I E16x442 Rev: 00 Page 35 of 73
5.2. Functions of Monitor 1667
For a detailed description of the individual functions refer to chapter 8.
Each monitor receives the signal from the three sensors and calculates the speed from each
signal. For the further evaluation it selects (depending on parameter settings) the calculated
speed value derived of its own sensor or the mean value of all three speed values.
Speed calculation is done by measuring the time in between the pulses. The minimum meas-
urement time is 5 milliseconds.
To compensate for an imperfect gear, a predivider may be introduced to reduce the signal fre-
quency to 1 pulse per revolution.
5.2.2. Functions for Overspeed Protection
Overspeed protection is done by :
Monitoring of Sensors
Monitoring versus Lowspeed as protection versus incorrect mounting or fault of speed
sensors.
Monitoring versus overspeed
5.2.3. Functions for External Trip by Voters
Trip is released, if one of the voters detects an external trip condition.
Voters may be configured as 1oo2, 2oo2, 2oo3 or 3oo3. High or low Input-Level as trip condi-
tion and response time is selectable.
5.2.4. Selftest of Monitor
Selftest is performed at an interval of 2 hours. Execution of Selftest is signalized on display
with message SELF. Selftest of the monitors are inhibited versus each other.
The Selftest routine includes
CPU RAM-Test
CPU EEPROM-Test
CPU Command-Test
CPU Register-Test
Voter Signal-input-Test
If the Selftest detects a malfunction, the monitor is set to trip-status.
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