What equipment is typically used to measure boiler pressure?

A pressure gauge is the correct choice for measuring boiler pressure because it is specifically designed to indicate the pressure within a system. This equipment provides a direct reading that helps operators monitor the pressure inside the boiler, ensuring it remains within safe operating limits. Maintaining the correct pressure is essential for both safety and efficiency in steam systems, as deviations from the recommended pressure can lead to hazardous conditions or equipment damage.

The other options serve different functions: a thermometer measures temperature, a water level indicator shows the level of water in the boiler, and a flow meter quantifies the flow rate of fluids. Each of these instruments is important in the operation and monitoring of a boiler but does not provide necessary information about pressure levels. This distinct role of the pressure gauge makes it the crucial instrument for ensuring the safe and effective operation of a boiler system.