The effect of electronic components on the cut-off frequency of the hot-wire system

The analytical solution for the frequency response of a constant temperature hot-wire system at given turbulent velocity fluctuations is used to investigate the effects on the cut-off frequency of the hot-wire system at different operating conditions. It is found that the optimal frequency response of the hot-wire system determined by the traditional square-wave test, under certain circumstances, cannot guarantee the stability of the hot-wire system from velocity perturbations. It is also found that the cut-off frequency depends not only on the hot-wire length to diameter ratio, the mean velocity, the hot-wire materials and the overheat ratio as previously found, but also on the gain bandwidth product of the amplifiers in the feedback circuit, the resistances used in the Wheatstone bridge and the gain of the amplifier in the feedback loop. Hot-wire systems with preferred operating conditions are recommended