Fluke 6105A - Page 205

Calibration
The Fluke Service Center Calibration System 7
7-11
The Sample Reference and the Phase Reference signals are provided on the 6100B rear
panel. Figure 7-4 shows the relationship between reference signals and the analog output.
The Sample reference is turned OFF and ON with GPIB commands. Sample Reference
pulses do not appear after an ON command until the positive zero crossing of the Phase
Reference occurs. Then the first falling edge is simultaneous with the Phase Reference
rising edge. The DMM samples the analog signal at each falling edge of the “trigger”
thereby phase-locking the sample to the analog output.
Analog Signal
Phase Reference
Sample Reference
Gpib Command
OUTPut:ROSCillator OFF
Gpib Command
OUTPut:ROSCillator ON
gdw49.eps
Figure 7-4. Waveforms
The system software programs the DMM to take the required number of samples so as
long as the minimum required time is allowed to elapse, the timing of the sample
reference off command is not critical. The sample reference frequency is always a binary
multiple of the analog fundamental frequency thereby simplifying the task of analyzing
the sampled data.