锁相频差超声流量计

用相位切换法测量声环的顺向、逆向频率，从两个环路频率之差可导出流速模型，用这种模型组成的超声流量计可消除温度的影响，并在较宽范围内使流量与频差呈线性关系。仪器电路采用取样锁相技术和电子切换开关，把双声道变为单声道，避免了声程不一致的安装误差。

Phase-locked Frequency-difference Ultrasonic Flow Meter

Asembles an ultrasonic flow meter after a flow model derived from the difference between the positive and negative frequencies of a sound loop determined by phase-converted neasurement. The meter, unaffected by temperature, maintains a wide-ranged linear relationship between flow and frequency-difference, and eliminates assembly error of inconsistant sound path by converting double channel into single channel through phase-lock sampling and electronic transducing switching.