Precision Analog Converter Gain Drift under Dynamic Thermal PCB Stress
Dynamic PCB thermal gradients cause substrate flexing that alters converter resistor ladder ratios via piezoresistive strain, driving gain drift.
Gain Error
Transfer Deviation
Amplifier or converter deviations represent the difference between the actual slope of the transfer function and its ideal value. This gain error causes the output of a measurement system to scale incorrectly across the full input range, leading to proportional inaccuracies in the collected data. Unlike offset errors, which remain constant, this error grows larger as the magnitude of the measured signal increases.
Correction of this deviation requires a scaling adjustment during calibration.
Calibration Compensation
Two-point calibration routines identify both the offset and the slope correction factors by measuring known reference voltages near the extremes of the operating range. To eliminate gain error, the firmware multiplies each raw digitizer reading by a correction coefficient stored in non-volatile memory. Precision reference sources with low temperature drift are necessary to ensure that this correction remains stable over time and across different environmental conditions.
Hardware Sourcing
Resistor matching in the feedback network dictates the stability of the system amplifier over its operating life. High-precision thin-film resistor networks with low tracking coefficients minimize the drift of this parameter.
Metrology Standard
Reference standards used for calibration must have an uncertainty at least four times smaller than the target tolerance of the instrument. This ensures that the calibration process does not introduce more uncertainty than it resolves.