[EMAIL PROTECTED] wrote: > Here's a thought. Perhaps there is a problem with the rear reference input; > A and B channels are fine since they read the same error. The question is > "Is there a way of adjusting the Reference Input so that it correctly read > the 10Mhz input?" > > I tried the same setup with my other counter and it read 10,000,000.0000 or > thereabouts correctly. So rule out the GPSDO and the cables. > > > > ----- Original Message ----- > From: "Dr Bruce Griffiths" <[EMAIL PROTECTED]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Wednesday, February 21, 2007 19:47 > Subject: Re: [time-nuts] SRS SR620 External Source Issue -- Help Request > > > >> Hej Magnus >> >> The Frequency measurement logic (before the interpolators) appears to >> use a pair of 2 bit synchonisers, one for the rising edge and one for >> the falling edge of the internally generated frequency gate. The >> synchronisers synchronise the respective transitions of the frequency >> gate signal to the external frequency being measured. >> One synchroniser uses U508A + U509A the other uses U508B + U509B, so >> that any mismatch in propagation delays between U509A And U509B will >> result in a small error in the time interval. Even for ECL flipflops a >> propagation delay difference between U50(A and U509B of 150ps wouldn't >> be unusual. As far as I can tell the calibration procedures do not >> address this issue. The uncalibrated differential delay through the >> interpolation circuit source selection multiplexer will also contribute >> an offset. >> Perhaps a better assignment of propagation delay differences may be >> U509A and U509B 50ps, multiplexer and wiring delay mismatches 100ps. >> >> Bruce >> >> _______________________________________________ >> time-nuts mailing list >> [email protected] >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >> > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Flavio
Not easily. However if you run a test with say a 0.1 sec gate time and average several readings, then if my model is correct the apparent offset in the mean will be increased by a factor of 10 over that for a a 1 second gate time. Bruce _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
