4 FDM - Frequency Deviation Monitoring
4.1.4.4 FDM Areva String
The Areva string is a sequence of 71 ASCII characters containing the frequency F, the frequency deviation FD,
the time deviation TD, the power line time PLT and the reference time REF (preceded by the 3 digit day-of-the
year), each item seperated by the characters Carriage-Return (Hex code 0Dh) and Line-Feed (Hex code 0Ah).
Each of the five data items is preceded by a fixed 3 digit address (020 ... 024). The string starts with the STX
character (start-of-text, Hex code 02h) and ends with a terminating ETX character (end-of-text, Hex code 03h)
on time with the change of the REF time seconds. The letters displayed in italics are replaced by the calculated
values whereas the other characters are part of the string:
<STX> 02049.984<CR><LF>
021-0.016<CR><LF>
022+00.378<CR><LF>
02315_03_30.378<CR><LF>
024068_15_03_30_<CR><LF>
<ETX>
The meaning of the several values is described below:
49.984
The measured power line frequency with a resolution of 1mHz
-0.016
The frequency deviation between alculated and nominal frequency,
with sign character (+/-), resolution:1mHz
+00.378
The time deviation between REF time and PL time,
with sign character (+/-), resolution: 1ms
15_03_30.378
The power line time, based on the mains frequency,
(hours_minutes_seconds.milliseconds)
Time jumps, like changeover in daylight saving or leap seconds,
will not be executed by the PL time!
068_15_03_30
The reference time from the preconnected clock,
(day-of-the-year_hours_minutes_seconds)
IMS-FDM Setup Guide
Date: 4th November 2020
19
