text: A common mistake when calculating the index error of these devices occurs when converting between the Kew and Fortin types.
full_question: A common mistake when calculating the index error of these devices occurs when converting between the Kew and Fortin types. Printed sheets explaining how to interpret readings from these devices were included on the reverse of the ones named for HMS Beagle captain Admiral FitzRoy. Airplanes usually make use of the smaller aneroid type of these devices. One often factors in the temperature and gravity when using a mercury-based device of this type. Some of these devices offer readings in millibars. For 10 points, name this type of device which measures the pressure of the atmosphere.
first_sentence: A common mistake when calculating the index error of these devices occurs when converting between the Kew and Fortin types.