Instrument utilises a flat sensor with a continuous double-spiral of electrically-conducting nickel metal etched out of thin foil and clad between two layers of Kapton
Heath Scientific has added the Hot Disk thermal constants analyser to its range of analytical tools.
Based on the transient plane source method, the instrument utilises a flat sensor with a continuous double-spiral of electrically-conducting nickel metal etched out of thin foil and clad between two layers of Kapton.
Although only 25um thick, Kapton provides both electrical insulation from the sample and mechanical strength for the probe.
The sensor is normally placed between the surfaces of two pieces of sample.
Virtually any sample geometry may be studied, says Heath Scientific, with flexibility in sample size and range in thermal conductivity.
The only requirement is that the sample surface facing the sensor should be relatively flat.
During measurement, a current passes through the nickel and creates an increase in temperature.
The heat generated dissipates through the sample on either side at a rate depending on the thermal transport characteristics of the material.
By recording the temperature versus time response in the sensor, the thermal conductivity and diffusivity can be calculated.
A transient method has several advantages compared with static methods.
The method is much faster, since there is no need to wait for a temperature gradient to form across the sample, but instead directly measure how the heat generated by the sensor probe propagates into the material.
The TPS method is not affected by contact resistance.
In static methods, this resistance causes inherent error as it builds up between the thermocouple and sample surface.
