This type of comparator has limited applications due to some of the disadvantages associated with it. But it is discussed here for the sake of the new and completely different method of expansion. In this comparator, a fine bore capillary tube is arranged so that its the lower end is placed in a chamber of relatively large cross-sectional area and containing a fluid of low viscosity. At the bottom of the camera, a diaphragm is mounted, which is deflected by pressure transmitted by the measuring plunger. Due to the deflection of the diaphragm, a the amount of liquid rises in the capillary tube. A scale is arranged on the side of the tube and the limit pointers are set with respect thereto to indicate the high and low limits of the dimension measured. These limits are obtained by master adjustment.