Q1. In a flow control loop method for which you are specifying a flow sensor, it is not desirable to insert any sensing device to the actual flow because of interference with the flow. Since of the corrosive nature and high pressure and temperature of the flow, only stainless steel pipes can be employed anywhere in the system. The liquid is non-conductive.

Propose a flow sensor, describing its operating principle.

Q2. A request has been received from the external customer for recommendations for linear position control sensors to be employed in an explosive environment. For this reason unsafe electrical contacts should be avoided. The sensors will be installed in locations which are harmful to access apart from when the plant is shut down annually for the maintenance. The span needed is 5 cm. The sensor case should not permit any ingress of dust or of water.

State what kind of position sensors you would propose and give your reasons. Sketch both the suggested sensor and circuit and describe its operation. Comment on how signal conditioning requirements can now be met. Identify the durability needed in respect of dust and water ingress.