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Old June 10th, 2021, 09:56 AM   #1
Jim G.
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Load cell monitoring

We have a web converting process that involves the web passing over rollers with load cells on each end. This provides a tension readout from an amplifier into the PLC as an analog input. This signal is the sum of the individual load cell inputs.
Is there a way to monitor each individual load cell signal before going into the amplifier? We would like to know the individual signals while running with out upsetting the process.


Any ideas?
Thank you.
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Old June 10th, 2021, 10:13 AM   #2
AustralIan
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You need a digital transmitter like the Laumas TLB4. This would send all four load cell values as well as the summed value to the PLC via your favourite comms protocol.


At one time we were using an Applied weighing AW190 intelligent junction box. Maybe this would be useful as a retrofit.
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Old June 10th, 2021, 10:14 AM   #3
busarider29
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Quote:
Originally Posted by Jim G. View Post
We have a web converting process that involves the web passing over rollers with load cells on each end. This provides a tension readout from an amplifier into the PLC as an analog input. This signal is the sum of the individual load cell inputs.
Is there a way to monitor each individual load cell signal before going into the amplifier? We would like to know the individual signals while running with out upsetting the process.


Any ideas?
Thank you.
Signal splitters? That would give you two outputs per load cell. One for your process and the other for monitoring. It's just one option. Could get expensive if you have a bunch of load cells. Just one option here

Last edited by busarider29; June 10th, 2021 at 10:23 AM.
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Old June 10th, 2021, 02:08 PM   #4
Peter Nachtwey
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Quote:
Originally Posted by Jim G. View Post
Is there a way to monitor each individual load cell signal before going into the amplifier? We would like to know the individual signals while running with out upsetting the process.
It can be done but not without a lot of work. Load cells usually have outputs in the range of millivolts. The amplifiers have very high gain and amplify the output to a range of 0 to 10 volts. Gains of 2000 are common.


The problem is can you design of find other amplifiers with the same kind of noise free high gain and connect them so no noise is getting induced. It would be much easier to look at the amplified signals in the 0 to 10 volt range.
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Old June 10th, 2021, 02:43 PM   #5
busarider29
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Originally Posted by Peter Nachtwey View Post
The problem is can you design of find other amplifiers with the same kind of noise free high gain and connect them so no noise is getting induced. It would be much easier to look at the amplified signals in the 0 to 10 volt range.
Just one of a few reasons I did away with all of our load cell amplifiers, and instead bring the load cell/s directly into a load cell terminal on the PLC.
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Old June 15th, 2021, 06:03 PM   #6
kamenges
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Whose load cells are you using? Not that it matters much. Most of the bigger players in the web tension game will have at least one amplifier n the stable that will provide left, right and summed outputs. If not, PM me. I would have a couple of options.

Full disclosure, I am part of an organization that manufactures web tension control products.

Keith
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