Protect Reed Switches from Failures

Reed switches and reed sensors are reliable components used across various industries, but like all mechanical devices, they are susceptible to failure under certain conditions. Understanding what constitutes a “failure” and what does not can help understand usage of reed based products and provide guidance on troubleshooting.

What Constitutes as a Failure

1. Contact Weld: One of the most common and severe failures is contact welding. This occurs when the reed switch is subjected to higher currents than its rated capacity or when switching inductive or capacitive loads without proper contact protection. The excessive current or in-rush current causes the reed switch’s contacts to fuse together, rendering the device useless. Solution: Ensure the reed switch is selected according to the load’s current and incorporate protection circuits to absorb spikes.
2. Intermittent Operation: Intermittent operation could be a result of a micro-cracked hermetic seal. If the seal is cracked or damaged, it could allow moisture or contaminants to interfere with the reed switch’s operation, causing inconsistent triggering. Solution: If you experience this, the reed switch needs to be replaced, as the crack cannot be repaired.
3. High Contact Resistance: High contact resistance often results from mishandling or dropping the reed switch, or it can occur if the switch is subjected to shock during transportation. This damage compromises the device’s electrical performance, increasing resistance and reducing its efficiency. Solution: Always handle reed switches carefully and ensure proper packaging during transport to avoid damage.

What does not Constitute as a Failure

1. Magnetic Sensitivity Variations: A common misconception is that reed switches always perform identically for a specified AT (ampere-turn) rating. However, different manufacturers use different test coils to measure these values. As a result, the actuating distance for the same AT rating may differ between manufacturers. Solution: Always perform distance trials before placing bulk orders to ensure that the reed switch meets your specific requirements.
2. Temperature Effects on Actuation Distance: Temperature changes can influence reed switch performance, but this is not a failure. When the temperature decreases, magnetic permeability increases, enhancing the reed switch’s actuation distance. Conversely, an increase in temperature decreases the permeability, reducing the actuating distance. Solution: Consider the operating temperature range when designing your application and select a reed switch that will operate reliably within that range.
3. Nearby Ferro-Magnetic Parts: Ferro-magnetic materials, such as steel or iron, can interfere with the magnetic field surrounding the reed switch, causing a reduction in the actuating distance. This is not a fault with the reed switch itself but rather the result of magnetic field disruption. Solution: If you notice reduced distance, try repositioning the reed switch away from ferro-magnetic materials, or use magnetic shielding to maintain the proper field strength.

While reed switches are generally robust and reliable, it’s important to understand the difference between actual failures and changes in performance that are due to environmental or installation factors. Addressing these issues, such as incorporating proper protection for high-current loads or testing different manufacturers’ reed switches, can prevent unnecessary replacements and extend the life of your reed switch or reed sensor system. Always remember that careful handling, appropriate selection, and thorough testing are key to ensuring the reliability of these components in your application. We look forward to assessing your application requirements and help select the best products for you!