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RIGOL DS1102E comparison - analog Oscilloscope
RIGOL DS1102E 2 Channel 100MHz 1G Sa/sec Oscilloscope V00.04.01
The first impression of the model DS1102E is that it is well made, having a very clean feel with decent hardware. The overall style is attractive. The cooling fan is audible to a point of slight distraction, but this is not a deal breaker.
The main consideration for any oscilloscope is accuracy in delivering a faithful representation of signals measured, and the ability to trigger on any signal in a predictable manner within the bandwidth limits of the oscilloscope.
The RIGOL DS1102E Digital oscilloscope was evaluated for performance in the X-Y mode. For comparison, a Hameg HM203-6 20MHz analog oscilloscope was used in the identical mode.
A stable square wave reference is converted to a linear ramp representing a reference musical instrument note frequency. In this example the frequency is C4 or "middle C" at 261.63 Hz.
The linear ramp will sweep the trace in the "X" input at a fixed rate. If the measured analog waveform, "Y input" or note "C4" in this case is pitch locked, it will not translate to the right or left. For example: if a note is sharp it will translate or move to the left.
It is helpful for the oscilloscope to have the ability to fine tune or "uncal" the volts/div range for X and Y in this mode of operation, and also the X position adjustment is critical for a centering of the waveform on the screen. This is to achieve a decent viewable image.
This is the real time measured signal. V-position and volts/div will set the vertical position and the height respectfully of the measured waveform.
The sweep width across the scopes screen is dependent on the volts/div setting and a fine adjust or "uncal" is necessary to fill the screen completely. There should be no dead or wasted space in the horizontal signal seen on the oscilloscope trace.
This adjustment is critical in centering the horizontal signal after the X-axis is adjusted.
The Hameg provided a very clean and trustworthy image due to the inherent adjustments of the oscilloscope.
The RIGOL DS1102E did not allow for the adjustments as stated above. There is no "uncal" position for the X or Y axis. Even with the finest increments available selected, the waveform remained truncated on the screen. The image was a coarse representation of the true analog counterpart. Every attempt was made to duplicate the results of the 20MHz analog scope with results that were unstable and unpredictable from the RIGOL DS1102E.
The sampling rate was toggled between Sa=500.0Ksa/sec and 50.0Msa/sec. The highest sampling rate produced an unintelligible signal with random sampling points. The digital representation on the RIGOL DS1102E has undefined samples at times defining impossible data values.
The RIGOL DS1102E was tested for trigger accuracy. The oscilloscope has issues with zero crossings and locking into the basic waveform of a bassoon reed.
The threshold must be set to capture the highest peak for this scope to lock into the analog waveform. All possible trigger combinations were tested with similar results.
The trigger was tested with the linear ramp and it performed perfectly at different thresholds. The trigger circuitry should be redesigned for stability in complex waveforms.
The HAMEG locked into the same bassoon reed waveform at any position of the trigger threshold translating it on the X-axis predictably.
Bandwidth limit was tested to try and clean up the waveform representation. It had no effect, as the digital representation was yarn like or fuzzy misrepresenting the real analog counterpart. HF rejection had no effect on the visual interpretation of the RIGOL DS1102E.
The Digital Filter was tested with a ramp of 261.63 Hz. The type was Low Pass, and the cutoff frequency was set to 20KHz. At a factor or 76 times the fundamental frequency there was significant ringing on the linear ramp. Overshoot occurred at 45KHz (Lo Pass cutoff), and increased significantly down to 20KHz. The intent of the Digital filter was to clean up the yarn like appearance of these waveforms.
As results caused overshoot and ringing, the filter was disabled.
Beautifully made and with a nice user interface the RIGOL DS1102E showed room for improvement in the above tests when compared to a 20MHz oscilloscope with technology that preceded it by 20 years.
The RIGOL DS1102E is a lobbyist oscilloscope at best.
A storage oscilloscope may be the best bet for those who would like to capture waveforms and make measurements by way of cursors.
For accuracy in waveform traces, an analog oscilloscope remains to be the best bet.
Sr. Electrical Design Engineer with 25 years of experience in analog signal design.