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RE: [TCML] Spark gap
Hi Scott,
The principal you suggest has in fact been done, successfully! I can't recall who first came up with it, but the deal is to take a small battery powered cassette recorder, place it near a running coil, then play the tape into the audio input of your PC's sound card and view the resulting waveform on any number of audio editing applications (Audacity is a free download), and count the blips in some time interval. Not as nice as looking at a meter with a digital readout, but the price is right. But I can't say that I've personally tried it.
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Scott Bogard
> Sent: Monday, February 25, 2008 10:50 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] Spark gap
>
>
> 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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> >>
> >>
> >
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>
>
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