4.1.4 Serial FDM Telegrams
4.1.4.1 Standard FDM String
The STANDARD string is a sequence of 62 ASCII characters containing the frequency F, the frequency devi-
ation FD, the REF time, the power line time PLT and the timedeviation TD, each item seperated by a space
character. The string is send out at the beginning of every new REF time second and ends with the characters
Carriage-Return (Hex code 0Dh) and Line-Feed (Hex code 0Ah). The letters displayed in italics are replaced
by the calculated values whereas the other characters are part of the string:
F:49.984_
FD:
-00.016
_REF:
15:03:30
_PLT:
15:03:30.378
_TD:
+00.378
<CR><LF>
The meaning of the several values is described below:
F:
49.984
The measured power line frequency with a resolution of 1mHz
FD:
-00.016
The frequency deviation between calculated and nominal frequency,
with sign character (+/-), resolution: 1mHz, maximum: +-09.999Hz
REF:
15:03:30
The reference time from the preconnected clock
(hours:minutes:seconds)
PLT: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!
TD:
+00.378
The time deviation between REF time and PL time, with sign character
(+/-), resolution: 1ms, maximum: +-99.999s
4.1.4.2 FDM Standard 2 Telegramm:
Like FDM standard, but it sends every 500ms instead of 1 per second.
4.1.4.3 Short FDM String
The SHORT string is a sequence of 23 ASCII characters containing simply information about frequency devi-
ation FD and time deviation TD, seperated by a space character. The string is send out at the beginning of
every new REF time second and ends with the characters Carriage-Return (Hex code 0Dh) and Line-Feed (Hex
code 0Ah). The letters displayed in italics are replaced by the calculated values whereas the other characters
are part of the string:
FD:-
00.016
_TD:+
00.378
<CR><LF>
The meaning of the several values is described below:
FD:-
00.016
The frequency deviation between calculated and nominal frequency,
with sign character (+/-), resolution: 1mHz
TD:+
00.378
The time deviation between REF time and PL time„
with sign character (+/-), resolution: 1ms
18
Date: 4th November 2020
IMS-FDM Setup Guide
