Techniques for Measuring Efficiency

Focus:

Approximately 10 minutes in length, this video describes two methods for quickly measuring the efficiency of a switched-mode power supply. The first and more-accurate technique uses a wattmeter and two digital multimeters (DMMs). The second technique uses four DMMs. This method is useful when you don't have a wattmeter, but it assumes that you can access components within the power supply for certain measurements. The video describes what equipment you'll need, how to set up and configure it, and how to take the measurements. The video also explains why you should measure inrush current before hooking up your DMM to measure input current. [But they forgot to mention you'll need a clamp-on current probe and oscilloscope to measure inrush current.] It also discusses the need to measure efficiency at different line levels and why efficiency drops at different line levels. A transcript of the video is provided in the course notes.

What you’ll learn:

• How to measure the efficiency of a switched-mode power supply using a wattmeter and two multimeters
• How to measure the efficiency of a switched-mode power supply using four multimeters

Notes:

Your must register to view PI University video courses. The test methods described in this video do not follow all the steps required to verify a power supply's compliance with energy efficiency standards (for that see "Testing Compliance to Energy Efficiency Standards" also available at PI University.)

View the Source

Author & Publication:

no presenter specified, Power Integrations, Vendor website, Oct 29 2009

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