See http;//www.ko4bb.com/Test_Equipment/Thunderbolt/PulseStreching/ Didier KO4BB
Sent from my Verizon Wireless BlackBerry -----Original Message----- From: Arthur Dent <[email protected]> Sender: [email protected] Date: Sun, 26 Sep 2010 05:07:50 To: <[email protected]> Reply-To: Discussion of precise time and frequency measurement <[email protected]> Subject: [time-nuts] Thunderbolt PPS Modification Here is a link to a photo of the 5V 10uS wide pulse. It is there but catching it on some scopes can be a problem because of its narrow width and low repetition rate. http://farm5.static.flickr.com/4013/4339027385_0d9f2bc055.jpg +++++++++++++++++++++++++++++++ Hal Murray: “The problem for me was that the PPS pulse wasn't wide enough for one of my PCs to catch. (Another one does catch it.) I changed the wire into a diode, resistor, and cap. It's a kludge, but it works."+++++++++++++++++++++++++++++++ I can see that there might be a problem relying on an RC time constant if you are interested in consistent pulses with minimum delay. What I had done on my Z3801 about 10 years ago was use an inverter to trigger a 555 pulse stretcher. I made the pulse about a 50-50 duty cycle because I was also driving an LED for indication the pulse was there. If you lower the values of the 1 megohm resistor and the .47uF capacitor you can narrow the pulse width you get at pin 3 of the 555 timer. A 10Kohm resistor and a .001uF capacitor will give about a 100uS wide pulse. You can check an online reference of the 555 datasheet if you want a specific pulse width. The consistent propagation delay thru the circuit is probably in the vicinity of 250nS. http://farm3.static.flickr.com/2679/4351301462_7cd9625a97_z.jpg?zz=1 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
