What device can be used to measure draft in a boiler?

A manometer is the correct choice for measuring draft in a boiler because it is specifically designed to measure the pressure difference between the inside of the boiler and the outside atmosphere. Draft refers to the movement of air or gases through the boiler and is essential for ensuring that combustion gases are properly vented outside. The manometer provides a precise measurement of this pressure differential, allowing operators to assess and maintain the optimal draft conditions necessary for efficient combustion and safe operation of the boiler.

In contrast, a barometer measures atmospheric pressure and is not suitable for assessing the specific draft within a boiler system. A thermometer measures temperature, which is useful for monitoring steam or water temperatures but does not indicate draft status. A flow meter measures the flow rate of liquids or gases but does not provide information about draft or pressure differentials required for effective combustion in a boiler. Therefore, the manometer is the only device from the list that directly addresses the need for measuring draft.