Paul:
  As a side-project for my HomeBrewedGlassPanel project, I am researching
  and soon will be acquiring sensors to feed analog data to my DLP-IO20
  data acquisition board.

  I believe that the automotive sensors that I have experience with
in the  past are all variable resistive devices of some sort. The internal
  bellows-construction of most old pressure-sensors is obvious. And I
  always had the impression that there was a little plunger on the
end of  of some pressure sensors. I also suspect that temperature
sensors were  nothing more than thermistors. These resistance-based
sensors would all  be relatively high-current devices... something I
would like to stay  away from.

  I once did an engine-swap on a Ford and managed to get my wires
crossed,  couldn't figure out at first why it took so long to get decent
  oil-pressure, and why the engine temperature was normal immediately
  after startup. :)

  So I am breaking ground here in the digital world. I would like
some  advice from the RotaryEngine bunch. Let's break down my search
for  sensors into catagories ...

  TEMPERATURE
  There is no problem finding low-current analog temperature sensors
for  use in the -50F to 250F temperature range, there are hundreds/thousands
  of them available. The only problem I will have is finding one/some
  inexpensive enough for my R&D budget that are bullet-proof enough for
  the FWF environment of an aircraft.  I might land up boring a hole
in a  bolt or brazing a plug into a pipe-fitting to make a socket
that will  accept a cheapy sensor, then epoxy the device into the
socket, leaving  some teflon-insulated leads exposed to the outside world.

  I know these cheap sensors should work for water temperature and
OAT,  but what about oil-temp, CHT, and perhaps even exhaust temp?  Platinum
  thermocouples are a bit out of range of my R&D budget, I think.
  I don't know how sensitive the A/D input is on the IO20 board, but
I  suspect that thermocouple-based temperature sensors would require
a  transistor or op-amp to give a usable signal. ???  Any suggestions.

  PRESSURE
  There are also quite a variety of pressure sensors available: classified
  as gauge-pressure, absolute-pressure, and pressure differential.
  It is interesting that some very inexpensive pressure differential
  sensors are available, they are used as water-level sensors on
  automatic-washers.  I should be able to find some of these and
create my  own test version of air-speed and vsi indicators.
 Somewhere in the last  month or two I saw a graph of pitot-tube air
pressue (in H20") vs  airspeed... I've got to track that down again.
 I'll probably have to  stick a pitot tube through the sun-roof of
my wife's Subaru and go out  and break a few speed limits to test
it.  Higher pressure/gauge-pressure sensors are more expensive, and perhaps
  picking up the voltage-drop across a resistor in an high-current legacy
  automotive oil-pressure sensor would be OK too.  Anyone know what latest
  cars use for oil-pressure sensing?

  ATTTITUDE
  As you've discussed, there are solid-state gyroscopes, and solid-state
  magnetic compasses available, and there are many solidstate
sensors out  there that are used in these products.  However, most
of these require  digital I/O, I believe.  And interfacing my
GlassPanelDislay with  several digital signals will require more
ports than are supplied on the  DLP-IO20 data acquisition-board. I
will need to do more studying on  these issues.

  So ... if anyone has any advice or experience with sensors, I am
  listening.

  R Berglund

  I am away from my hanger, but check out National semiconductors LM-
34 ( I  think) integrated circuit temperature sensor.

  It is a three wire device +12, GND, and output.  It puts out a linear
  voltage with temperature, and is good up to 300 F.

  Bill Schertz
  KIS Cruiser #4045
  N343BS
  Phase one testing Completed

  http://www.national.com/mpf/LM/LM34.html#Overview

  These pressure sensors are used in all sorts of equipment.
  Tracy uses them in his EFI and a lot of stand alone air data
instruments use  them. Air speed, altitude, rate of climb etc..

    Paul Lamar

Thx guys!

So what is the max oil temp that a gauge should read?  Probably a lot
less on a Mazda than on a Lycoming, I suspect.

How about CHT on an air-cooled or EGT? (EGT would be the most
difficult, correct?)

R

The oil temp does not hurt much if you are using synthetic.
We have tested Mobile one in the oven and other than turbine
oil no other brand. Regular oil breaks down around 250 F
while synthetic is good to 500 F. There are places in the
engine where high temps over 250 F happen. For example
the apex seals run over 500 F. Hopefully you are mixing
2 cycle oil with the fuel to cool the apex seals.

According to the racers however the oil temp affects power
so I think a hot oil cooled rotor is reducing VE due to
the higher temp of the rotor face.

I put a half ounce of 2 cy oil in my street RX8 per gallon.
That is in addition to the oil metering pump.

Paul Lamar


The oil temp sensed in most applications is the pan or in the block by the
filter. Spot temps in bearings and rings is considerably higher and may
approach the 500F point. IMHO the gauge should have a scale to 300F for oil
temp. If it gets that high in the pan or gallery to the internals you should
park and find the problem.
Air cooled CHT can be up to 400+F. Exhaust on a rotary needs a scale to 2000F
as they run at 1500+.

Dale Davies