Altitude encoder

Chad Lemmen wrote
I need a new encoder. I currently have a Trans-Cal D120-P2-T. I can get
an overhauled exchange for $230. Should I do that or just replace it with
a new ACK A-30 or Ameri-King AK-350? The Ameri-King is the cheapest at
$150. I believe both the ACK and Ameri-King use an oven to compensate for
temperature variations, while the Trans-Cal does not. Is it better to
have one with an oven or without? Is the Trans-Cal a better encoder
making it worth the extra money?

The Trans-Cal is not like the other encoders. It is built exactly
like an altimeter, bellows and all, but instead of a dial and hands it
has an optical encoder disk. The electronics are only used to change
the optical signals into electronic ones. No tuning, no drift - the
adjustments on a Trans-Cal are actually mechanical. What this means,
in practice, is that needing adjustment is VERY rare,

The ACK and Ameri-King are electronic beasts, they're analog, and they
drift. They tend to need adjustment every year or two, even with the
oven.

You can generally pick up a used Trans-Cal for about $100.

Michael