Measuring apparatus, purity controller, and mixing ratio controller for insulative fluid
A measuring apparatus correctly measures the purity, mixing ratio, and the like of an insulative (nonconductive) fluid such as ultrapure water flowing through a passage. The apparatus includes first to third sensors ( 19, 21, 23 ) to detect capacitance changes on the passage ( 1 a ) covered with an insulating resin pipe, a memory ( 41 ) to store reference capacitance changes, and a controller ( 35 ) to compare the detected capacitance changes with the stored reference capacitance changes, measure a purity of the insulative fluid flowing through the passage, and control the purity of the insulative fluid.
1. A measuring apparatus for an insulative fluid, comprising:
a capacitance sensor for sensing a detected capacitance change on in a passage, through which said insulative fluid is flowing, said capacitance sensor comprising:
a measuring electrode, and
a ground electrode, narrower than, spaced apart from, and paired with said measuring electrode;
with said measuring electrode and said ground electrode wound around said passage in a spiral, such that said spiral is oriented in a direction of flow of said insulative fluid;
a storage unit for storing a reference capacitance change; and
a ratio measuring unit for comparing the detected capacitance change with the reference capacitance change and for determining a ratio related to the insulative fluid flowing through the passage.
2. The measuring apparatus of claim 1 , wherein:
the ratio measuring unit measures a purity of said insulative fluid flowing through said passage.
3. The measuring apparatus of claim 2 , further comprising:
a filter, positioned upstream of said capacitance sensor, for removing foreign matter from the insulative fluid flowing through the passage;
an outlet, and a branch mouth, both arranged downstream of said filter;
an adjuster, for switching the flow of the insulative fluid to one of said outlet and said branch mouth; and
a controller, for controlling the adjuster to switch the flow of the insulative fluid to said outlet if the measured purity is within a set value, and to said branch mouth, if the measured purity is out of the set value.
4. The measuring apparatus of claim 1 , wherein:
the ratio measuring unit measures a mixing ratio of said insulative fluid flowing through said passage.
5. The measuring apparatus of claim 4 , further comprising:
a mixer, for mixing at least two kinds of insulative fluids with each other, and for pouring the mixed insulative fluids into said passage;
an outlet, and a branch mouth, both arranged downstream of the mixer;
an adjuster for switching the flow of the mixed insulative fluids to one of sid outlet and said branch mouth; and
a controller, for controlling the adjuster to switch the flow of the mixed insulative fluids to the outlet, if the measured mixing ratio is within a set value, and to the branch mouth, if the measured mixing ratio is out of the set value.