Measurement cell for liquids
View Patent ↗A cell for the measurement of resistivity and/or permittivity of a liquid, under variable ac frequency energizing, preferably includes a first set of n+1 metal plates interleaved with a second set of n places, both sets of plates preferably being of the same size and shape for the liquid filling the spaces between facing plates. The two sets of alternating plates are separately electrically interconnected. The plates are supported at their peripheries in spaced apart and insulated relationship so that, during variable ac frequency testing, current flow through the liquid is in a path perpendicular to the facing plates.
1. A measurement cell for determining the resistivity and/or permittivity of a liquid, the cell comprising:
a first and second set of electrically conductive metal plates with each plate having opposing plate faces, the first set of plates being interleaved in parallel and equally spaced plate facing relationship with the plate faces of the second set of electrically conductive metal plates, the number of plates respectively in the first set and second set, the dimensions of the plates, and the spacing between the alternating plates of the first and second sets being predetermined for the liquid to be placed or flowed between them for determination of the present value of the liquid's resistivity and/or permittivity;
a first set of electrical connectors between pairs of plates of the first set, the first set of electrical connectors being electrically insulated with a first insulation layer from interposed plates of the second set of plates;
a second set of electrical connectors between pairs of plates of the second set, the second set of electrical connectors being electrically insulated with a second insulation layer from interposed plates of the first set of plates; and
a first electrical connection to one plate of the first set of plates and a second electrical connection to one plate of the second set of plates for delivery of variable and high frequency electrical signals to the plates; the insulation of the first and second sets of electrical connectors between facing plates promoting current flow through an intervening liquid perpendicularly to the faces of each pair of facing plates.
2. A measurement cell as recited in claim 1 in which the first set of electrically conductive metal plates has one more plate than the second set of electrically conductive metal plates.
3. A measurement cell as recited in claim 1 further comprising;
first and second housing members, the interleaved sets of plates being attached to, but electrically insulated from, the first housing member, and
one of the housing members having an opening for admission of liquid to and between the interleaved sets of plates.
4. A measurement cell as recited in claim 1 further comprising:
first and second housing members, the interleaved sets of plates being attached to the first housing member with electrically non-conductive fasteners, and the interleaved sets of plates being insulated from the first housing member;
and one of the housing members having an opening for admission of liquid to and between the interleaved sets of plates and an opening for electrical leads to the first and second electrical connections.
5. A measurement cell as recited in claim 1 in which the interleaved plates of the first and second sets are of the same circular or regular polygonal peripheral shape and size, and each pair of facing plates presents faces having the same surface area for electrical conduction through an intervening liquid.
6. A measurement cell as recited in claim 5 in which plates of the first set have equally spaced holes at their periphery for electrical connections to other members of the first set of plates, and the plates of the second set have equally spaced holes at their periphery for electrical connections to other members of the second set of plates.
7. A measurement cell as recited in claim 3 in which the interleaved plates are attached to the first housing member with non-conductive, non-metallic bolts.
8. A measurement cell as recited in claim 1 in which the thickness of each metal plate is in the range of about 0.1 mm to about 3 mm.
9. A measurement cell for determining the resistivity and/or permittivity of a liquid, the cell comprising:
a first and second set of electrically conductive metal plates with each plate having opposing plate faces, the first set of plates being interleaved in parallel and equally spaced facing relationship with the plate faces of the second set of electrically conductive metal plates, the number of plates respectively in said first set and second set, the dimensions of the plates, and the spacing between the alternating plates of the first and second sets being predetermined for the liquid to be placed or flowed between them for determination of the present value of the liquid's resistivity and/or permittivity;
a first set of tubular electrically conductive metal connectors electrically connecting pairs of plates of the first set, the first set of tubular connectors having an external insulation layer for electrical insulation from interposed plates of the second set of plates;
a second set of tubular electrically conductive metal connectors electrically connecting pairs of plates of the second set, the second set of tubular connectors having an external insulation layer for electrical insulation from interposed plates of the first set of plates; and
a first electrical connection to one plate of the first set of plates and a second electrical connection to one plate of the second set of plates for delivery of variable and high frequency electrical signals to the plates; the insulation layers on the tubular connectors between facing plates promoting current flow through an intervening liquid perpendicularly to the faces of each pair of facing plates.
10. A measurement cell as recited in claim 9 in which the first set of electrically conductive metal plates has one more plate than the second set of electrically conductive metal plates.
11. A measurement cell as recited in claim 9 in which plates of the first set have equally spaced holes at their periphery for the second set of external insulation layer bearing tubular connectors, and the plates of the second set have equally spaced holes at their periphery for the first set of external insulation layer bearing tubular connectors, and the interleaved plates are attached to a first housing member with non-conductive bolts.
12. A measurement cell as recited in claim 9 in which the thickness of each metal plate is in the range of about 0.1 mm to about 3 mm.