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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? sensing

W5VO
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jeroncic
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1 Answers1

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

enter image description here

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

useful links :

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

ElectronS
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  • I will add the Linear's [Application Note 105](http://cds.linear.com/docs/en/application-note/an105fa.pdf). – Antonio Aug 11 '16 at 13:46
  • @Passerby , happy now ?? :) – ElectronS Aug 11 '16 at 17:26
  • Exceptionally :) – Passerby Aug 11 '16 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? – Justin Aug 11 '16 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. – ElectronS Aug 12 '16 at 07:58
  • @justin , the hall effect sensor is like a clamp meter you can use it in high side or low side no problem , but best in high side to measure the current entering a device . – ElectronS Aug 12 '16 at 08:01
  • @ElectronS, i found chip CS5490 for energy measurement, and i am trying to make a sort of power meter for monitoring the energy usage. That why i am trying to figure out which solution is better and where and how should i place my sensing resistor. – jeroncic Aug 16 '16 at 09:11
  • @ElectronS I'm fairly certain that Figure 1A is sensing on the high side (with CMV), and Figure 1B is low side (with reference to ground). You had it the other way around... – KMC May 02 '21 at 06:48
  • @KMC you are right , i reversed them – ElectronS May 04 '21 at 00:49