An automatic system for measuring micro flow rate of liquid is presented. A computer mouse device was modified as an optical encoder for this purpose. All the sensing and electrical signal are processed by the mouse device. A very simple structure has been realized using the PS/2 mouse interface to get electric power and transfer the data to computer directly. The data treatment was programmed using Microsoft Visual Basic. This system shows a useful solution for micropump evaluation. Because this device works in digital On/Off principle, there is no lower limit for measurable range of flow rate and bidirectional measurement is also possible. The full measurable range is up to 115 /spl mu/l/min, at which the measurement precision is assured within /spl plusmn/2%. The resolution is dependent on the sampling speed of the computer (0.05 second). The device is not affected by the change of temperature or thermal capacity of fluids. It is an alternate as a tool to calibrate mass flow meter. Automatic parallel measurements in multi-channel are also possible.
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