Re: [TCML] Spark gap

[Scott Bogard <teslas-intern@xxxxxxxxxxx>]

perhaps this is a very inaccurate approach, but, spark gaps all emit a 
certain pitch sound.  This is especially noticeable on rotary gaps.  You 
could use a tone generator to match the pitch of your spark gap, and 
calculate the BPS through the frequency of the sound.  As I said that 
will only give a rough estimate of the breaks per second (400ish...).  
You would probably be better off to put a photo sensor close to the 
spark gap, put it through a filter, and measure the flashes per second 
with an oscilloscope, as Bart already suggested.  Just musing.

Scott Bogard.

bartb wrote:
> Hi Gary,
>
> Actually that was my first thought on this. Simply trigger a pulse and 
> record it. But then I thought "well it's just as easy to record the 
> whole thing". I may end up doing that in the end. I could also measure 
> the voltage drop across the gap itself for each bang, but that does 
> take a bit more work and thought.
>
> Thanks for your input.
> Bart
>
>
> Lau, Gary wrote:
>> I would attempt some sort of low-pass filter at the receiving end - 
>> so that each bang results in a single blip and any stray HF stuff is 
>> attenuated.  But I think I tried as much, unsuccessfully, as had I 
>> been successful, I could have just fed the result into a counter with 
>> a suitably long time base for a good average PPS count.  Good luck!
>>
>> Regards, Gary Lau
>> MA, USA
>>
>>  
>>> -----Original Message-----
>>> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
>>> Behalf Of bartb
>>> Sent: Monday, February 25, 2008 9:46 PM
>>> To: Tesla Coil Mailing List
>>> Subject: Re: [TCML] Spark gap
>>>
>>> Hi All,
>>>
>>> With this thread, measuring static gap bps came up. I will attempt 
>>> this.
>>> I can record hours of run time if needed, but of course I'll record say
>>> a 10 minute run. This should give plenty of data for bps acquisition.
>>>
>>> I'll use a device specifically for data acquisition. This device plugs
>>> into my pc via shielded USB and can accept up to 60Vp-p signals.
>>> Although I do have the high speed unit capable of 14,400 samples/s, 
>>> I'll
>>> set the sample rate only to what is needed for a decent view. The 
>>> device
>>> however doesn't need to be near the coil (USB's are very prone to noise
>>> which causes device hardware connections to be lost). So, I'm thinking
>>> of using optics for isolation.
>>>
>>> Here is my very simple strategy:
>>> * Hook up fiber cable near first gap to capture the light created by 
>>> the
>>> spark (where it will always issue).
>>> * Convert light to DCV at opposite end.
>>> * Record voltage output over 10 minute run.
>>>
>>> Although I may go further with this, I'm just looking at getting the 
>>> bps
>>> data with the gap as is to start.
>>> This is only to measure bps and nothing more.
>>>
>>> I've used this device for acceleration impact testing up to 1050 LB 
>>> load
>>> dropped at various heights and even for a 2 week non-stopped testing of
>>> cycle times on actuation devices.
>>>
>>> But, I thought it wise to run by the TCML and see if anyone has tried
>>> anything like this with a static gap or similar and has any advice I
>>> should consider before I start. I'm not sure how the light source will
>>> stop and start at the gap.
>>>
>>> Take care,
>>> Bart
>>>
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>
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