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ray.l
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Join Date: Jun 2008
Posts: 11
Good Answers: 1

Hopper Level Control

09/17/2009 7:01 AM

Hi,

I am having some trouble with a hopper on my plant. I need to be able to detect the level of material in the hopper to close a control loop on a vibro feeder. My problems are many. first, I can only use a non contact type of material sensor due to the temp and corrosive properties of the material. secondly the material is very abrasive. The hopper is also quite remote from any control equipment and cost dictates I use existing cables.

I am considering a two wire, loop powered, radar but have realised that my tec department are having trouble supplying an analog input card on the closest remote PLC rack.

My question is......is there a product that will allow me to power the "loop powered" radar and at the same time convert the 4-20ma return signal to a simple, (hopefully adjustable) digital output.

Any help???
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redfred
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Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
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#1

Re: Hopper Level Control

09/17/2009 10:46 AM

You didn't give us enough information for a concise answer but you did give us enough for a sound start. As you stated your problem is in detecting the level in your hopper without touching it and you require this analog level to be a 4-20mA sensor. Without knowing the size of the hopper and what goes into the hopper, any answers from us will be just a guess. Radar though I'm certain is not what you want for this will likely not be cost effective. You might consider an ultrasound sensor pointed on an angle into the hopper. Another possible approach will be to include a load cell and to weigh the amount of additional material in the hopper. In any approach, I would let the decision making capability of your PLC to convert the analog signal (amount of material) to the digital add more material signal. In your PLC's software you should also be able to add some signal conditioning characteristics (hysteresis, timers) to prevent false triggers.

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Simon Wan
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Join Date: Apr 2007
Posts: 577
Good Answers: 10
#2

Re: Hopper Level Control

09/17/2009 9:07 PM

Can you please let us know what type is your material that you store in your hopper since your said, it is corrosive properties and the material is very abrasive?.

Secondly, what is your temperature of your material?.

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jcarter817
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Join Date: Aug 2009
Location: Memphis, Tennessee USA
Posts: 5
#3

Re: Hopper Level Control

09/18/2009 12:04 AM

Without seeing your operation, I would suggest you contact Globalspec or Thomasnet to find the closest product to fit your needs. Good luck.

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ffej
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Join Date: May 2007
Location: Geelong, Australia
Posts: 1084
Good Answers: 54
#4

Re: Hopper Level Control

09/18/2009 12:07 AM

I've used a lot of radar, ultrasonics, lasers etc. and find it's often cheaper and more reliable to stick load cells under the hopper and weigh the material.

Then the type of material, dust, vibration, water content, angle of repose etc don't matter.

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DreadZontar
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Join Date: Jul 2009
Location: Montreal, Canada
Posts: 284
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#5

Re: Hopper Level Control

09/18/2009 12:23 AM

Assuming that you're looking to measure a continuous level ('continuous' is bad grammar ... continual in time, continuous in space), 4-20 mA-style, consider using an monitor/display, such as ones made by Moore Industries (http://www.miinet.com/products/sg_process.shtml). Install the monitor in your control room, run a signal cable to your measurement instrument, and presto!

If you need level alarming, make sure that the monitoring you choose have alarm switches built in.

Hope this helps!
DZ

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bioramani
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Join Date: Jun 2009
Location: Bangalore, India
Posts: 725
Good Answers: 24
#6

Re: Hopper Level Control

09/18/2009 2:26 AM

http://www.sapconinstruments.com/admittance/sla.html

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Anonymous Poster
#7

Re: Hopper Level Control

09/18/2009 12:10 PM

I like the load cell idea but theres one better , straine gauge on the legs or the cone it's self seen it liked it got it!
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