This calculator converts the Variation in Output Frequency (Hz/kHz/MHz/GHz) to parts per million (PPM) or parts per billion (PPB).
It also calculates the Frequency Error (%).
- Center Frequency
- Peak Frequency Variation
ppm = (df/F)*106
- F is the center frequency
- df is the peak frequency variation
- ppm is the resulting value in parts per million
In the formula above, the factor 106 is used to convert to 1 million
- 1 PPB = 1000 PPM
The frequency error is expressed as a percentage and is given by the formula
Frequency error (%) = (ppm/106)*100
At a frequency of 1 GHz if the system is specified for a peak frequency shift of 100 Hz, then the reference oscillator has to be less than +/- 0.1 ppm.
What is frequency?
Frequency is the number of cycles or repetitions per unit of time. If a sine wave repeats 100 times every second, its frequency is 100 Hz.
An oscillator is an electronic device that is used to produce a sine wave and its primary specifications include the input power, voltage input, output frequency and the variation of the output frequency.
What is PPM?
The output frequency variation of an oscillator is measured in parts per million or ppm. This variation is due to a number of factors including: temperature, ageing, load conditions and frequency tolerance.
Let’s take a closer look at an oscillator data sheet.
The frequency tolerance, stability and ageing are all expressed in ppm. The total frequency variation over the span of 5 years is the sum of the three or + 2.6 ppm. This represents the total frequency accuracy of the clock.
Ideally a clock has zero variation in its frequency of operation and a 19.2 MHz oscillator such as the one above is at the same frequency for its entire life. However, practically this is never possible.
Note: An oscillator vendor will typically quote the stability specification as being representative of its frequency variation. In the above case it’s + 0.1 ppm. However, the total frequency variation is a much larger number. It’s therefore important to consult the data sheet for the full picture.
Why is frequency variation an important parameter?
Frequency accuracy is essential for system performance and reliability due to several reasons.
Firstly, many systems rely on precise timing and synchronization for their proper functioning, such as power grids, telecommunications networks, and computer systems.
These systems operate on specific frequencies, and any deviation from the intended frequency can lead to synchronization errors and disruptions in communication or power distribution.
Secondly, frequency accuracy is also crucial for the protection of system components. The correct frequency is often required for the efficient operation of electronic devices, and frequency variations can lead to increased stress on the components, causing premature wear and potential failures.
Finally, frequency accuracy is vital for ensuring the accuracy of measurements and feedback control systems, as any fluctuation in frequency can introduce errors in calculations and lead to incorrect results. Therefore, maintaining frequency accuracy and minimizing the frequency variation is critical to ensuring the reliability and proper functioning of various systems.
What is Frequency Stability?
Frequency Stability is defined as the allowable deviation over the rated temperature range. Typically -40° C to +85°C although in some cases it is defined over a narrower range -20° C to +70°C.
What is Frequency Tolerance?
Frequency Tolerance is defined as the allowable deviation from the specified Frequency when measured at 25°C or room temperature.
Note that while Tolerance is stated at one temperature and stability over a range that includes that specific temperature, the total accuracy budget is the sum of the two. This is why they are specified separately in the data sheet.
What is Ageing?
Within the context of oscillators ageing is the change in frequency with time due to internal changes in the oscillator. It is expressed as a function of time and in ppb or ppm.