[time-nuts] How to measure Allan Deviation?

[Dr Bruce Griffiths]

Didier Juges wrote:
> Hi Bruce,
>
> Dr Bruce Griffiths wrote:
>   
>> Didier Juges wrote:
>>   
>>     
>>> Dr Bruce Griffiths wrote:
>>>   
>>>     
>>>       
>>>> Didier Juges wrote:
>>>>   
>>>>     
>>>>       
>>>>         
>>>>> I do not understand the signal on the rear trigger outputs. At the 
>>>>> moment, I have a single 10 MHz sine signal fed to the START channel, and 
>>>>> the 5370 is set to  TI, MEAN, SAMPLE SIZE 1, + TI ONLY, START channel 
>>>>> triggers on rise and STOP channel triggers on fall, and START COM is 
>>>>> selected. The instrument displays about 60 nS (fairly stable, 150 ps 
>>>>> jitter) or so at the moment. The rear  START trigger shows a negative 
>>>>> going pulse (400uS wide, at 62 mS rep rate), with the rising edge 
>>>>> (positive going) synchronous with the 10 MHz signal and the phase is 
>>>>> adjustable using the *STOP* trigger level! When I trigger the scope on 
>>>>> the falling edge of the START trigger output, the 10 MHz signal seems to 
>>>>> drift, and the trigger setting has no effect, except that if adjusted 
>>>>> too far, the instrument stops updating the display.
>>>>>
>>>>> Apparently, the START trigger adjustment has no effect on the timing of 
>>>>> the rear START trigger output, but will cause the display to freeze if 
>>>>> the START trigger is set to either extreme, even though the START 
>>>>> trigger output on the rear does not change.
>>>>>
>>>>> The STOP trigger output works the opposite: it responds to the START 
>>>>> trigger level. Could it be that the outputs are reversed on my instrument?
>>>>>
>>>>> I am not sure this is a complete description, and maybe there is an 
>>>>> obvious answer that I am missing, but I am perplexed.
>>>>>   
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
>>>> Didier
>>>>
>>>> The 5370A processor can swap the front panel START and STOP inputs over 
>>>> via an ECL multiplexer on bord A22.
>>>> The rear panel outputs reflect the actual selected START and STOP events 
>>>> not necessarily the signals connected to the front panel START and STOP 
>>>> connectors.
>>>>
>>>> Bruce
>>>>   
>>>>     
>>>>       
>>>>         
>>> Good catch, but I thought that only came to play when +/-TI was 
>>> selected, and I have selected +TI ONLY?
>>>
>>> Didier
>>>
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>>>   
>>>     
>>>       
>> Didier
>>
>> That's not the way I interpret the manual or the article on the 5370 in 
>> the HP journal.
>>
>> +TI ignores all STOP inputs until after the START event.
>> +-TI  START before STOP is a positive time interval STOP before START is 
>> a negative time interval. Internal logic implements a precedence detctor 
>> so that the relative order of accepted start and stop events can be 
>> determined.
>>
>> Bruce
>>
>>   
>>     
> You are correct of course, I *assumed* the counter would automatically 
> swap the START and STOP rear trigger outputs as needed when the +/-TI 
> mode was selected, but that in +TI ONLY mode, there should be no need to 
> swap START and STOP, therefore the rear trig outputs would be fixed.
>
> I have a lot more reading to do, it's a big manual. I have a pdf of it 
> on my web site and I printed all this week end, big job!
>
> Can you send me the pdf of the HP journal about the 5370?
> If it's too big to attach, can you upload it to my web site?
> dns: ftp.ko4bb.com
> login: manuals
> password: manuals
>
> Thanks
>
> Didier
>
>
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>
>   
Didier

Will do as soon as I find the particular issue again.
May take a little while as I haven't looked at it for a year or so.

Bruce