So I purchased a 2kg scale with the intention to link it to an arduino to send the scale readings to the serial port for further use. I obtained a INA125P In-amp with the hopes to amplify the signal to do this. There are several examples out there of folks hacking scales in this manner. I am running into some issues where the output sweep seems to be limited and I'm not sure why.
The resistance on the bridge is 1k ohm (reading between V- and V+). The excitation V is 3.3V. The voltage to the INA125P is 3.3V. The reference is the INA125P on-board 2.5V. I have had trouble finding a solid gain to amplify the signal, and it seems a resistor of 22 ohm gives a reasonable sensitivity of the scale response to minimal weight but the amp seems to saturate at about 500g. When weight is applied the voltage drops from the max voltage to zero at about 500g and anything beyond that just sits at a little above zero. I was hoping to replicate the scale at the full 2kg. Why would the amp be saturating at only 500g? I've tried other gains with pots and resistors, but nothing really outputs a reasonable sweep beyond 500g, or requires too much force to sense readings from the sensors.
Greatly appreciate any insight & help. I am by no means an EE and am trying to learn! :)
This is essentially the circuit minus the shown RL resistor (from the data sheet).