Data quality flags in SCADA systems - Step-by-Step Execution

Process Flow - Data quality flags

Data Input

↓

Check Sensor Status

↓

Apply Quality Flags

↓

Store Flagged Data

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Use Flags for Decisions

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Alert or Correct if Needed

Data flows from sensors, quality flags are applied based on checks, then stored and used for decisions or alerts.

Execution Sample

SCADA systems

sensor_value = 75
if sensor_value < 0 or sensor_value > 100:
    quality_flag = 'BAD'
else:
    quality_flag = 'GOOD'
print(quality_flag)

This code checks if a sensor value is within a valid range and assigns a quality flag accordingly.

Process Table

Step	Action	Condition	Result	Quality Flag
1	Read sensor_value	N/A	sensor_value = 75	N/A
2	Check if sensor_value < 0	75 < 0	False	N/A
3	Check if sensor_value > 100	75 > 100	False	N/A
4	Assign quality_flag	Both conditions False	quality_flag = 'GOOD'	GOOD
5	Print quality_flag	N/A	Output: GOOD	GOOD

💡 sensor_value is within valid range, so quality_flag is set to GOOD

Status Tracker

Variable	Start	After Step 1	After Step 4	Final
sensor_value	undefined	75	75	75
quality_flag	undefined	undefined	GOOD	GOOD

Key Moments - 2 Insights

Why do we check both sensor_value < 0 and sensor_value > 100?

Because valid sensor values must be between 0 and 100. The execution_table rows 2 and 3 show these checks to decide if the data is good or bad.

What happens if sensor_value is exactly 0 or 100?

The conditions sensor_value < 0 and sensor_value > 100 would both be false, so the quality_flag will be 'GOOD' as shown in the logic at step 4.

Visual Quiz - 3 Questions

Look at the execution table, what is the quality_flag after step 4?

A GOOD

B BAD

C undefined

D ERROR

💡 Hint

Check the 'Quality Flag' column in row for step 4 in the execution_table.

At which step do we determine the sensor_value is valid?

A Step 1

B Step 2

C Step 4

D Step 5

💡 Hint

Look at the 'Result' column where quality_flag is assigned in the execution_table.

If sensor_value was 150, how would the quality_flag change in the execution_table?

A It would be GOOD

B It would be BAD

C It would be undefined

D It would cause an error

💡 Hint

Check the condition sensor_value > 100 in step 3 and its effect on quality_flag in step 4.

Concept Snapshot

Data quality flags mark sensor data as GOOD or BAD based on checks.
Check sensor values against valid ranges.
Assign flags accordingly.
Use flags to decide if data is reliable.
Helps detect sensor errors or bad readings.

Full Transcript

In SCADA systems, data quality flags help identify if sensor data is good or bad. The process starts by reading the sensor value. Then, the system checks if the value is within a valid range, for example between 0 and 100. If the value is outside this range, the data is flagged as BAD; otherwise, it is flagged as GOOD. This flag is stored with the data and used later to make decisions or trigger alerts. The example code reads a sensor value of 75, checks the conditions, and assigns a GOOD flag because 75 is within the valid range. This step-by-step check ensures only reliable data is used for control or monitoring.