1. Hotline probe

Hotline probe that the simple model shown in Figure 3-42. Slender metal wire placement perpendicular to the direction of airflow, fixed at both ends of the stent in a relatively bulky, metal wire from the current heated to a temperature higher than that measured media.

Figure 3-42 hotline model

In order to probe the use of the hotline to meet the demands that the material has a hotline:

of high temperature coefficient of resistance, in order to get a higher measurement sensitivity;

must be corrosion-resistant materials to ensure that there is sufficient stability;

materials should have a higher mechanical strength to prevent deformation and the impact of a vibration measurement accuracy;

wood by a good heat conduction properties

Usually, people used to meet the requirements of the tungsten wire, platinum and platinum plated wire or tungsten wire to create a hotline probe on the hot wire.

Hotline typical diameter of 0.5-10 m, a length of 1-3 mm. Consider this size in two major areas: improving the sensitivity hotline, the hope that the small diameter of the hotline, a longer length for good, but this will be their mechanical strength And spatial resolution decreased from the increased spatial resolution, the hotline hope the shorter the better, but might affect the measurement sensitivity.

Hotline at both ends of the welding rod to the two forks of the forklift tip, the fork at the other end of a welding wire, and guards, guards and fork-fill insulation material between. Fork-usually from 0.2-0.5 mm in diameter Help made of stainless steel, the top diameter of 0.05-0.1 mm. Fork-embedded in ceramics, nylon or other insulating materials, and probe the outside shell package.

2. Hot-film probe

In order to thermal gun technology applied to the liquid flow measurement, the development of the hot-film probe, its high mechanical strength, it can meet certain conditions worse than the flow (such as the flow of sewage flow, etc.). In addition, it's less affected by vibration, heat resistance by the film thickness adjustment, it easier to match with the amplifier to receive a higher signal to noise ratio. It is a measure of the shortcomings of narrower frequency range, the complex production process, work A lower temperature, these are restricted its application.

Deep-hot film from hot-film, substrates, wire insulation and a few parts. Hot-film splash in platinum is formed on the substrate, the thickness of 0.1-1 m around. Quartz substrate is made of glass or boric acid The cylinder in order to make thermal insulation and fluid membrane and prevent pollution, but also in the hot-film coating thickness of about 1 m around the quartz insulating layer.