800xA Log Template Sample Resolution
I have a customer who wishes to log data on a variable at a rate of 10 samples per second, or 1 sample every 100ms.
What is the fastest sampling rate that can be acheived with a Log Template with the 800xA platform? (we're not runnning the Information Management option)
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In theory you can set the Min Time parameter to 1 ms in Basic History Log Templates, but the OPC server in the source end might not be able to deliver this update rate.
For AC400, 1000ms is fastest possible.
For AC 800M the default fastest is 500ms but could be tweaked at the price of more MMS/second. 10 MMS/second leaves less headroom for code execution in an AC 800M than when using 1 MMS/second for variable updates. Code execution must be properly tuned to get real updates instead of copies of last read value in program. I don't recommend going below 500ms with AC 800M without proper investigation, maybe even a written permit (aka TSA) from Technical Product Management.
Faster update rate will scale the performance figures in the System Guide accordingly (less logs possible with faster logs).
1000 logs at 1 second sample rate equals one (1) log at 1ms rate...
Most figures are scaled for 1000ms update rate.
Basic History can handle more and faster logs when writing to a 15.000 RPM SAS disk in RAID0 (striping) handled by a high end RAID controller with write cache enabled than it would be when left with a 7.200 RPM SATA disk.