Conventional electrical unit

Abstract: A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck constant, h = 6.626 069 83(22) × 10(-34) J s. The relative standard uncertainty associated with this result is 34 × 10(-9).

Abstract: Basic concepts of modelling and measurement measurement of voltage and current measurement of power and energy measurement of impedances measurement of time and frequency tools and methods of signal analysis electrical units of measurement.

Abstract: A monitoring device for monitoring an array ( 4 ) of electrical units, in particular an array of high capacity light emitting diodes (LEDs) ( 4.1 - 4.12 ). The electrical units are connected in series and driven by a constant electric current (I). The monitoring device has a bypass means ( 4.1 a - 4.12 a ) for each electrical unit ( 4.1 - 4.12 ), operable to bypass the respective electrical unit in case of a disconnection of the respective electrical unit, and an evaluation unit ( 3 ) connected in parallel with the array ( 4 ) of electrical units, said evaluation unit ( 3 ) being adapted to determine a total voltage (UT) of the array ( 4 ) of electrical units and to output a control signal (CS) indicative of a function status of the array ( 4 ) of electrical units in accordance with a value of the total voltage (UT) relative to a predetermined threshold value (VREF). Thus is provided an electric circuitry which allows an easy and reliable detection of a malfunction of the array of electrical units, e.g. due to failure of individual LEDs because of short circuits and/or disconnection, while ensuring a continued operation of the array in case of only minor problems. The monitoring device can advantageously be used in signalling devices, in particular for railway signalling purposes.