Chuck wrote:

Here is the instrument I made to replace the water

manometer. It is a

Sen-Sym signal conditioned 0 to 1 PSI pressure

transducer from DigiKey

$47.70 P/N  287-1002-ND connected thru a voltage

divider to a LCD Panel

Meter from Jameco $14.95 P/N 108388 powered by two 9

volt batteries. It is a

differential transducer which means it has two ports.

The transducer has an offset so it reads about 260 at

room temp. with the

ports disconnected.  I have to read the offset with no

pressure applied and

then subtract that from the reading to get an accurate

absolute reading, but

it works great for relative measurements. It will read

to .435 PSI or about

11.3" of water or about 150MPH.

Each digit represents .00025 PSI or .0065" of water.

Which means it starts

reading at 3.6 MPH if used as an airspeed indicator.

Advantages over water

manometer: More resolution, easier to read, easier to

mount readout, no need

to add water to replace what evaporates over time.

Batteries should last a

long time. Disadvantages: Costs more, possibly harder

to interpret data.

So far, I have learned that I have hardly any (possibly

backwards!)airflow

thru the end of the oilcooler opposite the end where

the air comes in. I

will put a new duct on my list of things to do.

Chuck Dunlap

Snip

     Chuck,
       How about using a valve system to several pickup
points on A/C to avoid so many flights. Would you happen
to have a schematic for us electrically challenged?

    Kelly Troyer

Here is a quickie schematic. Keep in mind this is not optimized, just a
quick-and-dirty get-it-working lashup, it could be improved as Finn
suggests. The meter module has a calibration adjustment on it for fine
tuning.
I thought about using an aquarium gang valve, have not tried it.

Chuck Dunlap

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