What is PPM/PPB? How to determine PPM/PPB?
A.
"ppm" stands for parts per million, and "ppb" stands for parts per billion. In frequency components, ppm/ppb represents the ratio of frequency deviation to the nominal frequency. These units are commonly used in the frequency control product (FCP) industry to describe the frequency variation range of crystal oscillators.
Example:
Actual frequency (A.F.) = 24.999950 MHz
⇒ (A.F. - N.F.) / N.F. = (24.999950 - 25.000000) / 25.000000
= -0.000002
= -2 × 10⁻⁶ (parts per million)
= -2 ppm
Nominal frequency (N.F.) = 40.000000000 MHz
Actual frequency (A.F.) = 40.000000040 MHzz
⇒ (A.F. - N.F.) / N.F. = (40.000000040 - 40.000000000) / 40.000000000
= +0.000000001
= +1 × 10⁻⁹ (parts per billion)
= +1 ppb
Example:
Nominal frequency (N.F.) = 25.000000 MHz
Actual frequency (A.F.) = 24.999950 MHz
⇒ (A.F. - N.F.) / N.F. = (24.999950 - 25.000000) / 25.000000
= -0.000002
= -2 × 10⁻⁶ (parts per million)
= -2 ppm
Nominal frequency (N.F.) = 40.000000000 MHz
Actual frequency (A.F.) = 40.000000040 MHzz
⇒ (A.F. - N.F.) / N.F. = (40.000000040 - 40.000000000) / 40.000000000
= +0.000000001
= +1 × 10⁻⁹ (parts per billion)
= +1 ppb