A calibration circuit for a solid state electricity meter comprises a plurality of resistors formed on an integrated circuit. The resistors are connected by an on-chip array of electrically controlled switches, such as MOSFETs, to signal processing circuitry driving the meter. The resistors establish variable voltage divider networks which compensate the meter for phase, gain and offset errors distributed in the signal processing circuitry. The values of the variable voltage divider network may be established automatically during testing of the meter, by a digital computer, or semi-automatically, by a technician, to establish the "on" and "off" states of the various transistors of the array.

Adjustment circuit and method for solid-state electricity meter

A sensor is compensated through the use of a closed loop comprising a digital processor, a digital-to-analog converter and a comparator having inputs coupled to the converter and the sensor and an output fed back to the digital processor. During calibration of the sensor, a signal from the sensor is tracked by the digital processor and at least one of the values characteristic of the sensor signal is stored in the digital processor. The stored value is used as or in the computation of a reference by the digital processor which is compared with the sensor signal during operation of the sensor to appropriately compensate the sensor for gain, offset, drift or degradation in the quality of the sensor signal.

Method and apparatus for compensating a sensor

A power booster and current measuring circuit provides a quiet, accurate voltage to a load (such as a transistor during parametric testing) with a load current of up to 1 ampere, and can measure that load current to an accuracy of ±0.1 % over a range of currents extending nine orders of magnitude (e.g., 1 ampere to 10 −9 amperes). The load voltage is supplied by a sense driver, a bypass driver, or both. The bypass driver comprises a high-current operational amplifier with a direct feedback loop (e.g., a voltage follower). The sense driver comprises a high-impedance operational amplifier having a feedback loop comprising a high-current operational amplifier connected as a voltage follower and one of a series of sense resistors having different values. The load current is determined by measuring the voltage drop across the sense resistor in the high-impedance operational amplifier feedback loop using an instrumentation amplifier, and dividing the measured voltage drop by the known resistance of the selected sense resistor. Also disclosed is a method of providing a constant voltage to a load over a range of currents and for accurately measuring the current drawn by the load.

Power booster and current measuring unit

A system for detecting an abnormal condition of a high frequency output signal in its power level, comprising: a variable gain power amplifier which receives a high frequency input signal and produces an amplified high frequency output signal; a negative feedback control loop connected to the power amplifier, for automatically setting the power level of the amplified high frequency output signal to a desired one of a plurality of predetermined power levels, the negative feedback control loop being so arranged as to produce a DC signal which is constant in its magnitude so far as the power level of the high frequency output signal is maintained at its set value whichever one is selected from the plurality of predetermined power levels, the gain of the power amplifier being controlled on the basis of the DC signal; and a comparator which compares the DC signal with a reference signal to judge as to whether the high frequency output signal is abnormal or not in its power level.

System for detecting abnormal condition of high frequency output signal in its power level

The invention discloses a system and a method for detecting a distribution network automatic terminal. The system comprises a program control power supply, a standard meter and a detection device, wherein the program control power supply is used for supplying power and providing a test signal which comprises test voltage and test current to a detected terminal according to a signal command which is externally input; the standard meter is used for displaying the test signal which is generated by the program control power supply; and the detection device is used for sending the signal command to the program control power supply or the detected terminal, generating a detection result in response to the signal command according to the detected terminal, and storing the detection result. Functions, the accuracy and a communication protocol of the distribution network automatic terminal can be integrally detected. The invention is widely applicable to establishment of a distribution network automatic system, the performance and functions of the distribution network automatic terminal can be standardized, product quality is improved, the potential safety hazard of the distribution network automatic system can be effectively reduced, the level of safe and stable operation of a power distribution network is improved, the reliability of a power distribution system is improved, and solid foundation is laid for promotion of the establishment and application of a power distribution automatic system.

Method and system for detecting distribution network automatic terminal

A circuit for adjusting the amplitude of a reference signal to a predetermined level so as to permit subsequent data signals to be interpreted correctly. The circuit includes an operational amplifier having a feedback circuit connected between an output terminal and an input terminal; a bank of relays operably connected to a plurality of resistors; and a comparator comparing an output voltage of the amplifier with a reference voltage and generating a compared signal responsive thereto. Means is provided for selectively energizing the relays according to the compared signal from the comparator until the output signal from the amplifier equals to the reference signal. A second comparator is provided for comparing the output of the amplifier with a second voltage source so as to illuminate a lamp when the output signal from the amplifier exceeds the second voltage.

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Digital automatic gain amplifier

A computerized field meter calibration system which includes an apparatus for testing the calibration of field meters normally utilized for measuring electromagnetic field potential. A reference voltage is applied to the field meter for causing signals to be produced on the output terminals thereof. A bank of relays is provided for selectively connecting output terminals of the field meter to a multiplexer by means of a digital voltmeter and an oscilloscope. A frequency-shift-keyed receiver is also connected to one of the terminals of the field meter for transmitting and converting a frequency shift keyed signal to a digital signal which is, subsequently, applied to the multiplexer. A microprocessor is used for generating coded command signals to the bank of relays and also to the multiplexer for controlling the comparison of the output signals with information stored within the microprocessor to determine if the field meter is properly calibrated.

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Larry D. Holley

Papers

Digital automatic gain amplifier

Microcomputerized electric field meter diagnostic and calibration system