# ripple free dc voltage

Thread Starter

#### rodn.m

Joined May 3, 2006
12
what is meant by the term 120 volts dc ripple free?

#### Papabravo

Joined Feb 24, 2006
13,551
Originally posted by rodn.m@May 4 2006, 11:16 AM
what is meant by the term 120 volts dc ripple free?
[post=16800]Quoted post[/post]​
I would take it to mean that it is a constant voltage of 120 Volts. It has no periodic AC component that can be measured or observed. What can be measured or observed is naturally a subjective concept. It may or may not have random uncorrelated fluctuations, measureable or otherwise.

I don't consider this to be a very meaningful description of a DC source. In statistical terms it suggests a voltage source with a mean of 120 volts and a variance of zero. We know this to be a physical impossibility. Even a battery has a non-zero variance. Just think of the discharge curve as describing a very low frequency ripple.

Thread Starter

#### rodn.m

Joined May 3, 2006
12
Originally posted by Papabravo@May 5 2006, 07:28 AM
I would take it to mean that it is a constant voltage of 120 Volts. It has no periodic AC component that can be measured or observed. What can be measured or observed is naturally a subjective concept. It may or may not have random uncorrelated fluctuations, measureable or otherwise.

I don't consider this to be a very meaningful description of a DC source. In statistical terms it suggests a voltage source with a mean of 120 volts and a variance of zero. We know this to be a physical impossibility. Even a battery has a non-zero variance. Just think of the discharge curve as describing a very low frequency ripple.
[post=16809]Quoted post[/post]​
the reason i ask, is that this is the term used in the SAA Wiring rules of Australia/New Zealand 2003.

it refers to the maximum value of for Extra Low Voltage for a DC supply.

SAA means Standards of Australia something ?

thanks for the quick reply

watt's up with what!

#### thingmaker3

Joined May 16, 2005
5,084
"SAA" = "Standards Association of Australia"

The electrical wiring rules are AS 3000

The only documents I could find with numbers on "ripple free" were so full of legalese I couldn't be sure if they were giving allowance or documenting farm animal deaths.

#### windoze killa

Joined Feb 23, 2006
605
Originally posted by thingmaker3@May 7 2006, 01:28 PM
"SAA" = "Standards Association of Australia"

The electrical wiring rules are AS 3000

The only documents I could find with numbers on "ripple free" were so full of legalese I couldn't be sure if they were giving allowance or documenting farm animal deaths.
[post=16855]Quoted post[/post]​
Being Australian and also knowing a little about AS3000 the term 120VDC ripple free just means that it is DC and is not to be confused with AC unfiltered rectified AC. They have very specific voltage levels to determine who can and can't touch or work on various equipment.

As a side not, one of the states of this fine land has introduced legislation that makes it illegal to fix/work on a video recorder unless you hold an electricians licence. To obtain one of these you MUST do a 4 year apprenticeship.

#### Gadget

Joined Jan 10, 2006
614
To work on ANY mains powered appliance for profit, we must have a Minimum of a Current EST (electrical service technician) registration. Individuals can do what they want with their own gear, including breaking every plastic post, lever and gear in a VCR in a vain attempt to remove the stuck tape that was due back yesterday or making their own Power extension cord for the lawn mower.

#### Dave

Joined Nov 17, 2003
6,970
Originally posted by rodn.m@May 4 2006, 03:16 PM
what is meant by the term 120 volts dc ripple free?
[post=16800]Quoted post[/post]​
To add to earlier answers regarding the general idea of 'ripple-free', you must consider it in context of the application that you are working with. I have had people propose to me "ripple-free" Chebyshev filter designs for image-filtering. For those that are familiar with Chebyshev filter designs, they inherently have pass-band ripples traded against steep transition regions, but can easily be desribed as 'ripple-free' by their designers because the net effect on the image acquisition process is minimal and unaffected by the ripples.

Anyhow, I can't comment further on what has been said since I am unfamiliar with the wiring laws of Australia (and other countries).

Dave

#### radiosmoke

Joined May 30, 2006
17
Originally posted by rodn.m@May 4 2006, 08:16 AM
what is meant by the term 120 volts dc ripple free?
[post=16800]Quoted post[/post]​
Heres a picture with ripple on the top and one below that has less ripple. If there were no ripple the line would be flat. That would be accomplished by using coils and capacitors in the circuit.