I discovered two bugs in the burst mode of Rigol signal generators DG4062 and DG4102 and DG4162.
BUG #1:Summary: When bursting 1-cycle square waveforms, the duty cycle of the output waveform suddenly changes from 0.01% to 99.99% between pulse widths 70µs and 200µs.
Steps to reproduce:
1) Set CH1 of your signal generator to the Square waveform (Period:
70µS, StartPhase: 0º, Duty Cycle: 50%)
2) Set the Burst mode of CH1 to (Type: N_Cycle, Cycles: 1, Burst Period: 1sec., StartPhase: 0º, Source: Internal, Delay: 0 ).
This will set your signal generator to output a 35µs positive pulse every 1 second (very low duty cycle).
(the pulse is 35µs wide because the duty cycle of the square wave was set to 50% and ½ of 70µs is 35µs)
Now, slowly increase the period from 70µs to 200µs using the Square waveform menu of CH1 (which I have highlighted above in green color) and observe on a scope how the polarity of that positive output pulse suddenly changes to a negative going pulse (the CH1 waveform inverts)
Consequences: If you had a PWM amplifier/load connected to the CH1 output of that generator, then it would blow up as the driving signal suddenly inverted its duty cycle.
BUG #2: Several days later I have discovered another bug in the Burst mode.
Summary: When bursting 1-cycle square waveforms, the output signal suddenly disappears when the Burst mode Delay is rapidly decreased.
Steps to reproduce:
1) Set CH1 of your signal generator to the Square waveform (Period: 10mS, StartPhase: 0º, Duty Cycle: 50%)
2) Set the Burst mode of CH1 to (Type: N_Cycle, Cycles: 1, Burst Period: 100mS, StartPhase: 0º, Source: Internal, Delay:
89ms ).
3) Set CH2 of your signal generator to the same settings as CH1 was set above (it does not matter whether the output of CH2 is enabled).
4)
Rapidly decrease the Burst mode Delay of CH1 from 89ms to 0ns (marked above in brown color) by using the numerical keypad + Enter and observe how the CH1 output pulses
completely disappear for over 2 minutes. Rapidly decreasing this Delay with the knob can have the same effect.
5) Watch how the CH1 output signal stays completely disabled, (even if the CH1 Burst Delay is increased to the previous value) until the CH1 output is cycled OFF and ON again, ...or the Burst mode is cycled OFF and ON again, ...or after ~138 seconds elapse.
Models affected (both bugs):
All DG4xxxx models running firmware up to v1.08 and v1.10.
I did not test these bugs on firmware v1.09 and above but other people did.
I would appreciate a confirmation of this bug from people running firmware 1.09 and above.