How does poor grounding of the concentrator affect data acquisition?

Poor grounding of the concentrator introduces additional noise voltage and current, which are directly superimposed on the weak acquisition signal, leading to measurement errors. Common mechanisms include: excessively high grounding impedance reduces the high-frequency bypass effect of the filter capacitor (Y capacitor), causing common-mode noise to be converted into differential-mode noise and enter the sampling circuit; ground loops induce power frequency current in the sampling circuit, causing baseline drift; and unequal grounding potentials at multiple points cause reference voltage offset. For example, if there is a 100mΩ impedance between the ADC's AGND and the sensor ground, and a 10mA common-mode noise current flows through it, a 1mV error voltage will be generated, equivalent to 3 LSBs for a 5V full-scale 16-bit ADC. Diagnostic methods include measuring the noise voltage between AGND and PE; if it exceeds 10mV at 50Hz or 50mV at high frequencies, grounding is poor. Corrective measures include: improving the single-point connection between AGND and PE (using a ferrite bead), strengthening the grounding of the sensor shield, using differential input for the sampling line, and improving CMRR. After optimization, the error introduced by grounding noise can be controlled within 0.05%FS.