The effect of varying resistance ratio on the behaviour of constant-temperature hot-wire anemometers

The behaviour of the constant-temperature hot-wire anemometer as the resistance ratio becomes very low is examined in terms of the static and dynamic response. It is shown that a constant temperature anemometer may be used to measure temperature fluctuations but its usefulness is limited by the nonlinearity of the sensitivity. Systems which employ an amplifier with a frequency-dependent gain give rise to a step change in the sensitivity of the response at low frequencies. This step may be significant at all resistance ratios but generally increases as the resistance ratio decreases.