Hi,
To get a more complete picture of some function generators, I also made measurements on the SDG 2042-X and the Rigol DG4162.
The measurement conditions are almost the same, only I chose to measure the phase difference between the channels now at 120MHZ for these function generators.
Cable optimizationThere were more good cables here and I found two that were the same length within 1mm.
Then of course I still don't know, if the cables were made from the same production run....
Skew optimizationNow how can I make sure that some variables are reduced.
I did that by connecting the two cables coming from C1 and C3 of the scope to a Mini-Circuits ZFRSC-42 power Splitter.
I connected the input of the power splitter to one channel of the function generator.
Then from channel-3 I used the “Deskew” function to make the differences in the cable and scope inputs as small as possible.
Result of the optimization, 60 pSec correction was needed.
But beware, nothing is perfect. ;-)
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Here is the splitter mounted on the Siglent SDG2042.
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This is the power spitter with SMA/BNC reducers, both of the same brand to minimize errors.
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If all goes well, I have now minimized the differences in my measurement system, if I overlook anything, please let me know!
SDG 2042XThe Siglent SDG 2042X, it gives about 10 Degrees of Phase difference uncorrected, according to the scope measurement.
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And if I correct the phase in the SDG 2042X, it requires 7 Degrees of correction.
Probably the phase measurement in the scope is less accurate,
but it could also be in the generator, which is not easy to check now.
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Rigol DG4162First again the phase difference if the generator is not corrected.
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And this is the phase corrected in the DG4162, this corresponds better to the measurement of the Scoop.
The difference here is only 0.6 degrees.
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OWON DGE2070The last generator I have with two outputs, the OWON DGE2070.
This is an inexpensive two channel function generator that I bought specifically because it can be powered from a power bank.
Some measurements I do have a lot of commonmode problems and I then get rid of them when using this generator.
But because it is so cheap, not everything is done very well.
Let's see what the phase difference is and the amplitude of both channels....
But first a picture of this Baby generator.
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And this is the phase error and amplitude error of the DGE2070 at the maximum frequency of 70MHz and 500mVpp, not so nice...
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The correction needed to get the channels in phase at this 70MHz frequency is 104 Degrees!
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If you know the generator you are using a little bit, phase correction is quite simple to apply.
It gets a little trickier when the phase correction varies over the frequency range.
I don't have time to test all this, these kinds of measurements and the annotation in the pictures take a lot of time.
I hope this measurement session gives you some more insight into the channel differences of function generators with two outputs.
Only the cheap OWON function genrator also gave clear differences in the amplitude of the output signal.
So if this is important for your measurements, the OWON is not suitable for that.
With kind regards,
Bram