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, the lower the slope; for samples of low thermal conductivity, the higher the slope.

Thermtest MP-2 Measurement Platform Portable Meter

Picture 1. Thermtest MP-2 Thermal Conductivity Meter

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.

THW-L3 Sensor

THW-L3 Sensor transient hot wire

Picture 2. Thermtest THW-L3 sensor for use with the MP-2 portable meter.

The THW-L3 sensor is one of the many sensors offered with the Thermtest Portable Measurement Platform (MP-2). This sensor offers simple yet accurate measurements of liquids, pastes, and powders from 0.01 to 1 W/(m·K) via the transient hot wire method. The THW-L3 adheres with an internationally recognized standard of testing by complying with ASTM D7896-19. The THW-L3 has a 5% accuracy and a 2% reproducibility of measurement, making it a highly accurate and precise instrument for measuring the thermal conductivity of liquids, pastes, and powders.

The THW-L3 has a detect current setting that determines the appropriate amount of current to apply based on a test measurement. By reading the result of the test measurement, a current will be set that results in an optimal temperature rise of the sample during testing. Due to the compact size of the THW-L3 sensor, it can be inserted directly into the sample cell, making sample setup very straightforward (Picture 3).

Measurement Platform-2 (MP-2) with the THW-L3 sensor and sample cell

Picture 3: Measurement Platform-2 (MP-2) with the THW-L3 sensor and sample cell

Water and Ethylene Glycol

Water and Ethylene Glycol are both used as calibration liquids of a thermal conductivity device. The thermal conductivities of these materials are well-known which makes them excellent candidates for use in instrument calibration. This application sheet outlines the measurement of these two liquids with the Thermtest THW-L3 sensor.

Thermal Conductivity of Water and Ethylene Glycol

The thermal conductivity of DIUF Water and Ethylene glycol measured with a THW-L3 sensor from 10 °C to 40 °C. The DIUF water sample placed in the cell and then on a heating source to let the temperature stabilize at 20 °C. The power detected and then the sensor calibrated.

The temperature on the heating source set to 10 °C and when it was stabilized the power detect and set a measurement schedule. The same procedure repeated for the temperature measurements from 20 °C to 40 °C.

At the end of the measurements, the DIUF water sample replaced with EG and the heating source set to 10 °C and the measurements procedure as in the case of the DIUF water measurements.

Thermal conductivity measurements of DIUF Water and Ethylene glycol

Figure 1. Thermal conductivity measurements of DIUF Water and Ethylene glycol

Table 1. Average thermal conductivity results of DIUF Water and Ethylene glycol, and the relative standard deviations. For comparison, the reference values are given.

T (°C) λ (W/mK) λref (W/mK) %rsd
DIUF Water
10.10 0.586 0.579 1.21
19.45 0.596 0.597 -0.14
29.88 0.611 0.614 -0.56
39.81 0.623 0.628 -0.86
Ethylene glycol
10.35 0.250 0.251 1.15
19.15 0.250 0.251 0.36
29.77 0.250 0.252 0.77
39.11 0.251 0.253 0.59