Ignition Analyzers

To: tesla-at-poodle.pupman-dot-com
Subject: Ignition Analyzers
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 31 Mar 1997 11:54:01 -0600
Approved: tesla-at-stic-dot-net
Subject: 
        Ignition Analyzers
  Date: 
        Mon, 31 Mar 97 11:11:58 EST
  From: 
        pierson-at-gone.ENET.dec-dot-com
    To: 
       
mail11:;;;;;-at-us4rmc.pko.dec-dot-com-at-us4rmc.pko.dec-dot-com-at-digital-dot-com;;;;;;;;
(-at-teslatech)
    CC: 
        pierson-at-gone.ENET.dec-dot-com


>Subject: 
>        a thought on scopes - use an ignition scope
>  From: 
>        "William Noble" <William_B_Noble-at-msn-dot-com>
 
>I have an older (sun??) ignition scope sitting in my garage - it runs on 12VDC
>which mostly powers some tube filaments - it gets all the HV from the ignition
>coil - it connects to the coil secondary as well as the battery.
        An interesting idea.  My first thought is to beware the
bandwidth,
        In an ignition 'scope i doubt whether the 'high frequency' 
        performance is of importance.

        My SECOND thought is that IF it couples the voltages direct to
the
        deflection plates (?) the badnwidth may, in fact, be quite good
enough.
        As with any measuring device, understanding exatly what it IS
measuring
        is key.

>It would seem that this might be a useful way to look at tesla waveforms - what
>do you guys think.  I suppose once I could even go out to the garage again and
>look at it to refresh my memory about how it actually hooks up - I bought it on
>a whim for $2 at a car swap meet (it didn't work), and had to replace the HV
>rectifier tube to make it work - I used it once as an ignition scope to see how
>they worked and haven't looked at it in several years. 
        I'll admit to not being familiar with them, i suspect sweep
speed ranges
        are somewhat limited?

        How is the deflection coupled to the CRT?  If there is an
amplifier,
        understand what it is doing to the signal.

[Bandwidth of a scope...

        Any scope has a 'roll off' at the high end of the frequency
range where 
        it starts toi lose sensitivity.  By convention, this is
generally
        the point where the cope is 3db down, that is, the indications
are low
        by that amount.  Thus, whne i started, a typical industry scope
might
        be a 30 MHz or 50 MHz scope, with 200 Mhz costing serious bucks
        and Ghz more yet.  Now 500- 1 Ghz are the norm and faster is
exceeding
        common.

        EITHER/ANY of these are overkill for conventional coiling.  I
seem
        to recall that it is considered good practice to haev a scope
with
        10x the bandwidth of the signal of interest.  There is
interesting
        stuffe going on ABOVE the resonant frequency of the system, I'd
guess
        10 Mhz as sort a mimimal usable scope bandwidth, but Richard
Hull,
        or Dr Resonance or others could say more accurately.  The
problem with
        using a 'too narrow' band scope is that info gets lost & you
don't
        know you are missing it.  (been there, tripped on that...)

        A directly coupled scope (practical in ignition and tc work can
be
        QUITE fast....]

        regards
        dwp