CR4 - The Engineer's Place for News and Discussion®

Previous in Forum: What Is SCADA?   Next in Forum: Foundation
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







6 comments
Active Contributor

Join Date: Dec 2009
Location: India
Posts: 15

RTD Sensor

07/23/2012 5:30 AM

Please let me know whether the sensor diameter of RTD affect the accuracy of the temperature measured.

__________________
You only live once , but if you work it right once is enough.
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 22917
Good Answers: 591
#1

Re: RTD SENSOR

07/23/2012 6:08 AM

It will introduce a first-order lag between measured value and actual value that increases as the diameter increases.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply Score 1 for Good Answer
Active Contributor

Join Date: Dec 2009
Location: India
Posts: 15
#2
In reply to #1

Re: RTD SENSOR

07/23/2012 9:42 AM

Thankss for your swift response .

Here we ordered the sensor diameter with 0.236 inch but as per the standard it should be 0.250 inch sensor diameter .Please give your advice whether we can use 0.236 inch diameter sensor for RTD.

Thanks in advance.

__________________
You only live once , but if you work it right once is enough.
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 22917
Good Answers: 591
#5
In reply to #2

Re: RTD SENSOR

07/24/2012 3:10 AM

It will introduce a first-order lag between measured value and actual value that increases as the diameter increases.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Power-User

Join Date: Jul 2010
Posts: 105
Good Answers: 12
#3

Re: RTD Sensor

07/23/2012 2:51 PM

The thermowell used with an RTD is bored so that the RTD sheath is a slip fit. A smaller diameter sheath than the conventional 0.250" diameter will have an air gap creating an additional lag, if the thermowell is made for 0.250" sheath.

Register to Reply Score 1 for Good Answer
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Ketchikan, AK, USA
Posts: 15851
Good Answers: 621
#4

Re: RTD Sensor

07/24/2012 12:56 AM

You may be able to fill this small gap with thermal mastic. How fast does the temperature change, and how fast a response is really needed?

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Power-User

Join Date: Feb 2007
Location: Gdansk, Poland
Posts: 100
Good Answers: 2
#6

Re: RTD Sensor

10/16/2012 10:56 AM

Any gaps (especially air/gas filled gaps) between sensor and case, and case to measured object involve extra thermal resistance. This will increase sensor's temperature due to selfheating (dT = Power x Rth) above ambient (measured) temperature. This error is significant in precision measurements (<0.1deg), or when power dissipated in sensor is relatively high( >0.3mW). Follow PWSlack's advice (fill gaps with thermal grease) to make this error lower.

Register to Reply
Register to Reply 6 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Bud (1); czgut (1); PWSlack (2); sibisunny (1); Tornado (1)

Previous in Forum: What Is SCADA?   Next in Forum: Foundation

Advertisement