Inductive Sensors for flushed mounting used non-flush

Inductive sensors are a key component in many industrial applications. They are used to detect the presence of metallic objects without physical contact. The way these sensors are mounted can significantly impact their performance. This article will explore the effects of flush and non-flush mounting on the scanning range of inductive sensors.

Inductive sensors designed for flush-mounting are typically completely embedded in a metal surrounding (see Figure 1). When these sensors are used non-flush or mounted in thin metal sheet or non metal, the scanning range (SR) is usually reduced (see Figure 2).
This is due to the absence of pre-damping, which means the target material must get closer to the sensor to achieve the same amount of damping until the sensor reacts. 
It’s important to note that using a flush sensor non-flush does not imply that the sensor is of poor quality. It merely explains why the scanning range might be affected. In some cases/ sensor types, the scanning range might even be larger than normal, making the sensor more sensitive to other influences.

Let’s consider two sensor families as examples: the IME and the IMB.

The IME family of sensors, which are housed in brass, experience a reduction in scanning range when used non-flush.

On the other hand, the IMB family of sensors, designed for more advanced applications, are housed in stainless steel. Stainless steel, compared to brass, has different magnetic properties and lower conductivity. Therefore, when an IMB sensor is used non-flush, the scanning range might not shrink as much as with a brass-housed sensor. In special circumstances it could even happen the Sr is getting bigger.

Often the specified sensing range can´t be reached due to the sensor not being mounted in the specified way.
To reach the sensing range anyway, you can artificially pre-activate the sensors with threaded cylindrical housing in example by mounting 2 additional nuts close to active area, as you can see in the picture below:

While inductive sensors can be versatile, it’s recommended to use them as per their design specifications. Using a sensor outside its intended application could lead to unexpected results and performance variations. Always consider the material and design of the sensor, as well as the mounting method, to ensure optimal performance in your specific application.