# ppm?

#### ELECTRONERD

Joined May 26, 2009
1,146
Hey Guys,

Could someone please explain "ppm"? I believe it has something to do with error measurement because the reference I read said that an In-amp had a gain error typically less than 20 ppm and CMRR that exceeds 90dB (G = 1). What does ppm stand for and could someone please explain it?

Thanks!

#### jpanhalt

Joined Jan 18, 2008
7,699
In the context of your example:

ppm = parts per million

In other words, 1000 ppm error is 0.1% error.

PPM also means pulse position modulation, which is why I opened this thread.

John

#### ELECTRONERD

Joined May 26, 2009
1,146
In the context of your example:

ppm = parts per million

In other words, 1000 ppm error is 0.1% error.

PPM also means pulse position modulation, which is why I opened this thread.

John
So I assume 20 ppm is 0.002% error, correct? Therefore, you want to have the lowest ppm you can possible achieve?

Thanks!

#### jpanhalt

Joined Jan 18, 2008
7,699
So I assume 20 ppm is 0.002% error, correct? Therefore, you want to have the lowest ppm you can possible achieve?

Thanks!
Yes to the 0.002% , and "depends" to the second question.

If you are talking about airplane crashes, yes. If you are casting bricks for a house, 1000 ppm dimensional error is overkill and not worth the additional cost to achieve it. More seriously, depending on the field of study and what you are trying to do, there are various ways to calculate the level of accuracy you will need to get the job done.

John