B&R Industries Provit 5000, User Manual

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146 Provit 5000 User’s Manual
Controllers • Lifespan of Silicon Disks (Compact Flash, PC Card)
12.4 Calculation of the Lifespan
12.4.1 Example 1: Ring Buffer Data Storage
An application records the data every minute for the previous 5 hours. The data is saved on the
same sectors (ring buffer).
Specifications: 64 MByte silicon disk, 10 kByte per minute i.e. 10 *1,024 Byte / 512 Byte = 20
sectors per minute
1. Calculations of the sectors
User sectors: 64 * 1,024,000 byte / 512 byte = 128,000 sectors
Spare sectors: 1% of user sectors = 1,280 sectors
2. Write cycles per year
23 sectors per minute (20 data + 2 FAT + 1 directory)
(20 + 2 + 1) sectors * 60 minutes * 24 hours * 365 days = 12,088,800 write cycles per year.
Figure 85: Ring Buffer example