How to choose between proximity sensor, photo eye and fiberoptic sensor
A Control Design reader writes: We had downtime on a production machine due to failure of a presence sensor recently. The inductive sensor that failed had a unique form factor and was embedded in a part nest. My boss was not happy; production shut down for a day because the $37 "special" sensor couldn't be found in stock anywhere.
To keep this from happening in the future, the boss suggested we replace all nonstandard presence sensors with either a 12-mm barrel inductive proximity sensor, a diffused photo eye or some type of fiberoptic sensor. I don't think it is as simple as that and want to develop a document for presence-sensor standards and best practices that will help to define upgrades and future new equipment. What do you suggest?
What are the handful of sensors that can do it all for presence sensing in machine-control and part-handling applications?
No universal standard
Unfortunately, there is not a universal standard for all sensor products, and the performance of competitive products not always are exactly the same. From a housing stand point we suggest the following:
• For limit-switch applications, we recommend to use products that follow CENELEC EN 50041. This will ensure the devices have the same mounting pattern and actuation. In most cases, this means simplified replacement.
• For electronic sensors such as inductive, capacitive, ultrasonic and photoelectric, we recommend to use standard cylindrical diameters such as M8, M12, M18 and M30. This cylindrical universal housing allows more interchangeability with products from multiple vendors. Always use M12 and M8 connectors that allow you an easy replacement without having to rewire the sensors.
If you follow these basic rules, you will have a more flexible plant or machine. Always remember that the performance of products differs greatly between vendors, so always be sure to check the specs before purchasing.
Luis Torralva / Telemecanique Sensors sales & marketing manager / Schneider Electric
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