ION sense stuff

[steve ravet]

Peter Gargano wrote:

> Nic van der Walt wrote:
> 
> > I have looked at the ion sensing stuff and I really like the idea. Has anyone
> > got any more info on it? I'll build a flyback converter sometime to get
> > the 400V or so bias and start logging data for analisis. Does anyone know at
> > what bias voltage the plug will start sparking over? I'll want to push up the
> > bias enough to get a reasonable current to measure.
> 
> As I understand it, people have obtained reliable ION currents with sense voltages
> below 100 volts. On the other hand, many people have used voltages as high as 400.
> Only a simple circuit seems to be required to generate a bias voltage as there's a
> lot of both negative and positive current flowing from the kVs required to strike
> the plug. I'd like to see what's the simplest circuit (a cap + zener?) required to
> generate a bias. At the other end, I've heard that at least 12 bits of A to D are
> required to get a reliable sensed current due to the dynamic range of the signal
> but this may be only required for some of the newer applications that require "curve
> fitting" to do some fancy calculations.

There was some discussion about voltage levels in the archive.  As I
recall, Saab uses 2 voltage levels, about 80 and about 400.  I think the
reason had to do with lower voltage levels attracting particles to the
plug electrodes and cruding them up.  Someone else mentioned using an
A/C bias to combat the problem but I don't recall if that was tested.

This is from distant memory so it may be totally wrong...

Also, I moved this reply to diy_efi instead of efi332 as diy_efi is more
appropriate.

--steve

-- 
Steve Ravet
steve.ravet at arm.com
Advanced Risc Machines, Inc.
www.arm.com