Line Cycle Synchronization - Keithley 3700A Series Reference Manual

Section 8: Theory of operation

Line cycle synchronization

Synchronizing A/D conversions with the frequency of the power line increases common mode and
normal mode noise rejection. When line cycle synchronization is enabled, the measurement is
initiated at the first positive-going zero crossing of the power line cycle after the trigger.
The following figure shows a measurement process that consists of two A/D conversions. If the
trigger occurs during the positive cycle of the power line (Trigger #1), the A/D conversion starts with
the positive-going zero crossing of the power line cycle. If the next trigger (Trigger #2) occurs during
the negative cycle, then the measurement process also starts with the positive-going zero crossing.
8-2
Figure 101: Rear panel to backplane to DMM connect relays schematic
Series 3700A System Switch/Multimeter Reference Manual
3700AS-901-01 Rev. D/June 2018