I have a friend that needs a little cooling
system development. The cockpit is so small
there is no room for the traditional water manometer
so I decided to build an automated low pressure
data gathering system. The key is these FreeScale
pressure sensors that will measure pressures
as low as .1 inch of water. To put that into perspective
12 inches of water is only .444 psi. One inch of
water is therefore .037 psi. One tenth inch
of water is therefore .0037 psi.

How important is
that you might ask. Well if there is no pressure drop
through the radiator there will be no air flow
through the radiator. This applies to the cooling
fins on a air cooled engines as well.
For those of you that have my book "How to Cool Your
Wankel" all of this should be perfectly clear :)

Here is a picture of these tiny devices. About small
enough to fit inside a sugar cube.
There is a built in amplifier and they work off a tiny
strain gage. They put out zero to 5 volts signal
into a Hytech Automation data acquisition system.

We have already used a system like this to measure
the amplitude and frequency of pressure pulses in a
p-port intake system in real time.

The current drain is so low you can turn the device
on and forget it until you land. It stores data
every second in a 32 gig USB memory stick.

32 Gig is a huge amount of data. So large a number it is
difficult to comprehend much like the national debt. Probably
several days worth of data. You pull the USB stick and copy it
into your computer.

The Hytech data acq system has a 10 bit analog to digital
converter so it is accurate to one part in 1000 parts.
Max pressure the sensor can measure is 16 inches
of water so that is 0.016 inch of water or 0.000592
psi resolution. Extraordinary.

There are eight channels in the Hytech so I can use
one to measure the air speed of the air craft for reference
purposes and seven left over for pressure measurements in
the cooling system.

100 MPH is 26 pounds per square foot or .18 psi.
150 MPH is roughly .36 psi or 9.75 inches of H2O.

Since the critical thing is take off and climb out this is
an adequate range to detect small changes.

Cost of the system is quite high so I will loan it out given
a deposit.

Paul Lamar

Sounds like a job for atmel data acquisition.
We were talking about the problem using Megasquirt in aircraft.
A pressure sensor like this could send data through one of the
I/O ports to be used to adjust the map in megasquirt for  'lean'
cruise at high altitude. I'm not sure about this yet, I need to
study it, but atmospheric pressure should be one of the parameters
for setting up megasquirt for turbo charging.

I am going to try to get info about pressure compensation and
the Pikes Peak hill climb related to turbocharging. For many of
the competitors, it is a very high boost, (500hp in a 2 liter)
wide open throttle run to the top, starting at about 9000ft,
ending at 14000ft+. Just about the range where we want to fly
with our turbo powered aircraft.

Ed Carver

Yes an Atmel 1280n would work fine. It could also control
the EFI and turbo charger while it was at it. No need
for a Megasquirt. Data acquisition is intrinsic and trivial
to add. The BASIC command in QB is PRINT "xxxxx" in Zbasic
it is Debug.Print (xxxxx) or Console.Write (xxxx).

http://www.zbasic.net/Microcontrollers/ZX-1281n-Microcontroller/p-62.html

Paul Lamar