摘要:
A pulse-width modulator circuit includes a pulse-width modulator which has an input for a low-frequency modulation signal and an input for a carrier signal, a carrier signal generator which has an output connected to the carrier signal input of the pulse-width modulator for providing a carrier frequency, a buffer stage postcoupled to the pulse-width modulator, an output filter postcoupled to the pulse-width modulator, including a relatively narrow-band resonant circuit for damping the carrier frequency, and a regulating device forming a feedback path between the resonant circuit and the carrier signal generator for maintaining the carrier frequency substantially at the resonance frequency of the resonant circuit.
摘要:
A phase detector includes a pulse amplitude modulator and an integrator. The pulse amplitude modulator comprises a change-over switch the control input of which is fed by pulses which are subjected to mark/space modulation by means of a phase-shifted signal while the amplitude input of the pulse amplitude modulator is fed by a non-phase-shifted signal. The integrator includes an integrating amplifier, the output of which is connected by means of a capacitor to an inverting input of the integrating amplifier while the non-inverting input of the integrating amplifier is connected to ground by way of a further capacitor. The inverting and non-inverting inputs of the integrating amplifier are connected by way of respective resistors to two inputs of the integrator which in turn are connected to ground by way of respective resistors on the one hand and which on the other hand are connected by way of respective switch contacts of the change-over switch to the amplitude input of the pulse amplitude modulator. The phase detector requires only a single amplifier and may be used in phase-lock loops of static electricity meters which operate using the mark/space amplitude modulation method and which serve for the measurement of reactive energy, and which therefore require a 90.degree. phase shift provided by the phase-lock loop.
摘要:
In a system for optical display and photo-electric scanning of the contents of a counter equipped with counting wheels, and wherein each counting wheel includes a plurality of numeral members visually distinguishable from the periphery thereof, a coded optical marking member is associated with each numeral member of a respective counting wheel. The coded optical marking member includes at least one optical surface element, and the optical marking members of the counting wheels extend along respective rows, and may be scanned by a light ray moving along a corresponding row. The improvement includes one of the members being superimposed at least in part onto another of the members in a corresponding row, and being partially light-transmitting, while each optical surface element is light-reflective, so that the numeral members are visible upon being illuminated with diffuse light, but wherein a light ray directed onto a respective optical surface element is reflected therefrom.
摘要:
A precision measurement voltage transducer is fed from a reference alternating current source and comprises a transformer and a servo amplifier. The transformer comprises a feedback winding, a magnetizing winding and an output winding. The feedback winding and the magnetizing winding together with the servo amplifier form a feedback control regulating system, which adjusts the input voltage of the servo amplifier to zero. The latter comprises two amplifiers, which according to a first embodiment are connected in series and which according to a second embodiment feed the two poles of the primary winding of a second transformer, the secondary winding of which forms the output of the servo amplifier. According to the first embodiment the second amplifier is provided with a positive and an equally strong negative feedback and according to the second embodiment the transfer ratio of the second transformer equals the amplification factor of the second amplifier.
摘要:
A measuring transformer comprises a ferromagnetic core having a central branch. The central branch comprises at least one unit that is surrounded in part by an electrical conductor in the form of a U. Each unit of the central branch of the core has two outer air gaps and one or more central air gaps. Each outer air gap has length, that when measured in the longitudinal direction of the unit, is longer than the sum of the lengths of the one or more central air gaps. At least one magnetic sensor is contained in a central air gap of each unit and the central branch includes a total of at least two magnetic sensors. The measuring transformer is especially well suited for use in multifunction measuring instruments.
摘要:
An apparatus for determining the reactive energy of a circuit includes a mark-space modulator, which has an input terminal normally accepting a first signal input, and an output terminal, a pulse amplitude modulator which has a bipolar modulating terminal normally accepting a second and bipolar signal input, a signal output terminal, and a pulse input terminal, and a delay circuit which has a data input terminal connected to the output terminal of the mark space modulator, and which has an output terminal connected to the pulse input terminal of the pulse amplitude modulator. A predetermined phase angle at an operating frequency of the delay circuit normally occurs between the input terminal and the output terminal of the delay circuit. A regulator is interconnected between the mark-space modulator and the delay circuit so as to maintain the phase angle at the operative frequency as close as possible to 90 degrees, even when the signal input is subject to any level variations or to any interference.
摘要:
A circuit arrangement for the input circuit of a meter for simultaneously measuring two electrical quantities is disclosed. The circuit includes a current transformer including a primary winding, two substantially equal secondary windings and a pulse amplitude modulator associated with each secondary winding. Connections are made from each secondary winding to one terminal of its associated and non-associated pulse amplitude modulators, respectively. The circuit can be manufactured simply and economically while providing a high quality meter. Other embodiments provide additional advantages.
摘要:
The current transformer for instruments for measuring electric currents includes a magnetic core that has two cores and an inductive current divider with three parallel current paths. The current dividers form, together with cores, two current transformer stages whose magnetic fluxes mutually cancel one another. In a current transformer for AC currents having a DC component, the ratio of the ohmic resistances of the individual current paths is in direct relation to their transformation ratio.
摘要:
A circuit arrangement for finding a sum of electrical power outputs for use in a multi-phase electricity meter is disclosed. The circuit arrangement comprises a plurality of multiplier circuits arranged in sequence. The sequence of multiplier circuits has two poles which form the output poles of the circuit arrangement. Each multiplier circuit comprises a Hall element, an amplifier, and a polarity reversing switch.
摘要:
A current divider for use in connection with a measurement transducer. The measurement transducer includes a magnetic core, is formed as a substantially flat and longitudinal conductor with two longitudinal slits so as to partition the flat conductor into at least a measurement conductor, and at least two shunts are connected in parallel with the measurement conductor. The shunts define a plane, and the measurement conductor is disposed in the plane between the shunts. The flat conductor has two openings along the longitudinal direction, to receive the magnetic core. One slit communicates with one opening, and the other slit communicates with the other opening.