Pepperl+Fuchs Blog

Ask an Expert Industrial Sensors - Episode 4

Posted by John Appleson on Wed, Aug 13, 2014

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 on our BB10 Series photoelectric sensors:

Thru-beam photoelectric sensors

BB10-P-F1/25/33/35/102/115-7m and BB10-P-F2/25/33/35/102/115-7m

  • I want to use these thru-beam sensors on an application that counts people moving through a 3 ft. doorway. Do you think these sensors would be a good fit for this application? 
  • Do you anticipate any problems having two transmitters and receivers one inch from each other, since the F1 and F2 versions operate at different frequencies?
  • Do you see any reason to alternate the transmitters and receivers of these sensors?
  • What is the expected life span on the IR emitters for the BB10 thru-beam sensors?

Ask an Expert Industrial Sensors - Episode 4Feel 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 Casey Sutton. Casey works as an Application Engineer here at Pepperl+Fuchs. So welcome, Casey, and thanks for being here!

Casey: Hi John, thanks for asking me.

John: Ok, Casey, let's get started. The first question asks about our BB10-P-F1/25/33/35/102/115-7m and BB10-P-F2/25/33/35/102/115-7m thru-beam photoelectric sensors. The customer wants to place the transmitters horizontally, one inch from each other, on one side of a door frame. On the other side, they want to install matching receivers in the same manner, to count people moving through the doorway. Casey, do you feel that these thru beam sensors would be a good fit in this situation?

Casey: Yes - in this application you can use the BB10 photoelectric sensors side-by-side to count people moving through the doorway. With additional logic, depending on which sensor activates first, you can also monitor the direction each person is moving through the doorway.

John: Staying on the subject, do you anticipate any problems with having two transmitters and receivers one inch from each other when the F1 and F2 versions are used, since they operate at different frequencies? In other words, there should be absolutely zero interference, correct?

Casey: That is correct. With photoelectric sensors, a common issue that arises when mounting two sensors in close proximity, is cross-talk. This is what happens when the emitted light of one sensor is being received by the other sensor. By using two different frequencies for the emitted light, each sensor will only look for, and sense, its own emitted light.

John: Do you see any reason to alternate the transmitters and receivers? Meaning, instead of having both the transmitters on one side, and receivers on the other, would there be any benefit to having the receiver and transmitter on the same side, with the mating receivers and transmitters on the other?

Casey: No. Alternating transmitter and receivers is one way of dealing with cross-talk among multiple thru-beam photoelectric sensors. Since the two sensors are using two different frequencies, cross-talk will not be an issue, and alternating is not necessary.

John: Casey, what is the expected life span of an IR emitter?

Casey: The expected lifespan on the entire sensor is twenty years. This is for the sensor as a whole, including the IR emitters.

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

Questions about Industrial Sensors?  Ask an Expert!

Topics: Photoelectric Sensors, Ask an Expert

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