# Making Sense of Current Sensing

I am trying to understand the basic Sense Monitoring - High Side or Low Side wich is better and why? and does this also apply for AC voltage.

For example i insert Shunt resistor on phase line to the device.

So in this picture i measure current on high-end?

• Commented Aug 11, 2016 at 13:15
• Did you know that there is a circuit editing tool? Press Ctrl M when writing questions or press the button. Commented Aug 11, 2016 at 17:52

The web is full of such comparisions: Consider the following figure

Figure A :Low side sensing is simpler and less expensive (amplifier wise) due to the shunt being connected to ground . but many applications cannot tolerate the ground-path disturbance introduced by the sense resistor ( the ground offset casued by the voltage drop across shunt resistor).

Figure B: High side sensing requires differential amplifier common-mode voltage that is close to the supply voltage. It doesnot suffer the ground offset problem and it also allows the detection of accidental battery shorts to system ground

What’s The Difference Between High-Side And Low-Side Current Sensing?

High-Side Current-Sense Measurement: Circuits and Principles

and video :

Current Sensing: Low Side, High Side, and Zero Drift

• I will add the Linear's Application Note 105. Commented Aug 11, 2016 at 13:46
• @Passerby , happy now ?? :) Commented Aug 11, 2016 at 17:26
• Exceptionally :) Commented Aug 11, 2016 at 17:31
• In your answer and the links, it looks like this is mostly for low voltage DC. Does your answer apply for 120V or 240V AC as implied in the question? Commented Aug 11, 2016 at 17:36
• @Justin as far as i know , in 120 or 240ac systems : something called current sense transformer is used . Or Hall effect sensor . offcourse you cannot use an OPamp for AC , you would need Isolation anyway (hall effect and current transformer does this for you. Commented Aug 12, 2016 at 7:58