BPI Multifamily Building Analyst Practice Exam - Prep, Practice Questions, and Study Guide

The instrument used to measure a pressure delta is a manometer. A manometer is specifically designed to measure the difference in pressure between two points in a system, often displayed as a height difference in a fluid column. This makes it an essential tool in various applications, such as HVAC systems, where understanding pressure differentials is crucial for assessing performance and ensuring proper airflow.

In contrast, a barometer measures atmospheric pressure rather than the pressure difference between two specific points. A hygrometer is used to measure humidity levels in the air, and a thermometer measures temperature. These other instruments serve distinct purposes not related to pressure differentials, thus reinforcing that the manometer is the correct choice for measuring pressure delta.