Calculation Of The Data Log Size - Siemens S7-1500 Function Manual

Table 3- 2 Downloaded examples of data logs displayed in Microsoft Excel
Two data records written in a data log which
contains a maximum of five data records.
Five data records written in a data log which
contains a maximum of five data records.
After another data record has been written,
the 6th write operation overwrites the oldest
data record (record 1) with data record 6.
Another write operation overwrites data
record 2 with data record 7, etc.
3.2.5

Calculation of the data log size

The maximum memory size is allocated when you create the data log. Besides ensuring
enough memory space for all the data records, you must take into account the memory
space of the following elements for the memory allocation:
● Data log header (if used)
● Time stamp header (if used)
● Data record index header
● Minimum block size
The formula below represents a method to help you determine the estimated size of your
data log. Make sure that you observe the rule for the maximum size.
Data bytes of the data log = ((data bytes in a data record + time stamp
bytes + 12 bytes) * number of data records)
Structure and Use of the CPU Memory
Function Manual, 10/2018, A5E03461664-AC
Memory usage and application examples
3.2 Memory usage for data logging
53