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    How to Wire and Test an AC Current Sensor?

    The AC current sensor is a device for detecting AC current, which can sense the information of the AC current being measured, and can convert the detected and sensed information into electrical signals or other required forms of information output according to certain rules. AC current sensor can meet the requirements of information transmission, processing, storage, display, recording and control, and is the primary link to realizing automatic detection and automatic control.

    ATO current sensor/transmitter type has AC/DC input (0.1mA~20000A), output 4~20mA, 0~20mA. It uses rail installation, 1~6 are the input side, 7~12 are. the measurement side and the power supply side.

    1~6 input side

    Basic working principle of electrical isolation sensor

    The signal is isolated by CT and PT, the current is perforated input mode, and voltage is terminal wiring input mode. Among them, CT is a current transformer, PT is a voltage transformer, and the output is generally 0~5V or 4~20mA.

    DC signal is divided into DC voltage and DC current. DC current is generally sampled by resistance, and DC voltage is generally processed by resistance step-down. An isolated power supply supplies power to the preamplifier. There are two commonly used solutions for isolation principles, one is to use linear optocoupler isolation technology, the other is to use modulation and demodulation technology.

    Block diagram of DC signal detection

    Electrical isolation sensor characteristics

    1. There is necessary electrical isolation between the input power and the output analog signal or digital signal.
    2. There is necessary electrical isolation between the power supply and the input power.
    3. The input signal is connected to the primary circuit, and the output signal is connected to the secondary instrument.
    4. When the output is a digitally coded signal, it generally meets the requirements of the relevant protocol.


    Measure the coil current of this AC contactor with an AC current sensor. (Contactor power 8~ 10W/220V AC). Connect the coil in series to the input side 1 & 3 of the current sensor, 10 & 12 connect to the 24VDC power supply.

    AC current sensor


    • When the contactor is not energized, it is measured that the electrical industry between the output ports 7 & 9 is 0V.
    • After the contactor coil is energized, the voltage between 7 & 9 is 9.03V.
    • At this time, the current passing through the contactor is 45.15mA (9.03V*5mA).

    See more details about the wiring of the current sensor below.

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