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| DC bias (or offset) adjustment availability |
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| tautech:
--- Quote from: alm on November 25, 2023, 10:29:30 pm --- --- Quote from: rf-loop on November 25, 2023, 09:58:13 pm ---And in your link it is this very obsolete (look this address): siglentna.com/USA_website_2014/Documents/DataSheet/SDS1000X-E_DataSheet_DS0101E-E03A.pdf Also if look Siglent NA, there is current version available there is: siglentna.com/wp-content/uploads/dlm_uploads/2021/08/SDS1000X-E_DataSheet_EN04D.pdf --- End quote --- Hey, I can't help it if Siglent NA leaves old data sheets on their website, showing up for me as the first Google hit when I search for SDS1000X-E datasheet. Apparently even content from official Siglent websites can not be trusted :-//. --- End quote --- I would trust a Google hit less for being the most up to date version of any datasheet. YMMV |
| alm:
--- Quote from: tautech on November 25, 2023, 11:17:24 pm ---I would trust a Google hit less for being the most up to date version of any datasheet. --- End quote --- Siglent salesman blames Google instead of Siglent, what a surprise :-DD |
| tautech:
--- Quote from: alm on November 25, 2023, 11:31:55 pm --- --- Quote from: tautech on November 25, 2023, 11:17:24 pm ---I would trust a Google hit less for being the most up to date version of any datasheet. --- End quote --- Siglent salesman blames Google instead of Siglent, what a surprise :-DD --- End quote --- I use Google all the time but never have a problem getting the right, proper, correct and latest version datasheets here: https://int.siglent.com/download/documents/?CateIdss= |
| rf-loop:
--- Quote from: alm on November 25, 2023, 10:29:30 pm --- --- Quote from: rf-loop on November 25, 2023, 09:58:13 pm ---And in your link it is this very obsolete (look this address): siglentna.com/USA_website_2014/Documents/DataSheet/SDS1000X-E_DataSheet_DS0101E-E03A.pdf Also if look Siglent NA, there is current version available there is: siglentna.com/wp-content/uploads/dlm_uploads/2021/08/SDS1000X-E_DataSheet_EN04D.pdf --- End quote --- Hey, I can't help it if Siglent NA leaves old data sheets on their website, showing up for me as the first Google hit when I search for SDS1000X-E datasheet. Apparently even content from official Siglent websites can not be trusted :-//. --- End quote --- In this matter, Siglent needs to improve itself. Here was one, albeit small, example of how important it would be for device manufacturers (Siglent in this case, but in general for everyone) to take care of the quality of the documentation and that they are up-to-date. If one want to keep an out-of-date document available, for one reason or another, publisher should stamp it or indicate clearly in some other way that it is "Obsolete". But then, other problem is many sellers or others who copy document some day and share these without even try to keep them up to dated when new versions are available. However, this small detail shouldn't jump over the OP's point. Understanding this offset thing is one of the fundamentals of using an oscilloscope that everyone should understand, including automatic measurements. Including possible differences in different oscilloscopes. In addition, the matter is messed up and complicated by the fact that there is no completely uniform way of expressing things in the user interfaces of the devices. |
| rf-loop:
--- Quote from: taydin on November 25, 2023, 08:29:30 pm ---Ok, let's go based on an actual scenario: I have set my signal generator to generate 1 kHz, 200 mVpp sine wave with an offset of 8 V. I apply that to my SDS1104X-E with the input coupling set to DC. I set the vertical offset with the vertical position knob to -8V and reduce the vertical range. And I am hitting the limit where the range is 500 mV/div. So right now, if I measure RMS, it measures about 8 Vrms, And it measures 8 V average. But, if the front end would have removed the 8V offset, I would be able to go to a much lower vertical range (in case the sine wave amplitude was much lower), and I would be able to measure the ACTUAL RMS and average value of the sine wave that's riding on the DC offset. So I don't understand, how are these two scenarios equivalent? --- End quote --- At this time I have not SDS1000X-E for real test but yes it have offset range what it have. If you have example 200mVpp sinewave what have 8V offset. It can "remove" this 8V only if vertical V/div is 120mV/div or more (based to data sheet). It is its limit. Some other oscilloscope have different limits. How it "remove" this 8V. Input circuit have this (principle): When you adjust offset (position) there is DAC what produce this Offset voltage what is summed to input signal. If input signal offset is 8V and you add -8V this input signal offset is "removed" and result is zero. Now you can see signal center of image vertical. Note that in digital oscilloscopes ADC range is nearly same as displayed vertical range on screen. (In SDS1000X-E displayed vertical range is 8 div and ADC range is bit over 10 div. So always you adjust vertical "position" you add some voltage to input signal (+ or - add or subtract). But think now this your example and measurements. (and yes input DC coupled) 200mVpp sine with 8V dc offset. (7.9V low peak and 8.1V high peak) Its mean value is 8V and its RMS is 8.000312 V (if signal is perfect clean theoretical signal) And because lack of enough resolution both display perhaps 8.00V and it is just right. But now, if we are interested about this Sinewave part without DC offset. Oh well it is simple and also SDS1000X-E can do it just right. Now need measure AC RMS. (DC removed.) Just ask automatic measurement do it. Do not measure RMS if you do not want get RMS (8Vrms in this case) There it is: Stdev. (StDev is AC RMS) In measurement menu. This is for it. It remove this DC offset. But for keep measured signal with DC offset in visible on screen (ADC range) there user add offset voltage to signal using adjustment named as "Position". In this example I have used Cycle RMS and Cycle AC RMS aka Stdev If cycles in this case do not match with data length we get easy very wrong results. (in this particular case can also use just RMS or Stdev for whole data length) Here example how other model do it. Look these values. All they are ok but naturally user need understand limits of true accuracy. (note that this real input signal is dirty, not oscilloscope) just for example because many times we have dirty signals instead of school books theory signals) Input around 200mVpp sine with around 8V offset. One note. If anyone wants a feature where this 8V offset is subtracted from the signal so that the display shows the signal center is 0V on a general purpose oscilloscope (DC coupled) and then some designer does it, I hope this designer clears his desk and exits through cashier and then never come back. Just to avoid a complete mess. We have to keep the truth visible from the input signal as strictly as possible as main principle. If there is a DC offset, we need to know it until we don't want it. In this case, we can also switch to the AC input coupling, which removes the DC offset. Now if the user has done that, he is also responsible for where and how the measured values are applied. |
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