Re: [time-nuts] Reference oscillator requirements when measuring ADEV ?
Mark Spencer wrote: I'm curious in knowing if there are any rules of thumb as to how much better a reference oscillator needs to be than the device under test when measuring ADEV ? To provide a bit of context to my question I'm using a HP 5370B to repeatedly measure the time interval between the 10 Mhz signals from a FTS 1050 and rubidium oscillator. Having compared the FTS 1050 to another OCXO in the past I'm confident that it is meeting or exceeding it's spec of an ADEV of 1X10-12 or better at tau's of say 100 thru 1000 seconds. I'm also confident that at tau's of 100 seconds or more the noise introduced by the 5370B is less than 1x10-12. The underlying question that I have is how much confidence could I put in measurements that show the rubidium of having an ADEV of say less than 2.0X10-12 at a tau of 100 sec ? This is just for a hobby (: and I'm not looking for any degree of certainty but I'm curious in understanding how accurate the measurements might be and if changes in the measurements might not be caused by changes in the device under test. Thanks in advance for any replies. Regards Mark Spencer The reference oscillator needs to be at least a factor of 3 (preferably 10x) better for all Tau of interest. Unless of curse one uses a 3 (or N) cornered hat technique in which case the ADEV of the oscillators being compared may be similar for the Tau range of interest. However one needs to guard against correlations between oscillators due to injection locking, environmental fluctuations etc. For Tau= 100s relatively simple low cost three cornered hat setups (with an instrumentation ADEV noise floor below 1E-12) are feasible (provided on has a suitable offset oscillator) using inexpensive digital logic plus a suitable microprocessor. No complex interpolators are required. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Reference oscillator requirements when measuring ADEV ?
Hi You can be quite sure it's no worse than 2x10^-12. It is pretty common to scale by square root of two based on a they could be equal assumption. Bob On Jul 14, 2011, at 8:32 PM, Mark Spencer mspencer12...@yahoo.ca wrote: I'm curious in knowing if there are any rules of thumb as to how much better a reference oscillator needs to be than the device under test when measuring ADEV ? To provide a bit of context to my question I'm using a HP 5370B to repeatedly measure the time interval between the 10 Mhz signals from a FTS 1050 and rubidium oscillator. Having compared the FTS 1050 to another OCXO in the past I'm confident that it is meeting or exceeding it's spec of an ADEV of 1X10-12 or better at tau's of say 100 thru 1000 seconds. I'm also confident that at tau's of 100 seconds or more the noise introduced by the 5370B is less than 1x10-12. The underlying question that I have is how much confidence could I put in measurements that show the rubidium of having an ADEV of say less than 2.0X10-12 at a tau of 100 sec ? This is just for a hobby (: and I'm not looking for any degree of certainty but I'm curious in understanding how accurate the measurements might be and if changes in the measurements might not be caused by changes in the device under test. Thanks in advance for any replies. Regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
