What is a manometer used for?

• A. Measuring pressure
• B. Measuring temperature
• C. Measuring flow rate
• D. Measuring velocity

Answer: (A)

Measuring pressure is what a manometer is designed to do. It uses a column of liquid to balance the pressure from a system against a reference pressure, often the atmosphere. When the system pressure increases, the liquid is pushed further in one direction; when it decreases, it moves the other way. The difference in height of the liquid columns then directly indicates the pressure difference, with common readings in inches of water or millimeters of mercury. Simple U-tube manometers compare a system to atmospheric pressure, while differential or inclined manometers compare two pressures to each other, giving a direct measure of pressure change between points in a circuit or duct.

This isn’t how temperature is read—that’s what a thermometer or thermocouple does by measuring thermal expansion or electrical resistance changes with temperature. It isn’t used to determine flow rate—flow meters, rotameters, or orifice plates are designed for that by relating how much fluid passes a point in a given time. It also isn’t a direct measure of velocity; devices like pitot tubes or hot-wire anemometers are used to gauge air or fluid speed by relating pressure differences or other properties to velocity.