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Larry Pieniazek <lar@voyager.net> wrote in message
news:37F4B2C6.5A1298B4@voyager.net...
> This is the classic "how do you calibrate the measuring tool if you
> don't have a standard to start from".
For the development of my pressure sensor I used a digital pressure gauge
that you can buy for checking tire pressure. ($8.00 at KMart) It requires
removing the guts from a pistol shaped enclosure and connecting the pressure
line from the LEGOs directly to the its sensor. The only rub is the sensor
is designed to measure a peak pressure and hold the value. I had to install
a pneumatic switch in line with it and keep toggling in on and off to make
the sensor think it was being pushed up to a tire stem over and over to get
a near continuous measurement of pressure. The published values for the
Lucas sensor I used in my circuit and the tire gauge matched up very well so
I think it is fairly well calibrated tool.
The testing of my pressure sensor showed that the peak LEGO pressure was
about 40psi before the little valves in the hand pump seemed to quit
working. I'm sure you have all pumped the hand pump like crazy and felt it
kinda give up after a while and make a tiny pu-pu-cushion sound. Sometimes
tubes blew off also. The Lucas sensor I used is good to 30psi with a 3X
overload capacity so it is about prefect for the job. I calibrated my
sensor to read 100 in Light units for 33psi.
http://www.plazaearth.com/usr/gasperi/pressure.htm
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