The **LA55-P** is a closed-loop (compensated) current transducer based on the Hall effect principle. It is primarily used for the electronic measurement of currents (DC, AC, pulsed) with galvanic isolation between the primary circuit and the secondary circuit. --- ## 1. Technical Specifications The following table summarizes the key electronic characteristics of the LA55-P: | Parameter | Value | | :--- | :--- | | **Primary Nominal Current ($I_{PN}$)** | 50 A | | **Primary Current Measuring Range** | 0 to ±70 A | | **Secondary Nominal Current ($I_{SN}$)** | 50 mA | | **Conversion Ratio** | 1 : 1000 | | **Supply Voltage ($V_C$)** | ±12 V to ±15 V (±5%) | | **Accuracy (at $T_A = 25°C$)** | ±0.65% of $I_{PN}$ | | **Frequency Bandwidth (-1dB)** | DC ... 200 kHz | | **Dielectric Strength** | 2.5 kV | --- ## 2. Operating Principle: Closed-Loop Hall Effect The LA55-P operates using a **closed-loop system**, which offers higher accuracy and better linearity than open-loop sensors. 1. **Magnetic Flux:** The primary current ($I_P$) flowing through the conductor creates a magnetic flux in the magnetic core. 2. **Hall Sensor:** A Hall element located in the air gap of the core detects this flux. 3. **Compensation:** An internal amplifier generates a secondary current ($I_S$) that flows through a compensation coil. This secondary current creates an opposing magnetic field that exactly cancels the primary flux (null balance). 4. **Output:** The secondary current ($I_S$) is exactly proportional to the primary current based on the turn ratio (1:1000). --- ## 3. Connection Diagram & Pinout The device is designed for PCB mounting with 4 pins: | Pin | Symbol | Description | | :--- | :--- | :--- | | 1 | **+V** | Positive Supply Voltage (+12V to +15V) | | 2 | **-V** | Negative Supply Voltage (-12V to -15V) | | 3 | **M** | Measurement Output (connect to $R_M$) | | 4 | **NC** | Not Connected (Physical support) | ### Basic Application Circuit To convert the current output into a voltage that a microcontroller or ADC can read, a measuring resistor ($R_M$) is used: ```text [Primary Wire] ----> (Sensor Hole) ----> [Load] Secondary Side: (+V) ---- [+15V] (-V) ---- [-15V] (M) ---- [R_M Resistor] ---- [Ground (0V)] | └----> Voltage Output (Vout = Is * Rm) ``` --- ## 4. Key Advantages * **Excellent Linearity:** Because it operates at "zero flux," the non-linearity is less than 0.15%. * **Wide Frequency Range:** Capable of measuring high-speed switching transients in power electronics. * **Low Temperature Drift:** High stability over a range of -25°C to +85°C. * **High Immunity:** Robust against external magnetic field interference.