How does the TCi thermal conductivity MTPS sensor work?
The TCi MTPS sensor generates heat at the surface. The tested object must be flat in order to evaluate thermal properties. When placed on the sensor, it absorbs some of this heat and the rest of the heat causes a temperature rise at the sensor interface. Insulation absorbs less heat than glass or from the TCi MTPS sensor's reference, insulation leaves more heat behind than glass. The rate of temperature rise at the interface is evaluated to determine the thermal properties of the sample being tested. See also, C-Therm TCi - How It Works.
What about calibration?
TCi thermal conductivity sensors are factory-calibrated and provided with reference material(s). The standard reference materials are tested via traditional ASTM methods for thermal conductivity measurement by external third-party certified labs. NIST and NPL certified traceable reference standards are also available at a surcharge.
Can I touch the sensor while it is operating?
Yes and no. The TCi thermal conductivity sensor does not become too hot to touch during a test but the tested material or object must be in a constant state during a test to achieve the desired results. If it is moved during a test then a new portion is supplied with the C-Therm Technology.
What is the temperature accuracy of MTPS sensor?
Typically it is better than 0.5°C.
How flat does the sample have to be?
The TCi tests the properties of the material in contact with the sensor. If the tested material or object is not flat, the air in the cracks or buckles will be tested too. In some cases such as a porous foam, this is desired as the air forms an important part of the sample. Air is a good insulator (~0.025 W/mK) and it is why porous foams are such good insulators. However, if you are a testing a more conductive material and the crack is not an intended part of the sample it will introduce some error in the measurement. The same is true for ALL thermal conductivity measurement methods.
How thin of a sample can I test?
As the TCi employs a transient test methodology, it requires that the heat generated at the interface does not totally penetrate the tested material or object. It is suggested to be a minimum 2 mm thick for a 0.8 second (factory default timing parameter) test for materials under 2 W/mK - but the minimum thickness depends on the properties of the material and the length of the test (customizable with Max K "User Calibration Wizard"). It is possible to test thinner materials. Insulation material can be thinner than conductive materials. A Blotter Test can be performed to ensure the sample is sufficiently thick and a user can also stack thin samples such as films to produce a thicker cross section for testing as long as the material forms an intimate bond between layers.
How is this method different from hot plate?
The TCi employs an interfacial test method, meaning that the heat produced at the sensor is detected at the sensor. The hot plate method requires the heat generated at a sensor to penetrate the sample and be detected at the other side. For greater detail on a comparison of the TCi's modified transient plane source method to other traditional techniques for thermal conductivity please click here.
What are the advantages?
The test methodology allows for much faster, easier thermal conductivity testing. It represent a significant innovation in thermal analysis in reducint testing time to seconds from hours. Also, tested materials and objects do not have to be machined to precise dimensions for testing.
Are there any drawbacks to the TCi?
Yes. The methodology requires that the heat generated builds up at the interface and causes a temperature rise. For this reason the TCi is not recommended for super-conductive materials above 220 W/mK.
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