Keithley 2790, Reference Manual

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Model 2790 SourceMeter
®
Switch System Reference Manual 3-5
LSYNC (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.
Figure 3-1
shows the 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.
Figure 3-1
Line cycle synchronization
Perform the following steps to enable or disable line cycle synchronization:
1. Press SHIFT and then LSYNC to display the present state of line synchronization
(OFF or ON).
2. Use the up or down key to display “LINESYNC ON” or “LINESYNC OFF.”
3. Press ENTER. The instrument returns to the normal display state.
klqb
Line synchronization is not available for the AC functions (ACV, ACI, FREQ, or
PERIOD) and for integration rates <1 PLC, regardless of the LSYNC setting.
1 PLC
A/D
Conversion
A/D
Conversion
Trigger
# 1
Trigger
# 2
Reading
Done
Reading
Done