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Old November 8th, 2018, 07:44 AM   #1
deanfran
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Proper Non Contact Sensor for Water Based Solution in Glass Tank

We've had an intermittent issue with this for years. The application is sensing a level, or more accurately the absence of level in smallish ~5-10 liter Pyrex buffer tanks. The OEM solution i.e. a capacitive prox switch for the tank fill signal works very well, except for when the product is high conductivity, such as a 7% NaCl or 24% sugar solution. We don't know if the switch picks up whatever liquid is still adhering to the interior surface of the pyrex, or what. We've tried different sensing distances, but that doesn't seem to matter. The operators end up constantly fiddling with the sensitivity adjustment on the prox switch, and that just doesn't cut it. Any ideas, experience or, suggestions are appreciated.
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Old November 8th, 2018, 07:56 AM   #2
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The capacitive proximity sensor is the sensor for the application.
What about using something with a push button teach function? Similar to the following:
https://cdn.automationdirect.com/sta...x30mmcapct.pdf

The other option that comes to mind is the ultra sonic sensor. This must be mounted from the top looking down into the liquid to sense the level.
https://www.automationdirect.com/adc...ximity_sensors

Hope this helps you out.
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Old November 8th, 2018, 07:59 AM   #3
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Load cell, take into account the specific gravity of the fluid. So you need to know what's in the tank and when as a parameter, which includes the temperature
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Old November 8th, 2018, 08:00 AM   #4
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Put the vessel on load cells.
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Old November 8th, 2018, 08:47 AM   #5
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Radar level sensor
https://www.vega.com/en/home_us/Home...el-measurement
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Old November 8th, 2018, 09:18 AM   #6
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You dont think Radar is overkill for 5-10 liters ?
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Old November 8th, 2018, 09:42 AM   #7
danw
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The Siemens CLS100/200 capacitive point level sensors claim some discriminating sensing technology that can handle difficult level sensing apps.

I've used them for solids sensing - corn level through a glass sight window in a bin, and the level of resin media in industrial water softeners both by contact and through a sight glass. I was amazed that it could adjusted to tell the difference between water-and-resin and water only.

It's designed as a contact device with a tapered teflon coated sensor body so mounting externally is always a challenge and I'm amazed at what people come up with.

A Siemens distributor can probably come up one or the other to let you try one and see if it can avoid a false level reading due to residual liquid film on the pyrex (I think you're right on that point). My gut feeling is that it probably can.

Dan
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Old November 8th, 2018, 11:17 AM   #8
deanfran
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Load cells aren't really an option here, and punching through the 1 inch thick stainless steel top on these vessels isn't something I want to get into if I can help it. We've actually tried a couple of the teachable cap prox's from AD. They exhibit the same problem. I've contacted Banner Engineering. They claim to have some sensor solutions. I'm going to reach out to whomever our closest Siemens rep is too. One idea we've come up with is a plastic float if you will, that just stays inside the Pyrex container and would sit on the surface of the liquid. We could sense that easy enough. This is an aseptic application, so our float will have to meet a few requirements, clean, smooth, be able to survive steam in place operations. The tanks fill and empty from the center bottom, so a doughnut shape probably fits the bill.

Last edited by deanfran; November 8th, 2018 at 11:30 AM.
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Old November 8th, 2018, 03:32 PM   #9
brendan.buchan
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Not sure how appropriate these would be, but our rep recently made us aware of the Balluff Self-Adhesive Capacitive Strip Sensor.


They are designed to be stuck onto the outside of small plastic or glass vessels for a non-intrusive level measurement.
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Old November 8th, 2018, 05:43 PM   #10
GaryS
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Here is a solution that I think will work for you
Metritape
the question would be can you get them the size you need

http://jowa-usa.com/industrialMetritape.cfm
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Old November 9th, 2018, 02:45 PM   #11
tarik1978
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Check if this fit your needs :
IRU-5000 Self-Contained Ultrasonic Level Sensor

https://www.binmaster.com/products/p...s-to-79-inches

The LVU30A Series of CE and RoHS compliant low-cost ultrasonic sensors 365$
https://www.omega.com/pptst/LVU30A.html

Last edited by tarik1978; November 9th, 2018 at 02:56 PM.
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Old November 10th, 2018, 07:15 PM   #12
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in a glss tank you can use a simple light reflector, the light will reflect different when there is water in the container.
in very old days the level of the steamboiler worked with a light thru the glass tube.
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Old November 14th, 2018, 10:33 PM   #13
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Quote:
Originally Posted by JesperMP View Post
You dont think Radar is overkill for 5-10 liters ?
From my experience with Vega, they’re accurate and you can’t beat how versatile they are.
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Old November 16th, 2018, 01:14 PM   #14
deanfran
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Just in case someone stumbles across this in the future, I think we are going to go with this guy. Specifically tuned for water, fits standard 30mm threaded mounting, just the ticket. Needs an emitter and receiver, but its pretty slick.



https://www.bannerengineering.com/us...art.79177.html
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