Fluid Management and Measurement Systems, Devices, and Methods

A cartridge that is insertable into a medical treatment device, the cartridge comprising:

• a fluid circuit including
• fluid channels with at least one junction, the junction joining a common flow channel that leads from a water inlet to a medicament outlet;
• the junction being joined to a pumping tube segment connected to a source of medicament concentrate by a concentrate channel;
• the at least one junction being oriented in a predefined way relative to force of gravity;
• and
• the concentrate channel having a chicane that curves sharply up and sharply down before the concentrate channel meets the common flow channel;
• at least one conductivity sensor that measures conductivity of fluid in the fluid circuit, the conductivity sensor including
• a housing defining an internal fluid compartment, the housing having openings for receiving electrodes, the openings being round;
• each of said openings having inside portions closer to the internal fluid compartment and an outside portions further from an interior of the internal fluid compartment, said each of said openings having an axial section with a stepped profile such that said outside portion has a larger diameter than said inside portion;
• the inside portion having a rim extending axially at least partly into said outside portion;
• and
• said outside portion having at least three spacers extending radially inward toward an axis of a respective one of said openings;
• a drain line fluidly attached to a drain channel of the fluid circuit to convey waste fluid out of the fluid circuit, the drain line being made of an elastic material that allows the drain line to expand and contract, the waste fluid being pumped by a pump with fluctuating pumping pressure that causes the drain line to expand and to contract and thereby reduce attachment of fouling on an interior of the drain line;
• a fluid channel with a first wetted electrode and a second wetted electrode configured to directly contact a fluid flowing in the fluid channel;
• a first contact device including a first electrically insulating block wrapped by a first array of parallel electrically conductive wires that span at least a first side of the first contact device and a second side of the first contact device, wherein conductors on the first side of the first contact device are in electrical contact with the first wetted electrode;
• a second contact device including a second electrically insulating block wrapped by a second array of parallel electrically conductive wires that span at least a first side of the second contact device and a second side of the second contact device, wherein wires on the first side of the second contact device are in electrical contact with the second wetted electrode;
• a conductivity measurement circuit in electrical contact with the first wetted electrode via wires on the second side of the first contact device and in electrical contact with the second wetted electrode via wires on the second side of the second contact device;
• and
• a controller programmed to control the conductivity measurement circuit to pass a current through the fluid between the first wetted electrode and the second wetted electrode and measure a voltage difference between the first wetted electrode and the second wetted electrode as the current is passed, the controller being further programmed to determine a conductivity of the fluid based on the passed current and the measured voltage difference.