Question

Low air velocity will be measured by

• A. Kata thermometer
• B. Globe thermometer
• C. Wet thermometer
• D. Beckmans thermometer

Answer 1

The Correct Option is A

To accurately measure low air velocity, the most suitable instrument is the Kata thermometer. This device is specifically designed to evaluate the cooling rate of a heated thermometer bulb and is sensitive to low air speeds. The Kata thermometer works on the principle that cooler air moving over a heated object will remove heat at a rate proportional to its speed.

Let's break down the basic steps of using a Kata thermometer:

1. The thermometer is heated to a specific temperature, often using warm water.
2. It is then exposed to the air whose velocity is to be measured.
3. The time taken for the thermometer to cool down to a previously determined lower temperature is recorded.
4. This cooling time, along with calibration curves, allows the calculation of air velocity.

Among the provided options, the Globe thermometer measures radiant heat, the Wet thermometer is part of a psychrometer for assessing humidity, and the Beckmans thermometer measures small temperature differences, making them unsuitable for measuring low air velocity.