The **KUS-HA-R** refers to a high-accuracy, heavy-duty resistive fuel level sender (often used in marine and industrial applications). These sensors operate on simple yet robust electronic principles to translate physical fluid levels into electrical signals compatible with gauges and NMEA networks. ### 1. Core Electronic Components The KUS-HA-R sensor is primarily a **Resistive Output** device. Unlike capacitive sensors that measure electrical fields, the HA-R series uses mechanical and magnetic interaction. | Component | Description | Function | | :--- | :--- | :--- | | **Reed Switch Array** | A vertical PCB containing small magnetic switches. | Detects the position of the float. | | **Resistor Ladder** | A series of resistors soldered to the internal PCB. | Changes the total resistance based on which reed switch is closed. | | **Magnetic Float** | A donut-shaped float containing a permanent magnet. | Slides up/down the shaft to trigger the reed switches. | | **Sealing / Potting** | Epoxy resin filling the internal cavity. | Protects electronics from fuel, moisture, and vibration. | --- ### 2. Operational Logic The electronic circuit functions as a **step-variable resistor**. 1. **Magnetic Activation:** As the fuel level rises, the magnetic float moves up the stainless steel tube. 2. **Switching:** The magnet closes specific "Reed Switches" inside the tube at different heights. 3. **Resistance Mapping:** Depending on which switch is closed, a specific path is created through the resistor ladder. 4. **Signal Output:** The gauge measures the total resistance across the two output wires. --- ### 3. Electrical Specifications Most KUS-HA-R sensors are configured to one of two international standards. It is critical to match the sensor electronics to the gauge electronics. | Standard | Empty Range | Full Range | | :--- | :--- | :--- | | **European Standard** | 0 Ohms | 190 Ohms | | **American Standard** | 240 Ohms | 33 Ohms | --- ### 4. Technical Wiring Diagram The wiring for these sensors is generally simple, as they are passive devices (they do not usually require a dedicated power wire unless they are converted to 0-5V or 4-20mA). ```mermaid graph LR A[Ground/Negative] --- B(KUS-HA-R Sensor) B --- C{Gauge} C --- D[+12V/24V Power] ``` ### 5. Why "HA" (High Accuracy)? Standard resistive senders often have a resolution of 21mm between steps. The **HA (High Accuracy)** electronic variants typically feature: * **Denser Reed Switch Placement:** Reduces the "jump" of the needle on the gauge. * **Gold-Plated Contacts:** Prevents internal oxidation of the switches over decades of use. * **Filtering:** Some models include basic RC (Resistor-Capacitor) filtering to prevent the gauge from flickering due to fuel sloshing.