What is Temperature Uncertainty
All measurements are subject to some uncertainty. For example, if you use a ruler to measure a distance of 14.5 cm, you cannot be sure that the distance is exactly 14.5 cm because your eyes and the ruler cannot tell the difference between 14.5 and 14.499995. A more sensitive instrument will give you less uncertainty, but there will always be some uncertainty in your measurement. The same goes for temperature.
• Touch the thermometer to the object whose temperature you want to measure.
If your thermometer is digital, pay attention to the reading. If the reading fluctuates, the uncertainty is equal to the magnitude of the fluctuation. For example, suppose the temperature reading on a digital thermometer hovers back and forth between 20.12 and 20.18°C. Your uncertainty is 0.06 °C.
If the thermometer remains steady and constant, go to the last digit of the reading. In such cases, the last digit will be considered indeterminate. For example, if your thermometer reads 36.12 °C, the uncertainty will be 0.01 °C because the last digit (the 2 in 36.12) sets the limit of your accuracy.
If you’re using a traditional thermometer, watch out for mercury or alcohol in the column. If possible, read the temperature to the nearest 0.1 °C – if not, try reading it to the nearest 0.5 °C. Either way, your uncertainty will be equal to your precision limit. For example, if you can only estimate the temperature to the nearest 0.1 °C, then your uncertainty is 0.1. If you only hurt estimates to the nearest 0.5, and so on.