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

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.

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

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.

Relevant NI Products

Customers interested in this topic were also interested in the following NI products:

• Programmable DC Power Supplies and Precision Sources
• Modular Instruments (digital multimeters, digitizers, switching, etc...)
• LabVIEW Graphical Programming Environment
• SignalExpress Interactive Software Environment

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

Reader Comments | Submit a comment »

Then in a constant voltage mode, if the current varies & if their is a change in load, what will be the result of the load current?
- Jun 21, 2008

no
No because a voltage source is supposed to maintain a constant (unchanging) voltage between its terminals regardless of its load.
- Mar 24, 2008

Error?
The load regulation definition says "In constant voltage mode, variations in the load result in changes in the output current." I would expect a change in current if the load changes. Should the line read "In constant voltage mode, variations in the load result in changes in the output VOLTAGE."?
- Feb 20, 2007