Erik - I have been using a Gunsons for a while and also periodically remove
the pickup from the exhaust to check (and adjust if necessary) the
calibration from time to time as recommended in the instructions. However I
had not heard of purging the system after use, and cannot see reference to
this in the instructions. I don't see what difference having the tester
turned on or off makes as far as purging goes, unless yours has an electric
pump to draw the exhaust gases through the tester. Mine has a 'pulse pump'
arrangement whereby a one-way mechanical valve is opened and closed by the
fluctuating pressure in the exhaust to 'pump' the gasses through the tester.
Once the probe is removed from the exhaust the system purges or not,
depending on what the relative airpressures at the probe and the tester are,
irrespective of whether the tester is turned on or not.
What I have noticed, particularly on the roadster, is that the reading
varies considerably according to how far the probe is pushed in - the
further the higher. There is no reference in the instructions as to how far
it should be pushed in.
Cheers,
PaulH.
-----Original Message-----
From: Erik Brzoska <mowog77@hotmail.com>
To: mgs@autox.team.net <mgs@autox.team.net>
Date: 28 December 1998 16:24
Subject: Gunson Gas tester Discussion
>I will warn you now, this is pretty long-winded, but if you have a gas
>tester or are thinking about buying one, you may want to take five
>minutes and read it.
>
>Before you start testing, you have to get the tester to calibrate and
>settle at a reading of 2.0% in ambient air. Then you perform your tests,
>then you have to let the Gas tester reacclimate itself before turning it
>off, so you have to let it stand in clean open air for 10-15 minutes so
>it recalibrates and purges itself for next time.
>But also from this purge period, you can learn if the tester was out of
>calibrartion at all.
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