The working principle of a thermal mass flow meter is based on the concept of convective heat transfer. The flow meter consists of a heated element (often referred to as a sensor or probe) and temperature sensors. These sensors are usually located upstream and downstream of the heater. The heater continuously maintains a constant temperature difference (AT) relative to the fluid. As the fluid flows past the heated element, it absorbs heat due to convective heat transfer. The temperature sensors measure the temperature difference (AT) between the heated element and the fluid. This temperature difference is directly proportional to the rate at which heat is carried away by the fluid, which in turn correlates with the mass flow rate of the fluid. By knowing the heat input (power supplied to the heater) and monitoring the temperature difference (AT), the mass flow rate of the fluid can be calculated using specific calibration factors and the physical properties of the fluid (such as thermal conductivity and specific heat). The flow meter processes this data to provide an output signal that directly indicates the mass flow rate of the fluid.