As a confirmed analog-phile I've had the same experience, although I never
paid much attention to the analogue tacho anyway.
The difference however with a tacho (and a compass for that matter) is
that the reading is compared to a mental model of a range of numbers or a
predetermined desired number. For the engine other parameters, unless you
have a head for remembering figures, the position of a needle against a
coloured scale I find much easier. Admitted that it requires more
complexity to have alarms with analogue instruments.
Duncan McFadyean. .
On Saturday, September 14, 2002 5:36 PM, John & Paddy Wigney
[SMTP:johnwigney@worldnet.att.net] wrote:
> Dear Europaphiles,
>
> I would like to give my comments on RPM readout based on about 100 hours
> experience on my mono XS with a 912S engine. I installed an EIS panel
(see
> below) which has a digital RPM display and I also installed a Rotax R629M
2 inch
> analog tachometer since I believed that I would use the analog as the
primary
> tacho indication. Before flying the plane, I belonged to the school which
> believes that analog indication is the only way for quick understanding.
> Interestingly I had spoken to Greg Toman at Grand Rapids Technologies who
make
> the EIS unit on another matter and he explained that I would stop using
the
> analog gauge and would rely on the digital. I did not believe him, but he
was
> right. The EIS refreshes very rapidly, at least as quick as the needle
swings,
> and it is always extremely accurate. For example, I have a WhirlWind
constant
> speed prop and in cruise, I can adjust the RPM up or down within 10 rpm
by using
> about a quarter turn of the prop vernier. I find now that I never refer
to the
> analog tacho.
>
> I should explain that I have no personal or business relationship with
EIS but
> for those considering panel design,I can highly recommend the EIS 2000
unit. It
> has various pages which can be accessed as necessary and a default
"favourite"
> page where I display :-
> RPM
> Oil temperature
> Oil pressure
> Fuel pressure
> Fuel flow (this is an optional extra item)
> CHT
> EGT
> All the outputs can be set with high and/or low alarms which flash a
large red
> lamp.
>
> The other engine outputs available on my unit on the other pages are :-
> Total fuel remaining. (Reset at every fuel fill)
> Endurance time (Calculated by fuel remaining divided by current fuel
flow)
> Voltage
> Coolant temp
> Timer for current flight. (This resets automatically)
> Total engine time. (Equivalent to Hobbs time)
>
> Finally, analog gauges do have their place. I do use a Manifold Pressure
analog
> gauge to set my cruise throttle opening.
>
> Cheers, John
> N262WF
>
> Fred Fillinger wrote:
>
> > Nigel Charles wrote:
> > > ...
> > > An rpm gauge is the only engine gauge which I feel needs analogue
display.
> > > Ironically these are often the ones which need the most setting up.
Mine
> > > overeads by 200rpm at 5800rpm.
> >
> > RPM should be the most suspect of all. Convenient to think digital is
> > more accurate, but you can't just count pulses - accurate to within
> > parts per million, but at even 50RPM resolution, the display update
> > rate is unacceptable. Other approaches then become dependent on
> > mechanical and other issues in the stator ass'y from whence come the
> > pulses, with accuracy attainable with $$, unless the higher price is
> > just more profit. Same for analog gauges. Digital RPM checkers which
> > read optically are very accurate and affordable. Borrowing or buying
> > one of these is arguably a must! Or a freq counter from Radio Shack
> > and do the math.
>
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