is 10 measured step s 39 then the setting of the command is performed at the key entry unit 18 step s 40 in this case also in the same manner as the steps s 25 to s 27 when the up key 20 a is manipulated the value of the command is increased step s 41 while when the down key 20 b is manipulated the value of the command is decreased step s 42 accordingly the rotary shaft 30 is rotated corresponding to the change of the value of the command and the flow rate d of the fluid which flows through the valve 32 is changed step s 38 then the command b is changed such that the flow rate d takes the value proportional to the input signal a as shown in a straight line 76 in fig8 and the set key 20 c is manipulated so as to store this value of the command b n into the memory unit 56 step s 43 subsequently it is determined whether the value n set to the register is the value n max or not step s 44 since the value n is not the value n max in this case the value of the register is increased by 1 so that the value n is set to 2 step s 45 subsequently the operation returns to the step s 37 and the input signal a n which corresponds to the value n of the register namely the input signal a2 in this case is inputted to the.