Abstract: A pointer-type alarm mark structure of a micro-differential pressure gauge includes a transparent casing. The transparent casing has a shaft thereon. At least one alarm index is provided on the shaft. By adjusting the alarm index to a desired position, the user can know whether the pointer of the gauge is within a safe area.

Abstract: A pointer gauge surface structure with an indication mark. A mark member is coupled on the surface of a pressure gauge or a micro-differential pressure gauge to display a critical value for a person to read with ease. A circumferential portion of a transparent casing is provided with a slide rail for engagement and slide of the mark member. The mark member has a C-shaped cross-section to provide a tightening function relative to the slide rail.

Abstract: An alarm mark structure of a micro-differential pressure gauge includes a transparent casing. The transparent casing has at least one recess thereon. The recess is located corresponding to the range of movement of a pointer or a scale plate. At least one mark member is provided on the transparent casing. The mark member has an engaging portion. The engaging portion is inserted in the recess, such that the mark member is coupled on the transparent casing. The user can place the mark member on the recess corresponding to the numerical value on the scale plate as desired to know whether the pointer is located within a safe area.