Pepperl+Fuchs Blog

How to Install the MNI40 Incremental Encoder

Posted by Zach Steck on Tue, Apr 30, 2013

The MNI40 magnetic incremental rotary encoder is the most compact encoder in the Pepperl+Fuchs product line.  Even with its small size, this incremental encoder is extremely durable and is not affected by environmental conditions. It has an IP67 protectiMNI40 incremental rotary encoderon rating, so you can expect reliable performance in dirty, dusty, or even wet conditions.  It also has a large temperature range from -40 °C to 100 °C and has proven itself with a long service life at these extreme temperatures as well as operating at high speeds.

The MNI40 incremental encoder is made up of two components, a sensor head and a coded magnetic wheel. This wheel is also very robust due to its elastomer-coating, making it resistant to dirt as well as thermal or mechanical shock.  

Beyond durability, the MNI40 features internal intelligence and self-diagnostic capabilities to assist the user in installation as well as ensuring reliable operation. Two-color LED status provided by the encoder makes installation of this device simple.  Popular applications for this incremental encoder include:

  • Machine and plant engineering
  • Automotive industry
  • Mobile equipment
  • Renewable energy
  • Material handling
  • Print and paper industry
  • Packaging industry

Out of the box, you have the following parts to install the MNI40:

  • Sensor housing
  • Magnetic wheel
  • Two screws for attaching the sensor
  • Plastic mounting aid
  • M3 hex key to attach the magnetic wheel

MNI40 kit

The first step in the installation process is to attach the code wheel to a shaft. In the model number for the MNI40, the user will specify a bore hole size from the options of 6, 10, 12, or 15 mm (other mounting hole dimensions can be made available.) Slide the magnetic wheel onto the shaft and use the hex key to tighten the two M3 screws securing the wheel in place.

Attach the code wheel to the shaft

Once the wheel is set, the next step is to mount the sensor in position to take readings from the wheel. At this point, the plastic mounting aid is used to ensure the correct distance between the sensor face and magnetic wheel. The sensor face will have a target displayed which shows you where to align the sensor with the wheel. The center point of that target should be in line with the center point of the magnetic code wheel.

Align the sensor with the wheel

This sensor will allow a displacement of +/- 1 mm in either direction from the center so it has to be precise. The two components must also be mounted flush to the backdrop which needs to be a level surface. The angular displacement permitted is +/- 3 degrees so the two components should be set as flat as possible. Once you meet these conditions, you can attach the sensor housing in place using the two screws provided.

Mount flush to the backdrop

The MNI40 features a two-color LED status indication that can be used to ensure that the mounting is correct and to troubleshoot the device.  If the two pieces are aligned accurately, then the green LED should be flashing. Once it completes a full rotation for code verification, it will stop flashing and remain lighted (solid).

The encoder provides an output when the green LED is either flashing or solid.  If you see a solid red LED, then there is no communication between the sensor and wheel. The alignment is off or there is too much distance between the two.  If the LED is flashing red (this may appear to be a yellowish flashing light on the device) the wheel is slightly offset or not quite close enough. During normal use, if the red LEDs are displayed and all of the alignment positions are correct, this may indicate a velocity outside of the specified limits or a supply voltage drop.  In this case, verify the technical specifications of the complete model number that you are using.  If the red light is displayed in either form, no output is being transmitted by the encoder.


A simple installation process
The simple installation process of the MNI40 magnetic incremental rotary encoder can be completed in three basic steps:

  1. Attach the code wheel to the shaft using the hex key and two M3 screws 
  2. Align the sensor to the wheel using the plastic mounting aid and attach with the provided screws
  3. Verify operation of the device with the two-color LED status indication
Verify operation
Questions about Rotary Encoders?  Get the Quick Select Product Guide

Topics: Rotary Encoders, Troubleshooting

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