Question 16 1AE01 - First Assistant Engineer

The Correct Answer is C ### Why Option C (thermometer) is correct: A **salinometer** is an instrument used to measure the salinity (salt content) of a solution, often water or boiler feedwater. It typically works by measuring the electrical conductivity of the solution, which is directly related to the concentration of dissolved salts. However, electrical conductivity is highly sensitive to temperature. As the temperature of the water increases, its conductivity also increases, even if the actual salt concentration remains the same. Therefore, for a salinometer reading to be accurate or meaningful, the temperature of the sample must either be: 1. Measured precisely and then a temperature correction factor applied to the conductivity reading, OR 2. Controlled to a specific standard temperature before the reading is taken. In practice, a **thermometer** is always used alongside a salinometer to determine the exact temperature of the sample at the time of measurement, ensuring the final salinity calculation is accurate and properly corrected. ### Why the other options are incorrect: * **A) hygrometer:** A hygrometer measures humidity (the amount of water vapor in the air). This measurement is irrelevant to the salinity measurement of a liquid using a salinometer. * **B) hydrometer:** A hydrometer measures the specific gravity (relative density) of a liquid. While density is related to salinity, a hydrometer is a standalone instrument and is not *always* used in conjunction with a specialized electronic salinometer. Modern salinometers rely on conductivity and temperature, not specific gravity, for their primary operation. * **D) pyrometer:** A pyrometer is used to measure very high temperatures, typically without contact, by sensing thermal radiation (e.g., measuring the temperature of molten metal or a furnace). This instrument is wholly inappropriate for measuring the temperatures associated with water or boiler feedwater used with a salinometer.