air volume fastened at the measuring site e g the wrist of the body a sensor 40 coupled to the air bag 20 for sensing pressure change inside the air bag 20 a processor 50 for processing the pressure change a display 60 for showing the measured results of contraction pressure dilation pressure and pulses in a digital form and a compression assembly 10 during compression the compression assembly 10 is adapted to gradually exert pressure on the air bag 20 towards the measuring site such as the wrist the pressure is increased inside the air bag and the pressure change is detected by the sensor 40 during decompression the compression assembly 10 is adapted to gradually return to its original state and thus the pressure on the air bag 20 is decreased the pressure change inside the air bag 20 is detected by the sensor 40 this forms a small pump less mechanical compression sphygmomanometer sphygmometer of the invention referring to fig2 a and 2b components of the inventions will be described in detail below the compression assembly 10 comprises a holed annular seat 11 including a lower central cavity for receiving the air bag 20 two opposite upper arc walls 111 around a hole thereof and two opposite slots 112 an abutment disk 12 on top of the air bag 20 a sleeve like moveable member 13 on the abutment disk 12 the moveable member 13 being moveable within a predetermined distance to and fro in the hole of the seat 11 the moveable member 13 having internal threads 131 and two opposite projections 132 on its outer surface the projections 132 being slidably fitted in the slots 112 a force exertion assembly.