PURPOSE: To enable the lowering of the manufacture cost, by arranging a weighing section and a display section in a separate structure while those of desired specifications are made combinable with other sections easily to be adapted to diverse specifications.

CONSTITUTION: A flow rate transmitting section 20 has a light emitting diode 21 for transmitting a optical pulse signal proportional to the flow rate and a light transmitting body 22 which transmits the optical pulse signal from the diode 21 and a display section 10 is made up of a photodiode 11 for receiving the optical pulse signal therefrom 21, a preamplifier 12, an LCD display section 13 and the like. Then, the flow rate transmitting section 20 and the display section 10 are arranged in a separate structure and linked by a optical signal through the light transmitting body 22. Thus, the flow rate transmitting section 20 can select the display section 10 of desired specifications in the service to meet diverse demands while reducing the production cost.