Didier It would be useful if you describe in some detail your measurement setup. Which signals are connected to which inputs on the 5370A? How long are the cables? etc.,
Also given your source selection problems with the 5370A it may be instructive to run a simple test. Connect a low frequency square wave source to both the START and STOP inputs ensuring that the cable length to the STOP input is around 1m or so longer than the cable to the START input. Select TI and see if the time interval difference is around 5ns (for a 1m cable lenght difference) and the noise is substantially less than 100 picosec. Select the START and STOP inputs to trigger from the same edge of the input waveform. The jitter of the square wave source isn't critical. A resistive splitter can be used to ensure low reflections when both START and STOP inputs are selected for 50 ohm input. Otherwise the a BNC T can be used on the START input (select 1 megohm input ) with a 1m length of 50 ohm coax running from the BNC T to the STOP input which is set for 50 ohm input impedance. Reflections aren't a problem if the trigger thresholds are set correctly. The square wave source should be capable of producing an output of at least 800mV pp into 50 ohms. If you have nothing else the PPS output (suitably buffered) from a GPS receiver will work just fine. Typical measurement jitter for a good 5370 is about 35 picosec. If this works then you can have an increased confidence that the 5370 is indeed working as it should. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
