2 Error Over the Full Scale Range

At the lower end of the measurement range, the signal transduced by the shunt will suffer from greater influence of the offset voltage inherent to the amplifier. This results in an inverse proportionally increasing error as the measurement tends towards zero. Dependent on the shunt resistor chosen for the measurement maximum, it may even be found that the measurement at the lower bound is completely dominated by the offset voltage, and is effectively unusable due to the magnitude of the error. Current Sense Amplifier Error Curve Characteristics shows a generic error curve for a current sense amplifier, and the two dominating behaviors of the error curve as you move in each direction along the error curve.

As the measured signal diminishes, the proportion of the signal compared to the offset voltage of the device grows smaller, and offset error increasingly dominates the measurement, eventually rendering the measurement unacceptable in terms of error. As the signal grows and approaches the output limit of the amplifier, the voltage offset becomes a less important factor. However, constant error terms such as gain error and the tolerance error of the chosen shunt produce a y-axis asymptote that serves as a best case error measurement of the signal. For root sum square approximations that are often used to calculate total error, these static values become the dominant contribution at full scale, and result in a minimum limit achievable in terms of error.