Trend charts and historical data in SCADA systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Data Sampling Rate in Trend Charts

In a SCADA system, trend charts display historical data points collected over time. What is the main effect of increasing the data sampling rate on the trend chart?

A It decreases the number of data points, making the chart less detailed and faster to load.

B It increases the number of data points, making the chart more detailed but potentially heavier to load.

C It removes older data points to keep the chart size constant.

D It changes the color scheme of the trend chart automatically.

💡 Hint

Think about what happens when you collect data more often.

Increasing the sampling rate means collecting data more frequently. This results in more data points on the trend chart, which makes it more detailed but can also slow down loading and processing.

💻 Command Output

intermediate

Output of Historical Data Query Command

Given the SCADA command to retrieve temperature data for the last hour:

get_trend_data --tag temperature --duration 1h

Which output correctly shows the expected result format?

A [{"timestamp": "2024-06-01T10:00:00Z", "value": 22.5}, {"timestamp": "2024-06-01T10:05:00Z", "value": 22.7}]

B {"temperature": [22.5, 22.7], "time": ["10:00", "10:05"]}

C Error: Command not found

D [22.5, 22.7, 23.0]

💡 Hint

Look for a list of timestamped values in JSON format.

The command returns a list of objects, each with a timestamp and a value, representing the historical data points.

❓ Configuration

advanced

Configuring Data Retention Period for Historical Data

Which configuration snippet correctly sets the data retention period to 30 days in a SCADA system's trend data storage?

A retention_period = "30d"

B history.retention = 30

C data_retention_days = 30

D trend_data.retention_days = 30

💡 Hint

Look for a configuration that uses a string with a time unit.

Many SCADA systems use a string with a time unit like "30d" to specify retention periods. Option A correctly uses this format.

❓ Troubleshoot

advanced

Troubleshooting Missing Data Points in Trend Charts

A user reports that the trend chart for pressure data shows large gaps with missing data points. Which is the most likely cause?

A The chart color scheme is set to hide certain data points.

B The trend chart is configured to show only the last 5 minutes of data.

C The SCADA system's clock is set to the wrong timezone.

D The data sampling rate is too low, causing infrequent data collection.

💡 Hint

Think about what causes gaps in data over time.

If data is collected too infrequently, the trend chart will have gaps because no data points exist for those times.

🔀 Workflow

expert

Steps to Export Historical Trend Data for Analysis

Arrange the correct order of steps to export historical trend data from a SCADA system for external analysis.

A 1,3,2,4

B 2,1,3,4

C 1,2,3,4

D 3,1,2,4

💡 Hint

Think about the logical order from accessing the tool to saving the file.

First, open the export tool, then select tags and time range, choose file format, and finally export and save.