Portable hemodialysis machine and disposable cartridge with dialysis reservoir level sensor

A hemodialysis system with reservoir level sensor comprising:

• an arterial blood line for connecting to a patient's artery for collecting blood from a patient;
• a venous blood line for connecting to a patient's vein for returning blood to a patient;
• a dialyzer;
• a blood flow path connected to said arterial blood line and said venous blood line for transporting blood from a patient to said dialyzer and back to a patient;
• a reservoir for storing a dialysate solution, said reservoir including a nominal fill level below the top of said reservoir;
• a dialysate flow path, isolated from the blood flow path, for transporting a dialysate from said reservoir to said dialyzer and back to said reservoir;
• a first pump for pumping dialysate through said dialysate flow path;
• a second pump for pumping blood through said blood flow path;
• a filter connected to said dialysate flow path for removing uremic toxins from dialysate;
• a reservoir level sensor within said reservoir for measuring the level of dialysate in said reservoir, said reservoir level sensor including at least three electrodes and a ground path, said three electrodes positioned vertically in said reservoir to form an electrode array including a top electrode, a first middle electrode and a bottom electrode wherein said top electrode is positioned above said nominal fill level and said first middle electrode and said bottom electrode are positioned below said nominal fill level, and each electrode produces level sensor electrical signals reflecting the capacitance of fluid within said reservoir;
• and
• a processor connected to said reservoir level sensor for processing said level sensor electrical signals for determining the level of dialysate in said reservoir, said processor analyzing the level sensor electrical signals from said top electrode for determining a reference value for ambient capacitance coupling and said processor analyzing the level sensor electrical signals from said bottom electrode to determining a reference value for the capacitance coupling of fluid in said reservoir, said processor analyzing the level sensor signals from said first middle electrode for determining the level of dialysate in said reservoir, and said processor disables said hemodialysis system if said level sensor detects the level of dialysate in said reservoir is below a predetermined threshold.