Load Cell Interface

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Thread Starter

Weigh_man

I need to monitor 8 load cells simultaneously. I can go on serial port but it is too slow and I will not be able to monitor weight on each
load cell fast enough.

I can go to a load cell with RS485 output but I do not know if I can talk to a PLC. My preference is a Siemens S7-300 PLC.

Is there any converter that can connect to load cell and be connected to a PLC via PROFIBUS? That way the data from each load cell be there
on the PLC bus and there would be no speed problem.

Am I right in my assertion? Any one has suggestion per my scheme or recommend another?

Thanx.

Gulzar
 
H
I don't know about about profibus but I do know that Red Lion Controls makes a 4-20 MA load cell adapter. Then you can go to a analog card and read the cells in your PLC.
 
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Hakan Ozevin

RS485 is the name of the electrical signal standard for communication (hardware). Profibus is the name of a communication protocol
(software+hardware). Profibus uses RS485, but every RS485 interface does not need to support Profibus (hardware fits, software not).

Therefore, you should know the protocol your Rs485 interface is supporting and decide accordingly.
 
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Donald Pittendrigh

Hi All

Take a look at the following web site

"http://www.cs.purdue.edu/homes/bxd/jaguar.html":http://www.cs.purdue.edu/homes/bxd/jaguar.html

They deal with Jaguar scales from Mettler Toledo, I have just commissioned a machine with 4 of these units on Profibus to S7-400 and they seem to work well.

> > I need to monitor 8 load cells simultaneously. I can go on serial port
> > but it is too slow and I will not be able to monitor weight on each load
> > cell fast enough.

You an use RS 485 with a CP341 interfae, it is unlikely to be faster than a serial port (presuming you mean an RS232 port) however I am able to update a Citect SCADA system every 100ms from the CP341 serial card using RS232 so it depends on how fast fast is.

> > I can go to a load cell with RS485 output but I do not know if I can
talk
> > to a PLC. My preference is a Siemens S7-300 PLC.

Mine too.

> > Is there any converter that can connect to load cell and be connected toa
> > PLC via PROFIBUS? That way the data from each load cell be there on the
> > PLC bus and there would be no speed problem.

Regards
Donald Pittendrigh
 
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Anthony Kerstens

Is there a millivolt input module for the S7.

I've heard of load cells wired to mV input modules for Modicon Momentum.

Anthony Kerstens P.Eng.
 
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Shahid Waqas Chaudhry

You can use the Simatic Siwarex Module to directly connect the system with your S7-300 system. Check in the Siemens Catalog [CA01] or contact your local siemens dealer.

Thanks and Best Regards,
Shahid Waqas Chaudhry
 
Hello!

You must use the B&R make PLC.
B&R is having direct loadcell i/p to PLC, you do not have to do any thing extra.

Regards
upendra
 
Hi,
If you have already 8 load cells , presume that MV output. I was not understand you want to combine all 8 load cells and to be read the
summed output 0r not.

Advantech ADAM modules are available directly connect the load cells to DH 485 link. from dh 485 to Voltage.
it's cost you approximately 600 US Dollars . Again here speed is a question.
Alternatively you can try mercury make AD 4375 V weighing indicator with provision OP 7 direct millamps. Its cost you 1300 USD. Definitely
it will suit to the PLC languae , and which is Instrument user language 4-20ma
Regards,
mullapudir
 
Z
I want to make a circuit for link output of load cell to an A/D. how to do it? please send for me this circuit . thank you.
 
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