Importance of Measurement in Automation

Questions and Answers

What is a prerequisite for controlling a process?

Setting a desired output

Understanding the various things that you want to monitor

Having a wireless sensor network

The ability to measure the process (correct)

What is the purpose of measuring the current conditions in a room?

To measure the flow of a process

To control the temperature in the room

To compare it with the desired output (correct)

To simulate a changing input over time

What type of input would a door open-door closed switch be?

Discrete output

Digital input (correct)

Wireless sensor network

Analog input

What is an example of an analog input?

Temperature or flow measurement Signup and view all the answers

What allows an operator to change the input or output of a process?

Changing the set point variable Signup and view all the answers

What is the role of inputs in a process?

To provide context for the processor to understand the desired output Signup and view all the answers

What is an example of a discrete input?

A float switch that a level has reached a certain level in a tank Signup and view all the answers

What is used to collect data wirelessly in a process?

Wireless sensor networks Signup and view all the answers

What is the purpose of the low-level alarm in the water tank?

To indicate when the water level is too low. Signup and view all the answers

What type of input is used to detect the water level in the tank?

Analog input Signup and view all the answers

What is the function of the float in the low-level alarm?

To make electrical contact when the water level reaches a certain height. Signup and view all the answers

What type of card on the PLC backplane is used for the low-level alarm?

Discrete input card Signup and view all the answers

What is the role of the flow sensor in the water tank system?

To monitor the flow rate of water entering the tank. Signup and view all the answers

What happens when the flow sensor sends an electrical signal to the analog input card?

The signal is converted into a digital value for the PLC. Signup and view all the answers

Which of the following is NOT a type of input used in the water tank system described?

Discrete output Signup and view all the answers

What type of power source is typically used for the digital inputs in the water tank system?

AC power Signup and view all the answers

Study Notes

Importance of Measurement in Automation

Understanding and monitoring processes is crucial for automation.
Control is only possible when measurement is in place; "You cannot control what you cannot measure."
Reference to Lord Kelvin’s principle highlights the necessity of metrics for management.

Inputs in Automated Systems

Inputs serve as direct measurements of process conditions, providing context for output control.
Types of inputs include:
- Discrete/Digital Inputs: Represent binary states, e.g., switches indicating conditions like door position or liquid levels.
- Analog Inputs: Continuous measurements that change over time, such as temperature or flow levels.
- Wireless Sensor Networks: Collect various inputs wirelessly, allowing for more flexible monitoring.

Example: Water Tank Automation

A water tank provides a practical example to discuss input types.
Important inputs for the tank include:
- Low and high-level alarms to monitor water levels.
- Level indicating devices (like radar or sonar) to determine exact water height.
The tank setup likely includes:
- An input for water supply.
- An outlet pipe with a valve for flow regulation.
- A pump for water removal.

Digital Inputs and Alarm Systems

Digital inputs operate like simple on/off switches:
- Floats trigger contacts when water reaches certain heights.
- Electrical connections to input cards relay signals about water levels.
Input modules consist of two types:
- Discrete Input Cards for digital signals.
- Analog Input Cards for sensory data (e.g., flow rate).

Operational Mechanism Explained

The flow rate is monitored via sensors plugged into an analog input card.
Electrical signals from sensors are converted into digital values for processing by a Programmable Logic Controller (PLC).
Those signals drive response actions based on the set parameters in the automation system.