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CPU-95 ADVANCED DIGITAL IGNITION SYSTEM FOR INDUSTRIAL ENGINES
CERTIFIED
CLASS I, DIVISION 2, GROUPS C and D
CPU-95 ADVANCED DIGITAL IGNITION
SYSTEM FOR INDUSTRIAL ENGINES Microprocessor-based, crankshaftreferenced digital ignition
system for medium-sized natural gas-fueled engines Optimizes engine combustion and performance, as well as fuel
efficiency and spark plug service life Delivers full-time system, primary discharge, and secondary
discharge diagnostics (patented) Enhanced, user-friendly Display Module insures a convenient
means of adjusting system settings and access to critical ignition
operating information, including all diagnostic messages along
with datalogs, USB connectivity, and the ability to upload the
ignition programming code to the CPU-95 Ignition Module
Special CPU-95 variants for SI controller-equipped Caterpillar
3500 engines and for low BMEP, slow speed integral compressor
engines (VariSpark
TM
) Simple and cost-effective retrofit option for CPU-90, III-CPU, and
even Altronic III operators Class I, Division 2, Group C and D certified by the Canadian
Standards Association (CSA)
The Altronic CPU-95 is a 24 Vdc-powered, microprocessor-based digi-
tal ignition system designed for application to medium-range industrial
gas engines. Advantages include a full-featured user display and inter-
face, spark characteristic control, advanced timing adjustment options,
serial communications, and state-of-the-art diagnostics.
Full access to all CPU-95 operating data and control functionality is
available through an advanced, user-friendly Display Module as well
as via a PC operating the provided CPU-95 Terminal Program. Both
options display essential engine and ignition data such as RPM, timing
angle, spark energy level, and diagnostic messages, along with global
and individual cylinder timing adjustments, spark energy level control,
overspeed setpoint and double strike/extended spark (VariSpark
TM

variant) selectability. Additionally, the Enhacend Display Module
features extensive spark reference number graphing and trending.
Patented CPU-95 diagnostics and prognostics (predictive diagnostics)
supervise all ignition system-related functions. The secondary analysis
capabilities detect shorted spark plugs and leads, as well as spark
plugs that exhibit high voltage demand or are not firing at all. A display
of the relative voltage demand of each spark plug is provided, allowing
spark plug changes to be predicted and scheduled. Module and
pickup operation, timing input, and primary output functions are also
monitored for operation within preset limits.
The CPU-95 system is shop or field configurable. Using the standard
Terminal Program and the Enhanced CPU-95 Display Module, the
user has the added flexibility and convenience associated with a
USB-based connection to the system for programming. Operation
of the Enhanced Display Module also enables the user to download
and retain the ignition operating parameters (firing code, number
of monitored gear teeth, 4-20mA or RPM control loop, etc.) from
the connected Ignition Module. Should the ignition module ever
require replacement, the Enhanced Display Module can then simply
upload the correct ignition operating parameters into the new unit
without need for a laptop, the Terminal Program, or the services of an
instrumentation technician.
New Backward-Compatible Enhanced
CPU-95 Display Now Available IGNITION MODULE
IGNITION COILS
ENGINE
(1 TO 18 CYLINDERS)
1R
2R
3R
1L
2L
3L
RS-485
MODBUS
RTU
(ENHANCED DISPLAY ONLY)
MAGNETIC
PICKUPS
IGNITION
OUTPUTS
(UP TO 20)
PICKUP
SIGNALS
OPTIONAL PC OR
SCADA SYSTEM FOR
REMOTE MONITORING
AND CONTROL
HALL-EFFECT
CYCLE SENSOR
(4-CYCLE ONLY)
CAMSHAFT-
MOUNTED
MAGNET
(4-CYCLE ONLY)
USB (ENHANCED
DISPLAY ONLY)
RS-485
24 VDC
POWER
4-20mA TIMING
CONTROL INPUT
DISPLAY MODULE
System Components
Each CPU-95 system is composed of the Ignition Module, two
magnetic pickups and cables, a primary wiring harness, and
an ignition coil for each spark plug. A system Display Module,
typically used (but not required), is also available. A Hall-effect
pickup and cable, as well as a magnet turning at camshaft-
speed are utilized on 4-cycle applications only.

System Operation
The diagram above illustrates how these components are
integrated into an operating system. To insure that the spark
is delivered at precisely the right moment for each engine
cylinder on each revolution, the CPU-95 determines the posi-
tion of the engine crankshaft through the use of a magnetic
pickup sensing starting ring gear teeth or holes drilled into
the flywheel allowing precise determination of crankshaft
angular position in real time. Matching that to a pre-pro-
grammed system memory, the CPU-95 system can achieve
extremely high ignition timing accuracy. A second, flywheel-
based magnetic pickup, is used to generate a once per
crankshaft revolution reset pulse. Four-cycle applica-
tions also utilize a Hall-effect pickup sensing a magnet
turning at camshaft speed to determine the compression
cycle of the engine.
The CPU-95 Ignition Module is typically mounted on or
near the engine. This 24-VDC-powered module accepts
and processes the input data derived from the engine-
based pickups and any control data being brought into
the system through the CPU-95 Display Module, Terminal
Program, or engine management system (see review
to left). This control information, including timing adjust-
ments, spark energy control, and multi-strike or extended
duration (VariSpark) directly influences both the moment
at which the spark is delivered and the important charac-
teristics of that spark. A 4-20mA timing control input from
a supervisory control system or an instrument monitor-
ing a specific operating parameter (such as fuel manifold
pressure or air manifold temperature) is also available as
an additional means of optimizing performance.
System Overview System Features
Comprehensive Display Capability
Two-line, alphanumeric, backlit display indi-
cates the following operating parameters:
System status and mode
Ignition energy level, mode and number of strikes
Global timing (in degrees BTDC)
Individual cylinder timing
Value of timing control signal (4-20mA)
Relative spark plug voltage indication by cylinder
Engine speed (in RPM)
Engine overspeed setpoint
Diagnostic messages
Spark Characteristic Control
For improved engine performance and com-
bustion stability, ignition of lean mixtures for
emissions reduction or improved starting and
loading characteristics:
Double-striking mode (selectable ON/OFF)
VariSpark mode (selectable ON/OFF
VariSpark model only)
Manual or automatic ignition energy level
control (3 levels)
Ignition Timing Control Modes
Local and remote control of ignition timing
(global or individual cylinder) allows engine
starting and running performance to be opti-
mized.
One-step timing change vs. input signal or RPM
Keypad control via display module
Terminal program control via serial port
Analog 4 to 20 mA control
Timing control vs. RPM
Serial Communications to PC or
Engine Management System
All system features, display data, and configu-
ration inputs are accessible via an integral
RS-485 serial port. A new, dual port display
module enables simultaneous use of both the
system display, and a supervisory control sys-
tem utilizing ModBus RTU.
System Configuration
Engine-specific configuration parameters are
contained in a plug-in memory (EEPROM)
which can be moved to a spare unit if neces-
sary. The memory can be configured in the
shop or on location using a personal computer
connected to the serial port.
Engine firing pattern
Number of gear teeth or flywheel holes sensed
Timing control vs. 4-20mA and RPM
Diagnostics, Testing, Shutdown Capabilities
Advanced and patented diagnostics, self-test,
and alarm/shutdown capabilities are included
with each CPU-95 system:
Primary and secondary discharge faults
identified as to cylinder (see inset at right)
Status of system pickups
Verification of number of teeth/holes
Test firing of selected cylinder(s) (optional)
Overspeed condition
Alarm and shutdown outputs
Retrofit Existing Altronic III, III-CPU,
CPU-90 Systems
Retaining many system components makes
conversion to the CPU-95 simple and cost-effective.
Display Options
The CPU-95 Ignition Module is designed to operate in conjunction with
a variety of display/control options through its integral RS-485 commu-
nication port. This facilitates the application of CPU-95 systems to gas
engines operating at varying stages of automation and sophistication.
Display Module
The CPU-95 Display Module, typically mounted
in an engine control panel or other enclosure
off the engine, offers users comprehensive
display and control functionality. It features
an alphanumeric display, in conjunction with a
front-accessible, sealed membrane keypad and
gives users access to critical operating, setup,
and diagnostic information. Enhanced Display
Module is optional (see discussion at right).
Terminal Progr