Eagle Tree Thermocouple Expander User Manual

Eagle Tree Sensors

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Copyright © 2003 Eagle Tree Systems, LLC


Instruction Manual for the Data Recorder Thermocouple Expander

Document Version 1.3

Model # EGT-01, TC-01

Thank you for your purchase! This instruction manual will guide you through the installation and operation of your Dual Channel Thermocouple
Expander. Please read the entire manual carefully before proceeding. If, after you read the manual, you have further questions or problems, see the
Support page on


for additional information, or email us at [email protected].

Supported Products

The Thermocouple Expander is compatible with the Eagle Tree Systems Flight Data Recorder Pro, V2, Glide, Car Data Recorders and Boat Data Recorders. It is not
compatible with our Flight Data Recorder V1.

If you have purchased a Secondary or Tertiary Thermocouple Expander, allowing up to 6 channels of Temperature to be used simultaneously, please refer to the
Secondary Expander instructions for additional information, after reading the instructions below.

Packing List

Your package should include the following: Thermocouple Expander, a printed version of this manual, and either:


one EGT probe with 24” leads, one 1/8” NPT probe compression fitting (top, bottom and ferrule), or


one CHT probe kit with rings for #8 glow plugs, and 10mm spark plugs.

Please check our website for updates to this manual which may be included if changes were made after printing.

How the Thermocouple Expander Works

The Thermocouple Expander works with your Data Recorder to measure up to two channels of thermocouple temperature. It uses a K type Thermocouple mounted in
the exhaust stream, or the cylinder head, for this purpose. Since two channels are supported, one channel can be used for EGT, and the other for Cylinder Head
Temperature. Check our website for additional probes.

Assembling and Installing the CHT Ring Probe in your Model
(Skip this section if you are not installing the CHT ring probe)

First, ensure the inner diameter of one of the two included rings is just slightly bigger than the outer
diameter of your plug. If the correct sized ring is not included in your kit, your local auto parts or
hardware store probably has one that will fit, or email us at

[email protected]


Crimp the correctly fitting ring onto the brazed end of the thermocouple wire, so that the bare wire makes
good contact with the crimp area of the ring. If clearance is tight around your plug (common with glow
plug engines), the ring can be bent at right angles with the crimp with a pair of pliers – cover the ring with
a cloth when bending so that the ring will not be scratched. See the figure at right.

Once crimped, the ring is ready to be bolted under your plug. Normally, the ring will take the place of
your plug washer, if it appears to be approximately the same thickness.

Installing the EGT Sensor Probe in your Model
(Skip this section if you are not installing our EGT probe)

Permanent installation of the EGT probe involves drilling a hole to accommodate the compression fitting, possibly tapping threads in the hole, and inserting the probe
into the fitting. If this seems daunting or impractical, it may be possible for you to temporarily insert the probe through the exhaust pipe so that the tip of the probe is
close to the manifold. In this configuration probe will get oily and dirty which may shorten its life, readings may vary, and this has not been tested. If you do this
make sure also that the probe cannot enter the manifold and get caught in the piston!!! Alternative mountings may also be possible. If you have access to a K type
thermocouple probe with a mounting arrangement that you like better, it should work fine with the expander.

The following instructions pertain to permanent mounting of the probe. WARNING: Holes are forever! Take your time to plan your installation, and if possible
practice on a scrap piece of metal! To install the EGT probe, first determine where you will drill your hole. The best place for temperature readings is usually in
the muffler/exhaust pipe, as close to the exhaust manifold as feasible. The NPT fitting and the top of the probe will stick up between ½” to 1” above the mounting
surface, so make sure you have clearance above these.

First determine how you will create the hole for the NPT fitting. If the surface you are installing the fitting into is made of very soft, thin metal (such as aluminum) you
may not need a pipe tap. If the surface is thicker or harder, a pipe tap is required. If you are not sure, try to practice installation on a throwaway version of the same
material. To install without a pipe tap, first remove the muffler from the engine to avoid metal fragment contamination. Mark the center of your hole location with