### SEI RNF and RNMF Series Resistors The **RNF** (General Purpose) and **RNMF** (Miniature) series from **Stackpole Electronics, Inc. (SEI)** are high-quality metal film resistors. They are designed for precision applications where stability and reliability are required in a leaded (through-hole) format. --- ### 1. Key Technical Specifications The following table highlights the primary differences and commonalities between the standard RNF and the miniature RNMF series. | Feature | RNF (Standard) | RNMF (Miniature) | | :--- | :--- | :--- | | **Material** | Metal Film | Metal Film | | **Size** | Standard Through-hole | Reduced Size (Smaller Footprint) | | **Power Rating** | 0.125W to 2W | 0.125W to 1W | | **Tolerance** | ±0.1% to ±5% | ±0.1% to ±5% | | **Temp. Coefficient** | ±25 to ±100 ppm/°C | ±25 to ±100 ppm/°C | | **Voltage Range** | 200V to 500V | 200V to 350V | --- ### 2. Physical Characteristics - **Construction:** A thin film of metal alloy is vacuum-deposited onto a high-grade ceramic rod. The body is typically coated with a flame-retardant epoxy. - **Leads:** Tin-plated copper leads compatible with wave soldering and manual soldering. - **Marking:** Color-coded bands represent the resistance value and tolerance. --- ### 3. Comparison: RNF vs. RNMF The primary distinction lies in the **Power-to-Size ratio**: 1. **RNF Series:** These are the industry-standard sizes. They are used when board space is not the primary constraint but thermal dissipation and voltage handling are critical. 2. **RNMF Series:** These are "mini" versions. For example, an RNMF 1/4W resistor is roughly the same physical size as a standard RNF 1/8W resistor. This allows designers to save space on a PCB while maintaining a higher power rating. --- ### 4. Typical Applications These resistors are found in a wide variety of electronic circuits, including: * **Audio Equipment:** Low noise characteristics of metal film make them ideal for signal paths. * **Medical Electronics:** High precision (0.1% tolerance) for sensing and monitoring. * **Instrumentation:** Stable resistance over temperature changes (low TCR). * **Power Supplies:** Used in feedback loops and voltage dividers. --- ### 5. Part Numbering Example A typical SEI part number follows this structure: `RNF 14 F T D 10K0` * **RNF:** Series Name * **14:** Power Rating (1/4 Watt) * **F:** Tolerance (F = 1%) * **T:** Packaging (T = Taped/Reeled) * **D:** TCR (D = 50ppm) * **10K0:** Resistance Value (10.0 kΩ)