[time-nuts] How to measure Allan Deviation?

[Didier Juges]

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