Non-metallic flow-through electrodeless conductivity sensor and leak detector
View Patent ↗A non metallic flow through electrodeless conductivity sensor is provided with a conduit having primary and secondary process fluid flowpaths to form a fluid loop. At least one drive and one sense toroid surround the conduit on the fluid loop. Voltage supplied to the drive toroid induces a current in the sense toroid via the fluid loop to eliminate any need for metallic electrodes in contact with the process fluid. At least one additional drive and/or sense toroid is disposed on the fluid loop to enhance induction. Optionally one or more sense coils are disposed about the conduit outside of the fluid loop to cancel out stray electrical noise. An optional conductor disposed along the conduit detects any fluid leakage through changes in resistance thereof.
1. An electrodeless conductivity sensor for determining conductivity of a process fluid, said sensor comprising:
An electrically non-conductive conduit for the flow of a process fluid, said conduit having an inlet and an outlet;
said conduit diverging downstream of the inlet into first and second legs, said legs re-converging upstream of said outlet, to form a fluid-flow loop between said inlet and said outlet;
at least one first toroid configured as a first type coil disposed about one of said first and second legs;
at least one second toroid configured as a second type coil disposed about one of said first and second legs;
at least one third toroid configured as a redundant one of said first or second type coils disposed about one of said first and second legs;
wherein coils of the same type are disposed on opposite legs, in co-planar orientation with one another;
said first type and second type coils selected from the group consisting of drive and sense coils;
at least one other sense coil disposed about said conduit outside of said fluid loop; and
a connector configured to couple said first, second and third toroids to an analyzer.
2. The sensor of claim 1 , wherein said at least one other sense coil is connected electrically out of phase with sense coils disposed on said first and second legs.
3. The sensor of claim 1 , further comprising:
a housing enclosing said first and second legs;
a plurality of toroids of first and second types surrounding each of said first and second legs;
at least one toroid of said first type disposed between toroids of said second type on each of said first and second legs;
wherein said device is configured for use in a non-metallic fluid flow system;
shields interspersed between said coils, configured to magnetically isolate said coils from one another;
a calibration loop including an electrical conductor extending through said plurality of toroids; and
a leakage detector including an other electrical conductor disposed within said housing in spaced relation from said plurality of toroids, said leakage detector connectable to resistance measuring means.
4. The sensor of claim 1 , further comprising:
an electrical conductor disposed in leakage-contacting relation to the conduit;
said conductor having a predetermined electrical resistance;
a test port having terminals coupled to opposite ends of said conductor;
said test port being couplable to resistance measuring means for measuring resistance of said conductor.
5. The sensor of claim 4 , wherein said test port comprises a calibration port.
6. The sensor of claim 4 , wherein said conductor comprises an electric wire.
7. The sensor of claim 4 , wherein said conductor is wrapped helically around the conduit.
8. The sensor of claim 4 , further comprising a resistor disposed electrically in series with said conductor.
9. The sensor of claim 4 , further comprising a resistance detector coupled to said conductor, said resistance detector configured to detect any deviation from said predetermined resistance.
10. The sensor of claim 1 , wherein said coils of the same type comprise sense coils.
11. The sensor of claim 10 , wherein coils disposed on the same leg are coaxial with one another.
12. A method for fabricating a sensor for detecting conductivity of a fluid flowing through a conduit, said method comprising:
(a) providing a non-metallic conduit for the flow of a process fluid, the conduit having an inlet and an outlet;
(b) diverging the conduit downstream of the inlet into first and second legs;
(c) re-converging the legs upstream of the outlet to form a fluid-flow loop between the inlet and the outlet;
(d) disposing at least one first toroid configured as a first type coil about one of the first and second legs;
(e) disposing at least one second toroid configured as a second type coil about one of said first and second legs;
(f) disposing at least one third toroid configured as a redundant one of the first or second type coils about one of said first and second legs, wherein coils of the same type are disposed on opposite legs, in co-planar orientation with one another;
(g) selecting the first and second type coils from the group consisting of drive and sense coils; and
(h) configuring a connector to couple the first, second and third toroids to an analyzer.