Components of a control loop
1. Primary element/sensor 2. Transducer 3. Converter 4. Transmitter 5. Signal 6. Indicator 7. Recorder 8. Controller 9. Correcting element (=final control element) 10. Actuator
Process control loop is a ________________________ loop
feedback
What is dead time?
Length of time before a change in actuator which causes a change in the sensor
Examples of sensors
Heat sensor, humidity sensor, light sensor, pressure sensor, smoke sensor, sound sensor, tilt sensor, touch sensor.1. Thermocouples2. RTD for temp measurement 3. Strain gauge 4. Pressure-sensing diaphragm 5. Capacitative cells for pressure measurement 6. Orifice plate for flow measurement 7. Pilot tube for flow measurement 8. Magnetic flow tube for flow measurement
Transducers are also known as ________________
pick-ups
What are transmitters?
Devices that convert the signal into a standard signal that can be transmittable through the control loop.
Examples of transmitters
1. Pressure transmitters2. Flow transmitters3. Temp transmitters4. Level transmitters5. Analytic transmitters
Types of transducers
1. On the basis of usage : capacitate, inductive and resistive 2. Active/passive 3. Primary/secondary 4. Analog/digital 5. Transducer/ Inverse transducer
Types of signal
1. Pneumatic signal 2. Analog signal 3. Digital signal
What is pneumatic signal?
Pneumatic Signal is pressure of a gas (or air) in a pipe, instead of electrical current .A pneumatic signal is a pressure signal. many a times due to blockages or other reasons, pressure reaching the instrument may be zero where in fact it is not. Here is where the offset comes in. In the 3-15 psig range, no signal is indicated by a 3 psig pressure. A zero reading on the output will clearly indicate that some error has occurred somewhere. And regarding 15 psig limit, most instruments operate safely upto around 20 psig pressure. So incase it is over-pressurized, it will not damage the instrument uptil atleast 20 psig.
What is a PLC?
Programmable logic controller (PLC) units are effectively single-purpose or focused-purpose digital computers. PLC is connected to I/O devices and is programmed to respond to inputs by sending outputs to maintain all processes at a setpoint.
What is DCS?
Distributed Control System: control functions + reading of the status of the process + maintain databases + advanced man-machine-interface.
Name the final control devices for flow control system
Pumps and control valves
Name the final control devices for temperature control system
Heaters and boilers
Name the final control devices for pressure control system
Compressor and valves
How is an actuator controlled?
1. Pneumatically 2. Hydraulically 3. Electrically