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:
- What lengths of WCS absolute linear encoder system rails are available, and how do they connect?
- We are designing a cargo door locking system that has to be tamperproof. Would RFID technology work for this application?
- I was planning to use photoelectric sensors for people detection in a specific area. Which photoeye should I use?
- How do the wires connect in cable connector 42308C?
- How do I incorporate an AS-Interface network into an Allen-Bradley PLC?
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 Zach Steck. Zach works as an Application Engineer here at Pepperl+Fuchs. So welcome, Zach, and thanks for being here!
Zach: Hi John, thanks for asking me.
John: Ok, the first question asks about the lengths of our WCS (absolute linear encoder system) rails. Zach, what are the options, and how do the rails connect?
Zach: We do have some common lengths available, but in general, the WCS code rails are ordered to a user-specified length, up to 1030 feet. It's priced by the foot and has a typical delivery time of about five weeks. WCS code rail is offered in stainless steel or fiber laminate. It comes as one complete piece, though it would require additional hardware to mount.
John: In this next case, the customer is designing a cargo door locking system. It needs to be able to sense that an enclosure is open or closed, without any way to defeat the sensor configuration. This customer is thinking about using our RFID technology. Zach, what are your thoughts on this? What specific system and parts can you recommend?
Zach: There are a couple of options for this application when using RFID. First would be a standard system consisting of a controller read head and tag. This system is not foolproof, as the tags are not encrypted, so any tag of the same frequency could trigger an output. The second option would be a safety-rated RFID interlock switch. This would be the better choice if the enclosure door is protecting a person from injury. The RFID safety interlock switches cannot be bypassed or overwritten due to their factory programmed read-only code. These are part of AS-Interface Safety-at-Work, so they would need to be used with an AS-Interface network, or with a stand-alone safety monitor.
John: Zach, this next customer wants to detect when someone is inside a lavatory. The customer does not want to be dependent on continuous motion, for example, when the person is stationary, the sensor would maintain its output until the person leaves. The customer wants to be able to flushmount the sensor to the ceiling, without it looking conspicuous, like a camera. Perhaps the RL23-8-H-2000-IR/104/116/125 might serve well for this application. The FLT-D/38a is also of interest, but the customer felt that the range might be too long. Zach, can you please share your ideas, and if the customer's assumptions are correct?
Zach: It would be important to know the size of the lavatory and the area the sensor needs to cover. The two sensors mentioned are pretty different, and have their own pros and cons. The RL23-8-H-2000-IR/104/116/125 is a much smaller housing, and has a very precise sensing field that is only about 50 mm in diameter at the maximum range. If there is enough area inside the lavatory, a person may not be detected. The RL23-8-H-2000-IR/104/116/125 is also designed with industrial applications in mind, featuring bright LEDs and glass lenses, so it may look more suspicious to the lavatory user. The FLT-D/38a is an area scanner commonly used for automatic doors. It covers a very large area and also offers a lot of adjustibility. Since it is used for doors, the housing is designed to be less noticible. Both sensors could be possible solutions for this application.
John: Ok, switching gears, this customer wants to know how the wires are connected inside the 42308C cable connector. Zach, can you explain?
Zach: This connector uses solder terminals, so the customer would be required to solder their wires within its housing.
John: And the last question: This customer has an AS-Interface network, and he wants to know how to incorporate it into his Allen-Bradley PLC.
Zach: Allen-Bradley PLCs communicate through Ethernet/IP and are configured with the RSLogix software. Depending on the model of your PLC, you would use an Ethernet gateway or scanner card to interface the PLC to the AS-Interface network. To simplify installation, we offer downloadable EDS files, add-on instructions, and description files to be used with RSLogix 5000. The EDS file would require the software and PLC to be version 20, otherwise you would need to create a generic Ethernet module. For further information on this and setup videos, you can visit our website.
John: Well that concludes this segment of Ask an Expert. I'd like to thank Zach for joining me today, and thank our audience as well.