Master station and HMI in SCADA systems - Step-by-Step Execution

Process Flow - Master station and HMI

Start: Sensors collect data

↓

Data sent to Master Station

↓

Master Station processes data

↓

Master Station sends info to HMI

↓

HMI displays info to operator

↓

Operator sends commands via HMI

↓

Commands sent back to Master Station

↓

Master Station controls devices

↓

End

Data flows from sensors to master station, then to HMI for display; operator commands go back through HMI to master station to control devices.

Execution Sample

SCADA systems

1. Sensor data -> Master Station
2. Master Station processes data
3. Master Station -> HMI display
4. Operator inputs command on HMI
5. Command -> Master Station
6. Master Station controls device

Shows the step-by-step flow of data and commands between sensors, master station, HMI, and devices.

Process Table

Step	Action	Source	Destination	Result
1	Send sensor data	Sensors	Master Station	Data received by Master Station
2	Process data	Master Station	Master Station	Data analyzed and prepared
3	Send info	Master Station	HMI	Information displayed on HMI screen
4	Operator inputs command	Operator	HMI	Command entered on HMI interface
5	Send command	HMI	Master Station	Command received by Master Station
6	Control device	Master Station	Field Devices	Device action executed
7	End	-	-	Cycle complete, system waits for next data

💡 Cycle ends after device control; system loops for continuous monitoring and control

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
Sensor Data	Raw data	Sent to Master Station	Processed data	Processed data sent to HMI	Processed data displayed	Command input received	Command sent to Master Station	Device controlled
Command	None	None	None	None	Entered by operator	Sent to Master Station	Executed by Master Station	None

Key Moments - 3 Insights

Why does the Master Station process data before sending it to the HMI?

The Master Station processes raw sensor data to convert it into meaningful information for the operator. This is shown in execution_table step 2 and 3 where data is analyzed before display.

How does the operator's command reach the field devices?

The command flows from the operator to the HMI (step 4), then from HMI to Master Station (step 5), and finally the Master Station controls the devices (step 6). This chain ensures commands are verified and executed properly.

What happens after the device is controlled?

After device control (step 6), the system waits for new sensor data to start the cycle again, ensuring continuous monitoring and control as noted in the exit_note.

Visual Quiz - 3 Questions

Look at the execution table, at which step does the HMI display information to the operator?

A Step 5

B Step 2

C Step 3

D Step 6

💡 Hint

Check the 'Result' column for when information is shown on the HMI screen.

At which step does the Master Station receive the operator's command?

A Step 5

B Step 6

C Step 4

D Step 3

💡 Hint

Look for the step where the command moves from HMI to Master Station.

If the operator does not input any command, which step will not occur?

A Step 2

B Step 4

C Step 6

D Step 1

💡 Hint

Refer to the step where the operator inputs a command on the HMI.

Concept Snapshot

Master Station collects and processes sensor data.
Processed data is sent to HMI for operator display.
Operator commands entered on HMI go back to Master Station.
Master Station controls devices based on commands.
Cycle repeats for continuous monitoring and control.

Full Transcript

In a SCADA system, sensors collect data and send it to the Master Station. The Master Station processes this data to make it understandable. Then, it sends the information to the HMI, where the operator can see it. The operator can input commands on the HMI, which are sent back to the Master Station. The Master Station then controls the field devices accordingly. This cycle repeats continuously to monitor and control the system effectively.