[Dsg-hallb_magnets] [New Logentry] SOE Timestamps

[beng at jlab.org]

Logentry Text:
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While attempting to retrieve archived values from Mya it was found that it would only return scientific notation values and that there weren't any options to change the formatting. Additionally despite the PVs being DBF_DOUBLE Mya always stores them as single precision in order to reduce the storage space required.

Unfortunately for us the values for the SOE timestamps often lose precision when converted to singles, e.g. 458692463 is saved as 458692448 (when converted to an IEEE-754 single precision float).

Nathan tried changing the IOC to use a data type of DBF_LONG (32-bit integer) however after doing that the IOC wouldn't read the timestamp array tag properly (it's a 64-bit value broken up into 2 32-bit integers).

The IOC (initial testing was only done on the Solenoid MPS IOC) has been reverted back to the previous code which uses doubles.

The ca* family of commands do work properly with the current PVs. The -f0 option is so it won't print it out as scientific notation.

clasrun at clonsl2:clasrun> caget -f0 B_SOL:MPS:TSL_System_Cable
B_SOL:MPS:TSL_System_Cable     1241210247

A script will be made shortly in order to get these PVs so we don't need to connect to the PLC to get the timestamps until a proper fix can be deployed.

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/3606498
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