Polling vs report-by-exception in SCADA systems - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to show how polling works by regularly checking a sensor value.

SCADA systems

while True:
    sensor_value = read_sensor()
    if sensor_value [1] threshold:
        alert_operator()
    sleep(5)

Drag options to blanks, or click blank then click option'

A>

B!=

C<=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' will only alert if value equals threshold exactly.

Polling checks if the sensor value is greater than a threshold regularly.

2fill in blank

medium

Complete the code to implement report-by-exception by sending data only when it changes.

SCADA systems

previous_value = None
while True:
    current_value = read_sensor()
    if current_value [1] previous_value:
        send_report(current_value)
        previous_value = current_value
    sleep(5)

Drag options to blanks, or click blank then click option'

A<

B!=

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' will send report only if values are the same, which is wrong.

Report-by-exception sends data only when the current value is different from the previous one.

3fill in blank

hard

Fix the error in this polling loop that causes it to miss alerts.

SCADA systems

while True:
    value = read_sensor()
    if value [1] threshold:
        alert_operator()
    sleep(5)

Drag options to blanks, or click blank then click option'

A>=

B>

C<

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' misses the case when value equals threshold.

Using '>=' ensures alerts trigger when value equals or exceeds the threshold, avoiding missed alerts.

4fill in blank

hard

Fill both blanks to create a report-by-exception dictionary with sensor names and values only if value changed.

SCADA systems

reports = {sensor: [1] for sensor, value in sensors.items() if value [2] last_values.get(sensor)}

Drag options to blanks, or click blank then click option'

Avalue

B==

C!=

Dsensor

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' will include unchanged sensors.

The dictionary includes sensor values where the current value differs from the last reported value.

5fill in blank

hard

Fill all three blanks to build a polling loop that reads sensors, updates last values, and alerts if any value exceeds threshold.

SCADA systems

last_values = {}
while True:
    readings = {sensor: read_sensor(sensor) for sensor in sensors}
    for sensor, value in readings.items():
        if value [1] threshold:
            alert_operator(sensor, value)
        last_values[[2]] = [3]
    sleep(5)

Drag options to blanks, or click blank then click option'

A>

Bsensor

Cvalue

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' will alert for values below threshold, which is incorrect.

The loop alerts when value exceeds threshold, then updates last_values with current sensor and value.