Calibration Register

What this tool does

CM8-93 is a calibration register for measuring instruments — the list an auditor asks for within the first ten minutes of a quality audit. One row per instrument, holding its identity, its owner, its interval, its most recent calibration and the certificate that supports it. The tool works out when each instrument is next due, tells you what is overdue, what is about to be, and — most importantly — which instruments were found out of tolerance.

Everything runs inside this single file. There is no account, no upload and no network request of any kind, so your instrument list, your certificate numbers and your customer's tolerances never leave this computer.

What belongs in the register

Every instrument whose reading you rely on for a decision. That is a wider set than most registers contain:

• Product measurement — calipers, micrometers, gauges, height gauges, indicators, anything used to accept or reject work.
• Process measurement — thermometers, pressure gauges, flow meters, timers, scales, where the process setting depends on the reading.
• Tools that set a value — torque wrenches and torque tools apply a quantity as well as reading one, and they drift quickly.
• Reference standards — gauge blocks, reference weights, the meter you check other meters against. If the reference has drifted, so has everything checked against it.

Instruments used only for indication, where nobody acts on the exact number, can be excluded — but label them clearly as "indication only" so nobody uses them for acceptance. Record that decision somewhere; being unable to explain why an instrument is not in the register is the second-most common finding after being overdue.

Filling in a record

Each row holds one instrument, not one calibration event. When an instrument comes back from calibration you edit its row: new date, new certificate, new result, new as-found condition. Keep the certificates themselves — the register points at them, it does not replace them.

• Asset reference — the number physically marked on the instrument. If it is not marked on the instrument, it cannot be traced back to this row, and the register is decorative.
• Range, unit and tolerance — the range it is calibrated over and the accuracy you require of it. A caliper calibrated to 150 mm tells you nothing about a 200 mm measurement.
• Location and custodian — where it lives and who is responsible for producing it when the recall comes round. Unassigned instruments are the ones that go missing.
• Interval — in months. Leave it blank to use the default on the Settings tab. Enter 0 for an instrument that is verified before each use instead of on a fixed cycle; it then shows no due date.
• Notes — what was adjusted, what was restricted, and what was done about work already measured. This is the field an auditor reads.

How the next due date is worked out

The due date normally comes from the last calibration plus the interval:

Calendar months, not 30-day blocks: a 12-month interval from the 31st of a month falls on the last day of the target month where that month is shorter. Where the certificate or a customer fixes a specific date, enter it in "next calibration due" and it overrides the calculation for that row.

The warning window is set on the Settings tab and defaults to 30 days. Set it to the time it actually takes you to book a slot, send the instrument away and get it back — for an external laboratory with a two-week turnaround plus transport, 30 days is tight and 45 is realistic.

That is the number that matters. An overdue instrument sitting in a drawer is an administrative problem. An overdue instrument still being used to accept product is a defensible-measurement problem, and it is what the "in service" tile counts.

Retired, disposed and lost instruments are excluded from the overdue and due-soon counts by default, because they cannot be presented for calibration. Turn on "count retired and lost instruments as due" if you would rather a lost instrument kept appearing on the list until somebody finds it or writes it off properly.

The as-found reading is the important one

Most registers record only whether the instrument passed. That hides the single most valuable piece of information a calibration produces: what the instrument read before it was adjusted.

That is why "as-found condition" is a separate field from "result", why it has its own headline tile, and why it has its own table on the Reports tab instead of being buried inside a status column. A torque wrench that was found reading 7 % low did not simply pass after adjustment — it torqued several hundred joints incorrectly first.

When an out-of-tolerance finding appears, the work is not "book it in again". It is:

• Establish how far out it was, and in which direction, from the certificate.
• Establish what was measured with it since the previous calibration — that is the period the register estimates for you.
• Decide whether the error mattered against the tolerance of the thing being measured. Sometimes it does not, and you say so in writing.
• Where it did, recall, re-inspect, re-work or inform the customer, and record what you did in the notes.
• Consider shortening the interval, because the drift happened inside the last one.

The "estimated period in doubt" column works backwards from the calibration date by the instrument's interval, because this register holds only the latest calibration for each instrument. If you have the previous certificate, use its date instead — the estimate is only as good as the assumption that the interval was kept.

The register refuses to record an out-of-tolerance as-found reading with a plain "pass" result, because that combination is how the finding gets lost.

Traceability and certificates

Traceability means the instrument was calibrated against a reference that can itself be traced, through an unbroken chain of comparisons each with a stated uncertainty, back to a recognised national or international measurement standard. It is what makes your measurement mean the same thing as your customer's.

Tick the traceability box only where you hold a certificate that says so, and record its reference. The tool will not let you claim traceability without a certificate reference, because an untraceable claim is worse than an honest gap. An in-house comparison against a reference instrument is perfectly legitimate — but the traceability then belongs to the reference instrument, which must itself be in this register, calibrated externally and in date.

The "treat a missing certificate as a failure" setting decides whether uncertificated instruments are counted alongside the overdue ones as a compliance breach. Turn it on if your customers or your own quality system require a traceable certificate for every instrument in service.

Choosing an interval

Intervals are a judgement, not a rule handed down. Base them on:

• How the instrument behaves — its own calibration history is the best evidence you have. An instrument that comes back in tolerance three times running can usually have its interval extended; one found out of tolerance should have it shortened.
• How hard it is used — a caliper in daily production use and the same caliper in a laboratory drawer do not need the same interval.
• What it costs to be wrong — how much product would be in doubt if it drifted, and how long it would take to notice.
• What is imposed on you — customer contracts, sector schemes and instrument makers all set intervals in some situations. Those override your judgement.

Twelve months is a common starting point and nothing more than that. Record why you chose an interval, so the next person does not have to guess — and so that extending one looks like a decision rather than a slip.

Status, and what "in service" means

"In service" means available for use. It is the strongest claim in the register, and it is the status that turns an overdue date into a breach. Anything not fit to use should be moved out of it on the day, not on the day somebody notices:

• Out of service — away for calibration or repair. It will keep appearing on the due list, which is correct: the recall is still outstanding.
• Quarantined — physically prevented from being used. Use this for anything that failed calibration and is still on site. Label the instrument itself; a status in a file does not stop anybody.
• Retired — disposed of or permanently withdrawn. Keep the row and its history; do not delete it.
• Lost — missing. Worth keeping visible, because a lost instrument that reappears is often put straight back into use without being recalibrated.

Reading the charts and tables

The four charts answer four different questions. Instruments by type shows what the register is made of and which types keep running late. Calibration status shows the whole register in one circle — the proportion of red is the number an auditor will form an opinion from. Calibrations due by month is your booking workload: past months in red are already overdue, and a single tall month means every instrument was bought or calibrated at the same time and now recalls together. Overdue by location tells you where to walk.

The two tables are the action lists. Overdue and due soon is in date order with the custodian named, so it can be issued as it stands. Out-of-tolerance findings is the one to read first, even though it is second: each row is a period of production whose measurements are in doubt.

Every filter applies to the tiles, the charts, the tables, the printed report and the CSV export. Filter to one location and the whole page becomes that location's register.

Standing up in an audit

Auditors tend to work the same way. They take an instrument off a bench, read its asset number, and ask to see its record. Then they check three things: that the record exists, that the calibration is in date, and that the certificate supports what the record claims. Then they ask what happens when one is found out of tolerance — and they look for evidence that it has actually been done, not a procedure saying it would be.

So the register is only half of it. Keep the certificates, mark the instruments, and write in the notes what you did about the work already measured. A register with an empty out-of-tolerance table and a shelf of certificates is an easy audit; a tidy register with no certificates behind it is not.

Printing and sharing

Print Report produces a report from whatever the current filter shows: header, the six headline figures, the four charts, both tables, the full register and your closing notes. Print to PDF to circulate it or to file it as evidence of a review on a given date.

The scope line under the title states the filter in force. Clear the filters before issuing anything described as the complete register, and check the date on it — a calibration report is a statement about a moment in time, and every "overdue" on it is measured against the day it was printed.

Saving your work

Instruments, settings and the report header are written to this browser's local storage as you type, and the toolbar shows the time of the last save. That storage belongs to one browser on one computer: another browser, a private window, a second machine or a clean-up tool that clears site data will not have it.

Treat Export .json as the real save — one file containing everything, which Import .json restores anywhere. Export CSV gives you the register for spreadsheet work and includes every filtered record, not only those drawn on screen. Reset asks twice, then erases everything this tool has stored. There is no undo.

Calibration records usually have to be kept for years — often longer than the instrument itself lasts, because they support the product it measured. Export regularly and archive the exports alongside the certificates.

Accuracy & disclaimer

This tool records what you enter and calculates dates from it. It cannot calibrate anything, cannot check a certificate, cannot tell whether an instrument is suitable for the measurement being made, and cannot tell whether an interval is appropriate. If the last calibration date or the interval is wrong, the due date is wrong and everything derived from it is wrong with it.

Calibration requirements, traceability expectations, accreditation arrangements and record-retention periods differ by country, by industry, by certification scheme and by customer contract. Nothing here is specific to any of them. This is an internal record-keeping and date-calculation aid, not a quality management system, not a certificate of conformity, and not advice on what your obligations are.