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CanaanP

Ultrasonic for aggregate material?

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I'm starting up a job for an automated radial tele-stacking conveyor. It's PLC driven, and the previous model used a paddle switch for detecting when material was on the conveyor. That broke immediately, and replacements have all broken. The customer wants to consider an ultrasonic sensor of some kind as an alternative. Can anyone recommend something that will look at a 36" wide conveyor belt and tell if there is material present or not? The material is crushed rock, like 1/2 inch base. Preferred option would have a contact that fires back to a digital input on PLC. Thanks

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I've had pretty good results using the upk series from snt. you can get them with analogue or digital output. adjustment is by a pot. There are a lot of manufactureres around "omron,banner,sick" of the smaller higher frequency ultrasonic tranmitters, but most have buttons on the side of the sensor for calibration that require you to press the buttons in different combinations to make adjustments. This is alright until the sensor is mounted. In my opinion anyway.

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The part that makes this tricky is whether or not you need to "see" the whole 36" width of the conveyor. You may need to use multiples. I will be using an EchoPod ultrasonic sensor from Flow Line Options on a tank level system. This particular sensor has a range of 49.2" with only a 2" deadband. The beam width is 2" and touts an accuracy of 0.125" and a resolution of 0.019". It has 4-20mA out as well as 4 relays. The outputs are set up using a supplied software package. A comm adapter will need to be purchased, but the price was reasonable. The sensor will run me under $400 and the programming fob will run about $50. I have used similar sensors from Carlo Gavazzi that were in a 18mm tubular form, but the dead band was significant and they only provided 4-20mA output. If you need a wider view, or a longer range, you may need to look at radar. A laser scanner could also do the trick, but would be significantly more expensive.

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Well I don't think the entire width would be necessary... this is a quarry style conveyor - not sure what the official term would be, but it dips in the middle because of the way the rollers are configured. The material will be centered on the belt. I don't think lasers would be appropriate in this case because of the dust. I have been looking at SIC sensors today. I used one on a job before that the customer supplied, and I ended up really liking it. Edited by CanaanP

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