Ron (mainly)
OK I was exaggerating about the patch leads, we only used 26.
Nigel Beale, Mark (his son in law) and I spent Saturday afternoon
calibrating Skydrive's entire stock of 52 off 912 tachos. I generated a
representative waveform quite easily with a square wave and coupling
capacitor but we got a bit carried away getting the amplitude up to
representative levels - hence the gramophone/resistor/milk bottle.
BTW I did find during the course of the fun that the tachos are a bit
sensitive to supply voltage. I noted a 40 rpm increase when the supply
voltage was raised from 12.4v to 13.6v. So be careful out there if you're
trying to calibrate on the bench with a battery on its own.
Nigel did a final correlation check today with 4 samples and a real engine
(it was too
wet to do this on Sat.). These checked out fine, and now we think you'll
find that all the tachos in
Skydrive's stock are now accurate to within 50rpm at the nominal battery
(charging) voltage of around 13.6v.
Nigel says if there any owners who want their tachos calibrating, just send
them to Skydrive and he'll calibrate them FOC or replace (at his
discretion). You pay postage there; he'll pay postage back. Nigel is
investing in a properly sorted out calibration
set up to prevent this problem from recurring but it will not be ready
until about 4 weeks time;
if anyone needs an urgent replacement, he'll exchange,provided the original
is in perfect condition.
BTW I found 3 out of the 52 I checked were more than 500 rpm out. The rest
were within 200 rpm but all
reading low.
Dave Simpson
----------
> From: RonSwinden@aol.com
> Subject: Tacho's
> Date: 01 November 1998 22:23
>
> Dear Dave Nigel and co I showed your letter and photo to Kath and
explained
> the problem to her. She said "why don't they build em right in the first
> place?"
> She sort of gets to the heart of the matter I always think.
> By the way I know I'm a sort of poorly equipped builder but I do not
have 34
> patch leads. Anyone want to borrow one of my three spare scopes and the 4
or 5
> counters I've got lying around.
> Any chance of any help out there especially from the Rotax agent Ron S
No33
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