> Suitable TDC chips are available from http://www.acam.de/ <http:// > www.acam.de/> In particular the TDC-GP1 has a resolution of better > than 250picosec with a range of 200 millisec, which should be more > than adequate for measuring the time delay between GPS and local > standard derived PPS pulses.
> Although these chips are a little pricey at around the 100 euro mark > they are a lot cheaper than an Agilent/HP 53131 or its equivalent. Has anybody tried kludging something together without using expensive parts? I'm guessing that the general idea is something like an R/C feeding an ADC. Hold the R/C reset until time1, then let it start charging up. At time2, shut the door on a sample/hold that's probably built into the front end of an ADC. Then wait until things calm down and read the ADC. If I start with a 10 MHz clock, that's 100 ns. An 8 bit ADC gives a span of 2.5 clocks for a resolution of 1 ns. Lots of handwaving here. A 1 ns resolution needs an ADC or S/H with an input bandwidth in the ballpark of a GHz. My quick scan for a cheap/fast ADC didn't find anything interesting. So this is probably a wild goose chase. I wonder if it is reasonable to calibrate a slower ADC. The input signal will be stable. Digikey has the TI TLC5540 at under $6. It says 75 MHz input bandwidth but 30 ps aperature jitter. (That's just the first one I looked at. There are probably better ones.) -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
