| 摘要 |
An apparatus for measuring electrical energy includes an electrical energy meter having built-in gain and power factor calibration circuits. The calibration circuits can be factory set so that the meter accurately measures the actual energy consumed by an energy user during the lifetime of the meter and does not need to be field calibrated. The gain calibration circuit preferably includes a bank of parallel-connected resistors which are arranged as a resistance ladder. These resistors facilitate calibration of the full load gain of the meter because they are connected as the input resistor to the meter's full load gain amplifier. By disconnecting one or more of the resistors from the ladder, the full load gain of the meter can be adjusted so that approximately 100% full load registration is achieved. The power factor calibration circuit also includes two pairs of antiparalled-connected diodes. These diodes can also be disconnected from the meter during factory calibration so that a range of sixteen different possible phase delays between the sampling time of the line voltage and the line current can be achieved. In this manner, the non-unity power factor response of the meter can be calibrated.
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