58542 VXIbus Universal Power Meter
A-16 Publication 21555, Rev. E, September 2002
A.4.5 Reading Power Measurements Example 5
READ#? measurement response speed is slower at very low power levels and faster at high power levels.
This is due to a chopper stabilization system used in the NORMal Mode which is also used in the SWIFt
Mode, but not the BURSt mode. At the most sensitive gain ranges, chopper stabilization allows the very
small voltages from the power sensor to be accurately measured.
The following program configures the power meter for dual channel operation and uses the READ#?
command to return power measurement data in NORMal Mode.
260 ASSIGN @Pwr_mtr to 70101
270 CLEAR @Pwr_mtr
280 WAIT 1
290 OUTPUT @Pwr_mtr;CALC1:MODE NORM! Can ONLY send Configuration Commands in Normal Mode!!
300 OUTPUT @Pwr_mtr;CALC1:POW 1 ! Channel 1 configured to measure sensor 1 power
310 OUTPUT @Pwr_mtr;CALC1:UNIT W ! Transmitter output power in Watts.
320 OUTPUT @Pwr_mtr;CALC2:RAT 1,2 ! Transmitter gain stays in default, dBm.
330 !
340 OUTPUT @Pwr_mtr;TRIG:SOUR IMM ! TRIG:SOUR must be IMM when using READ#?
350 OUTPUT @Pwr_mtr;INIT:CONT OFF ! INIT:CONT arming must be OFF when using READ#?
360 !
370 OUTPUT @Pwr_mtr;SENS1:AVER:COUN 1
! Sets averaging to manual and one sample per reading.
380 OUTPUT @Pwr_mtr;SENS2:AVER:COUN 16
! Sets averaging to manual and 16 samples per reading.
390 !
400 OUTPUT @Pwr_mtr;SENS1:CORR:FREQ 1.44E9
! Applies Cal Factor for 1.44 GHz to sensor 1 data.
410 OUTPUT @Pwr_mtr;SENS2:CORR:FREQ 0.96E9
! Applies Cal Factor for 960 MHz to sensor 2 data.
420 !
430 FOR I= 1 TO 10
440 OUTPUT @Pwr_mtr;READ1?;READ2? ! Measures Power at sensors.
450 ENTER @Pwr_mtr;Chn_pow1
460 ENTER @Pwr_mtr;Chn_1rat2
470 PRINT Chn_pow1,Chn_1rat2
480 NEXT I
490 !
610 END
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