Absolute thermal conductivity measurement: Simpler than ever

In general, the guarded-hot-plate (GHP) as design for an absolute thermal conductivity measurement based on steady-state heat-flow is very well understood. The method is established in QA and certification on insulating materials and it is the basis for thermal conductivity check of every available thermal conductivity reference material for steady state methods. The standards ASTM C177 and ISO 8302 describe how to build a guarded-hot-plate.

In principle, you can GHP’s consider to be very complex devices! Users need to understand deeply, how the technology works and how to set up a proper measurement. The fact that these devices perform temperature measurements at countless locations sometimes makes it difficult – especially in self-built systems – to maintain the homogeneity of the measured temperatures required by the standard.

NETZSCH has created a groundbreaking solution for this with the newest SMART MODE Software for GHP. It raises the applicability of the method and the overview of the measurement signals to a completely new level – besides that it helps you to increase your efficiency in your lab .

For details on the instrument itself – see our Website!

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Pre-Defined Methods for absolute thermal conductivity measurement

Pre-Defined Methods make sure, that you check the instrument, like NETZSCH checked the instrument

Every delivered NETZSCH GHP comes with a set of “Pre-defined Methods”. It is forseen to check the functionality of a GHP in it’s temperature range with a set of reference materials, because you need to ensure the reliability and international comparability. Those checks are pre-definded as a measurement method and can easily be started by one mouseclick.

Wizards

The Wizards allow to easily define a absolute thermal conductivity measurement. You can enter the header-data easily, choose the type of cooling and change the cooling settings. The atmosphere and corresponding flow-rate makes sure, that the measurments are carried out under defined conditions and without the influence of condensation. We define every setpoint by:

• Mean Temperature
• Temperature-Gradient
• Heating Rate
• Type of Cooling
• Time Limit (time, when the setpoint will be skipped if steady-state is not reached)

Every defined measurement of recurring tasks you should stored as a “USER METHOD” because you can recall them very easily at the click of a mouse.

Measurement

The tab “Measurement” gives you a total overview over the defined absolute thermal conductivity measurement. During the measurment, you can check the actual stability, all signals, plate temperatures and Lambda, the sensors, the heating and cooling power and the final results.

Monitoring and Diagnosis – another big benefit

In the tab “Sensors” you see the total overview on all temperature sensors on the plates. The requirements of the standards are very strict in terms of homogenity of the temperature distribution. All installed sensors are from one lot and every single sensor has it’s own calibration. For every customer we stock spare-sensors from the same lot, because we want to provide you the best possible sustainability.

Results

In the “Results” tab you get every information that you need:

• mean-temperature
• delta temperature
• thermal conductivity (Lambda)
• standard devition of thermal condictivity
• combined uncertainty of thermal conductivity (see publication from Schindler et al.)
• thermal resistance
• standard deviation of thermal resistance
• uncertainty of thermal resistance
• duration of measurement

Report Generator – in the end you need documentation

Due to requirements in the standards ASTM C177 and ISO 8301, you need to document the results. No one wants to write report after reaching the final result, manually. Therefore NETZSCH included a report generator in the software. By clicking of “Report” you can create a simple report as a word-document. Above all you can choose also an extended report as an excel-file. In contrast to the simple word file, it provides you every single detail of the measurement.

Furthermore the details in plate-temperatue distribution are also part of the excel report.

Summary

The NETZSCH Guarded Hot Plate for absolute thermal conductivity measurement in conjunction with the newest SMART MODE Software is a powerful tool to gain simplicity in this complex method. The software makes you more efficient and makes the instrument easy to use.

The NETZSCH Guarded Hot Plate fulfills the tough requirements from ASTM C177 and ISO 8302 over the whole temperature range from -160°C up to 600°C. The vacuum-tight design is pre-condition for defined and dry atmospheres during the measurement. This ends up with the highest possible measurment accuracy. The robustness of the design combined with our software and the NETZSCH-Services ensures security of investment, highest efficiency and best sustainability.