I've got a friend (yes, really) who has an old vehicle dynamometer. At
the moment he uses a DC tacho generator attached to the floor roller
which puts out 8V per 1000rpm into the dynamometer, up to a limit
of 6000rpm. Doing it this way means the feedback is speed

He's wanting to use a dashboard tacho, to use rpm feedback, an
example of which he has and thinks puts out 1V per 1000rpm. The
active component is an SAK215

http://www.datasheetcatalog.com/datasheets_pdf/S/A/K/2/SAK215.shtml

The meter in this dash tacho is presumably a 10mA movement

What he's asked me to do is amplify the 0 - 6V (ie 0 - 6000rpm) range
of the dash tacho to 0 - 48V to feed to the dynamometer

One thought I have is to boost the 12V car supply to 48V with an SMPS,
and use a PIC to measure the voltage from the tacho and chop/integrate
the 48V to 8x that voltage

I think opamps are out because of the 48V, but would consider any
other linear suggestions anyone has, perhaps a modified audio amp
for example

TIA, wbr
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