It is important to understand in-amp error sources in a typical application. Figure 1 below shows a 350 Ω load cell with a fullscale output of 100 mV when excited with a 10 V source. The AD620 is configured for a gain of 100 using the external 499 Ω gain-setting resistor. The table shows how each error source contributes to a total unadjusted error of 2145 ppm. Note however that the gain, offset, and CMR errors can all be removed with a system calibration. The remaining errors—gain nonlinearity and 0.1 Hz to 10 Hz noise—cannot be removed with calibration and ultimately limit the system resolution to 42.8 ppm (approximately 14-bit accuracy).
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Editorial
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DAC 2012 at San Francisco CA - Jun 3 - 7, 2012
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