Hi,
I have to make an weighing system with load cells. Here is what I had understood until now:
Load cells:
Sensibility often 2mv/V
Recommended excitation voltage: often 10V
Rated capacity: let's say 5kg=5000g
At maximum load(5kg) we will have 2mV/V*10V=20mV to output
So at 5000g we have 20mV, then for 1g we will have:
5000g.......20mV
1g.......X mV
X=20/5000=0,004mV=4uV
So, my load cell, for 1g will indicate 4uV, for 2g 8uV and so on. It's seems
that the division per gram is 4uV that beeing the sensibility of the load cell
I want to evaluate the weight with a PLC, and so I will need a transmitter/amplifier whatever so my PLC can be capable of reading the load cell.I want that the transmitter to take out an 4-20mA analog signal.
On my PLC I have 27648 value at 20mA, so I have 20mA/27648=723nA per division.
Now my question is, and please give me concrete, not abstract answers:
On the 4-20mA range of the transmitter how do I know what value represents 1g.
I don't know to make the correlation between load cell sensor, load cell transmitter and PLC. I don't know how to chose and parameterize the transmitter. What I know is that my system has to measure with a tolerance of +/-3 grams but I don't understand correlation between transmitter resolution with the one of the PLC.
If you have experience with load cells, and transmitter and you want to help me please guide me to understand this process.
Thank you.
I have to make an weighing system with load cells. Here is what I had understood until now:
Load cells:
Sensibility often 2mv/V
Recommended excitation voltage: often 10V
Rated capacity: let's say 5kg=5000g
At maximum load(5kg) we will have 2mV/V*10V=20mV to output
So at 5000g we have 20mV, then for 1g we will have:
5000g.......20mV
1g.......X mV
X=20/5000=0,004mV=4uV
So, my load cell, for 1g will indicate 4uV, for 2g 8uV and so on. It's seems
that the division per gram is 4uV that beeing the sensibility of the load cell
I want to evaluate the weight with a PLC, and so I will need a transmitter/amplifier whatever so my PLC can be capable of reading the load cell.I want that the transmitter to take out an 4-20mA analog signal.
On my PLC I have 27648 value at 20mA, so I have 20mA/27648=723nA per division.
Now my question is, and please give me concrete, not abstract answers:
On the 4-20mA range of the transmitter how do I know what value represents 1g.
I don't know to make the correlation between load cell sensor, load cell transmitter and PLC. I don't know how to chose and parameterize the transmitter. What I know is that my system has to measure with a tolerance of +/-3 grams but I don't understand correlation between transmitter resolution with the one of the PLC.
If you have experience with load cells, and transmitter and you want to help me please guide me to understand this process.
Thank you.