The Measurement Platform-2 (MP-2) is an advanced meter with unique selection of transient thermal conductivity sensors for a variety of applications, with a focus on primary measurements. The transient thermal conductivity sensors share similar principles of operation. The sensor wire is heated using a constant current source (q) and the temperature rise is recorded by monitoring the change in electrical resistance of the wire (THW and EFF) or by resistance temperature detector device (TLS). For samples of high thermal conductivity, resistance increases more slowly over time; for samples of low thermal conductivity, resistance increases more quickly over time.
Thermal conductivity MP-2 users benefit from the convenience and accuracy gained when using primary testing methods. The MP-2 controller auto-detects the connected sensor and loads corresponding testing parameters. Measurements are easily performed with the smart on-board software and transferred to computer with an included Windows utility program.
The Thermtest Transient Line Source (TLS) meter adheres with an internationally recognized standard of testing by complying with ASTM D5334-22. The sensor can measure the thermal conductivity of solids and loose materials (like sand and soil) from 0.1 to 5 W/m K, thermal diffusivities from 0.05 to 1.5 mm2/s and auto-calculates volumetric specific heat. The needle consists of a heating wire and an epoxy layer enclosed in a stainless-steel case. The sensor is completely inserted into the sample to be tested. Heat is delivered to the sample using a constant current source (q) and the temperature rise is recorded over a defined time period. The slope (a) from plot of temperature rise versus logarithm of time is used in the calculation of thermal conductivity(k).
The TLS 100mm vCp sensor can be used to measure the thermal conductivity, thermal diffusivity, and volumetric specific heat of a variety of samples, including soils, pastes, powders, and polymers. This sensor is specified to record thermal conductivity with 5% accuracy and 2% repeatability; thermal diffusivity with 10% accuracy and 5% repeatability; and volumetric specific heat with 15% accuracy and 5% repeatability
The Thermtest TLS 100mm-vCp needle measures the thermal conductivity, thermal diffusivity, and volumetric specific heat of a sample all at once. In the experiment, the thermal properties of a nylon sample were measured every 10°C from 0°C to 50°C. The sensor and the sample were placed inside a temperature-controlled chamber, and the sensor was connected to the MP-2 device placed outside the chamber. Once the desired temperature was stabilized, the test begun. Three tests were measured per each temperature point with a 10 minute interval between tests to allow the sensor and sample to return to isothermal conditions.
In order to measure the thermal properties of the nylon sample, a hole was drilled in the sample. The TLS 100mm vCp needle was then covered with enough thermal paste to ensure proper contact between the sensor and the sample.
Table 1. Average of three thermal property measurements with Thermtest TLS-vCp 100mm sensor.