Pepperl+Fuchs Blog

Ask an Expert Industrial Sensors Episode 22

Posted by John Appleson on Fri, Jan 20, 2017

This episode of Ask an Expert for industrial sensors examines and provides answers to interesting sensing questions we've received from customers just like you. We explore and answer these questions:

  1. Do you have non-incendive inductive proximity sensors?
  2. Diffuse mode photoelectric sensors - what are the adjustment ranges?
  3. Do you have a steel-sensing sensor that can withstand temperature extremes, shock, and vibration?
  4. Can the inductive sensor NJ8-18GK-SN be ordered with terminal connections instead of leads?
Ask an Expert your questions about industrial sensors

Feel free to ask us your sensing questions, and we'll do our best to reply with the whys and hows of a particular solution.




John: Welcome to Ask an Expert! Hi, this is John Appleson, Marketing Manager with Pepperl+Fuchs. Today, I'm joined by Tracy Molnar. Tracy works as an Application Engineer here at Pepperl+Fuchs. So welcome, Tracy and thanks for being here!

Tracy: Hi John, thanks for asking me.

John: The first question asks about the NBB4-F1-E2-V3 inductive sensor and associated cable V3-GM-5M-PUR. Are they both non-incendive? The customer has a sensor and cable in a Class I, Div. 2 environment, and needs to ensure this is correct. He wasn't able to find this information on the specification sheet. Tracy, can you advise?

Tracy: The majority of our inductive, capacitive, and magnetic sensors, including the sensor this customer has, are rated non-incendive, and are FM approved for installation in Class I, Div. 2 environments. We have a control drawing we can send to customers, which details the requirements for such installation. These include the need to protect the cable and wiring by following the NEC guidelines for hazardous locations. Our cordsets, such as the one mentioned by this customer, have no hazardous ratings. So they would need appropriate protection, such as enclosure in a conduit, in accordance with the NEC.

John: Tracy, this customer needs to know what the adjustment ranges are for the ML17-8-450/136/143 diffuse mode photoelectric sensor. Can it detect an object at 20 mm, and ignore an object at 30 mm? The customer would like to know what the best color would be for the target?

Tracy: The data sheet for this customer's sensor lists an adjustment range of 60 mm to 450 mm. But in general, standard diffuse mode models like this one can't be adjusted as he describes. For detection of targets at a particular range, while ignoring targets at a greater distance, it's better to choose a sensor with adjustable background suppression. All photoelectric sensors detect lighter or brighter colors more easily than darker or duller ones. But a sensor with background suppression is designed to depend more on the angle of light reflected, so its black and white difference is smaller than a standard diffuse sensor. All of this means that the customer's question regarding target color really depends on the application, and the type of sensor being used. When using a standard diffuse model, lighter or brighter colors are best for targets, and any objects that you don't want to be detected should be darker or duller. But, when using a sensor with background suppression, target color doesn't play a big role in detection.

John: Tracy, this customer would like to find a sensor that can detect a one and one half inch diameter steel pin in a steel hole. The pin, which is used to ensure that a telescoping mast cannot collapse, is a safety-critical device. If the sensor fails to detect the correct location of the pin in the hole, an alarm sounds, and corrective action must be taken. If the sensor falsely detects the location of the pin, then the telescoping mast could collapse with disastrous results! This is why the customer needs a reliable sensor. He also notes that this is an oil field application with lots of vibration, shock, and extreme operating temperatures of -40 °C to +50 °C. Tracy, what would you suggest for this application?

Tracy: There's a lot going on in this application, but we can break it down and find a solution. For the detection of steel, an inductive sensor is best. These have a relatively short range, so the sensor can be mounted close to the pin, in a place where it's detected when in the proper position, but as soon as the pin moves away, out of its safe position, it won't be detected, and the sensor state switches. Since the pin is in a steel hole, The customer will need to select a sensor designed for flush installation in metal, also known as shielded or embeddable. And because the location is hazardous and safety is involved, I would recommend an inductive sensor with NAMUR output and safety function. An example is NJ2-12GK-SN. A quick look at the data sheet for this model, which the customer can download from our website, shows that this sensor has all the required specifications for operation in the harsh environment he describes. It should also be noted that this type of sensor output requires the use of an appropriate failsafe interface unit, to maintain both its intrinsic and functional safety features. An example of this is KFD2-SH-Ex1 switch amplifier.

John: In this next application, the customer would like to know if the NJ8-18GK-SN inductive sensor, instead of being pre-leaded, could be ordered with terminals connected to PTFE cables on site, and also with an LED option to facilitate installation. If not, Tracy, then what can you suggest?

Tracy: The sensor in question has an M18 threaded cylindrical housing. Some of our inductive sensor housings are available with terminal connections, but not this one. An example of one that does, and has the same safety NAMUR output, is NJ15S+U4+N. The limit switch style housing is larger than the M18 cylindrical, and the sensor has longer range. As for the LED switching status indicator, none of our sensors with safety NAMUR output include that feature, but if functional safety is not required, we offer NCN15-M1K-N0, which has standard NAMUR output, and LED indicator, and terminal connection, in a mini limit switch style housing, which is somewhere between the size of the M18 cylindrical and the larger limit switch style.

John: Well, that concludes this segment of Ask an Expert. I'd like to thank Tracy for joining me today, and thank our audience as well.

Questions about Industrial Sensors?  Ask an Expert!

Topics: Ultrasonic Sensors, AS-Interface, Photoelectric Sensors, Ask an Expert, RFID

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