7 Integrated Frequence Deviation Monitor Module - FDM
7 Integrated Frequence Deviation Monitor
Module - FDM
7.1 Overview
The module FDM180 was designed to calculate and monitor the frequency and its deviation in 50/60 Hz power
line networks.
The preconnected reference clock supplies reference signals, which significantly define the accuracy of the
measured values. In addition to the frequency calculation, the time is also calculated from the mains frequency.
The deviation of this calculated time (PLT) from the reference time (REF) is the time difference (TD).
7.2 Functional Principle of the FDM Module
The power line to be monitored is applied via the rear panel’s power supply socket, then filtered and down
transformed. To detect the mains frequency of 45 ... 65 Hz correctly the voltage of the connected mains must
be in the range of 70 V ... 270 V AC.
Afterwards the sine wave signal is fed into the microcontroller of the module.
The calculation of the PLT (Power Line Time) occurs by counting the periods of the mains frequency. De-
pending on the nominal frequency, the seconds are incremented after 50 or 60 periods. To initialize the PLT, the
REF time is also required. This is supplied to the module via the pulse per second and the time telegram of the
reference. The difference between PLT and REF, which is recalculated every second, is called time deviation
(TD) and is limited to +-1000 seconds.
7.3 EEPROM
The non-volatile EEPROM is used to store the settings of the FDM180. This ensures a proper restart without
any new configuration after the module was switched off for a certain time.
7.4 Mains Socket Power Line Input
The power line to be monitored has to be connected to the module via this power socket in the rear panel and
is completely separated from the power supply that is used to operate the LANTIME system itself. To detect
the mains frequency of 45 ... 65 Hz correctly the voltage of the connected mains must be in the range of 70 V
... 270 V AC. This input is protected by a 200 mA slow blowing fuse.
LANTIME
Date: March 1, 2022
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