Dbm - Agilent Technologies 3458A User Manual

The following program uses the real-time DB operation to determine an
amplifier's voltage gain. Line 40 stores the amplifier's input voltage (0.1 V)
in the REF register. The amplifier's output voltage is measured and the gain
of the amplifier is computed.
10 OUTPUT 722;"PRESET NORM"
20 OUTPUT 722;"ACV"
30 OUTPUT 722;"SETACV ANA"
40 OUTPUT 722;"SMATH REF 0.1"
50 OUTPUT 722;"MATH DB"
60 ENTER 722;A
70 PRINT A
80 END
For example, if the input voltage is 0.1 V and the output voltage is 10V, the
gain is:
20 log
·
The following program is similar to the preceding program except that it uses
the post-process DB operation.
10 OUTPUT 722;"PRESET NORM"
20 OUTPUT 722;"ACV"
30 OUTPUT 722;"SETACV ANA"
40 OUTPUT 722;"MEM FIFO"
50 OUTPUT 722;"SMATH REF 0.1"
60 OUTPUT 722;"MMATH DB"
70 OUTPUT 722;"TRIG SGL"
80 ENTER 722;A
85
90 PRINT A
100 END

DBM

The DBM math operation calculates the power delivered to a resistance
referenced to 1 mW. The equation is:
Result = 10
Where:
Reading is any voltage reading.
RES is the resistance value in the RES register (default = 50)
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"
20 OUTPUT 722;"ACV"
30 OUTPUT 722;"SETACV ANA"
40 OUTPUT 722;"SMATH RES 8"
50 OUTPUT 722;"MATH DBM"
!PRESET,NRDGS 1,AUTO, DCV 10, TRIG SYN
!AC VOLTAGE MEASUREMENTS, AUTORANGE
!ANALOG ACV METHOD
!WRITE 0.1 TO REF REGISTER
!ENABLE REAL-TIME DB OPERATION
!SYN EVENT, ENTER DB
!PRINT DB
(10/0.1 )= 20 log 100= 40dB
·
10 10
!PRESET,NRDGS 1,AUTO, DCV 10, TRIG SYN
!AC VOLTAGE MEASUREMENTS, AUTORANGE
!ANALOG ACV METHOD
!ENABLE READING MEMORY, FIFO MODE
!WRITE 0.1 TO REF REGISTER
!ENABLE POST-PROCESS DB OPERATION
!TRIGGER READING
!RECALL READING USING IMPLIED READ,
!PERFORM DB OPERATION
!PRINT DB RESULT
2
log (Reading /RES/1 mW)
·
10
!PRESET, NRDGS 1,AUTO, DCV 10, TRIG SYN
!AC VOLTAGE MEASUREMENTS, AUTORANGE
!ANALOG ACV METHOD
!WRITE 8 TO RES REGISTER
!ENABLE REAL-TIME DBM OPERATION
Chapter 4 Making Measurements 121