The **HMS100-5-R** is a high-precision, open-loop current transducer manufactured by **LEM**. It is specifically designed for measuring DC, AC, and pulsed currents with galvanic isolation between the primary circuit (high power) and the secondary circuit (electronic interface). --- ## 1. Technical Specifications The following table summarizes the key electrical characteristics of the HMS100-5-R: | Parameter | Specification | | :--- | :--- | | **Primary Nominal Current ($I_{pn}$)** | 100 A | | **Measuring Range ($I_{pm}$)** | 0 to ±300 A | | **Supply Voltage ($V_c$)** | +5 V DC (Single Supply) | | **Output Type** | Ratiometric Voltage ($V_{out}$) | | **Reference Voltage ($V_{ref}$)** | 2.5 V | | **Accuracy** | ±1% at $25^\circ C$ | | **Bandwidth** | DC to 50 kHz | | **Mounting Type** | Through-hole (PCB) | --- ## 2. Operating Principle The sensor operates based on the **Hall Effect**. 1. **Primary Circuit:** The high current to be measured passes through the central aperture of the device. 2. **Magnetic Flux:** This current creates a proportional magnetic field concentrated by a magnetic core. 3. **Hall Sensor:** A Hall element integrated into the air gap of the core generates a small voltage. 4. **Signal Conditioning:** Internal electronics amplify this voltage and output it as a ratiometric signal centered around the Reference Voltage ($V_{ref}$). --- ## 3. Pin Configuration and Integration The HMS series typically features a compact footprint with the following pins: ```text Pin 1: Vc (+5V Supply) Pin 2: 0V (Ground) Pin 3: Vout (Output Signal) Pin 4: Vref (Reference Voltage) ``` ### Output Calculation The output voltage is determined by the formula: `Vout = Vref ± (Sensitivity × Ip)` * At **0A**, the output is exactly $V_{ref}$ (2.5V). * As current increases in the positive direction, $V_{out}$ rises toward 5V. * As current increases in the negative direction, $V_{out}$ drops toward 0V. --- ## 4. Key Advantages and Applications ### Advantages * **Galvanic Isolation:** High safety; no physical connection between the high-voltage bus and the microcontroller. * **Single Supply:** Operates on standard 5V rails, making it ideal for Arduino, ESP32, or STM32 integration. * **Compact Design:** Small footprint compared to traditional current transformers. ### Typical Applications * **Solar Inverters:** Monitoring DC string current. * **Variable Speed Drives:** Motor control and protection. * **Uninterruptible Power Supplies (UPS):** Battery management. * **Power Supplies:** Switched-mode power supply (SMPS) monitoring.