热膜式空气质量流量传感器的动态响应

Frequency response of hot-film air mass flow sensors

应用理论分析和试验的方法,研究了热膜式空气质量流量传感器的静态响应和动态响应特性。通过对传感器单元在非稳定气流情况下存在的热滞后现象的分析,推导出恒流和恒温测量法的时间常数表达式,并对影响时间常数的各种因素和测量补偿方法进行了讨论。结果表明,恒温法的时间常数比恒流法小2g(Rr-1)倍;恒温法的动态响应取决于反馈效率,如果使反馈过程迅速有效,便可实现对热滞后的瞬时补偿;恒温法热膜式空气质量流量计不易污染,测量精度较高,动态响应好,使用方便。

This paper studied the frequency response of hot-film air mass flow sensors by the theoretical analysis and experimental research methods. The expression of the time-constant was derived by analyzing the phenomena of heat-delay in sensor unit under gas unsteady flow. And the all sorts of influence factors for the time-constant and also the compensation methods were dis- cussed. The results indicate that the time-constant with constant temperature measuring method is 2g（Rr,-1） times less than that with constant electric current measuring method, and the frequency response with constant temperature measuring method is decided by the feedback efficiency. If feedback process is very quick and effective, the instantaneous compensation can be realized for the heat-delay with constant temperature measuring method. 4 figs, 6 refs.