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Pepperl+Fuchs Blog

How Do I Program a Laser Displacement Sensor?

Posted by Sean Miller on Tue, Jul 23, 2013

When you purchase a laser displacement sensor, it will likely not be set up for your specific application out of the box. Programming instructions are included, but can be confusing tVDM28 laser sensoro a first-time user. Let‘s take a look at programming one of the more popular series.

The VDM28 Series offers a low-cost solution to applications that demand long-range accuracy. To program the laser displacement sensor, you set the target distance by using the rotary switch located on top of the unit. Most VDM2s have two outputs that you can program. For example, if you want to set up a window, you can have the output turn on when an object enters the range covered by the window, and turn off at a closer or farther distance when the object is outside the range of the window. See the B>A quadrant shown below. You can also program the opposite, as shown by the A>B quadrant below.

Programming a laser displacement sensorYou can use the Run switch shown below during operation. The lines above the x-axis in the graph shown above mean that the output is on. The A leer graph provides an example for teaching the simple threshold value.

Line up the laser sensor at the threshold distance and move the selector switch to position B on the output you are using, depending on how it is wired. Push the Set button for about 1 second until you see the LED lights flash. The output stays on as long as the target remains at that distance or closer. An object any farther away does not trigger the output. Refer to the diagram below.

Setting threshold distance on a laser sensorTo set up a window farther away, place the laser sensor farther away and set the A position to the output configuration seen in the lower left corner of the graph. Reset the unit if the setup is unsuccessful. You can reset the unit by pressing the Set button and holding it for about 10 seconds until the LED lights stop flashing. The outputs can be reset individually. If you want to reteach only one of the outputs, move the selector lever to the desired output and perform the reset.

Laser displacement sensor outputsThe graph above lists the discrete or digital outputs. We also offer models with an analog output that are capable of giving off a rising or a falling ramp on a 4 mA ... 20 mA signal. The Teach-in procedure is the same as before, except that an analog output model such as the VDM28-8-L1-IO/73c/110/122 has an analog output instead of a separate discrete output. For example, if you want to have a 4 mA signal when the target is close and a 20 mA signal at the farthest distance from a target, move the selector switch to A on Q2 and perform the setup when the target is at the near distance. Then place the sensor at the far distance and teach in the new distance with the B selected. The opposite would be taught in for a falling slope. You can then use run mode.

Please note that models with two discrete outputs such as the VDM28-8-L-IO/115b/136 can have two separate outputs, one for each Teach-in (Q1 and Q2). This design allows two different windows or thresholds to be taught in and can reduce setup time if more than one Teach-in value is needed to operate the sensor.

It is also important to note that the sensor does not have to be taught in in the application. At times it might be difficult to teach in a product in the application. The sensor can be taught in from a desk or outside the application when necessary. Doing so requires using a similiar target to ensure consistent performance within the application.

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Topics: Troubleshooting, Laser Sensors

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