[ntp:questions] Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)
hmurray at suespammers.org
Fri Aug 25 23:54:19 UTC 2006
In article <1156547281.444666.212940 at h48g2000cwc.googlegroups.com>,
"simonpg" <paul at thesimonet.org> writes:
>Hacking up a serial cable is no problem. I'm just worried about frying
>something inside the 486-DC. Could I expect to see an LED lighting up
>on one of those RS-232 signal testers? How about a Volt/Ohm Meter? Or
>am I worring about nothing? So I'll hook the ring of the BNC to pin 1
>of the DB-9, and the tip to whatever DCD is? Do I need to worry about
>ground loops if I use the same serial port? (whine, whine, whine)
>It's just hard to get the 486-DC fixed; know what I mean?
You can sanity check the ground loop problem with a voltmeter.
A scope would be a better tool for checking the PPS signal.
A meter might show something, but I'd expect troubles from
the long averaging times.
You could also put the scope/meter on the input to the DCD pin
to make sure you have an input rather than an output. It's
probably pulled up to a few volts. Look at others to see
what an output signal looks like.
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