Thermal flow meter

A flow rate sensor for sensing the flow rate of a fluid passing through a channel of a disposable manifold that is installed in a dialysis machine, comprising:

• An excitation probe having a body and a contact surface, wherein said excitation probe is located within said disposable manifold, wherein at least part of said excitation probe is physically positioned within said channel, and wherein the excitation probe generates a wave within said fluid in response to a first signal;
• A receiver probe having a body and a contact surface, wherein said receiver probe is located within said disposable manifold, wherein at least part of said receiver probe is physically positioned within said channel, and wherein said receiver probe senses a wave within said fluid;
• A heat source in said dialysis machine, wherein said heat source comprises a contact surface that is on a surface of said dialysis machine and is configured to engage with said excitation probe only when said portion of said dialysis machine is placed in physical contact with said disposable manifold;
• and
• A temperature sensor in said dialysis machine, wherein said temperature sensor comprises a contact surface that is on the surface of the portion of said dialysis machine, wherein said temperature sensor is configured to thermally engage with said receiver probe only when said portion of said dialysis machine is placed in physical contact with said disposable manifold, and wherein said temperature sensor generates a second signal.