Modular reservoir assembly for a hemodialysis and hemofiltration system

1. A reservoir module for use in a portable dialysis system comprising: a reservoir housing having four sides, a base, and a top, wherein said four sides, base surface, and top surface define an internal space;

a reservoir pan located within said internal space for supporting a volume of dialysate, wherein said reservoir pan is further configured as a scale to measure a weight of the volume of dialysate; and

a conductivity sensor in built into a bottom surface of said reservoir pan and positioned below said volume of dialysate, wherein said conductivity sensor comprises a flat coil having a plurality of turns, a capacitor in electrical communication with said flat coil, said flat coil and capacitor defining a circuit, and an energy source in electrical communication with said circuit, wherein said flat coil generates a magnetic field and wherein said circuit is adapted to detect changes in said magnetic field.

2. The reservoir module of claim 1 wherein the energy source is configured to maintain a substantially constant voltage across said capacitor.

3. The reservoir module of claim 1 wherein said conductivity sensor is configured to outputs a value indicative of a sodium concentration in said dialysate based on an energy input required from said energy source to maintain the constant voltage across the capacitor.

4. The reservoir module of claim 1 wherein the coil has a radius between 2 and 6 inches.

5. The reservoir module of claim 1 wherein a heater is in thermal contact with said reservoir pan.

6. The reservoir module of claim 5 wherein the heater is integrated into said reservoir pan.

7. The reservoir module of claim 1 wherein said scale comprises a plurality of flex points physically attached to said top.

8. The reservoir module of claim 1 further comprising a container wherein the container is a disposable bag.

9. The reservoir module of claim 1 wherein said reservoir housing further comprises a gutter.

10. The reservoir module of claim 9 wherein the gutter is in fluid communication with a wetness sensor.

11. The reservoir module of claim 1 wherein a door providing internal access to said reservoir housing is integrated into one of said four sides.

12. A module for use in an extracorporeal system comprising:

a housing having four sides, a base, and a top, wherein said four sides, base surface, and top surface define an internal space;

a container positioned within said internal space and adapted to contain a liquid, wherein said container comprises a bottom surface and is configured to weigh said liquid; and

a conductivity sensor located in a bottom surface of said container, wherein said conductivity sensor comprises a flat coil having a plurality of turns, a capacitor in electrical communication with said flat coil, said flat coil and capacitor defining a circuit, and an energy source in electrical communication with said circuit, wherein said flat coil generates a magnetic field, wherein said flat coil is positioned below said liquid such that at least a portion of the liquid lies within said magnetic field, and wherein said circuit is adapted to detect changes in said magnetic field.

13. The module of claim 12 wherein said conductivity sensor is configured to output a value indicative of an ion concentration in said liquid based on an energy input required from said energy source to maintain a constant voltage across the capacitor.

14. The module of claim 13 wherein said ion is a sodium ion.

15. The module of claim 12 wherein the flat coil has a radius between 2 and 6 inches.

16. The module of claim 12 wherein the energy source is adapted to maintain a substantially constant voltage across said capacitor.

17. The module of claim 12 wherein the conductivity sensor further comprises an oscillator.

18. The module of claim 12 wherein the conductivity sensor further comprises automatic gain control.