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A cheap thermocouple for stove tinkering

This post is about the effective use of a cheap and effective thermocouple meter and K-type probe for measuring high temperatures (up to 1,300C or 2,372F). I now use it on my backpacking stove testing. It is much more accurate than the equally cheap infrared thermometer that I have used for stove temperature for many years.

A cheap thermocouple

Much better than cheap infrared thermometers.

It is easy to measures hot stove surfaces with this cheap thermocouple and is much more accurate than cheap infrared thermometers that were targeted at the same hot surface. Also, my infrared thermometers were limited to a maximum of 550C and higher temperatures can be encountered on my tiny and efficient tent stoves.

Thermocouple and infrared thermometer. The fused tip of the pair of thermocouple wires is shown above the meter. The thermocouple provides a much more accurate measurement of temperatures encountered by DIY ultralight stove jacks. — Thermocouple (left) and infrared thermometers (right). The fused tip of the pair of thermocouple wires is shown above the meter. The thermocouple provides a much more accurate measurement of temperatures encountered a hot stove surface while tinkering.

Less interference with cheap thermocouple

Unlike the the infrared thermometer, the temperatures measured by this cheap thermocouple are not affected by the poor surface emissivity of the stove metal. Also, the measurements are not affected by the radiant heat emitted from other neighbouring very hot stove surfaces.

For example, with a stove running at a temperature of about 500C, the infrared thermometers underestimated the temperature by about 100C. Conversely, if the surface being measured is in line with the emitted radiation from a much hotter stove part the measurement can be inflated by 100C. These issues are absent with the thermocouple measurement in the same situations.

Fast response time

The tiny metal junction ‘blob’ on the terminal end of the thermocouple (Shown in the photo below.) is where the strength of the voltage is generated according to its temperature. It can quickly change temperature according to the surface that it is touching. This means that the thermocouple meter reading can also quickly change according to the surface temperature.

Examples of cheap thermocouple uses

Test rig 1. I made the test rig shown below to monitor the temperature of a roll up stove pipe on a very hot backpacking tent stove. At a close location on the rig, I tested the survival (or decay) of samples of heat resistant fabric that would potentially be used to make heat resitant DIY stove jacks for tent stoves.

Thermal testing rig to determine temperatures and thermal decay in a DIY stove jack. It has a calibrated test bench with a spring clip that can hold the fabric sample at various distances from the flue pipe (5mm in the photo and the tests below). The test bench is located above the mounting ring that holds the rig to the flue pipe. The thermocouple temperature probe is just touching the flue pipe and is located below the mounting ring. — A thermal testing rig that uses the temperature meter coupled to a K-type thermocouple probe. I use it to determine temperatures and thermal decay temperature for DIY stove jack materials that contact very hot stove pipes. It has a calibrated test bench with a spring clip that can hold the fabric sample at various distances from the flue pipe (5mm in the photo below). The test bench is located above the mounting ring that holds the rig to the flue pipe. The thermocouple temperature probe is just touching the flue pipe and is located just below the mounting ring.

Test rig 2. Running a stove to do my extended testing on the operational stove pipe became a chore. Consequently I used one of my turbo candles to heat a small tube to emulate the high temperatures on a stove pipe. The little test rig shown below could run for a long time just by topping up the turbo candle wax dish with small bocks of wax.

Testing rig for exposing DIY stove jack fabrics samples to sustained high temperatures. The sample shown is silicone embedded cotton directly contacting the hot pipe (275C) of the test rig. The strip of foil on the top of the pipe was placed there to choke the airflow and raise the temperature a little. A more detailed photo of the damaged test strip is shown below. — Testing rig for exposing DIY stove jack fabrics samples to sustained high temperatures. The sample shown is silicone embedded cotton directly contacting the hot pipe (275C) of the test rig. The strip of foil on the top of the pipe was placed there to choke the airflow and raise the temperature a little.

Conclusion

The only fault that I found was that the little black sleeve near the terminal junction melted. However, it was easily repaired with my RTV silicone rubber and whipping thread. A higher temperature repair could be made with my high temperature refractory from sodium silicate.

This sweet and cheap little meter with a 1-meter long thermocouple in the package work accurately and conveniently over a massive temperature range and it would make a great addition to a stove tinkers tool kit.

Addendum

You may be wondering what sized thermocouple to get to use with the meter. It came with a very thin long one and that was good. However, I found that it is easily damaged by simply making contact with hot surfaces. Luckily I can cut off the broken tip spot weld the wire together to form a new tip.

When I purchased the meter with the long thin sensor, I ordered an additional short thick one shown in the photo below. When I finally got around to using it I knew it would be very strong, but I was surprised to find that its response time was very slow.

Two K-type thermocouples and a meter. The fine long one (left) is delicate but is great to use for quick temperature checks with a very fast response time. The thick one (right) is short and tough with a slow response time. "Together they make a comprehensive kit to go with the meter." — Two K-type thermocouples and a meter. The fine long one (left) is delicate but is great to use for quick temperature checks with a very fast response time. The thick one (right) is short and tough with a slow response time. “Together they make a comprehensive kit to go with the meter.”

This means that the big one will be good for monitoring temperature where it can be left in place while the long thin one will be best for quick spot checks. “So the short answer is to get both.”

Ultralight Backpacking Gear

A cheap thermocouple for effective stove tinkering