210 SERIES SIGNAL MONITOR
OPERATIONS MANUAL
Eberle Design Inc. Page 3
Section 3
GENERAL CHARACTERISTICS
3.1 HARDWARE FEATURES
The 210 series Signal Monitor is a dual microprocessor based unit. Since all critical timing functions
are accomplished by the microprocessor, the quartz crystal based accuracy results in very precise and
repeatable measurements. This accuracy is maintained on functions from timing fault conditions to
implementing a unique firmware based digital sampling and filtering algorithm. This algorithm is applied
to all AC field signals to help eliminate false detection in a "noisy" AC line environment.
Input voltages are measured using a true Root Mean Squared (RMS) technique. A dedicated
microprocessor RMS-Engine controls the analog to digital (A/D) hardware which samples each AC
input voltage 32 times per cycle. The RMS-Engine then calculates the true RMS voltage value
producing accurate results which are very insensitive to changes in frequency, phase, wave shape,
and distortion.
A nonvolatile EEPROM device is utilized to retain fault status information in the event of an AC Line
power interruption. The correct fault indications will be displayed upon restoration of AC Line power.
This EEPROM device requires no battery back-up.
3.2 AC LINE BROWN-OUT DETECTION
When the AC Line voltage is below the "drop-out" level the Signal Monitor will suspend all fault
monitoring functions, close the Output relay contacts, and enable the Stop-Time output to the controller.
The AC POWER indicator on the front panel will flash at a rate of 2Hz to indicate the brown-out status.
When the AC Line voltage returns above the "restore" level the monitor will resume normal operation
and the AC POWER indicator on the front panel will remain illuminated.
3.3 NON-VOLATILE FAULT MEMORY
The Signal Monitor stores the fault and channel indicator status at the time the fault occurs into a non-
volatile EEPROM device. Should an AC Line power interruption occur while the monitor is in the fault
mode, then upon restoration of AC Line power, the Output relay and Stop-Time output will remain in
the fault mode and the correct fault and channel indicators will be displayed.
3.4 PCA (PROGRAM CARD ABSENT) INDICATION
If the Program Card is absent or not seated properly in the edge connector, the Signal Monitor will enter
the fault mode causing the Output relay contacts to close and enabling the Stop-Time output to the
controller. The PCA indicator will illuminate to indicate this condition. A manual or external Reset is
required after the Program Card is properly seated.
3.5 INTERNAL MPU WATCHDOG
The Signal Monitor generates an internal watchdog pulse from its microprocessor. This occurs at least
once per cycle. If the internal hardware does not detect a watchdog pulse within approximately 325
milliseconds, the Signal Monitor will enter the fault mode causing the Output relay contacts to close
and enabling the Stop-Time output to the controller. The DIAGNOSTIC indicator on the front panel will
illuminate to indicate a monitor hardware and/or firmware failure. This type of failure is configured as
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