Portable pressure measuring apparatus

It is an object of the present invention to provide a portable pressure measuring apparatus to be used as an altimeter, which can be automatically switched to an optimum sampling period in accordance with a use of the apparatus before a pressure measurement at all times. The portable pressure measuring apparatus comprises a measurement means for sampling a pressure; a display to display a real-time altitude; a rate of altitude change operation means for calculating a changing rate of altitude; means for setting N-1 thresholds from a maximum threshold to a minimum threshold, and wherein pressure is measured in the Nth (minimum) sampling period when the rate of altitude change is equal to or greater than the maximum threshold, in the first (maximum) sampling period when the rate of altitude change is smaller than the minimum threshold, or in a sampling period having a length corresponding to respective thresholds when the rate of altitude change is between the maximum and minimum thresholds. N may equal 3.