Reed sensors in Contact protection Circuits
Contact protection is required for any heavy load switching device, such as pumps mechanical, magnetic or solid state, when switching loads other than purely resistive. This is because inductive and capacitive loads such as pumps and motors, cause high in-rush current to be drawn across the reed contact. This will most certainly degrade it.
To prevent the switching device from early failure if in-rush current is too high, contact protection circuits needs to be embedded to protect the reed contact.
Most reed switch and reed sensor based products requiring contact protection, require a snubber or an RC network that softens the inrush current, thereby protecting the reed contact. These resistors and capacitors values need to be carefully selected depending on the nature of the load and the quantum of the in-rush current. More information about contact protection circuits is available here.
Specially designed reed sensors with inbuilt resistors, that are normally used in accurate liquid volume applications also double as devices for contact protection as the same circuits within the reed sensor are modified with a resistor-capacitor network. This simple choice of circuit with built-in resistor are suitable for use in in-rush current applications. This way, application designers do not need to add extra circuitry for contact protection, but use what is in-built in the Reed Sensor itself to save space.
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.
The Reed Switches and Sensors used in such 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.
IR-xxxx Reed Sensor with Integrated Resistor
IR-xxxx Reed Sensor DrawingIR-xxxx Reed Sensor PCB Layout Drawing starFeatures10W Contact Rating. Includes integrated Resistor.
Oct 30, 2020
MS-216 Standard size Cylindrical Sensor
MS-216 Magnet Sensor Drawing starFeatures10W Contact Rating. Normally Open contact. Three sensitivity bands. Sputtered Ruthenium
Oct 30, 2020