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一、原理与标定热线风速仪是基于热平衡原理和电子补偿技术来实现对流体平均速度和脉动速度进行测量的。目前普遍采用恒温型电路方式,其原理简图如图1所示。探针R_w接在惠斯登电桥的一臂中,电流通过就有了一定的温度。当流体速度变化时,由于热交换的原因,金属丝的温度和电阻随之改变,并导致电桥偏离平衡。在电桥D、B两端的电位差,经过放大器后又反馈到电桥的顶端,进行补偿使电桥恢复平衡,并实现R_w有“恒温”。反馈讯号的大小就反映了流速的瞬时变化量,即:
First, the principle and calibration Hotline anemometer is based on the principle of thermal balance and electronic compensation technology to achieve the average fluid velocity and pulsation velocity measurements. The current universal temperature circuit type, the principle diagram shown in Figure 1. Probe R_w connected to the arm in the Wheatstone bridge, the current there will be a certain temperature. As the fluid velocity changes, the temperature and resistance of the wire change due to heat exchange and cause the bridge to deviate from equilibrium. The potential difference across the bridge D, B, through the amplifier and then fed back to the top of the bridge to compensate for the bridge to restore balance, and to achieve R_w a “constant temperature.” The size of the feedback signal reflects the instantaneous changes in the flow rate, namely: