Which device measures the pressure differential across the burner opening and develops a loading signal proportional to the rate of airflow per burner?

The airflow transmitter is the device designed specifically to measure the pressure differential across the burner opening while producing a loading signal that is directly proportional to the airflow rate per burner. This functionality is crucial in combustion systems as it allows for continuous monitoring and adjustment of airflow, which is essential for efficient and safe burner operation. By measuring the pressure difference, it can accurately determine how much air is entering the system, thus providing vital information for combustion control and efficiency.

In contrast, while a pressure switch does measure pressure, it typically functions as an on-off device rather than providing a continuous signal proportional to airflow rate. A flow meter measures the actual flow of fluid, which may not directly correlate to pressure measurement in the context of burner operations. Lastly, a temperature sensor is designed to measure temperature, which is unrelated to the measurement of airflow rates or pressure differentials in this scenario. Therefore, the airflow transmitter stands out as the correct choice for this application.