Factors affecting the measurement accuracy of thermal flow sensors

The influence of the closeness of the heat flow sensor and the object to be measured on the heat flow measurement accuracy: The closeness of the heat flow sensor and the object to be measured has a great influence on the stabilization time of the heat flow. The tighter the adhesion, the faster the stabilization and the smaller the measurement deviation; conversely, the greater the measurement deviation. Therefore, in the use of transient heat flow sensors, it is necessary to try to ensure that the heat flow sensor can be closely attached to the object to be measured, so as to reduce the measurement time and improve the measurement accuracy. The application of
thermal conductive glue (thermal conductive silicone grease) provides very good conditions for solving this problem. The influence of the thickness of the heat flow sensor on the heat flow measurement accuracy:
When the thickness of the heat flow sensor is 0.1mm, the heat flow on the surface of the object to be measured stabilizes very quickly. It only takes about 0.5s from the beginning to stabilization. The heat flow value through the heat flow sensor differs from the actual value by 2.92%. When the thickness of the heat flow sensor increases to 1mm, the stabilization time reaches 8s, which is 16 times the original, and the deviation of the heat flow value reaches 6.26%. This is mainly due to the increase in the thickness of the heat flow sensor, which increases the thermal resistance introduced by the heat flow sensor, causing a large deviation in the heat flow value passing through the heat flow sensor.
The influence of the side length of the heat flow sensor on the accuracy of heat flow measurement:
The change in the side length of the heat flow sensor does not have much impact on the stabilization time of the heat flow, but it brings a large deviation to the stable value. When the side length changes from 5mm to 10mm, the stable heat flow value decreases by 8.4%, which is 6.51% different from the actual value; when the side length changes from 10mm to 20mm, the heat flow decreases by 4.3%, which is 1.94% different from the actual value; when the side length changes from 20mm to 30mm, the heat flow only decreases by 0.4%, which is basically the same as the true value. This shows that the longer the side length of the heat flow sensor, the more accurate the stable value, and there must be an optimal value for the side length. This optimal value can ensure that the heat flow sensor is as small as possible and the accuracy of the measured heat flow. According to the calculations in this article, this optimal value is about 20mm. When the surface of the object being measured is approximately considered to be semi-infinite, 20 mm may be the optimal combination of measurement accuracy and heat flux sensor size.