Oscillator Error Calculator

Frequency offset interpretation

Oscillator error is typically expressed as relative frequency offset. A +1 ppm offset means the output runs 1 microhertz per hertz high, so a 10 MHz source is about 10 Hz fast. In mixed-signal systems, this offset drives baud-rate tolerance, sampling alignment, and clock-domain crossing margins.

To compare devices, normalize to ppm or ppb and note the measurement method. Reciprocal counters, long gate times, and GPSDO references reduce uncertainty. Always separate systematic frequency error from short-term jitter when diagnosing failures.

Environmental sensitivity modeling

The calculator lets you layer temperature and supply effects onto the measured offset. Use datasheet sensitivity numbers when available, but prefer lab characterization for your exact PCB, load capacitance, and enclosure. Even small gradients can dominate, especially for low-power crystals operated near their turnover point.

When offsets change abruptly, inspect solder stress, load capacitors, and ground noise coupling.

Aging and long-term stability

Aging is a slow, mostly monotonic drift caused by stress relaxation and contamination. Vendors often specify a first‑year value and a reduced long‑term slope. If you only know a single ppm/year estimate, the linear model here is a practical planning tool for maintenance intervals and recalibration triggers.

Converting ppm to time drift

Time drift follows directly from fractional frequency error. Multiply the fraction by the interval in seconds. For example, 2.5 ppm equals 2.5×10⁻⁶, which becomes about 0.216 seconds per day. This conversion helps translate spec-sheet numbers into user-visible effects such as timestamp error or synchronization slip.

During validation, compute drift for the worst-case mission duration as well as per day. This is essential for data loggers, metering, and industrial control loops that can run unattended for months.

Calibration and reporting practices

Use the trim recommendation to select a programming offset, trimmer setting, or digital calibration constant. Record nominal, measured, temperature, supply, and date with each run so you can trend stability. Exported CSV supports audit trails, while PDF snapshots are convenient for test reports and customer deliverables.

After trimming, re-measure at multiple temperatures and supply corners. A good record includes uncertainty, instrument traceability, and the chosen correction sign. Consistent documentation speeds future debug and supports quality audits.

FAQs

What does a positive ppm result mean?

A positive total offset means the oscillator runs fast relative to nominal. Your clock will gain time; the drift table shows how many seconds accumulate per hour, day, and month.

Should I enable temperature contribution if I only measured at one temperature?

Enable it only if you have a reliable coefficient and a reference temperature. Otherwise, leave it off and treat the calculation as a measurement-only estimate for that operating point.

How accurate is the trim recommendation?

It is a first-order correction equal to the negative total offset. Final trim accuracy depends on measurement uncertainty, non-linear temperature behavior, aging curvature, and how your hardware implements the correction.

Why do my readings vary between runs?

Short-term instability, measurement gate time, reference clock quality, and supply noise can change the apparent frequency. Use longer durations and stable references to reduce variance, and average multiple measurements.

Can this be used for crystals, TCXOs, and OCXOs?

Yes. Enter the nominal and measured frequency, then add contributions that match your device model. For compensated or ovenized parts, vendor coefficients are typically smaller but still measurable.

What data should I store for audits and troubleshooting?

Save nominal, measured, duration, temperature, supply voltage, enabled coefficients, date, and instrument details. Trending these values helps detect step changes from damage, rework, or component drift.