RTD classes maximum temperature? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 28, 2014, 10:22:46 pm
content: I see in the specification of RTDs often that class A might be to 300C, class B to 500C, class 1/10 din to 150C.Is it inappropriate to use say a class 1/10din @ 300C? Is the specification only for accuracy (i.e. @ 500C the class A rtd will be out of a class A spec)or is it also to avoid hysteresis/etc (I.E. bringing up a 1/10 din RTD to 400C would change the material property of the platinum and lead to damage that is detectable @ that accuracy?I also noticed that the thin film RTD have diff max temperature then the wound ones. Again, does this mean that they will be out of spec or does the thermal cycling/strain gauge effects cause damage @ elevator temperatures?

author: MK
author_rank: Regular Contributor
timestamp: September 29, 2014, 05:59:31 am
content: It is differences in the potting and sgeathing that dictates the maximum temperature, the platinum itself is not likely to be the issue.

author: mzzj
author_rank: Super Contributor
timestamp: September 29, 2014, 07:22:04 am
content: Quote from: SArepairman on September 28, 2014, 10:22:46 pmAll of the above.high temperatures cause drift and hysteresis effects in the sensor and it will drift outside of the 1/10 din specification if used at temperatures above 100-200C or so.And there is differences in the internal construction, ie 1/10 din rated sensor assembly may use ptfe insulation whereas 600C rated sensor uses mineral insulated metal sheath. ptfe-insulated sensor would be totally scrapped if used to 600CBut mostly its a drift/hysteresis problem. So its easier to stay within b-class specs if the pt100 is used at high temperatures.

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 29, 2014, 05:54:31 pm
content: but the amount of error

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2014, 07:22:56 pm
content: The platinum film will always survive, but the substrate, leads and the casing will not, and will degrade very fast leading to the sensor failing either as out of spec at best or open or short at worst, or shorting to the casing. The higher temp devices are going to be more accurate at lower temperature as they will be more stable, and will last a long time if run within the operating limits. Running near the max or beyond results in a very short life.

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 30, 2014, 02:45:48 am
content: Why can't they do din 1/10 stability @ 500 degrees C ?

author: Vgkid
author_rank: Super Contributor
timestamp: September 30, 2014, 04:08:17 am
content: http://www.omega.com/pptst/P-Ultra_RTD.htmlprice isnt to bad.

author: mzzj
author_rank: Super Contributor
timestamp: September 30, 2014, 06:37:39 pm
content: Quote from: SArepairman on September 30, 2014, 02:45:48 amStability: YesRange: YesCheap: No (ballpark of 1-2k$)http://us.flukecal.com/products/temperature-calibration/probessensors/secondary-standard-prts/56085609-secondary-prts-calib?quicktabs_product_details=2(these are not your typical IEC-751 sensors and can not be used instead of "industry standard" Pt100)