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Subject: | Re: time drift in camonitor timestamps |
From: | Michael Davidsaver <[email protected]> |
To: | [email protected] |
Date: | Thu, 03 Jan 2013 18:22:36 -0500 |
I mean, the difference between two consecutive samples is always higher than the SCAN value, accumulating an error.
Just to make certain I understand you. Do you mean that the difference increases with each iteration? Or that the scan start time is moving (precessing) relative to start of the system clock's second?
In case you have not seen it, the code in question is periodicTask(). http://bazaar.launchpad.net/~epics-core/epics-base/3.15/view/head:/src/ioc/db/dbScan.c#L561 On 1/3/2013 4:36 PM, Mark Rivers wrote:
What is the magnitude of the error? How long does it take before the error is 1 second, for example?
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of [email protected]
Sent: Thursday, January 03, 2013 3:09 PM
To: [email protected]
Subject: time drift in camonitor timestamps
Hi,
We have realized that when monitoring periodic PVs, provided by soft IOCs in
standard machines under Windows/Linux/MacOS, it is observed a drift in the
timestamps (server time) . I mean, the difference between two
consecutive samples is always higher than the SCAN value, accumulating an
error.
It seems that this issue does not occur in RT systems such as VxWorks (as
expected).
We are wondering if this is a known issue. In our opinion, this fact could
lead to
malfunction problems, especially if it is not taken into account.
Does anyone in the list experienced this problem?
thank you