How to measure internal resistance of a power supply

[newbieinelectronics]

Hi.

Suppose that I have a power supply that I know its output voltage and its maximum current.

How can I measure the resistance of this power supply?

Thanks.

 

[flatulent]

You measure the output voltage with two different resistor loads which draw two different currents. Then compute delta voltage divided by delta current. This is the static output impedance.

This is different from the dynamic impedance. For that you need to rapidly switch between two load currents. This can be done with a FET which switches in another resistor.

 

[echo47]

If you wish to measure the power supply's output impedance over a frequency range, try browsing slides 19 through 22 of this Agilent product note. It shows the basic technique, and how to do it with a network analyzer:
**broken link removed**

 

[newbieinelectronics]

Your answers helped me a lot.

Thanks.

 

[quaternion]

Also you can sweep the load current & monitor the variation in the output voltage.