In the list of components observed during the churn test, which item is not a measurement instrument?

• A. Circulation relief valve
• B. Diesel engine tachometer
• C. Diesel engine temperature gauge
• D. Pressure relief valve

Answer: (D)

When assessing components in a churn test, you’re looking at which items actually provide readable data versus those that control or protect the system without giving a measurement. A tachometer and a temperature gauge are measurement instruments because they display engine speed and engine temperature, giving you quantitative data to evaluate performance. A pressure relief valve, however, is a safety/control device that opens to relieve excess pressure; it does not display or provide a reading. So it isn’t a measurement instrument. (Circulation relief valves are valves too, but the crucial distinction here is that only the pressure relief valve serves primarily as a pressure-relief control rather than as a data-collecting instrument.)