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Review: Hantek DDS 3X25. Anyone own one?
alm:
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---The other part of resistor articles from those references say that the frequency response deteriorates at increasingly higher resistance ratings but moreso for carbon composition resistors, CCR [excluding standard wire wound for obvious reasons.]
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That sounds more believable.
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---Probably the best thing we can do is get a spec sheet from a CCR manufacturer, I'm sure they won't deceive us!
http://www.koaspeer.com/pdfs/RC_SS-263_R4.pdf
--- End quote ---
Thanks for the real data, most manufacturers don't give any data beyond DC.
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---See the frequency spec with its X axis being MHz*MOhm.
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That would explain the conflicting information. The 50 ohm resistors I quoted would be good up to 10GHz or so. Unlikely, since lead inductance will be an issue, but never mind that, 350MHz should be fine. A 1Mohm resistor would only be good to 0.5MHz or so.
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---I think that if a device worked with variable frequencies, one could compensate for the changes in impedance by choosing resistors of lowest values, whenever possible. This causes higher power consumption but more consistent response.
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You usually want lower impedance circuits at higher frequencies anyway, because otherwise parasitic capacitance (eg. between traces) will swap your resistors, even with ideal resistors. Plus 1Mohm transmission lines are kinda impractical ;).
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---Likewise, if the device worked at a narrower range of frequencies and required high value carbon composition resistors, then even if actual resistances are reduced, a designer could work with that predictable characteristic and simply choose a higher ohm resistor to compensate for the reduction.
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I'm not sure how stable the parasitic capacitance is, both over time and between samples. The figures give just typical data. But there's really no reason not to use something superior like thin film these days, you don't want those inductive leads at high frequencies anyway.
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---Here's a US Navy document regarding application of CCR in USN electronics:
http://www.google.com/url?sa=t&source=web&cd=17&ved=0CDsQFjAGOAo&url=http%3A%2F%2Fwww.everyspec.com%2FUSN%2FNAVSEA%2Fdownload.php%3Fspec%3DTE000-AB-GTP-010_R1-CHG-A.030031.pdf&rct=j&q=variations%20of%20carbon%20composition%20resistor%20high%20frequency%20use&ei=lnuCTZXOA474gAeBy7jbCA&usg=AFQjCNGTf2y90OvaLGY6o3qA0mLGOYEyPg&cad=rja
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They suggest up to 1MHz, which agrees with Koa's data with resistances up to 1Mohm or so.
--- Quote from: saturation on March 17, 2011, 10:23:52 pm ---In this rather large image, a curious enthusiast note that the only way to confirm a CCR is really to break in open, stating that some CCR sold since the 1970s actually contained film technology:
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So that's who the Chinese distributors selling carbon film as metal film learned from ;).
saturation:
Here's an interesting article about the history of film vs carbon composition, in the context of Japan's emergence from WWII. Not many historical articles exist about component development at an industrial level.
http://ieeeghn.com/wiki/images/c/c2/Takahashi,_Japanese_Electronics_after_WWII.pdf
Mechatrommer:
this is an update. and partly a correction to my previous post/report on "leap year", "dajones glitch" and "non-synched non-multiple" effect. now i'm not sure whether the internal firmware/software in hantek 3x25 is problematic, but i think there is workaround. my last report is worsen by the fact that the pc software dds-3x25 usb (3.2.1.7) is not done properly to handle this "buggy" effect. hence uploading a flawed data to the 3x25 and revealing the "buggy" effect especially the worst out-of-synch "signal" vs "synch out" output.
with proper calculation on the data length to be sent to the 3x25, from my incomplete observation, all the three unwelcomed effect seem to be resolved (dissapear), as demonstrated by this demo tool. there is no more "not-multiple and glitch/out of synch", except the 3x25 "synch out" signal seems to have lower resolution at high speed signal ie you cannot type in freq 35MHz and expect the synch signal to be exactly that, there is gap that it will only generate signal either 33.3MHz or 39.999MHz etc. the same to the reported capability of 75MHz, its not, even if the signal can generate 75MHz sine, but its synch output will only be 100MHz at some signal freq range (70-75MHz), this explained why "out-of-synch" occured. and lastly the sine attenuation at that (fast) frequency is also a pc-software artifact, not entirely hardware.
bottom line. all the reported bugs so far, are easily avoided by pc software means. so up to now i will give hantek 3x25 AWG a full "four" thumbs up!
ps: i forgot to mention that i found out something like "golden frequency" for this device is 50KHz or 200MHz, but i cannot explain what or how, its just there.
edit: demo.zip is just a simple tool with nothing much to do, browse further this thread for more complete software tool. cheers
Mechatrommer:
i've been lack in sleep for the past several hours. tried to work hard to get my hantek synch stable and in phase. i ask help if any hantek owner can make a test on this little demo/tester program if it can generate stable and in-phase signal vs synch output on their 3x25 unit. any reply and pictures will be appreciated. it use a re-calibration table (calib.csv) so you can adjust the shift angle value in there. just dont abuse the little tool, such as entering alphabet in frequency value etc. i havent made any proper checking for invalid input. hope will hear my program works.
saturation:
AWESOME WORK Mecha, will give it a try and report back.
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