From: charlie@elektro.cmhnet.org (Charlie Smith)
Subject: Re: Tire gauges (was: Re: ME33A Laser wearing too fast...)
Organization: Why do you suspect that?
Date: Thu, 31 Dec 92 15:35:31 GMT

In article <3240@contex.contex.com> frank@marvin.contex.com (Frank Perdicaro) writes:
>In article <1992Dec28.155914.3898@i88.isc.com> jeq@i88.isc.com (Jonathan E. Quist) writes:
>>In article <23005@drutx.ATT.COM> car377@druhi.ATT.COM (RogersC) writes:
>>
>>Any suggestions where to get an accurate gauge?  
>
>I went to a local compressed gas place and bought the best guage
>they carried, and then the correct tire fittings.
>
>I have a Matheson "Hospital Grade" guage marked "Oxygen"; heck, its
>even chromed.  Seems to work well, but I have not calibrated it
>recently.

>	 Frank E Perdicaro, Systems Admin, etc.		Xyvision Color Systems

You do realize, don't you, that if you are interested in accuracy what you
need to do is temperature compensate the pressure guage reading!  

What you need to do is mount the "Hospital Grade" oxygen guage in a console
along with a thermocouple based temperature guage and an ambient temperature
guage.  You also need an A/B switch for the input sensor so that you can 
measure both the temperature of the air in the tire and the temperature of
the air coming out of the air hose.  You need to do this, as sometimes the
air that's just been compressed is real hot.  You also need a mercury tube
manomometer to get the current barometric pressure.  I don't think you
need to take atmospheric humidity into account, but if you do then you
will need a wet bulb thermometer in lieu of the above mentioned ambient
air temperature guage.  I'd be interested in hearing the wisdom of the
wreck.moto whizzards on the need for humidity compensation here.

To use this setup, you need to draw up some pressure / temperature curves 
on log paper so that after you take readings from the thermocouple sensor
mounted under the tire's valve stem, readings from the thermocouple sendor
permanently affixed to the air supply hose, a reading from the hospital grade
oxygen pressure guage, and a quick reading from the ambient air temperature
guage you can then apply the correction factors and run it through a quick
calculation with your hand held calculator.  This is then compensated by the
corrected reading for current barometric perssure.  This gives you an 
accurate corrected tire pressure reading!

By the way, I plan on introducing a "Super Precise Accurate Motorcycle (SPAM)
Pressure System" (tm) meter in the near future.  It will be based on a 80586 
notebook computer with 894 MB of disk space running AT&T SysV UNIX, so that
all of the above computations are performed automagically.  Advertisements
for this SPAM meter will be posted in the near future on a newsgroup near you!

The SPAM meter will be availavle with a V32.bis / PEP option that will permit
support of usenet online while riding.  Having this option will allow you
to automagically create a post to wreck.moto to update the world on your
latest tire pressure readings.  An EPROM can also be supplied that has your
DoD number and .sig stored on the chip.

The SPAM meter will post nothing but the latest *accurate* readings, to put
to rest the contention that DoD is reducing the signal to noise ratio of
wreck.moto postings.



Charlie Smith   charlie@elektro.cmhnet.org  csmith@dsac.dla.mil  whois ces10
MOA# 52888, RA# 15633, DoD# 0709, AMA# 574722, Buckey Beemers 411, BK Ohio V
               BMW K1100-LT, R80-GS/PD, R69S, R27, Triumph TR6