Usage:
Detonation Analysis
This service procedure assists the field technician in performing detonation analysis on a G3600 Engine using an oscilloscope. The procedure provides instructions for setting the Fluke 97 ScopeMeter and probe signal connections. The procedure provides instruction for analyzing the detonation signals to distinguish combustion detonation and mechanically induced, or "false" detonation. Detonation sensors are mounted on each bank of the engine to monitor the engine vibrations. The sensor outputs an electrical signal of the frequency and amplitude of the mechanical vibrations. The SI Timing Control (TCM) monitors all the detonation sensors to determine the detonation level. This detonation level is used by the G3600 Engine Control to provide protection. The control will retard the ignition timing for light detonation levels and will shut down the engine for severe detonation. The detonation signal indicates the amplitude and frequency of the mechanical variations. This information is used to determine the presence and severity of the detonation. Most mechanical vibrations produce a frequency outside of the detonation range. Occasionally, some mechanically induced vibrations fall within the detonation frequency range and are interpreted as combustion detonation. This mechanically induced, or "false", detonation generates control action causing reduced performance or engine shutdowns.
NOTE: This procedure requires the use of an oscilloscope to perform the analysis. The minimum requirements for a scope in this procedure is 2 input channels and an external trigger, or 3 input channels. The Fluke 90 Series ScopeMeter meets this requirement. The Fluke 97 ScopeMeter is available through Caterpillar Parts. It is recommended that all the scope probes used be 10: 1 probes. Following are the scope settings for an oscilloscope and the tool setting for a Fluke 93, 95 or 97 ScopeMeter.
The Fluke 90 Series ScopeMeter probes and adapters needed are:
* 3 PM 8918/002 10:1 Probes
* 1 PM 9081/001 Banana/Female BNC Adapter
This procedure shows how to set the Fluke 90 Series ScopeMeters for detonation analysis. Some of the following steps apply only to the Fluke 97. If using a Fluke 93 or FLUKE 95 ScopeMeter, simply skip those steps which do not apply.
1. Press the SCOPE Key.
2. Press the LCD Key.
3. Press the PROBE CAL soft key.
4. Using the UP/DOWN Arrow keys, select the 10:1 display under Channel A. Press the ENTER soft key.
5. Press the PROBE CAL soft key.
6. Using the UP/DOWN Arrow keys, select the 10:1 display under Channel B. Press the ENTER soft key.
7. Press the PICTURE soft key.
8. Use the UP/DOWN arrow keys and the ENTER soft key to select DOT JOIN and DOTSIZE 1. These selections are active in the box before the text is LARGE.
9. Use the UP/DOWN arrow keys to select FULL. Press the ENTER soft key.
10. Press the BACK LIGHT soft key. Use of backlighting is recommended only when the scope is powered by the adapter.
11. Use the UP/Down arrow keys to adjust the screen contrast for best viewing.
12. Press the SCOPE Key.
13. Press the SINGLE/RECURRENT soft key to select RECURRENT.
14. Press the FREE RUN soft key to deselect FREE RUN.
15. Press the CAPTURE soft key to select 20 DIV.
16. Press the MIN MAX on A so it is NOT selected.
17. Press the CHAN A B key.
18. Press the A INVERT key to select A.
19. Press the B INVERT ley to select B.
20. Press the TRIGGER key.
21I. Press the EXT/A/B soft key to select EXT.
22. Press the +SLOPE/-SLOPE soft key to select -SCOPE.
23. Press the LEVEL soft key to select 2V.
24. Press the DELAY soft key to open the window.
25. Use the UP/DOWN arrow keys to select TIME DELAY. Press the ENTER soft key.
26. Press the DELAY ZERO soft key.
27. Press the CHANNEL AC/DC GND Key to select GND.
28. Press the (CHANNEL A) to move the trace to the second grid line from the bottom.
29. Press (CHANNEL A) to select a vertical scale of 10 V.
30. Press the CHANNEL AC/DC GND Key to select the DC COUPLING.
1. Press the CHANNEL AC/DC GND Key to select GND.
32. Press the (CHANNEL B) to move the trace to the second grid line from the bottom.
33. Press the (CHANNEL B) to select a vertical scale of 1 V.
34. Press the CHANNEL AC/DC GND Key to select the DC COUPLING.
35. Press the (s TIME ns) key to select a horizontal time scale of 10 ms/DIV.
Scope Probe Connections
1. Select the red and gray 10:1 scope probes and a third 10:1 scope probe. Connect the red 10:1 probe to CHANNEL A and the gray 10:1 probe to CHANNEL B. Connect the third 10:1 probe to the EXT TRIGGER IN using a dual-banana to female BNC adapter. The black, or ground, banana plug MUST be connected to the black COM socket of the EXT TRIGGER IN.
2. Connect the Channel A probe (red) to the combustion buffer signal for the appropriate engine bank.
Connect the Channel B probe (gray) to the detonation signal for the appropriate engine bank.
4. Connect the EXT TRIGGER IN probe to the Cylinder #1 Combustion Buffer Signal (S780/WH). Connect the Ground of the EXT TRIGGER IN probe to the Detonation Sensor GND.
5. With the engine running at 1000 rpm, the scope traces should resemble Figure 15.
Figure 15 - Right Detonation Signal (top trace) with Odd Combustion Buffer Signal (bottom trace) (G3612).
Time Delay Values For Cylinder Location
The Time Delay feature is used in this procedure to allow the horizontal time scale to be set small giving good resolution on the detonation sensor signal. If it is desired to view the detonation signal during combustion of a specific cylinder, the cylinder can be located by scrolling the combustion signals and knowing the cylinder firing order. This is accomplished by setting the Time Delay to ZERO, increasing (or decreasing) the Time Delay value and counting the combustion signals as they appear on the screen.
To simplify this event, Time Delay Values Tables have been developed for the G3600 engines. The tables show the Time Delay value to position the ion buffer signal for a specific cylinder on the left side of the screen, based on the horizontal time scaling. The tables are for 900 and 1000 rpm operation and should be used as general guidelines. Applications may have these values off by one Time Delay number.
Time Delay Procedure For Fluke 90 Series
This procedure shows how the set the Time Delay on the Fluke 90 series Scopemeters.
1. Press the TRIGGER key.
2. Press the DELAY soft key to open the window.
3. Use the UP/DOWN arrow keys to select TIME DELAY. Press the ENTER soft key.
4. Use the UP/DOWN arrow keys to change the time delay.
G3606 Time Delay Values
Figure 16 - Time Delay Values For Locating Combustion Buffer Feedback Signal on the left edge of the scope screen.
G3608 Time Delay Values
Figure 17 - Time Delay Values For Locating Combustion Buffer Feedback Signal on the left edge of the scope screen.
G3612 Time Delay Values
Figure 18 - Time Delay Values For Locating Combustion Buffer Feedback Signal on the left edge of the scope screen.
G3616 Time Delay Values
Figure 19 - Time Delay Values For Locating Combustion Buffer Feedback Signal on the left edge of the scope screen.
Fluke Operation
This section provides a brief description of triggering and the time delay features of the Fluke 90 Series ScopeMeters. The descriptions discuss the effects of these functions of the scope traces on the screen.
Time Delay
The Fluke 90 Series ScopeMeters offer a display feature called Time Delay. The time delay allows the user to view the signals at a defined point in time before or after the trigger occurs. This feature allows the horizontal time scale to be set small to get good resolution and still be able to view the desired waveform segment on the screen.
The time delay value indicates the number of horizontal divisions the displayed traces are delayed from the trigger event. The Fluke 90 Series can be used to show the traces anywhere from 20 divisions (2 screens) BEFORE the trigger event to 640 divisions (64 screens) AFTER the trigger event. The displayed traces are shifted an integer number of horizontal time divisions before or after the trigger. An increase in the time delay number scrolls the waveform to the left. A decrease in the time delay number scrolls the 'waveforms to the right. Figure 20 shows the same signal with a +0 and a +1 Time Delay. The location of the trigger event moves the same as the waveform as the Time Delay value is changed.
The horizontal time scaling defines the amount of time delayed from the trigger event for a given TIME DELAY value. For example, if the time scale is set at 10 mS/DIV and the TIME DELAY is at +6, the left edge of the scope screen is 60 mS after the trigger event.
Figure 20 - Effect of Time Delay on the position scope traces (Dot indicates same point on both traces): Signal with +0 Time Delay (top trace) Signal with +1 Time Delay (bottom trace)
If the time scale is set at 5 mS/DIV and the TIME DELAY is at +6, the left edge of the scope screen is 30 mS after the trigger event. This indicates that different TIME DELAY values are needed to keep the left edge of the screen at the same time after the trigger.
External Triggering
Triggering generates a synchronized and stable display from a repetitive signal. The trigger signal can be connected to any of the display inputs or the external trigger input. The trigger signal controls the position of screen data and the update (sweeping) of the scope display. When the trigger signal crosses a preselected slope and voltage level, the scope sweeps the display. After sweeping the display, the scope waits for the next trigger event before updating the screen display. External triggering uses the signal on the external trigger input. This signal, however, is not displayed on the scope screen. The trigger slope and trigger level determine the point when the trigger signal will generate the trigger event. The trigger slope indicates whether the slope of the signal should be plus (positive) or minus (negative) when the trigger event is generated (See Figure 21). The trigger level determines the voltage value at which the trigger event is generated. When the trigger signal passes the trigger level with the chosen slope, the trigger event is generated. For this procedure, the triggering is set to 2V, -SLOPE on the cylinder 1 combustion signal. The trigger event will be generated when the signal voltage passes m 2 V on a negative-going slope.
Figure 21 - The trace segments from 1 to 2 and from 5 to 6 are examples of positive slopes. The trace segment from 3 to 4 is an example of a negative slope.
External Triggering Signal Location
The external trigger signal is not displayed on the scope screen. This technique allows both display inputs to be used for other signals while using a different signal to control the display stability. The scope locates the trigger event at the left edge of the scope screen (refer to Figure 22), regardless of the horizontal time scale. This procedure uses the Cylinder 1 Combustion Buffer signal as the trigger source. This signal provides only one trigger event between all the cylinder firings. It provides a time reference point for all the cylinder firings.
Figure 22-External Trigger Signal from Cylinder 1 Combustion Buffer (top trace), Odd Buffer Signal (middle trace), and Even Buffer Signal (bottom trace).
Detonation Sensor Signal Analysis
Detonation Signals
Detonation in a cylinder will occur 5 mS to 10 mS after that cylinder fires on G3600 engines at 900 or 1000 rpm. This time is called the detonation window. The detonation signals strength will generally be different from one firing to the next.
The signal frequency will be between 2 and 4 kHz on G3600 engines. A typical signal containing detonation is displayed in Figure 23.
Detonation is measured as the largest signal strength divided by the smallest signal strength (background noise) on the detonation signal. The larger the amplitude of the signal, the more severe the detonation. Figure 23 shows an example of a cylinder detonating.
NOTE: The amplitude of the signal during detonation is much larger than the background noise.
Figure 23- Detonation Sensor output signal containing actual detonation - top trace Combustion Buffer output signal - bottom trace.
False Detonation Signals And Valve Noise
False detonation can be caused by anything else on the engine that causes vibration. However, it is typically caused by valve noise. Valve noise is generally constant from firing to firing. Its frequency is typically higher than actual detonation (10 to 12 kHz on G3600 engines).
An example of valve noise is pictured in Figure 24. Valve timing charts are included at the back of this document. They are useful in determining which valve is causing the false detonation. A formula to convert degrees to mS on the timing chart is:
mS = (167 / RPM) degrees.
Figure 24- Detonation Sensor output signal containing false detonation - top trace Combustion Buffer output signal - bottom trace.
G3606 Camshaft Events
3608 Camshaft Events
3612 Right Bank Camshaft Events
3612 Left Bank Camshaft Events
3616 Right Bank Camshaft Events
3616 Left Bank Camshaft Events
Figure 25: Cylinder Ignition System
Figure 26: Cylinder Ignition System
NOTE: There are two basic wiring arrangements used on G3600 engines. The early engines used hard conduit on the engine and the engine mounted junction box terminals were labeled from 101 to 458. The later engines used individual flesible stainless steel harnesses and the junction box terminals were labeled from 610 to 958. The later version has been upgraded over time to include the Caterpillar Ignition System (CIS), Detonation Mixing Control (DMC), and the Hydrax actuators. The harnesses and junction box termination labels have remained essentially the same with necessary hardware additions and deletions. The schematics in this publication show only the later version terminal points. For early versions reference the Electrical Schematics for termination points.
NOTE: For Generation III engines, refer to Schematic, SENR5083 (in-line) and Schematic, SENR5082 (VEE).