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Important knowledge of Reed switch Parameters

- May 22, 2018 -

Reed switch parameters

Ampere Turn (AT or NI) - Reed Switch AT (Amperage)

Pull-in value (PI, Pull-in Value) is the product of the current required to drive the coil excitation and the number of turns of the coil. The unit is AT. The value of AT is also called the reed switch sensitivity value. The important parameters of reed sensitivity, the lower the AT value, the higher the sensitivity, and the lower the

In general, the AT value of the reed switch (reed switch) will be marked on the outer packaging. The AT value is a parameter that determines how much magnetic field strength is required to pull in. The higher the AT value, the stronger the generated magnetic field.

Disconnect value (DO, Drop-out Value)

The product of the current flowing through the coil and the coil when the contact is released, in units of AT.


Form A

The normally open contact (NO) is a one-way single throw (SPST) normally open (N.O.) switch.


Form B

The normally closed contact (NC) is a one-way single throw (SPST) normally closed (N.C.) switch.


Form C

The changeover contact (SPDT), which is a one-way double throw (SPDT) switch, pulls the normally open switch before the normally closed switch opens.


Form D

It is a one-way double throw (SPDT) switch. The normally open switch will close before the normally closed switch is closed.



Contact resistance (CR value)

When the contact is closed, the impedance between the two terminals, including the resistance of the wire section


Open impedance (OR value)

Impedance between two terminals when the contact is open, including the resistance of the wire section


Contcat Capacitance Contact Capacitor

The electrostatic capacitance between the contacts at the time of contact release equals the product of the contact voltage (maximum voltage allowed to be applied to both contacts when the contacts are open) and the product of the contact current (the maximum current allowed to pass through the contacts when the contacts are closed).


Insulation Resistance

Insulation resistance between the two terminals of the reed switch


Contact Resistance (CR) Contact Resistance

The resistance at the closed contact in milliohms


Coil disk

It is an electromagnetic component, usually made of one or more insulated copper wires wound around the spool, when the current flows in the coil, the magnetic field will be generated to operate the reed relay and electromechanical relay.


Chatter trembles

Unwanted intermittent open contacts close or open and close contacts. May occur when the reed contacts, releases or is subjected to external shock or vibration.


Coercivity Coercivity

The force required for demagnetization reduces polarization or induces zero.


Dynamic Contact Resistance Dynamic Contact Resistance (DCR)

When the contact is running the resistance of the closed contact continuously under load


Action Time Action Time

The action time is to close or open a closed contact with the first open contact from the initial energization time, excluding any bounce.


Bounce Bounce

The connection of the initial contact due to the mechanical rebound occurs after intermittent opening and closing of the contacts. Or mechanical shock, vibration generated by the installation drive or off. Intermittently separating and closing the contacts or closing and opening the open contacts usually means touching the movement caused by the collision.


Bounce Time Bounce Time (ms)

The time needed for a rebound.


Breakdown Voltage Breakdown Voltage

The insulation component that can be applied to the reed contact is free from damage, arc breakdown or maximum voltage causing excessive leakage.


Max switching voltage

Contact and maximum voltage as switch


Min breakdown voltage

If the voltage between the contacts exceeds this value, the contact will breakdown damage


Max switching current

The contact can be used as the maximum current of the switch


Switching Frequency Switching frequency (in Hz)

The highest frequency of reed contact operation


Max carry current Maximum load current

The maximum current that the contact can energize, and the number of currents that can continuously energize the contact point. The unit is ampere.


Release time Release time

The time for returning the contacts is removed when the voltage applied to the exciting coil is removed.


Contact Contact

The current-carrying parts of the reed contact circuit are closed or opened.


Static Contact Resistance Static Contact Resistance (CR)

The end-to-end closed reed contact resistance measured at its associated terminal


Reed Sensor Reed Sensor

The reed sensor is able to withstand impact with additional functions such as a reed switch, making it easier to install, but requires additional intelligent circuitry and other equipment


Insulation Resistance Insulation Resistance

Measure the resistance between insulated terminals


Operate AT(OAT)

Reed contact closure measurement at AT. This is an effective form A, B, E type reed contact, closing operation from the normally closed contact normally closed contact switching operation of C type and D type reed contact.

Output Offset Voltage

Measure the voltage lost through the closed switch and the measurement unit is usually one millionth of a volt (mV). This voltage appears in the isolation amplifier and is grounded to the input voltage.


After the amount of voltage or amperage is applied to the switch connection, the switch contact resistance is usually measured with 100% overdrive.


Close Differential

The difference is a minimum of 70%.


Contact Rating Contact Rating (W)

The maximum power required to switch a reed contact


Contact Gap gap

When the reed switch is in the open state, the gap between the contact points.

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