-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 9/7/2012 9:04 AM, Kent A. Reed wrote: > Has anyone come up with simple (e.g., inexpensive) ways to measure > latencies in the range we are interested in - say a range of 1K - > 100K pulses per second with pulse widths on the order of > microseconds. > > Back when the world was young and we wannabe researchers avidly > read from cover to cover in each new data-book from the likes of TI > and Motorola, I used to design and build comparable circuits, but > then I had the bench instrumentation to test my testers, so to > speak. Now I'm in a catch-22 situation. > > If I could turn back the clock, I'd probably use this problem as a > reason to explore FPGA, but instead I'm noodling about using a > Beaglebone or somesuch as a starter. > > Thoughts, anyone?
I've crafted a variety of fine-scale time-sensing circuits using a constant current to charge a cap. Adjust the current and cap value to the time-scale of interest and use some simple digital logic and CMOS analog switches to craft some sample/hold logic appropriate to your signal. Buffer the cap with a CMOS op-amp to avoid loading the sample/hold circuit and you can read out time with a volt meter. ...of course, you still need some sort of reference for calibration. If you don't have a 'scope you could use a long (and hopefully fairly accurate) SW generated pulse to calibrate the capacitor value using a small current, then scale the current source to your range of interest. Accurate resistors are pretty available, while capacitor tolerance is pretty lousy by comparison. NOTE: This technique works a *LOT* better in today's world with CMOS analog switches and op-amps (and their pico-amp leakage current and minimal charge injection) than back in the 'old days' when everything was bipolar (or vacuum tube based!). :) - -- Charles Steinkuehler char...@steinkuehler.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlBKAPwACgkQLywbqEHdNFy+XwCgr5e3kEJvi2rf5Bl0Z82gZjr8 YKQAn2QEe/A6zKyVTw6OjNPgi6E5Ux+K =JRRj -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
