Keysight Technologies P Series Programming Manual page 660

17 IEEE 488.2 Command Reference
*OPC
The *OPC (OPeration Complete) command causes the power meter to set the
operation complete bit in the Standard Event Status Register when all pending
device operations have completed.
Syntax
*OPC
Query
*OPC?
The query places an ASCII 1 in the output queue when all pending device
operations have completed.
660
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Keysight N8262A Programming Guide