Part Per Million Conversion

part per million simply means a ratio of number of parts per million parts. One part per million, for example, is one part in one million parts (one millionth, 0.000001, 0.0001%).

It is often used to define reject rates, acceptance limits, or, in your case, precision or accuracy.

Dear Zidny, I will try. The issue is what is being measured.

Lets say laser wavelength is 1000nm.

lets say error of measurement by your interferometer is 0.001 nm

0.001/1000= 1 /1000000 or 1 ppm.

Maybe you have an extremely stable internally standardized helluva interferometer made by the fascists of precision company.

Again, the laser wavelength is 1000nm.

But this frighteningly accurate interferometer can measure to 0.0001nm.

You ppm would be 0.1ppm; thats 0.0001/1000000.

ppm is just long division, BUT YOU MUST CALL OUT THE UNITS OF THE MEASUREMENT.

The point you need to understand is the units being measured, whatever the ppm is must be those units.

milo

As the other commentators have mentioned it all depends on what is being measured (and the units of measurement involved)

It is widely used to measure levels of impurities / concentration ratios.

ppm (parts per million), ppb (parts per billion), ppt (parts per trillion) etc.

It is just a quick ratio of the measurement of one component to the other

Example:

Note: '^' refers to the power of something

1ppm ≡ 1mg/1kg or 1x10^-3 g/1x10^3 g ≡ 1x10^-6 g or 0.000001g (1mg per kg)

Remember when you divide powers, you subtract the power indexes so its

10^(-3 -(+3)) ≡ 10^(-3 -3) = 10^-6

And again:

1ppb ≡ 1μg/1kg or 1x10^-6 g/1x10^3 g ≡ 1x10^-9 g or 0.000000001g (1μg per kg)

Why a million, billion, trillion etc. How many zeros do they have????

Apologies for the crude equations, I tried to upload equation created in word but failed

Thank you for your help