The primary elements provide the input to the secondary element which provides
for indications, alarms, and controls.
Given a block diagram of a typical flow detection device,
STATE the purpose of the following blocks:
Differential pressure (DP) transmitter
STATE the three environmental concerns which can
affect the accuracy and reliability of flow sensing
Figure 11 shows a block diagram of a typical differential pressure flow detection circuit. The
DP transmitter operation is dependent on the pressure difference across an orifice, venturi, or
flow tube. This differential pressure is used to position a mechanical device such as a bellows.
The bellows acts against spring pressure to reposition the core of a differential transformer. The
transformers output voltage on each of two secondary windings varies with a change in flow.
Figure 11 Differential Pressure Flow Detection Block Diagram