The **LA55-P** is a high-performance Hall Effect current transducer manufactured by LEM. It is widely used in industrial automation and power electronics for the non-intrusive measurement of DC, AC, and pulsed currents. --- ### 1. Key Technical Specifications The LA55-P operates on the **Closed Loop (compensated)** principle, which ensures high accuracy and linearity. | Feature | Specification | | :--- | :--- | | **Primary Nominal Current ($I_{PN}$)** | 50 A | | **Measuring Range ($I_{PM}$)** | 0 to ±70 A | | **Secondary Output Current ($I_S$)** | 50 mA (at $I_{PN}$) | | **Conversion Ratio ($K_N$)** | 1:1000 | | **Supply Voltage ($V_C$)** | ±12 V to ±15 V (±5%) | | **Accuracy** | ±0.65% of $I_{PN}$ | | **Frequency Bandwidth** | DC to 200 kHz | --- ### 2. Internal Electronic Components The device consists of several critical stages integrated into a single PCB module: 1. **Magnetic Core:** A high-permeability ring that concentrates the magnetic flux generated by the primary conductor. 2. **Hall Effect Sensor:** A semiconductor element placed in the air gap of the core that generates a voltage proportional to the magnetic flux. 3. **Compensation Circuitry:** A sophisticated operational amplifier circuit that drives a secondary coil (the compensation winding). 4. **Secondary Winding:** A coil with 1000 turns ($N_2$) that creates an opposing magnetic field to "cancel out" the primary flux, maintaining the core at zero flux. --- ### 3. Connection Diagram (Internal Logic) To use the sensor, a measuring resistor ($R_M$) must be connected to convert the output current into a readable voltage. ```mermaid graph LR A[Primary Current IP] --> B(Magnetic Core) B --> C(Hall Element) C --> D(Amplifier) D --> E(Secondary Coil IS) E --> F(Measuring Resistor RM) F --> G(Output Voltage VO) ``` ### 4. Application Considerations * **Mounting:** The LA55-P is designed for **PCB mounting** with 4 pins (Positive Supply, Negative Supply, Output, and Common). * **Thermal Management:** The device is rated for temperatures between -40°C and +85°C. High current loads can generate heat in the secondary coil and $R_M$. * **Galvanic Isolation:** Because there is no electrical connection between the primary circuit and the measuring circuit, it provides high safety for microcontrollers and sensitive ADCs. ---