On Sunday, December 17, 2017 at 12:23:21 PM UTC-5, JS wrote:
Linking a couple of recent threads: Connecting multiple varios and how to change ASI markings....

I discovered the reason for a flight computer's inconsistent readings was the bezel on the ASI not being tight enough to seal. Snugging it up resulted in a more accurate ASI and flight computer.
Checking each instrument is a good winter project. Techniques are described in the back of Reichmann's "Cross-Country Soaring".
Jim

Whether the advances on the original dual thermistor vario ( Crossfell)
made by Raouf were new thinking or just tweaking, is the stuff for
patent examiners to argue.
In 1962/3 I made several three thermistor varios based on what I knew about the Crossfell. They were donated to Mid Atlantic club, being an improvement on
the pellet type. Like the Crossfell they all suffered from temperature related
drift, which I solved by adding a shutoff valve in the flow line, plus
zero adjuster.
Raouf analysed the problem as unbalance in the slope of the temp/res
characteristic; he then chose balanced thermistors and trimmed the current setting.
This I think, was game changer, producing a reliable instrument.

I used one for years.

John F