Neil:
I know all this stuff. I have lectured on it, and published several papers.
In my "corporate" days, I represented the U.S. to I.S.O. in Industrial Heat
Flow, and in Infrared Thermography.
Everybody (except for Mayf and John) seems to have gotten the wrong idea
about what my concern is. Extreme absolute accuracy (either lack of bias,
or great precision) is probably of little benefit in LSR. What I'm
concerned about is REPEATABILITY, reliability of the data-- especially if
you need to change one or more components in the system.
Although, as you suggest, some brands of TCs are quite unreliable-- their
demise is usually pretty obvious; you don't get tricked into thinking you
are still getting good data. I am less concerned about the sensors
themselves than the other parts of the systems. Inconsistent field amps,
for example, have probably cost the petrochemical industry billions in
inability to control the manufacturing processes. They could hurt our
ability to control our tune-ups, too.
Russ, #1226B
BTW-- RTDs -- besides not liking high temperatures-- also don't like
vibration. They don't seem a likely choice for automotive aps, to me.
-----Original Message-----
From: Albaugh, Neil [mailto:albaugh_neil@ti.com]
Sent: Friday, May 09, 2003 4:59 PM
To: 'Russel Mack'; 'Keith Turk'; 'Nigel Shaw';
'land-speed@autox.team.net'
Subject: RE: Quick Data Connectors
Russ;
The key to accuracy, of course, is to use TI amplifiers! :)
Seriously, if absolute accuracy is a requirement, beware of using
uncalibrated thermocouples. The thermocouples themselves can vary from
unit-to-unit by quite a few degrees and this variation is not linear with
temperature.
A much more accurate temperature probe is made with a fine platinum film or
wire. This is called an RTD; it has far higher accuracy than a thermocouple
(TC) but it is not available in as high temperature rating as a TC (NG for
measuring EGT, for example). It is not a "self generating" type of sensor
like a TC; An RTD changes its resistance with temperature so it needs to be
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