Polling vs report-by-exception in SCADA systems - Hands-On Comparison

Polling vs Report-by-Exception in SCADA Systems

📖 Scenario: You are working with a SCADA (Supervisory Control and Data Acquisition) system that monitors temperature sensors in a factory. The system can collect data in two ways: polling (asking sensors for data regularly) or report-by-exception (sensors send data only when temperature changes significantly).

🎯 Goal: Build a simple program that simulates both polling and report-by-exception methods to collect temperature data from sensors. You will create data, configure thresholds, apply the main logic for each method, and display the collected data.

📋 What You'll Learn

Create a dictionary called sensors with sensor IDs as keys and their current temperatures as values.

Create a variable called threshold to set the temperature change limit for report-by-exception.

Write a function called polling_collect that returns all sensor data.

Write a function called report_by_exception_collect that returns only sensors with temperature changes greater than threshold compared to previous readings.

Print the results of both collection methods.

💡 Why This Matters

🌍 Real World

SCADA systems monitor industrial equipment and processes. Efficient data collection helps reduce network load and speeds up response to important changes.

💼 Career

Understanding polling and report-by-exception is key for roles in industrial automation, system monitoring, and network optimization.

1

Create initial sensor data

Create a dictionary called sensors with these exact entries: 'sensor1': 22.5, 'sensor2': 23.0, 'sensor3': 21.8.

SCADA systems

# Create the sensors dictionary with exact temperature values
# Your code here

Need a hint?

Use curly braces to create a dictionary with keys as sensor IDs and values as temperatures.

2

Set temperature change threshold

Create a variable called threshold and set it to 0.5 to represent the minimum temperature change for report-by-exception.

SCADA systems

sensors = {'sensor1': 22.5, 'sensor2': 23.0, 'sensor3': 21.8}
# Set the threshold variable to 0.5
# Your code here

Need a hint?

Just assign the number 0.5 to the variable named threshold.

3

Implement polling and report-by-exception logic

Write two functions: polling_collect that returns the full sensors dictionary, and report_by_exception_collect that takes previous_readings dictionary and returns a dictionary of sensors where the absolute temperature difference is greater than threshold.

SCADA systems

sensors = {'sensor1': 22.5, 'sensor2': 23.0, 'sensor3': 21.8}
threshold = 0.5

# Define polling_collect function
# Define report_by_exception_collect function
# Your code here

Need a hint?

Use a for loop to compare current and previous temperatures. Return all sensors for polling.

4

Display collected data

Create a variable previous_readings with {'sensor1': 22.0, 'sensor2': 23.0, 'sensor3': 21.0}. Then print the results of polling_collect() and report_by_exception_collect(previous_readings).

SCADA systems

sensors = {'sensor1': 22.5, 'sensor2': 23.0, 'sensor3': 21.8}
threshold = 0.5

def polling_collect():
    return sensors

def report_by_exception_collect(previous_readings):
    changed = {}
    for sensor, temp in sensors.items():
        if abs(temp - previous_readings.get(sensor, temp)) > threshold:
            changed[sensor] = temp
    return changed

# Create previous_readings dictionary
# Print polling_collect() result
# Print report_by_exception_collect(previous_readings) result
# Your code here

Need a hint?

Use print statements to show the full sensor data and the sensors with significant changes.