Design and Development of Signal Conditioning Card for Load Cell

In industry environment the most commonly measured parameters are strain, force and pressure. The most commonly used sensing devices in order to measure above parameter are strain gauge load cell. There are different types of strain gauges are available resistive, capacitive, piezoelectric transducer type and semiconductor type strain gauges are there. Strain gauge sensor is a passive transducer that converts the mechanical elongation, displacement produced due to force or load acting on them into change in resistance, capacitance and inductance value. They are low impedance devices, they required exact excitation (input) value because there signal (output) will be in milli volt range, the typical load cell will be having four strain gauges which are all arranged in Wheatstone bridge manner with impedance of 270 ohms or 350 ohms. The load cell will be having six wires, two of them for “excitation” voltage, two of them is for giving “signal” and two of them are for “sens”, in order to maintain the excitation voltage as the output from load cell are in milli volt range they need to be conditioned for next stages with low cost, high precision, reliability, amplification and noise reduction capability. The low output signal after amplification is to be send to filtering, analog to digital conversion then the output is programmable controlled by microcontroller ATmega 168p then they again converted to analog signal using digital to analog converter (DAC) because the next level will be of analog component in industry that is programmable logic controller (PLC) in order to display the weight and to send the packed things to suitable place.