A method and circuit for determining the accuracy of a measurement of a bit line voltage or a charge distribution for readout from FeRAM cells uses sense amplifiers to compare a bit line voltage to a series of reference voltages and then determines upper and lower limits of a range of range of reference voltages for which sensing operation provide inconsistent results. One embodiment uses an output signal of a sense amplifier to control a pull-down transistor of an I/O line and alternative precharging schemes for the I/O line allow determining both limits using the same compression circuitry to process a result value stream on the I/O line.