Products > Test Equipment
Siglent SDS1x04X-E BodePlot II (SFRA) features and testings
Performa01:
--- Quote from: Pitrsek on January 05, 2020, 01:46:54 am ---Any clue as to why is the low limit set to 10Hz?
--- End quote ---
The Bode Plotter uses AC coupled input channels, which simplifies operation significantly. Even though the corner frequency is below 3Hz, the phase shift is significant even above that frequency and slight differences between channels (component tolerances) cause additional phase errors in the measurement channels with regard to the reference channel. This is the reason why 10Hz has been chosen.
In DC coupled mode, any DC offset can easily ruin the dynamic range. The DC offset might be too high to be compensated by the internal offset DAC, and even if it is within range, this would cause additional effort.
Knowing all this, I've still requested a lower frequency limit of at least 0.1Hz a long time ago, but it seems that Siglent doesn't see much benefit in spending the effort to implement this, since the practical use cases are limited indeed.
One Argument is that the Bode Plot (that is not fast anyway) would get painfully slow at frequencies that low: at 100mHz, a single measurement takes at least 10 seconds, filtering/averaging not even factored in. This means, if Siglent ever implements that, you need to be aware that this option is for tests running over night only ;)
mrprecision:
--- Quote ---These attenuators are relay operated and quite obviously the 2nd attenuator causes additional time delays that are not allowed for in the Bode plot firmware
--- End quote ---
I understand the problem with the 2nd attenuator, you think that could be fixed by Siglent. Why are no additional time delays are allowed for the bode plot firmware?
rf-loop:
--- Quote from: mrprecision on January 05, 2020, 11:57:59 am ---
--- Quote ---These attenuators are relay operated and quite obviously the 2nd attenuator causes additional time delays that are not allowed for in the Bode plot firmware
--- End quote ---
I understand the problem with the 2nd attenuator, you think that could be fixed by Siglent. Why are no additional time delays are allowed for the bode plot firmware?
--- End quote ---
I belive there is wrong word (allowed). Perhaps it is something like "additional time delays are not been adquately addressed" Lets hope some future FW fix this.
rf-loop:
--- Quote from: Performa01 on January 05, 2020, 11:39:20 am ---
One Argument is that the Bode Plot (that is not fast anyway) would get painfully slow at frequencies that low: at 100mHz, a single measurement takes at least 10 seconds, filtering/averaging not even factored in. This means, if Siglent ever implements that, you need to be aware that this option is for tests running over night only ;)
--- End quote ---
^ This.
@mrprecision
SDS BodePlot works using frequency selective "receiver" principle (receiver center freq sweeps together with generator sweep, bit like SA with tracking generator. Even more, BP also adjust RBW during sweep related to current freq. It adjust receiver center during sweep and also it adjust Resolution Band Width automatically proportional to frequency) and naturally this part is very slow when go to very low frequencies specially with sub Hz selectivity because...
Try play under 10Hz and down to under 1Hz with good resolution using FFT... we just meet limits of this kind of systems. 0.5kEur oscilloscope can not be everything. Still its SFRA performance is far over any others in this <1kEur price group (scope + generator) and even in bit higher class. With these limits we need live.
And of course hope they find solution for this attenuator delay time better or what ever is this reason. It have been quite long time this problem has been found.
mrprecision:
It seems to be a timing problem with the 2nd attenuator.
Secound run with 6Vpp:
Secound run with 0.5Vpp
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