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Contact-Closure Sensor

Magnetic proximity switches for closure monitoring.


Remotely monitor magnetic contact-closure sensors using ControlByWeb modules. The GRI Closure Sensors can be installed on most doors, windows, cabinets, security/control boxes, and more.

How do contact-closure sensors work?

Contact-closure sensors are comprised of two parts: a magnetic reed switch, and a magnet. The magnetic reed switch is mounted on the door or window frame, while the magnet is mounted to the door or window itself. When the magnet comes in range of the magnetic reed switch, the switch turns on or off based on the wiring configuration.

Magnetic contact sensors with ControlByWeb® products

Connected to a ControlByWeb product's digital input, once the magnetic switch is in proximity of the magnet, it will open or close its contacts (depending on configuration), turning the digital input on/off. The ControlByWeb product can send an email/text and/or trigger a relay in a local or remote location.

Contact-closure sensors connected to the X-408


  • Options for N/O or N/C circuits
  • Reliable magnetic reed switches
  • Easy to install

  Compatible Products

Contact-closure sensors are compatible with all ControlByWeb® products that have a digital input.

Contact-Closure Sensor Wiring Diagrams

Both the 29C and 28C have 3 terminals which allow to choose between a normally-open (NO) or normally-closed (NC) configuration.

The MPS subminiature sensor has a pre-attached wire, and is configured as a fixed normally-open (NO) configuration.

Closure-sensor wiring diagram

Wiring the GRI-29C to a ControlByWeb product

GRI-28C Closure-sensor wiring diagram

Wiring the GRI-28C to a ControlByWeb product

MPS Closure-sensor wiring diagram

Wiring the MPS to a ControlByWeb product

COMPARE Contact-Closure Sensors

Part Numbers GRI-29C-W GRI-28C-W MPS45WGW
Terminal Locations Side Bottom -
Lead Length - - 12"
Circuit Types N/O and N/C N/O and N/C Fixed N/O
Gap Distance 1" (5/8" on steel) 1" (5/8" on steel) 1 1/4" (3/4" on steel)
Mounting Options Wall screw mounting Wall screw mounting Adhesive strips or wall screw mounting
Dimensions (Length × Width × Height) 2 1/2" × 1/5" × 5/8" 2 1/2" × 1/5" × 5/8" 1" × 1/4" × 1/4"
Price $21.99 $21.99 $14.99

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