Siglent 1104X-E BodeII voltage limit? - Page 1
Forum section: electronics / testgear

author: Roman oh
author_rank: Regular Contributor
timestamp: July 22, 2021, 03:12:27 am
content: I have been using my 1104X-E (6.1.35R2) for Bode plots and, despite a few quirks which I might ask about later, it generally works reasonably well.But the question for this post is - during config, it will not allow the stimulus voltage to be set higher than 6.00 volts - neither by knob or by keyboard. It’s like this whether or not an AWG is actually connected.What am I doing wrong?

author: tautech
author_rank: Super Contributor
timestamp: July 22, 2021, 12:18:24 pm
content: Quote from: Roman oh on July 22, 2021, 03:12:27 amNothing.6V is the BPII Stimulus limit for the SDS1004X-E range be it from a SAG1021I or a standalone SDG.It appears this will be addressed soon in coming firmware for the SDS2000X Plus range and the limit lifted to 24V however I do not know if 1000X-E models will get a similar stimulus limit lift.

author: mawyatt
author_rank: Super Contributor
timestamp: July 22, 2021, 12:57:28 pm
content: As tautech said, this is also the limit for the two SDS2000X+ we have. Can't think of a reason why this limit is imposed, so hopefully with the new firmware release mentioned it will improve.Never considered the Bode Plot something useful to consider until we acquired our 1st SDS2000X+. This feature has been utilized often and proven very valuable. Siglent with the help of some beta testers have not only created a very useful Bode plot tool but expanded the DR by cleverly scaling the input level and output scale factor. This proved worthwhile when testing some high attenuation filters, so the increased input limit should immediately beneficial.Best,

author: Roman oh
author_rank: Regular Contributor
timestamp: July 22, 2021, 01:28:47 pm
content: Thanks, guys. I’m a tad surprised that Siglent set an arbitrary limit like this, for not much apparent reason, and omitted to mention it in the documentation.I’m not sure what their policy is wrt software upgrades, but I hope they haven’t put this model in the “too old” bin yet…..

author: mawyatt
author_rank: Super Contributor
timestamp: July 22, 2021, 02:03:54 pm
content: Hopefully Siglent won't forget about those older scopes, because they may just be the foundation for a newer scope purchaseBest,

author: rf-loop
author_rank: Super Contributor
timestamp: July 22, 2021, 03:02:08 pm
content: Limit come from SAG1021.This limit is stimulus limit. It is not at all highest limit FRA itself can handle. It can handle full SDS1000X-E input voltage scale.This stimulus limit is wrong (some kind of mistake perhaps) and it need change. Because FRA can use with all Siglent SDG's.At this time I do not have on my table SDS1004X-E and SDG1032X. So I can not test if there is any problem with next trick..But, for other things... example doing FRA where DUT example subtract or add frequency offset. In this case SDG can also sweep using freq. offset so that DUT out signal is same as reference freq (because FRA works as frequency sensitive level receiver, it listen this freq what it command out from SDG).But then, SDG can also do level offset so perhaps this can use for walk over this problem if really need sweep with higher than 6V with just SDG alone without any extra things.Trick is. FRA use and command SDG channel 1. But naturally it do not know anything about whewre from true signal come.There is some limits in this trick but...Idea is this.FRA control normally SDG but set CH2 follow CH1 with level offset. You can get out same sweep from CH1 with 6V but from channel 2 you get exaple 12V if you set offset for this. Now use this CH2 output instead of signal from CH1. Depending other things you can even take reference to FRA from SDG CH1 and signal to DUT input from SDG CH2All can think self how to continue...This do not help lot and not perhaps suitable for all cases but ... least with this trick can play and exercise.Also need think if it is better to use FRA vertical display in Vout/Vin mode or just Vout specially when play with this level trick and separate reference in (default scope Ch1 but user can define it) and DUT in signals.And of course if do not need maximal dynaamic but speed is priority then Channel Gain Hold. But before use this there need manually find what is best V/div setting for DUT output so that signal do not just clip in any frequency and/or if there is also level profile (user defined variable level profile) in use. If use 50ohm impedance systems then these scopes what have internal 50ohm there is limit. Maximum continuous input level is 5Vrms what responds 27dBm and in many scopes maximum V/div is limited to 1V/div (but SDS1000X-E series do not have internal 50ohm terminators).

author: mawyatt
author_rank: Super Contributor
timestamp: July 22, 2021, 04:45:12 pm
content: If one needed more input signal level for the Bode Plot, couldn't you use an external amplifier before the DUT. For example the inexpensive Juntek DPA-1698 has 40Vpp output, and the DPA-2698 has 25Vpp, both are 2X gain We have a couple custom designed high voltage dual amplifiers that augment an AWG output to 180VPP and 340VPP for investigating a new proprietary technology, but these high voltages be useful for working with some piezo electric devices.Just thought of a use, a few years ago we developed some piezo electric devices for ultra precise linear movements used to position a camera system to sub-micron levels. We sorta guessed at the piezo electric to dual bridge position sensor transfer function, this was an extremely complex system and used flexures instead of bearings, so no mechanical noise was introduced. Never thought of even attempting a Bode plot of that system until now, so something to consider later maybe.Since we guessed at the Transfer Function, and these systems are expensive and delicate, the system was carefully operated initially open loop before the loop was closed. We used a "ping" method from long ago to emulate the impulse response of the open loop system and since most systems can be distilled down to a second order system, used this to evaluate the expected closed loop performance. We got lucky and everything worked as planned, actually betterWould be interesting to run a Bode plot and actually "see" how this system behaves, and how close the "ping" method and 2nd order assumptions were.Fun stuff indeed!!BTW, thanks for all the great work you did on the Bode Plot.Best,