Unit 5 — Verification and Logging

TM-CAL-003 — Open Handout TM Chapters: Chapter 6, Chapter 7 ELOs: Apply adjustments; perform independent verification; produce calibration log Estimated time: 45 minutes (hands-on lab)

Step 1: Read the TM

Open TM-CAL-003. Read Chapter 6 and Chapter 7 completely.

Then come back here.

Chapter 6 — Tuning and Adjustment

6-1. PLL LOOP FILTER TUNING

The PI control loop has two parameters: proportional gain (Kp) and integral gain (Ki). Too high Kp causes oscillation; too low causes slow lock. Start with Kp = 0.1 and Ki = 0.01, then increase Kp until oscillation appears, then back off 50%.

NOTE: The Si5351A frequency resolution is approximately 0.01 Hz at 10 MHz due to the 27-bit PLL multisynth fractional divider. This limits PLL granularity but is adequate for most calibration applications.

Chapter 7 — Verification

  1. Measure GPSDO output against WWV 10 MHz carrier using zero-beat method. Error should be <1 Hz.
  2. Confirm GPS lock: check satellite count in NMEA GPGGA sentence (≥4 sats required).
  3. Verify 1PPS LED or debug output shows TIMEPULSE active.
  4. Connect GPSDO to TinySA Ultra reference input (if equipped) and confirm TinySA frequency readouts are consistent with GPSDO.
  5. Log: date, firmware version, GPS module serial, lock time, frequency error.

Calibration vs. Verification

These are two different things:

Calibration (Chapter 5): You apply reference inputs and record what the instrument reads. You may adjust the instrument during this process. The result is a set of measurements taken while you are actively tuning.

Verification (Chapter 7): After all adjustments are complete, you perform an independent confirmation measurement. You do not adjust during verification — you are testing whether the calibration held.

Locate the verification criterion in Chapter 7.

If verification fails, you do not re-adjust and re-verify in one step. You return to Chapter 5, re-calibrate, and then re-verify from scratch.

Lab Checklist

Work through this with equipment in hand. Check each box when complete.

  • [ ] Chapter 4 setup complete
  • [ ] Chapter 5 calibration procedure complete
  • [ ] Any adjustments applied per Chapter 6
  • [ ] Chapter 7 verification measurement performed
  • [ ] Verification criterion met

  • [ ] Calibration log entry completed:

  • [ ] Date

  • [ ] Instrument type and model
  • [ ] TM number and procedure
  • [ ] Reference standard used
  • [ ] Measured values
  • [ ] Errors (% or ppm)
  • [ ] Pass/Fail result
  • [ ] Operator name

Self-Check Questions

SC5-1. What is the verification acceptance criterion per Chapter 7? State it with units.

SC5-2. What is the difference between the Chapter 5 calibration and the Chapter 7 verification?

SC5-3. Your Chapter 7 verification fails. What is the correct next step per the TM?

SC5-4. List the required entries in the calibration log.

SC5-5. Why must the log be completed before the calibration is considered finished?

Answer Key

SC5-1. See TM Chapter 7. Copy the criterion exactly with units and section number.

SC5-2. Chapter 5 is the active calibration — you apply references and may adjust. Chapter 7 is an independent confirmation after all adjustments are locked in — no further adjustment during verification.

SC5-3. Return to Chapter 5 and re-calibrate. Do not re-adjust and re-verify without re-doing the full calibration procedure.

SC5-4. See TM Chapter 7. List every item the TM specifies.

SC5-5. A calibration with no record did not happen in any traceable sense. The log is the evidence that the procedure was followed, the results were within specification, and who performed it.

Checkpoint

TLO-1 is complete when: - [ ] Verification criterion met (Chapter 7) - [ ] Calibration log entry completed with all required fields - [ ] You can explain the difference between calibration and verification

→ Proceed to Final Assessment