How to Choose a Photoelectric Sensor

Photoelectric sensors may seem rudimentary to a lot of people out there especially if you’re a seasoned vet. If you’re a new guy it may seem a little daunting since there’s so many different options, so many different shapes, sizes, options available, and boy if you pick the wrong one you’ll know it quick. It can definitely be the difference between being a stable logic program that depends on that sensor to make decisions, and also just the stability of the throughput on the line. So you really want to make sure you pick the right photo electric sensor, and it’s not rocket science as there’s really 3 basic types of photoelectric sensors.

The first type is a through beam sensor, which is basically an emitter and a receiver that just look right at each other. So, if you break the beam there’s an output, or there may be an output whenever the beams see each other. That’s one way to look at it.

There’s also what’s called retroflective and that’ll be where you use a reflector and a sensor. The sensor basically sees its light source bounce off the reflector and come back to the receiver that’s in the same housing.

The third type is diffuse reflective which requires no sensor so the light will bounce off the object and come back into the receiver itself.

The differences between the three typically are gonna affect your sensing distance and also it can really hinge on the reflectivity of the object that you are trying to sense. So really you just need to take a look at your application, the mounting location of the sensor, how far away you can be or how close you can be to the object your trying to sense. Those factors can really help determine which one of those 3 are going to be the best for you.

There are different light sources inside of the sensor and that can affect the sensing distance. It can also affect the stability of the signal, and also in certain environments where there can also be contaminants in the air or light pollution, external light pollution that affects the receiver, you might need a different light source to mitigate some of those. Your typical light sources that you’re going to find in today’s market are gonna be LED lights, infrared lights, laser lights, and every now and then you’ll run into an application that calls for an ultraviolet light inside of a sensor. And again that’s just gonna affect the sensing distance, the stability, things of that nature.

Really the number one thing I can recommend when trying to find a sensor and make sure that it’s right is to get a sample and test it, and retest it, and test it with different types of sensors and different types of environments. Always remember to test for the extreme. Don’t test under normal operating conditions because if one day it’s cloudy out or one day the sun is right in your eyes, if you didn’t test for that, if you were just testing for the normal operating environments you’re gonna get an unstable signal. So always test for the worst case scenario, the extremes are what you really want to look for. Another good rule of thumb if you can, is to try to use models with quick disconnects on the back. That’s a major plus for your maintenance staff whenever you need the ability to change a sensor quickly without having to replace the entire wire all the way back to the cabinet it’s wired into –  that’s why they designed these. And most sensor manufacturers are going to give you the option to either have a flying lead coming out of the sensor or on the back end of it you’ll have a little M12 or M8 through your 4 pin quick disconnect that this can just hook right into.

And so like I said it’s not rocket science, just make sure that you test. I can’t stress enough how many times people think that they know that a sensor will work in an application, they never tested it, and then we get a call saying they need to return the model for a different one because for some reason it didn’t work for one reason or another that would have been easy to test. Omron even manufactures a checker, which is basically a DC power supply that you can wire a sensor into with a little light output that tells you when the output of a sensor turns on. You can even turn on a little buzzer so it’s really handy to be able to hook up a sensor, go out on your line and just start testing stuff and see when you get your output and make sure its stable.

If you have any questions, you need help with this, there’s always new sensors coming out, all kinds of new technology that makes them more powerful, gives them extended range, and that’s something Innovative-IDM can really help you with because it’s our job to know that kind of stuff and to be able to help you with any applications that come up. We also have a sensor specialist we can bring in if necessary, you can also find a lot of this information on our website which is innovativeidm.com. Go to our Knowledge Center, where you can find white papers for our different types of sensor applications and best practices. After all we are Home of the Legendary Customer Experience.

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