Keysight Technologies 3458A Guide D'utilisation page 183

You can change the value in the RES register using the SMATH command.
The following program uses the real-time DBM operation to determine the input
power to a loudspeaker. Line 40 stores the speaker's impedance in the RES
register (for this example, 8 W). The input voltage to the speaker is then measured
and the DBM operation is performed.
10 OUTPUT 722;"PRESET NORM"!PRESET, NRDGS 1,AUTO, DCV 10, TRIG SYN
20 OUTPUT 722;"ACV"!AC VOLTAGE MEASUREMENTS, AUTORANGE
30 OUTPUT 722;"SETACV ANA"!ANALOG ACV METHOD
40 OUTPUT 722;"SMATH RES 8"!WRITE 8 TO RES REGISTER
50 OUTPUT 722;"MATH DBM"!ENABLE REAL-TIME DBM OPERATION
60 ENTER 722;A!SYN EVENT, ENTER DBM
70 PRINT A!PRINT DBM
80 END
For example, if the input voltage is 10 V, the power is:
The following program is similar to the preceding program except that it uses the
post-process DBM operation.
10
20
30
40
50
60
70
80
85!PERFORM DBM OPERATION
90
100 END
Keysight 3458A User's Guide
2
10@log (10 /8/1 mW) = 40.97 dBm
10
OUTPUT 722;"PRESET NORM"!PRESET, NRDGS 1,AUTO, DCV 10, TRIG SYN
OUTPUT 722;"ACV"!AC VOLTAGE MEASUREMENTS, AUTORANGE
OUTPUT 722;"SETACV ANA"!ANALOG ACV METHOD
OUTPUT 722;"MEM FIFO"!ENABLE READING MEMORY, FIFO MODE
OUTPUT 722;"SMATH RES 8"!WRITE 8 TO RES REGISTER
OUTPUT 722;"MMATH DBM"!ENABLE POST-PROCESS DBM OPERATION
OUTPUT 722;"TRIG SGL"!TRIGGER READING
ENTER 722;A!RECALL READING USING IMPLIED READ,
PRINT A!PRINT DBM RESULT
Making Measurements 4
183