Electronic versus Pneumatic compensation (conclusions)

Well, I think the jury has some verdicts in this trial.

Background: I recently bought a V2C with an existing Sage CV vario, and
had a new LX7000 and C-302 installed. The Sage installation was not
modified and I assumed it was connected to the TE probe somehow, even
though the lower ("S") connector went to static pressure and the
glider pressure source labeled "TEK" (which I later verified was
"TE") wasn't connected to anything when I received the glider. I
installed the LX and 302 to use electronic compensation, therefore
connecting their TE/static ports to static sources and setting the
internal TE compensation settings from 0 to 100%, as per their manuals.

The first two flights on 17 September revealed problems with the Sage.
The needle swung with such frequency and magnitude as to be unusable.
Another pilot (amazing how much HVAC guys know about glider plumbing!)
suggested I add a flow restrictor in the form of a cigarette filter.

Flight 3 the next day showed great improvement - the Sage was
readable, but clearly uncompensated. And I wasn't sure about the
vario readings from the LX and 302 - I could induce stick thermals on
those as well.

Prior to flight 4, I did some more vario installation research and gave
the plumbing a much closer inspection and verified that yes indeedie
the Sage was connected to static source. So I moved it to TE, without
the filter, leaving the LX and 302 on electronic compensation (static
source to TE/static input).

Flight 4 (last Saturday) showed vast improvement in the Sage. The stick
thermals were gone, but without a restrictor the needle still moved a
bit too aggressively. And I was still not satisfied with the vario
readings from the LX and 302. The Sage largely agreed with the feel of
lift and sink, but while the LX and 302 vario needles usually pointed
in the same direction, most of the time they didn't make sense.

So Sunday morning I put the LX and 302 on the TE as well, resetting the
internal compensation settings to 0% as per the manuals. I also set the
LX's vario type to "NETTO" and put the flow restrictor back in
the Sage's TE line. This time I got the results I wanted: all the
instruments agreed; they reflected what I felt in the seat of my pants;
and all were immune to stick thermals. All that's left is to learn how
to waltz in a glass slipper.

As for putting multiple instruments on the TE, the conventional wisdom
seems to be that not more than one of them can use a capacity, as my
Sage does.

I must confess to being surprised at the difference between electronic
and pneumatic/TE compensation on the LX and 302. Maybe it's just
something about the static source on this particular glider (I recall
how wildly the Sage needle moved when it was on static). I used
electronic compensation for the 302 in my previous glider and it seemed
to work fine there. Go figure ...

-ted/2NO