User Manual 36 < back to the table of contents > 1. Select device: Select the DAT-Module from which the measured values should be displayed. 2. Select measured values: Choose up to 6 measured values from the previously selected DAT-Module. 3. Select time resolution: Defines the time interval over which the data is averaged. For more information on time resolution averaging, see Chapter 9.1 Time Resolution of the Database. 4. From: Select the date and time at which the data query should start. 5. To: Select the date and time at which the data query should end. 6. Display historical data: Executes the database query. 7. Export filtered historical data to CSV: Creates a .csv file with the selected measured values. Configuration options for the file are described in Chapter 12.4.5 CSV Configuration. 8. Export historical data to CSV: Downloads all measured values from the previously selected DAT-Module using the selected time resolution. 9.1 Time Resolution of the Database The database is used to store measured values from the DAT-Modules and display them as historical data. The database storage is divided as follows: 1. Direct Database: Located in volatile memory (RAM), it allows fast access to data from the last 5 minutes. However, this data is lost when the system is powered off. 2. Averaged Database: Permanently stored and contains averaged values from the direct database, which are retained even after a system restart. Measured values are automatically transmitted via radio from the measurement modules to the communication module at the configured interval (default: 2 seconds) and immediately stored in the Direct Database. Every 300 seconds (5 minutes), average values for each measurement module are calculated and stored in the Averaged Database. Every 1,800 seconds (30 minutes), the 5-minute averages are further averaged and stored in another table within the database. This process continues up to a 43,200-second (12-hour) average. This results in a lean and efficient database where the resolution (intervals) of the data records becomes coarser as the data ages. The individual steps in which the data is stored are shown in Figure 31. Figure 31: Schema of data storage in the database
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