107 results about "Ohm's law" patented technology

The present invention provides methods and apparatus for determining a dynamical property of the systemic or pulmonary arterial tree using long time scale information, i.e., information obtained from measurements over time scales greater than a single cardiac cycle. In one aspect, the invention provides a method and apparatus for monitoring cardiac output (CO) from a single blood pressure signal measurement obtained at any site in the systemic or pulmonary arterial tree or from any related measurement including, for example, fingertip photoplethysmography.According to the method the time constant of the arterial tree, defined to be the product of the total peripheral resistance (TPR) and the nearly constant arterial compliance, is determined by analyzing the long time scale variations (greater than a single cardiac cycle) in any of these blood pressure signals. Then, according to Ohm's law, a value proportional to CO may be determined from the ratio of the blood pressure signal to the estimated time constant. The proportional CO values derived from this method may be calibrated to absolute CO, if desired, with a single, absolute measure of CO (e.g., thermodilution). The present invention may be applied to invasive radial arterial blood pressure or pulmonary arterial blood pressure signals which are routinely measured in intensive care units and surgical suites or to noninvasively measured peripheral arterial blood pressure signals or related noninvasively measured signals in order to facilitate the clinical monitoring of CO as well as TPR.

A combiner that calculates energy produced by each panel feed during the daytime, and calculates a resistance value needed to calculate the energy by injecting a known current into each panel feed at nighttime and measuring the resulting voltage across a resistive element in each panel feed. A voltage tap across the protection device in each panel feed allows logic and control circuitry to measure the voltage across each protection device. At nighttime, a known current is injected into each panel feed and the voltage across each protection device is measured. Plugging the current and voltage into Ohm's Law, a resistance of each protection device is calculated, then that resistance value is used during the daytime to calculate energy produced by each string in real time and to monitor each string's performance. When an individual string's performance wanes, an alarm is indicated to help the operator troubleshoot which individual panel(s) within the string is responsible for that string's underperformance.