This is a ready-to-use log for the periodic manual time check on standalone or legacy GxP instruments that cannot synchronize to the network time service. A standalone instrument whose clock nobody checks is a recurring inspection finding; a tight, evidenced manual check is the compensating control that closes it. Replace every <<FILL: ...>> placeholder, keep one row per check, and maintain the log under document control. A field-definition table, the blank log, instructions, and a filled specimen follow. Verify each cited regulation against the current source. This is general guidance to adapt, not legal or regulatory advice. This log is the record referenced by the SOP: Time Synchronization and System Clock Control for GxP Systems.
Log header
| Field | Entry |
|---|---|
| Log number | <<FILL: LOG-ID>> |
| Instrument / ID | <<FILL: make, model, asset ID>> |
| Location | <<FILL: room / lab>> |
| Check frequency | <<FILL: e.g. weekly, or before each use>> |
| Tolerance | <<FILL: e.g. within 60 seconds of the reference>> |
| Reference used | <<FILL: e.g. a synchronized wall display / NTP-synced workstation clock>> |
Field definitions
| Field | Format | Required | Who | When |
|---|---|---|---|---|
| Date/time of check | Date + time | Yes | Operator | At each scheduled check |
| Reference time (source) | Time + named source | Yes | Operator | At the check |
| Instrument time displayed | Time | Yes | Operator | At the check |
| Difference | Seconds (signed) | Yes | Operator | At the check |
| Within tolerance? | Yes / No | Yes | Operator | At the check |
| Action if out of tolerance | Text + reference | If No | Operator / QA | At the check |
| Operator | Initials / signature | Yes | Operator | At the check |
| Reviewed by | Initials / signature | Yes | Supervisor / QA | At review |
Blank log
| Date/time of check | Reference time (source) | Instrument time | Difference (s) | Within tolerance? | Action if out | Operator | Reviewed |
|---|---|---|---|---|---|---|---|
<<FILL>> | <<FILL>> | <<FILL>> | <<FILL>> | <<FILL: Y/N>> | <<FILL>> | <<FILL>> | <<FILL>> |
<<FILL>> | <<FILL>> | <<FILL>> | <<FILL>> | <<FILL: Y/N>> | <<FILL>> | <<FILL>> | <<FILL>> |
Instructions
- Perform the check at the defined frequency (and before use if that is your rule).
- Read the reference time from the named synchronized source and the instrument’s displayed time at the same moment.
- Record the signed difference in seconds (instrument minus reference).
- If the difference exceeds the tolerance, do not simply reset the clock and move on. Record the out-of-tolerance value, assess whether any GxP data was generated since the last in-tolerance check that could be affected, correct the clock only under the controlled procedure, and route to QA per the deviation process if data may be affected.
- A supervisor or QA reviews the log on a defined cadence and at the point any GxP result from this instrument is reviewed.
- Retain the log for not less than
<<FILL: retention period>>.
Out-of-tolerance action (summary)
| Situation | Action |
|---|---|
| Within tolerance | Record and continue |
| Out of tolerance, no data since last good check | Correct under procedure, note cause, continue |
| Out of tolerance, GxP data generated since last good check | Quarantine the affected data, assess impact, raise a deviation, correct under change control |
References
21 CFR Part 11.10(e) (computer-generated, time-stamped audit trails). 21 CFR 211.68 (automatic, mechanical, and electronic equipment), 211.194 (laboratory records). EU GMP Annex 11 (computerised systems). MHRA GxP Data Integrity Guidance and Definitions (2018). PIC/S PI 041, Good Practices for Data Management and Integrity.
Confirm the current version of each reference before issue.
Filled specimen
Illustrative rows for a standalone plate reader checked weekly against an NTP-synced workstation, tolerance 60 seconds.
| Date/time of check | Reference time (source) | Instrument time | Difference (s) | Within tolerance? | Action if out | Operator | Reviewed |
|---|---|---|---|---|---|---|---|
| 2026-06-08 08:05 | 08:05:10 (WS-QC-04, NTP-synced) | 08:05:22 | +12 | Yes | none | J.K. | R.G. 2026-06-08 |
| 2026-06-15 08:10 | 08:10:03 (WS-QC-04, NTP-synced) | 08:11:47 | +104 | No | No GxP runs since last check; clock corrected under CR-2026-0455; DEV not required | J.K. | R.G. 2026-06-15 |
In the second row the drift exceeded tolerance, so the operator did not just fix it silently: they confirmed no GxP data was affected, corrected under a change record, and had it reviewed. Had a run occurred in the drift window, the row would instead reference a deviation and an impact assessment.
Common inspection findings this log prevents
- A standalone instrument drifting for months with no evidence anyone ever checked its clock.
- A clock quietly reset with no record and no assessment of data generated during the drift.
- Manual checks performed but never reviewed, so an out-of-tolerance reading goes unnoticed.
How to adapt this log
- Set the instrument, frequency, tolerance, and named reference source.
- Decide your rule for “before each use” versus a fixed cadence based on the instrument’s drift and criticality.
- Point the out-of-tolerance action to your real deviation and change-control procedures.
- Confirm every regulation against the current published version before issue.