All Blogs EGT Probe

The most notable difference between a thermocouple and an RTD (Resistance Temperature Detector) is the principle of operation. A thermocouple operates on the principle that two dissimilar metals joined together will produce a voltage related to a temperature difference. An RTD, operates on the principle that electrical resistance of certain metals changes in a predictable way depending on the rise or fall in temperature.

A customer recently purchased a new 3/16" Diesel & Bio-Fuel EGT probe from us, and after installing, found it was reading about 200F lower than their old probe.  After some emails back and forth we learned that the probe they replaced was also an enclosed tip probe but was smaller in diameter and about 50% shorter than the new probe.

Not inserting the EGT Probe tip completely into the center of the exhaust stream can result in low EGT temperature readings.

After installing our Marine Series EGT Digital Pyrometer Kit on their boat a customer called to ask why their EGT temperature readings were hundreds of degrees below expected. They were reading 157 °F@ idle, 184 °F @ 1000 rpm, and 213 °F @ 1500 rpm.

We recently created an NPT Compression Fitting Technical Guide.

The guide includes detailed information about the compression fitting dimensions, threads, ratings, assembly, and installation.

You can download it from here:

Marine Engines are critical components to maritime vessel operations either for propulsion, power generation or auxiliary machinery operation. Typically these systems employ diesel engine management systems that rely on sensor inputs to manage operating performance for efficiency and shutdown to prevent catastrophic engine failures.

I have a Mercedes turbo diesel and my idea is to monitor both the exhaust temperature and the temperature of the incoming air in the intake manifold. Is there enough range on your EGT probe to measure also lower temperatures (min. about -10 Celsius)?

The easist way to identify your CHT sensor thermocouple type (or most any thermocouple for that matter) is to look at the colors of the wire jacket insulation.

Type K
Yellow (+ leg)
Red (- leg)

Type J
White (+ leg)
Red (- leg)

But in some cases, the wire jacket insulation has been stripped away or is frayed & the colors are not obvious.
In this instance, you can use a magnet to help determine the thermocouple type.

There are many factors to the "accuracy" any sensor. The most important aspect is what accuracy is needed to satisfy the actual requirement and the evaluation process to get there. Typically if your EGT sensor is within 1%  to 5% of the actual temperature will satisfy most requirements. The major factors are probe accuracy and the indicator accuracy, taking these both in account will give you a close estimate of the actual temperature you are reading from the indicator(s).

Q: I am looking for several EGT sensors for tuning a normally aspirated 2.3 L gasoline engine with 1 5/8” exhaust tubing. Are there any available guidelines about what size EGT probe is recommended, 1/8”, 3/16” or 1/4”?

A: We find that, for most applications, the 3/16” EGT probe is suitable.  It’s our most popular probe, with nearly 75% of the probes we sell being this diameter.