Principles and features of thermal flow meters
Various types of flow meters and flow sensors are available. This section summarizes the principles and features of thermal flow meters.
When fluid comes into contact with a heated object, the fluid takes heat away from the object, increasing the temperature of the fluid. A thermal flow meter uses this principle to measure flow. Thermal flow meters can be divided into two groups:
THERMAL FLOW METER
A heater is installed in the fluid, and fluid temperature is measured at 2 points, upstream and downstream. Then flow is determined by the temperature difference between these 2 points. This is primarily used for applications with low flow rates.
A heater is installed in the fluid and fluid temperature is measured at 2 points, upstream and downstream. The heater is controlled to constantly maintain a fixed temperature difference between these 2 points. Flow is determined based on the amount of power required to maintain this temperature.
PROS | ・Able to detect gases ・There is basically no pressure loss ・Can measure mass flow |
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CONS | ・Errors occur when the temperature of the fluid changes ・It is difficult to set-up specifications that match the type and composition of the fluid. ・Errors occur when there are deposits/buildup on the temperature sensors or heating element. |
CHAPTER 2
FLOW METER TYPES & PRINCIPLES
CHAPTER 2
FLOW METER TYPES & PRINCIPLES