Digital I/O Sinking and Sourcing

Publish Date: Mar 16, 2011 | 50 Ratings | 3.24 out of 5 | Print

Overview

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.


Table of Contents

  1. What is Sinking and Sourcing?
  2. Sinking Devices
  3. Sourcing Devices
  4. Recommended NI Products that Connect to Sinking and Sourcing Devices

1. What is Sinking and Sourcing?

Sinking and Sourcing are terms used to define the control of direct current flow in a load. The concept of sourcing and sinking is independent of the component (transistor, mechanical relay) that implements the operation. While this concept applies to any DC circuitry; the component that implements the circuitry may vary.

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2. Sinking Devices


A sinking device provides a path for the current to ground and is not responsible for powering the device. Terms used to describe sinking devices include NPN, Open Collector, Normally High, and IEC Negative Logic.

Figure 1: Sinking

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3. Sourcing Devices


A sourcing device provides the power or a positive potential. Sourcing devices 'push' the current through the load. Terms used to describe sourcing devices include PNP, Open Emitter, Normally Low, and IEC Positive Logic.

Figure 2: Sourcing

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4. Recommended NI Products that Connect to Sinking and Sourcing Devices


NI 6509
NI 6514
NI 6515
NI 6528

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