Device for measuring pressure in an extracorporeal blood circuit

A method for calibrating at least one pressure or force sensor, which is configured to measure a tube internal pressure in an extracorporeal circuit tube, which is filled with fluid, wherein the at least one pressure or force sensor is integrated into or inserted in a clamping device, the method comprising:

• locating the at least one pressure or force sensor in an extracorporeal circuit of a dialysis machine;
• locating at least one dialysis fluid side force or pressure reference sensor in a dialysis fluid circuit of the dialysis machine, wherein the at least one dialysis fluid side force or pressure reference sensor is not provided in a clamping device;
• receiving a pressure or force signal from the at least one pressure or force sensor;
• receiving a dialysis tube internal pressure in the dialysis fluid circuit from the at least one dialysis fluid side force or pressure reference sensor;
• and
• calibrating the pressure or force signal from the at least one pressure or force sensor based on the received dialysis tube internal pressure in the dialysis fluid circuit;
• wherein the dialysis machine comprises a dialyzer having a semipermeable filter membrane between the extracorporeal circuit and the dialysis fluid circuit, and the at least one dialysis fluid side force or pressure reference sensor is arranged on a dialysis fluid inlet tube of the dialyzer, or on a dialysis fluid outlet tube of the dialyzer;
• wherein the method further comprises:
• providing a bypass operation in which a dialysis fluid in the dialysis fluid circuit does not flow through the dialyzer but does flow through a bypass line, and a main connection operation in which the dialysis fluid flows through the dialyzer,
• switching from the main connection operation to the bypass operation, and
• waiting for a predetermined period of time to allow a pressure equalization to occur in the dialyzer between the dialysis fluid circuit and the extracorporeal circuit across the semipermeable filter membrane of the dialyzer before calibrating the pressure or force signal.