Een beschrijving van de testprocedure voor NiGK thermolabels
Introduction : The Thermo Labels® are used to register the maximum temperatures reached on a surface. An original white temperature sensitive area (square or circular spot) on the Thermo Label® will turn irreversible from white to a specific colour as its specific temperature "switch" level is reached or exceeded. Under normal atmopsheric pressures (sea level) and under normal conditions the accuracy is within +/- 2C of the labels temperature rating.
Test Rig Set-up: To test simultaneously several labels the temperature on the test surface must be identical or with a minimum of deviations (gradients). An aluminium block of minimal 50 mm (=2 inch) thickness and a foot print of 150 x 150 mm is placed on a thermostat temperature controlled heating plate, eg as found on a cooking oven in a kitchen. A 2 mm diameter and 5 mm deep hole is drilled in the center of the alumina block. A thermocouple sensor is plugged into that hole. The sensor connects to a digital thermometer. The thermometer is arranged near the alumina block (attention heat transfer from block to thermometer might deform the plastic case). The alumina test surface is cleaned with an alcohol, for example spirit, an isopropylic alcohol (= Isopropanol) to give a maximum adherance (and therefore a good thermal contact) of the thermolabel to the test surface.
The to be tested Thermo Labels® are now applied on the alumina test surface as close as possible to the central temperature sensor.
A digital video camera recorder is mounted on a stativ. Zoom is adjusted until screen displays the Thermo Label® and the thermometers temperature display.
The alumina block is now put on the heating plate. A convenient heating power is selected and actuated. The heating power should result in a temperature rise that does not exceed 150C/hr. The heating power should also not be too high to allow an equal diffusion of the heat through the alumina to the test surface. At a too high power setting the alumina test surface might show gradients caused by the actual heating coils in the heating plate and temperature rise at the surface might be too quick. The digital thermometer takes at least per second three readings. If the temperature rise of the block is too quick then the measured temperature on the display and the one on the test surface are not anymore synchronized. The temperature correlation of Thermo Label® and thermometer display are developing an error gap.
It might be advisable to run a few test measurements to find out a reasonable heating power.
Using the free Video Software, the digital video data is then imported from the VideoCamera into your computer. The software allows to inspect frame by frame (if such a resolution ever might be needed) the images recorded. The movie can be edited and again be exported in various formats to be used for example as a compressed web video. The attached video clip shows such a test sequence.