Using integrated AC excitation mode to remove system offset
Many types of industrial end-equipment employ resistive bridges to sense changes in physical variables such as strain, force, pressure or flow rates. A common industrial application for resistive bridges is precision weigh scales. In this application, weight is translated into a voltage using a resistive bridge embedded in a load cell.
Resistive Bridge in a Load Cell Such a four-wire load cell requires an excitation voltage, VEXC± , and outputs a differential signal voltage, VSIG± , proportional to the applied weight. Typically, VSIG± (max) is on the order of tens of millivolts, requiring a low-noise, precision delta-sigma ADC with integrated gain to provide repeatable measurements for such low-level signals.
ADC accuracy parameters such as offset error, offset drift, gain error and gain drift are also important to ensure the weigh scale output correlates to the correct weight. Furthermore, accuracy can be improved at a system-level using techniques such as AC bridge excitation.
To meet the demanding performance needs of precision resistive bridge measurements, Texas Instruments has released the ADS1261, a 24-bit, 40 kSPS, 10-channel, delta-sigma ADC with integrated AC excitation output drive circuitry.
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