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Effective June 2013
Supersedes October 2005

Technical Data 

TD05301003E

iProx inductive proximity sensors—
optimizing hysteresis

Description

The iProx

 family of inductive sensors features extremely 

high sensing performance. Like many sensors, the various 
operating characteristics, such as range, hysteresis, and 
output, have been preset from the factory to be ideal for 
a wide variety of sensing applications. Where iProx differs 
from other sensors is in the ease of changing these default 
operating characteristics to suit specific applications. This 
document will cover hysteresis—what it is, the benefits of 
modifying it, and how to change it.

Hysteresis and why it is important

All sensing devices incorporate some level of hysteresis. 
Hysteresis is the difference between the signal levels at 
which a sensor turns off and turns on. This difference can 
usually be observed by slowly bringing a target toward the 
sensor until it turns on and then moving it away until it turns 
off. The point where the sensor turns on will be slightly closer 
to the sensor than the point it turns off (see 

Figure 1

).

Sensor

Sensor

Turn-On Point

Turn-Off Point

Hysteresis

Figure 1. Hysteresis in Presence Sensing

This difference, usually in the area of 10% to 15%, is 
necessary to reduce the sensor’s sensitivity to noise and 
vibration. It also eliminates multiple transitions (called 
“chattering”) at the point where the output switches.  
A mechanical version of this effect can be found in many 
electrical switches. For instance, as you move the handle 
just past the center point, a spring in the switch will pull the 
handle all the way over, ensuring that the switch ends up in 
a definite ON or OFF state.

When it is necessary to adjust hysteresis

As stated before, the factory preset hysteresis setting is 
appropriate for most sensing applications. But for some, the 
ability to fine-tune the sensor hysteresis setting will greatly 
increase reliability. For others, it may be the only way to solve 
the application.
For sensing applications that occur in areas of high shock 
or vibration, a wider hysteresis setting may be necessary to 
ensure reliable machine operation (see 

Figure 2

).

Sensor

Factory Preset Hysteresis

Heavily Vibrating Target
Exceeds Standard Hysteresis
Limits and Causes Unreliable
Sensor Operation

Wider Hysteresis Setting to
Accommodate Unintentional
Target Movement

Figure 2. An Example Requiring Increased  
Sensor Hysteresis

By increasing the hysteresis, you can accommodate 
unintentional movement of the target due to shock or 
vibration without causing multiple output signals during  
one sensing event.
When widening the hysteresis, it is important to ensure  
that the normal travel of the target will take it far enough in 
both extremes to ensure reliable turn-on and turn-off events 
(see 

Figure 3

).

Wider Hysteresis
Setting

Vibrating Target

Target Must Travel
Far Enough in Both
Directions to Ensure
Reliable Turn-On and
Turn-Off Events

Sensor

Sensor

Figure 3. Target Travel Considerations With  
Increased Hysteresis

On the other end of the spectrum, you may have an 
extremely precise and stable application where you need 
highly accurate results. In this case, setting the hysteresis  
to a tighter setting than the factory preset will provide this 
high accuracy.

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