Thanks all for your info about these modules. Daniel
On 26/04/2015 01:26, Bill Byrom wrote:
I still work for Tektronix, but not in Service or the sampling scope product line. I'm a Tektronix field RF Application Engineer. You can find the service manual for the SD-24 at: http://www.tek.com/oscilloscope/sd24-manual/sd-24-service-manual But it's not user repairable, so there are no schematics (just block diagrams). The SD-24 was introduced about 25 years ago for the 11801/11802 family of sampling scopes. The SD-24 is a dual TDR sampling head, so it can generate a fast risetime step from either or both outputs. The steps can be the same polarity (for common mode testing) or opposite polarity (for differential mode testing). The sampling bridges measure both the incident (forward) and reflected pulses. The SD-26 is basically the same product without the TDR pulse sources. The SD-22 is a lower noise (and lower bandwidth) version of the SD-26. As pointed out by others, these heads aren't useful without a 11800 or CSA800 family mainframe. The SD-series measure signals using sequential equivalent-time sampling. * Single events can't be measured. Only repeating signals with a low-jitter trigger source can be measured. The trigger must be an externally input signal (unless you use the SD-24 with the internal TDR step source or an external signal pickoff transformer). * Each trigger edge which is accepted by the mainframe is delayed by a precise amount and then used to create a sampling strobe which is sent by the mainframe to the sampling head. * The sampling head (SD-24/26/22) actually measures the error difference between an internal feedback loop and the sampled input voltage. Since the sampling bridge has a high loss, the error voltage is multiplied by the assumed bridge loss to create the new feedback loop voltage. A high resolution low-noise A/D converter measures the loop voltage for the microprocessor-created raster scan display on the CRT. * The sampling system takes around 10 microseconds to reset between triggers. So no more than about 100K triggers and samples can be made per second. It might be a little slower than this - I'm remembering this from my experience over 20 years ago. * The delay from the trigger input to the sampling strobe (sent to the SD-xx sampling head) is sequentially delayed by slightly increasing time delays to create a time domain display. The delay increment between samples can be less than 1 ps (down in the 100 fs range). * Since the signal is not actually sampled in real time, this is called equivalent-time sampling. In this case, the sampling strobe is sequentially advanced in time upon trigger signal acceptance. This results in very high time accuracy with low jitter (a couple of ps RMS jitter in these older products). * The voltage measurement range is usually a few hundred millivolts peak-peak, while the damage level is at around 3 volts. -- Bill Byrom N5BB On Fri, Apr 24, 2015, at 10:42 PM, Ivan Cousins wrote:Since I was working at Tektronix at the time, I still remember the first instruments that were in the family. Like the main frames 11801, 11802, CSA801, CSA802, CSA803, etc and sampling heads SD-20, SD-22, SD-24, etc. You can try a google search like "Tektronix 11801 filetype:pdf". You can also try a google search like "Tektronix SD-24 filetype:pdf". If you want to know more about google filetypes, enter "google filetype search" into a google search. To find out more about sampling heads you can look for information on the instruments they connect to. w140.com has a lot of information on both the mainframes and the sampling heads. http://w140.com/tekwiki/wiki/Main_Page#11000_Series http://w140.com/tekwiki/wiki/SD-24 It is good to know more google-fu. It is even better to be able to still remember about any of this. :) Ivan Cousins _________________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there._______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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