What is the purpose of a common ground connection in power supplies?

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In summary: When you are looking at voltages that are close to the 0V rail you may not see as much voltage because it is essentially being pulled down to that level. For example if you are looking at a +5 volts scope and you have a voltage at +4.9 volts and then you have a voltage at +5.1 volts, the 5.1 volts would be seen as the peak voltage as it is closer to the 0V rail.
  • #1
matinm90
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Okay so I've seen that some not all power supplies have a positive and negative side for the voltag output and in addition have a common ground connection, exactly what is that used for?
 
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  • #2
matinm90 said:
Okay so I've seen that some not all power supplies have a positive and negative side for the voltag output and in addition have a common ground connection, exactly what is that used for?

Ohhhh ? like to show an example of one that doesn't :)
All the many and varied PSU's I have worked with over the last 40 years all have a positive and negative output. bit difficult to complete a circuit without a negative rail ;)
Some may also have a ground/chassis connection and that connection may or may not be commoned with the negative

Dave
 
  • #3
Lol let me explain that differently, all of the power suPplies I've seen have a positive and a negative, and some also have standalone ground connection or common ground, so what is it exactly? I know what ground is but what is a "common" ground for?
 
  • #4
matinm90 said:
Lol let me explain that differently, all of the power suPplies I've seen have a positive and a negative, and some also have standalone ground connection or common ground, so what is it exactly? I know what ground is but what is a "common" ground for?

ok it may be as said in the last part of my comments.

a common ground may be connected to the negative rail.

do you have any circuit examples to look at and confirm ?

D
 
  • #5
Some what, an op-amp circuit. The positive and negative feed the power for the op amp while the common ground, is used to ground the rest of the components that may be used, such as a function generator or oscilloscope, now is it necessary to use common ground for everything else? Or can we just use the low Potential or - for everything?
 
  • #6
Ahhh ok

in that case its a little bit different, as its not the standard + and - rails where the ground and/or chassis is connected to the negative. Thats a split rail supply. Its specifically designed for components that need to work with a positive and negative rail, say +12 and -12 Volts. Other parts of the circuit may well just use the +12v and 0V rails

Now that 0V rail may or may not be connected to chassis ground. Thats really up to the designer of the circuit and what they are trying to achieve.

Dave
 
  • #7
Ohh Okay. Well thank you that cleared things up for me, I appreciate it :-)
 
  • #8
...For your oscilloscope testing you would use the 0V for the GND lead of the scope and the probe is free to measure voltages that may be more positive or more negative than the 0V rail.
 

1. What is common ground?

Common ground refers to a shared understanding or agreement between individuals or groups. It is a point of agreement or overlap in beliefs, values, or interests that can be used as a basis for communication and cooperation.

2. How is common ground established?

Common ground is established through open and respectful communication, active listening, and finding areas of agreement. It requires a willingness to understand and consider different perspectives and find commonalities.

3. Why is common ground important?

Common ground is important because it allows for effective communication and problem-solving. It helps bridge differences and build relationships, leading to better understanding and cooperation among individuals or groups.

4. Can common ground change over time?

Yes, common ground can change over time as individuals or groups learn more about each other and their beliefs and values evolve. It is important to continuously communicate and reassess to maintain a strong common ground.

5. How can lack of common ground impact relationships?

Lack of common ground can lead to misunderstandings, conflicts, and strained relationships. It can also hinder progress and cooperation in achieving common goals. It is important to actively work towards finding and maintaining common ground to avoid these negative impacts.

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