A device comprising a sampling probe configured to sample a fluid, and an ultrasound sensor coupled to the sampling probe and configured to transmit and receive ultrasound energy, the ultrasound sensor further configured to generate a first signal by receiving ultrasound energy reflected from a fluid surface of the fluid is provided. A light to voltage converter circuit generates a DC voltage proportional to detected incident light. The application may run on the operating system. In one embodiment, a procedure for a lead or catheter placement is described in which a combination deflection mechanism, balloon catheter, and sheath assembly access the coronary sinus ostium via a superior approach. The present invention is described in greater detail hereinafter in conjunction with the following specific embodiments.