Measuring temperature of diced chicken I purchased an analogue instant-read meat thermometer (link to the precise product).

I fried some diced chicken in a little lime juice and olive oil in a frying pan on a medium-high heat. I periodically measured the temperature by sticking the end into the centre of a piece of chicken.

At no point (even after 10+ mins) could I get the thermometer to read above 40 C (whereas it should reach at least 68 C), even increasing the heat had little effect. I ended up overcooking the chicken in an attempt to increase the temperature measurement.

I stuck the thermometer in boiling water to check it was working properly and it indeed gave a reasonable measurement.

Question: Can anyone explain what I may have been doing wrong?

Is there a knack to performing the measurements? Are the thermometers intended for measuring large pieces of meat only? Or did I likely fail to heat the chicken correctly? In which case, what should I do to get the temperature up? Like I said, even on a high heat still wouldn't push the temperature above 40 C.
Here's a technical explanation as to what happened. An analog thermometer works on the principle that different metals expand more than others when heated. There is a bi-metallic strip in the pen part of the thermometer in the shape of a spiral coil, which is attached to a piece of metal which turns the pointer. The outside of the strip expands more when heated and contracts more when cooled than the inside, so when heated the coil will twist the pointer in the direction of the spiral. 



As the pen part of the thermometer heats up the coil changes shape and adjusts the temperature. As you can see from the picture the sensitive area of the thermometer is the length of the coil, that entire area needs to be heated up to the same temperature in order to read correctly. In your case what you were trying to measure was too small and had to compete against the ambient temperature of the air. 

Digital thermometers work on a different principle entirely, using an electrical device called a thermocouple on the end of a probe. 


The bead at the end is the actual sensor, and as it is much smaller it is therefore more precise than a bi-metal coil. However, I still think one of these wouldn't work because again the size of the meat isn't enough to heat the probe's sheath enough for the sensor to read correctly.