Principles and Features of Constant Temperature Anemometers

热风速计的核心是两个传感器：空气速度传感器和温度补偿传感器。通过控制电子设备，将速度传感器加热至升高温度（相对于周围空气）。

温度补偿传感器会感觉到环境或周围的气温，并迫使速度传感器保持在环境上方的恒定“过热”。

The sensors form two opposite legs of a Wheatstone bridge (Figure 1). The circuit forces the voltage at points A and B to be equal by means of an operational amplifier. Air flowing past the velocity sensor tends to cool the sensor, thus driving down its resistance.

The operational amplifier responds by immediately delivering more power to the top of the bridge to maintain voltage equilibrium at points A and B. As more air flows past the sensor, more power is required to maintain a balanced bridge. Thus, the power going into the top of the bridge is related to the velocity of the air flowing past the sensor. This is the basic principal of operation for constant temperature thermal anemometers.

Figure 1:Wheatstone Bridge Diagram

Types of Constant Temperature Anemometers

Following are two types of constant temperature anemometers:

• 热线风速计
• 热膜风速计（IST AG）

恒温风洞测量的测量原理

Constant Temperature Anemometry (CTA) is used to measure fine structures in turbulent gas and liquid flows. The working principle is based on the cooling effect of a flow on a heated body. The CTA measures velocity at a point and provides continuous velocity time series, which can be processed into amplitude and time-domain statistics. Examples are mean velocity, turbulence intensity, higher order moments, auto-correlations and power spectra.

恒温风速计的特征

恒温风速计的特征include:

• 测量速度从几cm/s到超音速
• 高时间分辨率：高达几百kHz的波动
• 高空间分辨率：涡流降低至1毫米或更少
• Measures all three velocity components simultaneously
• Provides instantaneous velocity information

Heat Transfer from Cylinders

对流传热Q来自电线的函数是速度u，电线过度温度TW -T0和流体的物理特性（K，R，M）。L.V.建议将Q和U之间的Q和U之间的基本关系与流动垂直于流动。国王（1914）。它以最简单的形式读到：

Q = (T_W- T_O) A_Wh = a+buⁿ;n =0.5ì

Advantages of Constant Temperature Anemometry

恒温障碍的优势包括：

• 非常易于使用，因为没有单个传感器外壳（所需的渠道）
• measure in turbulent and laminar flow profiles
• Heater is also the sensor. It measures by itselfs
• 参考传感器在同一芯片上
• High flow rates possible

恒温风洞测定法的缺点

The disadvantages of Constant Temperature Anemometry include:

• 流信号取决于传感器对齐
• 加热器和传感器之间有热耦合
• Chip contamination possible, no flow direction detectable
• 相对较高的加热能力

Calorimeter Flow Sensors

FS2 tFlow Modules

FS2 tFlow Module uses the temperature distribution over a heating element with two or more temperature sensors left and right. For accurate measurings a laminar flow is required to keep up the temperature distribution gradient.

mikroflowsens流动传感器

mikroflowsensFlow Sensors uses the temperature distribution over 4 heating/sensor elements with serial down / up- stream arrangement. For accurate measurings a laminar flow is required to keep up the temperature distribution gradient.

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