Fluid level monitoring on Automobiles Using Reed Switches

In today’s automobiles, providing comprehensive information on various fluid levels is essential for maintaining vehicle performance and safety. From windshield wiper fluid to brake oil, power steering oil, and radiator coolant, accurate monitoring of these fluids ensures optimal vehicle operation. Reed Switches emerge as indispensable components for liquid level sensing applications, renowned for their reliability and versatility.

One of the key advantages of Reed Switch is their hermetically sealed construction, making them suitable for use even in harsh environments such as fuel tanks. Molded for durability, they can withstand the rigorous shock and vibration levels commonly encountered in automotive settings. Moreover, they exhibit remarkable thermal stability, capable of maintaining consistent performance even at high temperatures, ensuring reliable operation under varying conditions.

Detecting the actual volume of a liquid typically requires additional circuitry, but detecting low levels is a simpler task. Reed Switch based float switches excel in detecting low liquid levels, offering a cost-effective solution for this critical function.

In liquid level sensing applications, tanks are equipped with a foamed magnet float attached to the inside stem of the cap. Positioned in the middle of the tank, the float remains relatively unaffected by liquid movement when the vehicle is in motion. A reed switch is mounted outside the tank at the near-empty level, providing accurate low-level detection.

Alternatively, the magnet and reed sensor can be integrated into a single float switch, which is inserted directly into the tank for streamlined installation. The signal generated by the reed sensor based on the fluid level triggers an LED on the driver information panel, alerting the driver to low fluid levels and prompting timely maintenance.

Some automobile manufacturers opt to mount the reed sensor to sense a full tank instead of an empty tank, as this simplifies malfunction detection. By monitoring the full tank fluid level, any anomalies or malfunctions in the sensing system can be promptly identified, ensuring accurate and reliable liquid level monitoring.

Application Classification

Applications are classified as Position Sensing, Pulse Counting, Electromagnetic or Relay, Temperature Sensing or Magnet Biasing types. This application is classified as follows and the link gives more information on best practices to help select the most suitable AT band and matching magnet.

Position sensing Type

When an application requires the end position of a movement sensed, or the sensing of a part when it comes into a zone, or when the Continue reading -> Jul 14, 2025

Recommended Products

The Reed Switches and Sensors used in such fluid level sensing applications need to be robust, durable and efficient in meeting a high life expectancy. Our engineers work hard in life testing our products under various conditions, and our intention is to ensure end product durability and life. Although we wouldn’t want to restrict any of our products for use in only certain applications, the recommended products for use in this application are listed below.

Micro Miniature Reed Switch, MM-1018

Full Length LeadsCropped LeadsSMD Formed LeadsLeads Formed for Horizontal MountingLeads Formed for Vertical Continue reading -> Sep 29, 2024

Micro Miniature PCB Mountable Reed Sensor, MS-105

Drawing of MS-105 Reed SensorDrawing of MS-105 PCB Pad Layout starFeatures10W Contact Rating. 12.7 mm PCB Pitch. Normally Open Continue reading -> Jun 18, 2025

Sub Miniature Reed Switch, SM-1322

Reed Switch with Full Length LeadsCropped LeadsSMD Formed LeadsHorizontal MountingVertical Mounting starFeaturesRelease AT Continue reading -> Jul 14, 2025