style housings for speeds between 0.1 Hz … 100 Hz. A potentiometer is used to set the frequency. If the measured value is greater than the set value, the output is switched on. It also features multiple LEDs for easy installation and a startup override allowing time for the system to get up to normal operating speed.
Example model: NJ15+U4+DW2-100

Q8: What would you suggest to detect a metal float inside of a 3/4" plastic pipe? We are using this for a max level indication of the liquid in our tanks.

A: For this application, I would recommend a ring style inductive sensor. Based on the diameter of the pipe, the RJ21-E2 is the best option because it has a 21 mm diameter ring. The sensing field is concentrated on the inside diameter of the ring, making the target position less critical. Level control using metal floats is a very common application for this type of sensor.
Example model: RJ21-E2

Q9: I need a sensor that will be used in a hydraulic cylinder for end-of-stroke detection. The issue here is that the sensor will be exposed to very high pressure (~5000 PSI). Do you have anything capable of withstanding this much pressure? I noticed the cylinder position sensors max out at 3000 PSI.

A: The high-pressure inductive sensors that we offer are rated to 5,076.4 PSI so they would definitely be an option for this application. These sensors are identified with a –D in the model number, for example, NJ1.5-18GM-N-D. They are generally very short range (< 2 mm) and available with a fixed cable or quick disconnect.
Example model: NJ1.5-18GM-N-D

Q10: Do you have an inductive sensor that can tell me how far the metal target is from the sensing face? I need to be able to detect if the target is shifting over time.

A: This application can be solved with an inductive sensor featuring an analog output. Depending on the model, these sensors provide a 0 mA … 20 mA, 4 mA … 20 mA, 0 V … 5 V, or 0 V … 10 V analog output based on the distance from the sensor to the target. This is the best choice for distance measurement on a very small scale.
Example model: NBB5-18GM60-I3

Questions about Inductive Sensors?  Get the Quick Select Product Guide

Topics: Inductive Sensors, Applications, Ask an Expert

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