Time Latency of DC Input Path for 3458A Sampling Multimeter

The Keysight 3458A is a common digitizer because of the great accuracy and small integration time. The bandwidth of its DC input path varies depending on the magnification of input amplifier of different ranges, which causes time latency of input signal. A method to measure the latency based on aperture time is introduced. When the aperture approximately equals to the period of the signal under test, extremum of sampling value reflects signal's initial phase. Experiments at 1V and 10V ranges with input signals of 25kHz and 50kHz were carried out and the time latency were measured. Then the bandwidth were calculated which were the same of about 120kHz for these two ranges.