# Line and Load Regulation for Programmable DC Power Supplies and Precision DC Sources

Publish Date: May 06, 2014 | 33 Ratings | 3.15 out of 5 | Print

## Overview

This tutorial is part of the National Instruments Measurement Fundamentals series. Each tutorial in this series, will teach you a specific topic of common measurement applications, by explaining the theory and giving practical examples. This tutorial contains information you may find useful as you connect specific types of loads to a power supply.

For additional power supply only concepts, refer to the Power Supply Fundamentals main page.
For the complete list of tutorials, return to the NI Measurement Fundamentals Main page.

### 1. Line Regulation

 Line regulation is a measure of the ability of the power supply to maintain its output voltage given changes in the input line voltage. Line regulation is expressed as percent of change in the output voltage relative to the change in the input line voltage. For NI DC power supplies, the line regulation specification refers to the auxiliary power input.

Load regulation is a measure of the ability of an output channel to remain constant given changes in the load. Depending on the control mode enabled on the output channel, the load regulation specification can be expressed in one of two ways:

In constant voltage mode, variations in the load result in changes in the output current. This variation is expressed as a percentage of range per amp of output load and is synonymous with a series resistance. In constant voltage mode, the load regulation specification defines how close the series resistance of the output is to 0 ohms - the series resistance of an ideal voltage source.

In constant current mode, variations in the load result in changes to the current through the load. This variation is expressed as a percentage of range change in current per volt of change in the output voltage and is synonymous with a resistance in parallel with the output channel terminals. In constant current mode, the load regulation specification defines how close the output shunt resistance is to infinity—the parallel resistance of an ideal current. In fact, when load regulation is specified in constant current mode, parallel resistance is expressed as 1/load regulation.

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For the complete list of tutorials, return to the NI Measurement Fundamentals Main page.

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