in a data acquisition instrument with dual a / d converters in each measurement channel , phase corrections between the paths are computed using a locally generated calibration signal . the calibration signal goes through dual paths simultaneously and is stitched into a single signal for analysis by a processor running a fourier transform where phase differences are easily identified and used to establish a phase correction signal applied to a single master clock supplying clock signals to both paths . a switch allows the calibration signal to be applied to each channel or to no channels when actual data is being collected .