How to amplify output voltage from load cell?help please:(

Wayne0809 said:

Hi,I followed your circuit and I get around 3.7V for 1KG thing and 1.1V when there is nothing on the scale. I should short 1 pin of the variable resistor to the middle pin of the resistor right?Thank you

Click to expand...

hi,
Yes, connect one end of the pot pin to the centre wiper pin, see my earlier diagram.

You should also be able to reduce the 1.1V [ Zero pot] with no weight closer to 0V for Vout. this will make around +3V for 1Kg as I said earlier.. OK

E

ericgibbs said:

hi,
Yes, connect one end of the pot pin to the centre wiper pin, see my earlier diagram.

You should also be able to reduce the 1.1V [ Zero pot] with no weight closer to 0V for Vout. this will make around +3V for 1Kg as I said earlier.. OK

E

Click to expand...

Hi,so I only can adjust the zero pot to reduce the voltage?How about the offset pot?I can get only 0.6V when there is no weight on the scale.

Wayne0809 said:

Hi,so I only can adjust the zero pot to reduce the voltage?How about the offset pot?I can get only 0.6V when there is no weight on the scale.

Click to expand...

Wayne,
Measure the Vout of the AD620, adjust the Offset pot to give the lowest possible Vout with no weight.

You cannot get Zero V out from the AD620, as I have explained, its designed ideally to work from a dual supply.

Also the LM324 Vout will not go to zero Vout, the OPA is not designed to do that with a single supply.

You will have to get the Vout to the ADC input as low as possible and use the LPC program to cancel out the Vout when there is no weight on the scale.

E.

EDIT:
Add a 2k2 resistor from the LM324 Vout [ADC] pin to 0V, this will enable a Vout closer to zero volts.