You can calibrate it, but I don't believe you can adjust it.
Fill a cup with ice and that top it with water, let it sit a moment and insert the probe, it should be close to 32-33°
Stick the probe into boiling water, and depending upon your elevation, it should reach close to 210°.
However keep in mind....
We must bear in mind that we are dealing with consumer grade components and not scientific measuring equipment capable of detecting nano changes in temperature.
With consumer grade components there is always going to be a give and take in the design and the selection of components to keep the price affordable to the targeted consumer group. Different components, materials, and manufacturing processes will yield different products which will operate and respond differently to the same environment. Differences in materials used in the manufacturing process will also effect how temperatures are sensed and the time it takes to recognize that change and process it to the digital / analog display.
Two thermometers made by separate manufacturers can yield differences in readings even if both thermometers were calibrated on the same test equipment. Components used in the manufacturing process can cause some thermometers to take a substantial amount of time to display the correct reading. Some cheaper thermometers may take up to 3 minutes or more to register the proper temperature, while other more expensive thermometers have a very fast response time.
There will also be differences between thermometers due to their reaction times, placement in the cooker, and even how the sensor responds to the relative humidity.
There are many things that can effect temperature readings between different thermometers as indicated above, construction and placement are usually the most common causes in differences.
I, myself, also follow my Digi-Q and I don't believe I look at the Tel-Tru except in the warm-up process.
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