The PT is sensitive to radiation
The PT has a large exposed surface to make it more sensitive to radiation than a standard thermocouple (T/C). You place it in the furnace so that it receives the same radiation as the specimen. The back is insulated from radiative influence from the specimen.
The PT has a fast response
The PT is very thin, only 0.7 mm. Therefore it responses nearly as quickly as a standard T/C to changes in furnace temperature. The time response is fast. Thus the temperature delay is negligible except readings during the first few minutes of a standard ISO 834-1 test.
The PT is a simple and robust instrument. It can be used over and over again like ordinary T/C's. A shielded T/C (type K) is carefully welded or squeezed by mutual strips to a steel plate (see figure below). The plate thermometer is made of Inconel 600 stainless steel. The front side facing into the furnace is treated to give it an emissivity of about 0.8. The PT is mounted in the furnace with a supporting tube. The T/C shall be replaced after 50 h testing according to prEN 1363-1.
A mount with an internal R 1/4" thread may then be welded directly to the edge of the plate. A piece of stainless steel tubing of desired length may be screwed into this mount. The in-side diameter of the steel tube should be at least 6.5 mm.
The PT is mounted near the specimen
The PT is placed in the furnace near the specimen with the front-side facing the interior of the furnace. Additional PT's are used to measure variations of the thermal impact along the surface of the specimen (see prEN 1363-1).
prEN 1363-1 Fire resistance tests - Part 1 General requirements
Reports in the subject
|| Modification of the Plate Thermometer - Proving Tests at SP and WFRC|
|| The Plate Thermometer - Practical Aspects|
||The Plate Thermometer - A Simple Instrument for Reaching Harmonized Fire Resistance Tests|
|| A Proposal regarding Temperature Measurements in Fire Test Furnaces|
Please contact Inger Hansson if you are interested in ordering any of these reports.
How to get the Plate Thermometer
PT's can be obtained from Pentronic by E-mail or phone +46 (0)490 670 00, fax +46 (0)490 237 66. The article number is 5928 060-001.