Chapter 1 Introduction | Series 830/840/860 Instruction Manual |
| |
The Series 800 Flow Sensing Principle
The operating principle of Sierra’s Side-Trak and Auto-Trak flow meters and controllers is based on heat transfer and the first law of thermodynamics. During operation process gas enters the instru- ment’s flow body and divides into two flow paths, one through the sensor tube, the other through the laminar flow element bypass. The laminar flow element bypass generates a pressure drop, P1–P2, forcing a small fraction of the total flow to pass through the sensor tube (m1) which is then monitored.
Figure 1-1. Flow Paths through the Transducer
Two resistance temperature detector (RTD) coils around the sensor tube direct a constant amount of heat (H) into the gas stream. In ac- tual operation, the gas mass flow carries heat from the upstream coil to the downstream coil. The resulting temperature difference (∆T) is detected by the RTD coils.
Figure 1-2. Flow Measuring Principle
