Abstract: The present invention relates to a measuring instrument, in particular for measuring waste gases from heating installations, comprising at least one sensor and pump arranged in a measuring channel, a microcomputer for controlling the measuring sequence and for processing the sensor signals, which is connected to an alphanumeric display device and two control elements, wherein one control element serves for paging in a selection menu, by which one menu item is displayed on the display device, and wherein the other control element serves to input in accordance with the menu item displayed.