The **CMK-R020** is a specific model of a **Current Sensing Resistor** (Shunt Resistor). These components are designed to measure current flow by creating a small voltage drop that can be monitored by a microcontroller or an analog circuit. --- ### 1. Key Technical Specifications Based on the standard nomenclature for the CMK series, here are the primary technical attributes: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Resistance Value** | 0.020 $\Omega$ (20 m$\Omega$) | The "R020" signifies 20 milliohms. | | **Power Rating** | 1W - 2W | Typically rated for high power dissipation relative to size. | | **Tolerance** | ±1% or ±5% | Precision level of the resistance value. | | **Technology** | Metal Plate / Alloy | Uses a solid metal element for stability and heat handling. | | **Package Size** | 1206 or 2512 | Commonly found in Surface Mount Device (SMD) footprints. | --- ### 2. Physical Construction The CMK series usually utilizes a **Metal Plate** construction rather than a thick-film paste. This provides several advantages: * **Low Inductance:** Crucial for high-frequency switching applications. * **High Thermal Mass:** Better at handling short-duration current surges without burning out. * **TCR (Temperature Coefficient of Resistance):** Very low (typically ±50ppm to ±100ppm), meaning the resistance doesn't change significantly as the part gets hot. --- ### 3. Functional Application In a circuit, the CMK-R020 acts as a "Current-to-Voltage Converter." #### Basic Calculation Example: If you are passing **5 Amperes** through a CMK-R020 (20m$\Omega$): 1. **Voltage Drop:** $V = I \times R \implies 5A \times 0.020\Omega = 0.1V$ (100mV). 2. **Power Dissipation:** $P = I^2 \times R \implies 5^2 \times 0.020 = 0.5W$. #### Common Use Cases: * **Battery Management Systems (BMS):** Monitoring charging and discharging currents. * **DC-DC Converters:** Providing feedback for over-current protection. * **Motor Controllers:** Measuring phase current to regulate torque. --- ### 4. Circuit Schematic Representation The resistor is placed in series with the load. The voltage is measured across the two terminals of the resistor. ```text [Power Source (+)] ----+---- [Load] ----+---- [Ground] | | +---[CMK-R020]---+ | (To ADC / Sense Amp) ```