[T3] Pressure Sensor repair and calibration

[Jim Adney]

For several years I've been able to recalibrate the '68-9 and '72-3 
pressure sensors, but I had never taken the time to sit down with the 
'70-1 versions to figure out what they required. The problem was due 
to the fact that they have a diaphram and there are 3 separate 
adjustments that all interact. That makes it potentially very 
complicated. Add to this the fact that some of these diaphrams are 
starting to fail, and this adds the burden of having to figure out 
how to replace the diaphram.

Today I sat down with one of those Pressure Sensors and figured out 
how to do each adjustment and in what order, so that part is 
finished. Now I just need to find or make diaphrams.

I think I need .0035" Beryllium-Copper sheet to make these if they 
are going to be reliable. Then I need to form it into a corrigated 
diaphram. I have a die I had made, but I think I need to polish it so 
the material can slide, rather than tear, while it deforms.

Is there anyone out there with access to this kind of material? Could 
you supply me with small amounts of it? I found suppliers here in the 
US, but they require more of a purchase than I can afford. Their rep 
seems willing to help, but he needs more of a commitment than I can 
honestly give him.

If any of you know of diaphram suppliers that might have something I 
could modify and use, that would be even better.

In the meantime, I'm ready to try to calibrate some C Pressure 
Sensors (the ones with the slots or holes in the cover) but I'm not 
yet able to replace cracked diaphrams.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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