How can you identify the sensors and actuators in your control system?

Sensors and actuators often work in tandem, but they are essentially opposite devices. A sensor monitors conditions and signals when it detects specific, pre-determined changes. An actuator receives a signal and performs an action, often in the form of movement in a mechanism Controllers & sensors are imp parts of the control system; without information from the sensor, the controller cant make a decision and instruct the valve to work. An on/off valve and actuator eg., can be operated directly from a thermostat. e.g is the operation of high limit safety controls, which have a ‘snap’ action to close valves or to switch off fuel supplies. when the control requirements become more sophisticated, a controller is needed to match

It's essential to grasp not just the steady-state behavior but also the dynamics of the process. This means understanding how variables change over time, including response times and delays. In the context of room temperature control, this might involve recognizing how quickly temperature changes when the heating system is activated or how long it takes for the ventilation system to influence room conditions.

In a system, sensors detect and respond to physical changes (e.g., temperature, pressure, flow, level) by converting them into electrical signals (input variables) using transducers. Actuators, on the other hand, convert electrical signals into physical movement or changes (linear or rotary) (output variables). For instance, a pressure sensor detects a pressure drop and triggers a pump motor to start. To identify sensors and actuators, one can create a process flow diagram (PFD) of the system, pinpoint the necessary sensing elements, and then identify the corresponding actuators that act upon the sensed inputs to control the system.

In my experience, Identity may be as simple as this: your sensors will be high impedance devices with smallish conductors; whereas actuators will be low impedance devices with more power requirements, and (relatively) larger conductors.

Sensors and actuators monitor and control the refining process to ensure safety and efficiency. When choosing sensors and actuators for a refinery project, consider the following factors: Accuracy and reliability: The sensors and actuators must be highly accurate and reliable to ensure the safety and efficiency of the refining process. Environmental conditions: The sensors and actuators must be able to operate in harsh environmental conditions, such as high temperatures, high pressures, and corrosive atmospheres. Safety: The sensors and actuators must be designed to meet all applicable safety standards.

Before anything else, you must choose the kind of sensor principle that should be used, to make a decision on this, many factors must be carefully considered. Additionally the type of output mode that must be used, such as a 2-wire or 4-wire current signal, a 0-20 mA, a 4-20 mA, a 0-10 V voltage signal, or any protocol communication, must also be mentioned.

Sensor Redundancy: In some cases, especially for critical applications or when data accuracy is paramount, consider implementing sensor redundancy. This involves using multiple sensors of the same type or different types to cross-verify measurements. Redundancy can enhance the reliability and fault tolerance of your system by providing backup data sources and early detection of sensor failures.

In the context of Safety Instrumented Function (SIF) loops, the selection of sensors and actuators should center on their reliability, repeatability, and adherence to the necessary Safety Integrity Levels (SIL). This is paramount to uphold the integrity of the safety system. Practicality-wise, it’s imperative to opt for an Original Equipment Manufacturer (OEM) that not only provides the right components but also commits to offering sustained technical support and a steady supply of spare parts throughout the lifecycle. This proactive approach ensures that clients won’t have to deal with obsolescence issues shortly after installation, delivering long-term reliability.

It's interesting reading "the responses" to the question "How do you Identify...". As an Instrumentation and Controls person, the very FIRST step is to IDENTIFY the parts and pieces with a Tagging convention that INCLUDES Operator, different from Actions, different from Owner (IED, Device or Sets of Devices ganged together) and Result(s) that "happened" AFTER the request of "the Operator". AND the SECOND step is to CLASSIFY the Result(s) with Good, Bad, Not Operating, Fault (not Failed), Failing but still Operating, etc. (the Conditional Evaluations are numerous). the THIRD step is RESPONSE to the combined effects of Operator and Classification of Operation. Continue in ONE of the many Modes (e.g. Continuous Process = 145 Modes).

It is crucial to select the right actuator types based on the specific requirements of your output variables. Consider factors such as force, torque, speed, position, power, cost, size, and compatibility with your control system. Additionally, it's essential to have knowledge of how to effectively control, connect, and safeguard your chosen actuators to prevent issues like overload and failure, ensuring the reliable operation of your control system.

Different types of functional and durability testing including FAT and then on-site testing helps to ensure that sensors and actuators are reliable and perform as expected in the field. For e.g.,a pressure sensor that is not properly tested may fail in a high-pressure environment, causing damage to equipment or injury to personnel. Similarly, a temperature sensor that is not properly tested may provide inaccurate readings, resulting in process control problems and wrong interpretations.

For any integration, Sensor input will be stored in main control system (Can be processor of PLC or microcontroller) with supported algorithm. Then based on application purpose central processing unit will send command to output where actuators will play as per necessity. Visible/invisible wiring can be done based on platform and obviously power supply will be connected to the main board and will be distributed to several unit as per requirement.

In complex cases, it could also require a database in the middle that gathers the sensors data and run the algorithms for control

In addition to the previous points, it’s essential to maintain comprehensive documentation, including spare part numbers, vendor data sheets, drawings, and technical support details for all installed sensors and actuators. This ensures readiness for emergencies. Furthermore, opting for the same OEM/Model of sensors and actuators for similar applications allows for interchangeability in case of emergency replacements. This approach also boosts the maintenance crew’s technical troubleshooting skills, enhancing overall equipment reliability.

A comprehensive Operation and Maintenance (O&M) manual shall be furnished upon project commissioning to ensure that the system is upheld and serviced in strict accordance with established industry standards.

If there are any difficulties during adjustment, then try to eliminate as many influencing factors as possible. Often inexperienced personnel establish false causal relationships. They see the happening phenomenon, but misunderstand its causes and mechanisms. Therefore, get to the bottom of the matter, do not skip steps in the reasoning, even if they seem obvious to you, and keep the purity of the experiment.

You can use a multimeter, an oscilloscope, or a data acquisition system to measure the electrical signals from the sensors and to the actuators.