Timestamping Type 3458A Multimeter Samples

Often, AC signals are sampled using type 3458A digital multimeters in DC mode with an external trigger signal. Different algorithms can be used to determine RMS value and phase of the signal of interest. Especially when the phase information is required, knowledge about the timing is essential. This can be achieved modifying the clock source of the multimeter, forcing the multimeter to operate on an external clock and removing the synchronisation jitter of the trigger input TRIG IN. Another option is to use the EXT OUT signal generated by the multimeter for timestamping. This paper compares both methods.