The **KRS-3B-R** is a specific model of a **magnetic proximity sensor** (often categorized under reed switches or magnetic cylinder sensors), commonly used in industrial automation to detect the position of pneumatic cylinders. --- ### 1. Technical Specifications The electronic components inside the KRS-3B-R are designed to interface between mechanical motion (a magnet) and a PLC (Programmable Logic Controller) or relay. | Parameter | Specification | | :--- | :--- | | **Switching Logic** | SPST (Normally Open) | | **Sensor Type** | Reed Switch | | **Operating Voltage** | 5V - 240V AC/DC | | **Switching Current** | 100mA Max | | **Contact Rating** | 10W Max | | **Voltage Drop** | 2.5V Max (when LED is active) | | **Indicator** | Red LED | --- ### 2. Internal Electronic Components The device is relatively simple but robust, consisting of three primary electronic elements: #### A. The Reed Switch The heart of the KRS-3B-R is a glass-encapsulated reed switch. It consists of two ferromagnetic blades. When a magnetic field (from a piston magnet) comes near, the blades are magnetized with opposite polarities and pull together, closing the circuit. #### B. The LED Indicator A small **Red Light Emitting Diode (LED)** is wired in series or parallel with the switch. - **Function:** Provides visual confirmation that the sensor has been triggered. - **Circuit Protection:** Usually accompanied by a small resistor to limit current to the LED. #### C. Varistor / Protection Circuitry Standard models often include a small Zener diode or a Varistor to protect the reed contacts from "arcing" or voltage spikes when switching inductive loads (like small solenoids). --- ### 3. Wiring Configuration The KRS-3B-R is typically a **2-wire** sensor. Because it operates on a wide range of voltages, it is highly versatile. ```mermaid [Power +] ---- [Load/PLC Input] ---- (Brown Wire) ---- [KRS-3B-R] ---- (Blue Wire) ---- [Power -] ``` * **Brown Wire:** Connects to the positive side or the load. * **Blue Wire:** Connects to the negative/common side. --- ### 4. Key Electronic Advantages 1. **No Standby Current:** Since it is a mechanical reed contact, it consumes zero power when the switch is open. 2. **High Voltage Range:** Unlike 3-wire Hall Effect sensors (which are usually limited to 10-30V DC), the KRS-3B-R can handle high AC voltages up to 240V. 3. **Galvanic Isolation:** The physical gap in the reed switch provides a layer of isolation when the sensor is inactive.