Analog Gauges / Air-core meter

[Jeff Webb]

I have a couple of questions involving analog gauges.  From what I
understand, there are two main types of analog automotive gauges: the
standard galvanometer-type meters, and the new air-core (moving-magnet)
meters.  Is my terminology correct?  I assume the air-core meter gauges
are the ones found in most new cars (where the needle does not return to
zero when the power is turned off).  The air-core meters seem to use two
coils (sine and cosine) instead of one coil and a spring as in the
galvanometer type.

I would like to drive several analog gauges from a microprocessor.  I
would prefer to use the new style gauges, if possible.  The only source of
information I have found so far is National Semiconductor's LM1819
Air-core meter driver datasheet.  Are there any other similar drivers
available?  Would it be hard to design a home-built driver?

My main question is where to buy these sort of gauges.  Is there a cheap
source of new gauges, or is my best bet to scavange them from a junk yard?
If so, are all air-core meters alike?  What differences might I find?
Please note that I do not want to buy a whole tachometer (expensive) from
someone like Autometer or VDO - I just want the gauge itself since I will
be driving it from a microprocessor.

I apologize for the length of this post, but I wanted to be as clear as
possible.  I would appreciate feedback from anyone who has experience with
this type of analog meter.  Thanks for your help - this list is a great
source of information.

Jeff Webb
mustang at eel.ufl.edu