I have an S-type load cell to measure weight up to 100 Kg. Its datasheet mentions 3mV/V against full range and excitation voltage.
When no weight is applied, the voltage is 9.9 mV (Excitation is 10 V). When I press the load cell manually, the voltage rises a few mV (like 14 to 17).
I designed a dual stage amplifier using an LM358 IC to amplify the voltage. The first stage is a differential amplifier with gain of 10 and the second a non-inverting amplifier, with a variable gain of 0 to 50 to achieve an output of around 10 V to feed to a PLC.
I get a 4 V output at LC2_O/P and doesn't change if I press the sensor. However, if I apply somewhere between 0 - 0.1 V from my lab bench power supply, it shows a steady range of amplification.
Can someone please help?