Abstract: The specification discloses an apparatus and method for measuring the velocity of a moving mass. A noncontact heat source, such as a high powered infrared laser, intermittently heats and creates a hot spot on the moving mass in a first position in space. The heat source remains out of contact with a moving mass while heating it. A noncontact detector, such as an infrared heat detector, detects the hot spot at a second position in space and remains spaced apart from second position while detecting the hot spot. The second position is spaced a predetermined distance from the first position and, with respect to the first position, is disposed in the direction of the travel of the moving mass. The noncontact detector generates a detection signal when the hot spot is in the second position, and a monitor is responsive to the detection signal to determine when the hot spot is in the second position.

Abstract: Methods and apparatus for on-line detection and measurement of degradation or undesirable changes in the time constants of sensors used in monitoring a system are disclosed. Methods and apparatus of this invention are particularly suitable for use in complex and high-risk industrial processes or other operations where it is undesirable and expensive or dangerous to allow certain parameters of the operation to change above or beyond a predetermined amount. This invention includes a detector for determining when a signal from a sensor crosses a preselected signal level such as for example a zero level. The output of the detector or zero crossing detector is provided to a counter or other means which determines the rate of the zero crossing by counting the number of crossings per a specific time period provided by a timer.