MMU-16LE
SmartMonitor
Operations Manual
Eberle Design Inc.
Page 13
Section 3
Enhanced Features
The following enhanced features are provided on the Eberle Design MMU-16LE
SmartMonitor
®
for additional monitoring functions and to increase the reliability of the MMU-
16LE
SmartMonitor
®
monitor operation.
3.1 HARDWARE FEATURES
The MMU-16LE
SmartMonitor
®
is a dual microprocessor based unit. All monitoring
functions and features are firmware programmable which permits upgrades or
modifications by simply reprogramming the Flash memory device containing the firmware
with the upgraded version. Thus, most changes to the MMU-16LE
SmartMonitor
®
specifications may be accommodated without modifying the hardware.
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 microcontroller RMS-Engine
®
controls the analog to digital (A/D) hardware that
samples each AC input voltage at least 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. Voltage references
are temperature compensated for constant voltage levels within the operating temperature
range.
A nonvolatile EEPROM device is utilized to retain fault status information and event logs
through 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. The time
of day in the MMU-16LE
SmartMonitor
®
is stored in a battery-backed real time clock circuit.
Should this battery fail, only current time of day and date information will be lost. No
monitor configuration programming is stored under battery power.
3.2 DUAL INDICATION MONITORING
In Type 16 mode this monitoring function detects simultaneous input combinations of active
Green (Walk), Yellow, or Red (Don’t Walk) field signal inputs on the same channel. In Type
12 mode this monitoring function detects simultaneous input combinations of active Green
and Yellow, Green and Red, Yellow and Red, Walk and Yellow, or Walk and Red field
signal inputs on the same channel. When voltages on any two inputs of a channel are
sensed as active for more than the Dual Indication Fault time (Section 9), the MMU-16LE
SmartMonitor
®
will enter the fault mode, transfer the OUTPUT relay contacts to the Fault
position, and display the DUAL INDICATION status screen. When operating in the Type 16
mode with Port 1 communications enabled, Bit #68 (Spare Bit #2) of the Type #129
response frame will be set to indicate a Dual Indication fault has been detected. The MMU-
16LE
SmartMonitor
®
will remain in the fault mode until the unit is reset by the RESET
button or the EXTERNAL RESET input. When voltages on any two inputs of a channel are
sensed as active for less than the Dual Indication Fault time, the MMU-16LE
SmartMonitor
®
will not transfer the OUTPUT relay contacts to the Fault position.
Dual Indication Monitoring may anticipate and prevent a possible conflicting signal display
in the intersection in the event that a proceed signal on the current phase hangs up and is
constantly detected as active. An open or no load condition (i.e., burned-out bulb) may be
also detected as an active signal depending on the output impedance characteristics of the
load switch (i.e. load switch leakage current), and may cause a Dual Indication Fault.