The **NJM5N-R** refers to a high-performance, high-voltage proximity sensor manufactured by **Azbil (formerly Yamatake)**. It is primarily used in industrial automation to detect the presence of metallic objects without physical contact. --- ## 1. Technical Specifications The following table highlights the core electronic characteristics of the NJM5N-R: | Parameter | Specification | | :--- | :--- | | **Detection Distance** | 5 mm | | **Output Type** | DC 2-Wire (Normally Open) | | **Operating Voltage** | 12 to 24 VDC (Typical range 10-30V) | | **Switching Frequency** | Up to 1 kHz | | **Leakage Current** | $\le$ 0.8 mA | | **Housing Material** | Nickel-plated brass / Plastic sensing face | | **Protection Rating** | IP67 (Water and oil resistant) | --- ## 2. Key Electronic Components & Working Principle The NJM5N-R functions using **Eddy Current Killed Oscillator (ECKO)** technology. Inside the unit, several key stages work together: ### A. The Oscillator Circuit The sensor contains an LC (Inductor-Capacitor) oscillator circuit. This circuit generates a high-frequency electromagnetic field that radiates from the sensing face. ### B. The Detection Loop (Eddy Currents) When a metallic object enters the magnetic field, **Eddy currents** are induced on the surface of the metal. These currents create a counter-magnetic field that dampens the amplitude of the oscillations in the sensor's internal circuit. ### C. Trigger and Output Stage 1. **Schmitt Trigger:** An internal comparator monitors the oscillation amplitude. Once the amplitude drops below a certain threshold, the trigger flips its state. 2. **Switching Element:** Usually a solid-state transistor (in 2-wire DC models, this acts as a variable impedance) that allows current to flow to the load. --- ## 3. Wiring Configuration The NJM5N-R is a **Non-Polarity DC 2-wire** sensor, which simplifies installation as it functions like a standard switch in series with a load. ```text [ Power + ] ----( Brown Wire )---- [ Load ] ----( Blue Wire )---- [ Power - ] ``` ### Important Electronic Considerations: * **Residual Voltage:** Because it is a 2-wire device, a small voltage drop (usually <3-5V) remains across the sensor even when "ON." * **Minimum Load Current:** It requires a minimum current (typically 3mA) to keep the internal electronics powered. --- ## 4. Application Areas * **Positioning:** Detecting the end-of-travel for pneumatic cylinders or CNC axes. * **Counting:** High-speed counting of metal parts on a conveyor belt. * **Safety Interlocks:** Ensuring a metal guard or door is closed before a machine starts.