WARNING about installing EGT probes

The minimum radius of bends in wire groups or bundles must not be less than 10 times the outside diameter of the largest wire or cable, except that at the terminal strips where wires break out at terminations or re-verse direction in a bundle. Where the wire is suitably supported, the radius may be 3 times the diameter of the wire or cable. Where it is not practical to install wiring or cables within the radius requirements, the bend should be en-closed in insulating tubing. The radius for thermocouple wire is 20 times the diameter.

The first thing to troubleshoot is do I have a good ground?

How is my ground strap?

Example of good ground strap

Example of a bad ground strap

If your ground strap is similar to the top picture enjoy your new G Series Engine Monitor.

If your ground strap is similar to the bottom picture you will be talking to Insight tech support.

If you are having erratic fuel flow or any other function other than EGT, CHT or TIT’s please take time to inspect the wiring in the D sub connector on back of G Series monitor.

Example of good job

 Come on, smarten up!!!

If upgrading from a previous GEM be sure to install the supplied “snap-on” ferrite suppressor over the unshielded wires.

Do NOT ground the G Series monitor or any other instrument to a painted panel – Run a separate ground wire to a CLEAN airframe ground.

NOTE: For GPS interface you must have software Version UPDATE: 185 in G3

To view and graph your G3 logged vibration data this Excel file will help.

Click on Excel file and follow instructions.

Insight G3 Vibration Log Graph Tool (V1.14) - Click Here

Trouble-shooting G3

The following is a compilation of the common symptoms and causes of problems which may be experienced with the GEM Systems. Close examination of these symptoms should assist in identifying the cause of the problem.

Symptom: The G3 series Display does not illuminate.
Cause: No ground return at Pin 15, of the edge connector either from the engine case or from airframe ground

Symptom: The G3 series Display does not illuminate.
Cause: Voltage is missing at Pin S, of the edge connector from the circuit breaker or bus.

Symptom: One or more columns will not illuminate.
Cause: Try recycling power to check the Display. If all columns do not illuminate, the GEM series display has been damaged or is inoperative.

Symptom: One or more columns will not illuminate. Cause: Check the probe connections, the display will blank columns with poor EGT and CHT connections. Columns 5 and 6 shouldn’t illuminate on a 4 cylinder engine. Turn top knob on G3 to the probe analysis page to check probe Integrity. For 8 foot harness on probe analysis page resistance should be 8 - 3 EGT / 1 - 6 CHT For 24 foot harness on probe analysis page resistance should be 26 - 10 EGT / 4 - 18 CHT

Symptom: No EGT in one or more columns.
Cause: Errors in harness wiring. Visually check probe connections and polarity. Check for probe continuity at the display connector. The resistance of the lead wire is approximately 1 ohm per foot. Take extreme care to not damage the connector terminals with the meter probes. Turn top knob on G3 to the probe analysis page to check probe Integrity.

Symptom: No CHT in one or more columns.
Cause: Errors in harness wiring. Visually check probe connections and polarity. Check for probe continuity at the display connector. The resistance of the lead wire is approximately 1 ohm per foot. Take extreme care to not damage the connector terminals with the meter probes. Turn top knob on G3 to the probe analysis page to check probe Integrity.

Symptom: No CHT in one or more columns.
Cause: Faulty probe. Turn top knob on G3 to the probe analysis page to check probe Integrity. For 8 foot harness on probe analysis page resistance should be 8 - 3 EGT / 1 - 6 CHT For 24 foot harness on probe analysis page resistance should be 26 - 10 EGT / 4 - 18 CHT

Symptom: No CHT in one or more columns.
Cause: Faulty probe. Turn top knob on G3 to the probe analysis page to check probe Integrity. For 8 foot harness on probe analysis page resistance should be 8 - 3 EGT / 1 - 6 CHT For 24 foot harness on probe analysis page resistance should be 26 - 10 EGT / 4 - 18 CHT

Symptom: Display goes out during engine start.
Cause: Voltage transient or over voltage condition. The display should not be turned on during engine start. An Avionics Master or separate power switch should be installed to apply power to the display.

Symptom: Display is unstable.
Cause: Noisy or defective magneto or ignition harness. Check operation on left and right magnetos. The temperature should rise slowly and may stabilize slightly or completely on one or the other magneto. Single magneto operation will pinpoint the problem to one ignition harness, unless both are faulty. Verify that the probe wires and GEM series system harness are isolated from the ignition harness. If necessary, repair or replace the faulty ignition harness to eliminate ignition related interference.

Symptom: Display is unstable.
Cause: Magneto ungrounded or defective P-lead. Check ignition harness for proper shielding, grounding, and loose spark plug caps. Check magnetos for proper grounding or evidence of arcing. Disconnect magneto P-leads one at a time. If this eliminates or reduces the problem, replace the P-lead. A faulty ignition harness will typically cause all EGT readings to "dance" up and down. The GEM series Display will detect this type of fault long before standard test methods, thus eliminating the potential of more serious problems.

Symptom: Display is unstable.
Cause: Noisy or defective alternator, defective generator or faulty ground connection. Try operation with alternator or generator off.

Symptom: Display is affected by radio transmissions.
Cause: Proximity of probe and/or display unit to the radio power wiring and away from radios and antenna coax. Check radio rack connector for missing 50 ohm matching device. The 50 ohm matching device is a thick washer-like component part that is installed underneath the connector end cap. The end cap will have to be unsoldered to check for the matching device. This seemingly unimportant component is supplied with all connectors and is required for proper operation of the connector. Utilize shielded-twisted pair for power leads.

Symptom: EGT indication is not uniform.
Cause: The EGT indication for a fuel-injected engine will typically vary a bar or two from perfectly uniform when leaned for cruise. Clean the fuel injection nozzles. Non-uniformity is normal in carbureted engines. All cylinders are measured by the same circuitry. It is almost impossible to not have identical response on all channels of the GEM series.

Symptom: A sudden or gradual reduction in the EGT indication can be symptomatic of several engine faults.
Cause: Exhaust leaks above the probe and poor compression due to bad rings, valves or valve guides. If a probe substitution does not reveal a faulty probe, check for mechanical faults in the engine. Consult the GEM series Pilot’s Guide for more detailed engine diagnostic information.

Symptom: All EGT readings too high.
Cause: Readjust the EGT "BAR HEIGHT" on the Display. Use DVM a (digital voltmeter) to measure the difference between the Display ground and engine block ground with the engine running and the battery charging. If the difference is greater than or 2 V DC with the alternator charging, remove the G3 series ground and provide an extension directly to the engine block. If this solution fixes the problem, a ground fault exists between the engine and air-frame which should be remedied.

Symptom: Display indicates full scale or blanks out.
Cause: This can be symptomatic of an intermittent ground fault between engine and air-frame. See "All EGT readings too high".

Vibration Analysis on the G3

Tech Note

Introduction:

Following the update of the G3 Graphic Engine Monitor to V1.78 or higher, the Vibration Analysis screen will now appear among the supplementary screens when the PG knob is turned. In order for the vibration analysis to function your G3 must be equipped with a vibration sensor and a connection to the magneto for RPM measurement.  If your instrument was purchased prior to September 2011, Insight will be sending you a vibration sensor shortly.  Instruments purchased after this date will ship with the sensor included with the main kit.

Installing the Vibration Sensor:

IMPORTANT NOTE:

Airplanes equipped with 24V electrical systems require a 750 ohm 1/2W resistor installed in line with the power lead of the vibration sensor. This lead may be identified as the orange/white lead that is connected to the aircraft voltage buss. Do not install the vibration sensor in 24V airplane without this critical component.

The sensor is connected to the G3 using a 7-pin connector included with your kit. Refer to the G3 Installation Manual, drawing number 610C-315 Option A for wiring connections. Do not forget the 750 ohm 1/2W resistor, which is not shown on earlier copies of the drawing.

After the electrical connections to the sensor are made, then sensor may be tested simply by powering up the G3 and vibration sensor. It is not necessary to start the engine to perform this test. The sensor LED should flash briefly and rapidly when power is first applied until communication is established with the G3, at which time the LED blinks more slowly (approximately once per second). When the LED indicates communications with the G3 has been established select the Vibration Analysis screen by turning the PG knob. While observing the vibration graph disregard the “RPM Required” message and rap lightly on the vibration sensor with the handle of a screw driver. The graph should register the impacts.

The sensor should then be firmly mounted directly to the engine case, preferably oriented in such a manner as to match the small airplane symbol engraved on the sensor body. In some rare cases it may not be possible to mount it in this manner, and the installer will have to fabricate an appropriate bracket or else be prepared to compensate for the change in orientation when viewing the vibration data. A representative installation is shown in the following figure:

 Location of vibration sensor

Using the Vibration Analysis Screen on the G3:

The sensor detects vibration in all 3 axis (fore-aft labeled x, up-down labeled z, and left-right labeled y) which are presented on different sub-screens. The vibration analysis only functions when the engine is running and a valid rpm signal is detected.

 In regards to the vibration graph, the vertical axis represents the amount of vibration energy and the horizontal axis represents the frequency spectrum expressed as multiples of crankshaft rpm. When the engine is running, the screen will come alive with a waveform that represents the engine motion, presented in a spectral format with the crankshaft energies appearing at the 1x mark on the bottom scale. Propeller vibration will likewise be synchronous with the crankshaft vibration. Other sources of vibration will tend to produce energies at other frequencies. For example, camshaft vibration tends to accumulate at the .5x mark, since the cam turns at 1/2 the rate of the crankshaft. Magneto vibration will appear at 1.5x mark in a 6-cylinder engine. Alternator vibration may appear somewhere around 3x or 4x, depending on the ratio it is driven at.

A gear-driven alternator may appear in a different axis than the crankshaft does  if it is mounted at 90deg to the engine, although ANY source of vibration will show some energy in all three axis. Complex vibration as generated by reciprocating machinery will also produce a great number of harmonic spikes, which at first glance may seem confusing. The user should experiment with running the engine at different power settings under different conditions to get a feel for what is a "normal" spectrum for their particular engine. 

A simplified case of vibration is shown in the following figure:

In the example shown above the main source of energy is at the 1x mark, and represents the crankshaft rpm. The smaller spikes at the 0.5x mark and the 1.5x point are probably created by the camshaft and the magneto, respectively. The user should be aware that a multi-cylinder reciprocating engine produces energies at a multitude of frequencies and directions, which reinforce and subtract from each other to create a very complex waveform. It is the responsibility of the user to gain familiarity with a waveform that is typical of their particular engine, so that unusual readings can be detected and interpreted.

The user may examine the various sub-screens by pushing the top button (PG). There are presently six screens to examine, each of the primary axis (X,Y,and Z) and an averaged version of each (denoted Ax, Ay, and Az). The averaged version will be much "cleaner" and contain less noise than the raw measurement and is the preferred screen to examine for each axis. The bottom knob (SEL) controls a cursor which will "snap" to nearby vibration spikes to make it easy to examine them closer. The bottom knob can also be pushed to enter a zoom mode. When in zoom mode, turning the bottom knob will allow you to scroll through the waveform. Continue to press the bottom knob to set progressively higher zoom modes. A further press when at maximum zoom will return you to the overall view.

Pressing and holding the PG button will trigger the G3 to save the present vibration waveform for future reference. The waveform will be stored as a series of hexadecimal bytes in the current log file. Insight can provide a tool for examining this waveform using Excel or a similar spreadsheet. The tool is presently in the earliest functional stages of development, and will be improved over time.

It is expected that the vibration functions will be used as a "condition-monitoring tool". Since every engine and accessory combination is different, everyone's vibration spectrum will look unique and it would be impossible to generalize the interpretation of the spectrum. The user will come to recognize what a "normal" spectrum looks like for their engine and by periodically scanning the vibration screen can recognize when potential trouble is developing. When a new spike appears or an existing spike begins to show signs of higher than normal amplitude further investigation is warranted. The source of the spike can be interpreted by noting its primary axis and its frequency relative to crankshaft RPM as discussed above. By periodically saving their vibration data as discussed above, the user can create a database of reference waveforms for future comparison.

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