The result shows that liquid junction equation deduced from irreversible process is the same as reversible process thermodynamics, but the former can reflect the root of liquid junction potential, and the latter is not.

Operation principle of GY-IB type fibre-optic liquid level gauge is explained, test results by workers and technicians of the Metrological Test Institute are introduced and some defects and applied prospects of the gauge are analyzed.

The principle of reflective moving grating optical-fiber displacement sensor and the method for eliminating signal drift of system by use of compensating circuit are deseribed,and on this basis,an optical-fiber liquid level gauge for C6H6 storage tank is designed.

It discussed the application for the magnetostrictive level meter about the tanks of the service station supervisory metering system.

This paper introduces an isolated measuring technique with the external level meter.

After analyzingof the traditional floater level meter,a newmethod to improve the traditional floater levˉel meter is introduced in this paper,a electrocircuit schematic is also given.