Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2001-10-22
2003-11-18
Patidar, Jay (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S691000, C324S444000
Reexamination Certificate
active
06650127
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for measuring electric conductivity, and specifically, relates to an apparatus for measuring electric conductivity capable of measuring electric conductivity of a substance to be measured stably and accurately at all times.
BACKGROUND OF THE INVENTION
Electric conductivity is especially employed as a scale to measure a concentration of ions capable of migrating in an aqueous solution, and an apparatus for measuring electric conductivity is used to measure ion concentrations in many kinds of aqueous solutions. An apparatus for measuring electric conductivity, generally, determines an increase or a decrease of the ion concentration of an aqueous solution by measuring the resistance of the aqueous solution existing between an electric conductivity detection electrode and an electric current supply electrode connected to a power source.
Namely, a conventional apparatus for measuring electric conductivity is constituted, for example, as depicted in FIG.
9
. In an apparatus for measuring electric conductivity
101
shown in
FIG. 9
, a power source electrode
104
and a detection electrode
105
for detecting electric conductivity are disposed apart from each other relative to a fluid
103
to be measured which flows into a measurement tube
102
or which is stored in the measurement tube
102
. An AC constant voltage is applied to the power source supply electrode
104
, for example, from a power source (not shown) through an amplifier
106
. An electric current from the detection electrode
105
for detecting electric conductivity is output through an electric current amplifier
107
, and is served for measuring electric conductivity. The measurement tube
102
is composed of an insulation material (for example, a polyvinyl chloride tube) at at least above-described portion for measuring electric conductivity, but the measurement tube is usually in a substantially grounded condition (a grounded point
108
) at any position of extending portion of the tube.
In the apparatus for measuring electric conductivity
101
thus constructed, since a resistance corresponding to an electric conductivity of the fluid
103
to be measured exists between the electrodes
104
and
105
, a small electric current flowing from the power source electrode
104
to the electric conductivity detection electrode
105
via the resistance is amplified by the electric current amplifier
107
, and an output signal therefrom is determined as a value corresponding to the electric conductivity of the fluid to be measured.
However, in the apparatus for measuring electric conductivity
101
having such a constitution, since the measurement tube
102
is substantially grounded at any position of the extending portion thereof, an electric current from the electric conductivity detection electrode
105
flows into the electric current amplifier
107
, and at the same time, a smaller electric current flows into the grounded point
108
. Namely, from the electric conductivity detection electrode
105
, a current leakage occurs more or less, independently of the electric current for measuring electric conductivity.
Since the position of the grounded point
108
is not fixed, and therefore the resistance between the electrode
105
and the grounded point
108
varies, and since a small electric current flowing between them flows into the electric current amplifier
107
via the earth, the leaked electric current flowing from the-above-described electrode
105
to the grounded point
108
is a factor varying the electric current detected from the electric conductivity detection electrode
105
. Therefore, the existence of such a leaked electric current causes the measurement accuracy of the electric conductivity to be reduced. Further, the variation of the leaked electric current induces not only reduction of the measurement accuracy of the electric conductivity but also scattering of measured data of the electric conductivity.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus for measuring electric conductivity capable of measuring electric conductivity with a high accuracy by measuring electric conductivity of a substance to be measured stably at a condition with no variability at all times.
Further, it is another object to measure electric conductivity stably and accurately especially through the entire measuring period even when organic substances are contained in a substance to be measured, while making the above-described high-accuracy measurement possible.
To accomplish the above-described objects, the present invention relates to an apparatus for measuring electric conductivity comprising three electrodes brought into contact with a substance to be measured, the three electrodes including a detection electrode for detecting electric conductivity of the substance to be measured, and two AC current supply electrodes disposed on both sides of the electric conductivity detection electrode with respective distances, an AC current of the same phase being applied to the two AC current supply electrodes (a first apparatus for measuring electric conductivity). A substance to be measured is generally an aqueous solution, but a gaseous or slurry-like substance can also be measured.
In this first apparatus for measuring electric conductivity, although it is preferred that a constant voltage with the same electric potential is applied to the above-described two AC current supply electrodes, the potentials of the voltages applied to the two AC current supply electrodes may be different from each other. However, even in the latter case, the voltages applied to the respective AC current supply electrodes are to be predetermined constant voltages.
Further, an apparatus for measuring electric conductivity according to the present invention comprises three electrodes brought into contact with a substance to be measured, the three electrodes including a detection electrode for detecting electric conductivity of the substance to be measured, an AC current supply electrode disposed on one side of the electric conductivity detection electrode with a distance, and a grounded electrode disposed on the other side of the electric conductivity detection electrode with a distance (a second apparatus for measuring electric conductivity).
In this second apparatus for measuring electric conductivity, it is preferred that a constant voltage is applied to the above-described AC current supply electrode.
In the first and second apparatuses for measuring electric conductivity as described above, when organic substances and the like are contained in a substance to be measured, advantage can be taken of the photocatalytic activity of titanium oxide which decomposes organic substances or the super-hydrophilicity of titanium oxide in order to efface the influence on the measurement of electric conductivity exerted by adhesion or adsorption of organic substances to the electrode surfaces.
Namely, each of the above-described three electrodes can be constructed so that its electrode surface is formed by a titanium oxide layer provided on a surface of an electrode body made of a conductive metal. It is preferred that light irradiating means is disposed against the titanium oxide layer to exhibit a photocatalytic activity on the titanium oxide layer. For example, a construction can be employed, wherein the apparatus has a space for storing a substance to be measured defined between respective electrode surfaces of the above-described three electrodes, and light irradiating means that irradiates light onto the respective electrode surfaces.
In these apparatuses for measuring electric conductivity, it is preferred that the light irradiated by the above-described light irradiating means has a wavelength which brings about a photocatalytic activity of the titanium oxide layer. For example, light with a wavelength from about 300 to about 400 nm can be employed. As means for irradiating light, a light source composed of means fo
Nguyen Vincent Q.
Norris & McLaughlin & Marcus
Organo Corporation
Patidar Jay
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