Load cell characteristic value

abdulrehman

Member
Join Date
Feb 2011
Location
Karachi
Posts
2
Hi,

I am working on packaging machine having 16 load cells.the output of the load cell varying from 0 -25mv and there is no specifications mentioned on that.

1:what is characteristic value?How to find the characteristic value of the load cell?
2:Is the charactersitic value dependant on the load or excitation voltage?,in other words if i change the value of the nominal load like 50 to 100 gram then what will be the caharcteristic value? load cell excitation voltage is +7,-7V volts
3: Can i use the Fatek load cell module(FBs-1LC) with my load cell in which there are only four ranges 2mV/V,5mV/V,10mV/V,20mV/V?My maximun load range will be 100 gram.
4:I wanna convert/amplify this signal to either 4-20mA or 0-10V output?plz suggest the signal conditioner. ..

Regards
AR
 
25 divided by 14 is around 2 so go with that number.
what is the max the loadcell can have?
putb that max into one cell and measure the outcoming voltage.
Better is not to use converters but direct into a PLC and if speed is not important you could use some cheap relays.
WAGO has direct loadcell inputs.
 
What brand of load cell is it, and what is the MV/V rating on it as well as capacity? I have used Hardy C2 cells that have 3mV/V output, meaning that at 5Vdv excitation, the output is from 0-15mv. That output value was depending on load ie 0mv for no load, 15mv out for full load as rated on load cell. The load cell module may depend on whether or not there are comms between the controller and load cell, or strictly a mV signal. The range (mV/V) of load cell detrermines what range you would use on the controller. I'm not sure of a signal conditioner. I've used Hardy Waversaver in the past and it has an option for analog out. I always used RI/O back to the plc for the communications.
 
Basically ,its a packaging machine and based on microprocessor based cards and i have to replace it with PLC.When i search out for Load cell specification ,i got nothing.suppose if the load cell has max weight of 25gm and the full scale output is 10mV at excitation voltage of 7 volts,then sensitivity will be 10/7=1.428mV/V,is it right or wrong? can i change the sensitivity by varying excitation voltage??
 
On load cells sensitivity is based on deflection of the transducer. This is a mechanical function. The material the load cell is made of bends as weight is applied. This in turn changes the magnetic field in the transducer and from there you get your signal back. So in effect your sensitivity is your deflection. This is expressed on the load cell as a percent error with a maximum weight. What you are trying to do seems a bit strange to me. What you need is a strain gauge converter. Instead of trying to scale the mV signal get the proper hardware that is designed for this type of input. Depending on the brand PLC you are using you may find you can simply purchase a card to install in your PLC.
 
Loadcell cards

I have used the Hardy cards with great results. Easy to set up, good documentation, and great (read patient) (y)phone support!
 
I always use the model API 4059 G, Strain Gauge (Bridge) to DC Transmitter, Isolated
http://www.api-usa.com/pdf/api/api_4059g.pdf

Sometimes we locate them in the field, sometimes in the main control panel. Depends on the distance. They take the mv signal from a loadcell and converts it to 4-20ma or 0-10vdc, your choice. We use ma and take it straight in to a 16-bit analog input module in the plc.
 

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