The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
Date: Thu, 14 Nov 2002 20:14:11 -0500
From: "Raymond E. Rogers"
X-Mailer: Mozilla 4.76 [en] (Win95; U)
Subject: Re: Temperature Measurement Stability
References: <3DD2EC20.2FB10158@maine.rr.com> <3DD39EFC.8DE0895B@iinet.net.au>
X-Comments: This message was posted through Newsfeeds.com
X-Comments2: IMPORTANT: Newsfeeds.com does not condone, nor support, spam or any illegal or copyrighted postings.
X-Comments3: IMPORTANT: Under NO circumstances will postings containing illegal or copyrighted material through this service be tolerated!!
X-Report: Please report illegal or inappropriate use to
X-Abuse-Info: Please be sure to forward a copy of ALL headers, INCLUDING the body (DO NOT SEND ATTACHMENTS)
Organization: Newsfeeds.com http://www.newsfeeds.com 80,000+ UNCENSORED Newsgroups.
Thanks, comments follow inline.
> The stability requirements are certainly achievable with RTD's. I don't
> believe it is achievable with thermisters or semiconductors.
The NIST paper is at:
> Ensuring performance is a different matter alltogether. Annual recalibration
> is typical but elements and instruments can change in that time. RTD's are
> more fragile than one might think so a serious bump can change the
> characteristics. To achieve the performance you are after and to do it
> consistently I would recommend an in-house calibration check facility as
> close as possible to the temperature of interest. A gallium melt cell is
> ideal. It has a temperature of 29.7646 deg C. You also need a bath in which
> to operate it although there are other less expensive ways. I think there
> are check systems specifically for body temperature that may be suitable for
> your use. Some of the contacts below may be able to advise you about that.
We did buy a $4000 NIST traceable thermistor thermometer to do
calibration. I gave up on interchangability; to expensive.
> I achieve an uncertainty of 0.01 deg C with an Isotech TTI5 meter and 1/10
> DIN RTD's. The TTI5 has two channels. I use an Isotech industrial standard
> PRTD with certified calibration with the TTI5 for calibration of the other
> RTD's. I have a stirred bath, a water triple point cell, a gallium melt cell
> and a precision low temperature coefficient resistor. I use the resistor
> before and after every series of measurements to check the instrument and
> periodically check each system combination using the WTP and gallium melt
> poimt cells. The largest deviation from calibration that I have seen so far
> using the cells is 0.006 deg C. The method using the cells has a certified
> uncertainty of 0.0005deg C.
> I would suggest that you talk to your nearest representative of either HART
I will have to rethink the RTD's. The common ones seem to drift about
.05-.1 degC/yr though. That means I am back to higher priced items.
> or Isotech. For thermister information I would recommend you contact YSI.
> Here are some links that might be helpful:
We obtained our present parts from YSI; pricey. I hope to bring the
price down a lot in production.
I would still like some authoritative reference to emphasize the
importance of doing this right up front.
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup