Proximity / Limit Switches

This document is part of a comprehensive tutorial on industrial Digital I/O and Counter/Timer hardware. Learn about National Instruments product offerings for digital and timing I/O, the Industrial Feature Set including watchdog timers and isolation, complementary devices like relays, solenoids and encoders, concepts like sinking and sourcing, and see how these devices can be used in your industrial application.

For more information return to the Complete Industrial Digital I/O and Counter/Timer Tutorial

Introduction to Proximity / Limit Switches

A limit switch is an electromechanical device that is initiated by physical contact of any object using the activator of a switch. Proximity switches/sensors are initiated by a physical presence near them. Distance is the main factor determining their operation. They can be a sensor or transducer, an instrument or meter, a gauge or indicator, a recorder and a controller.

Recommended NI Products that Connect to Proximity / Limit Switches

Digital I/O Boards	Counter/Timer Boards
NI 6509	NI 6601
NI 6514	NI 6602
NI 6515	NI 6608
NI 6528	NI 6624

Technical Overview

The limit switch uses physical contact to change state. Upon contact, the activator is moved to a specific limit where the state is changed. They are used mostly in industrial environment because of their rugged design. In spite of their rugged design, the mechanical parts of the device can wear over time compared to proximity sensors. There are different technologies that the proximity sensors depend on. They include capacitive, eddy current, inductive, photoelectric, ultrasonic, and Hall effect. Proximity sensors may be a contact or non-contact type.

Find a Proximity / Limit Switch

Search for Limit Switches in GlobalSpec
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