Actuator current source

The mean fluorescence lifetime may also be determined by continuous intensity measurements, if the exciting light intensity is modulated at a high frequency. Fluorescence is excited by light modulated sinusoidally at a known frequency (ajln Hz). The emission is a forced response to the excitation, and is therefore modulated at the same frequency, but with a phase shift, due to the time-lag between absorption and emission. The intensities of the two beams are monitored by photomultipliers. The difference in phase (0) between the two intensities is determined electronically. The lifetime r is given by cox = tan<. The modulation frequency must be made comparable to the decay rate, e.g., around 30 MHz for a mean lifetime of 30 ns. Such frequencies can be achieved by using a hydrogen lamp actuated by a suitably modulated current source. Commercial equipment is available. The method has been applied to quinine sulphate, fluorescein, and acridine, for example, with a precision of 1-2%. It is especially useful for very short (sub-nanosecond) lifetimes. 

Actuator Application with Voltage and Current Source... 

To induce mechanical deformation with an actuator based on piezoelectric material, electric power needs to be supplied. In electrical engineering, two ideal power sources are distinguished. A voltage source provides a constant voltage, while the wattage may then be adjusted via the current. A current source the other way round keeps the current constant, while the wattage may then be adjusted via the voltage. 

When a current source is connected to the electrodes of a piezoelectric actuator, the electric potential p is unknown. Therefore, the contributions of the principle of virtual electric potential of Eq. (3.53) need to be retained. Since the current describes the derivative trend of charge with respect to time, it prescribes the area charge qsA on the electrodes. An adequate formulation of the principle of virtual work from Eqs. (3.62) and (3.63), in consideration of Eq. (4.36), reads... 

Derivation of a general solution via the formulation of spatial beam finite elements, accounting for arbitrary combinations of actuator and sensor applications with voltage and current source, respectively measurement, to capture the dynamic behavior of the rotating structure. 

The magnetic circuit breaker is designed to respond to an induced electrical field and will be actuated if the field strength exceeds the preset current limit. This type of device is generally unaffected by temperature, but is more sensitive to current fluctuations than the thermal device. Some devices are available which combine the characteristics of both types, but all of these devices require a large, transient surge of current to operate, such as occurs when two conductors or current sources come into contact. 

Consistent vrith current practice, active systems are used as first defense level against more probable events. These systems "termed as non-safety systems" establish and m ntain safe shutdown conditions. This requires at least one non-safety AC power source to be available. These systems include the Chemical and Volume Control System (CVCS), the Startup Feed Water System (SFWS), the Normal Heat Removal System (RNS), Spent Fuel pit cooling System (SFS), and the Diverse Actuation System (DAS). The later provides the defense in depth function of system actuation to back up the Safety Monitoring System (PMS) and to protect against common mode failure. 

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