Laboratory Sample Chain-of-Custody, Load & Turnaround

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 12 inputs are read from the form on every keystroke: Lots Received per Day, Samples Drawn per Lot, Tests per Sample, Mean Hands-On Time per Test, Technicians on Shift, Shift Length, Productive Fraction of the Shift, Conditioning Period, Mass Drawn per Sample, Portion Retained After Test, Custody Transfers per Sample and Working Days per Year.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Technician Utilisation together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Turnaround per Sample, Test Hours Demanded, Productive Hours Available, Surplus or Shortfall, Samples Registered, Tests Performed, Custody Records Generated and Retained Sample Mass — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

Substituting

The laboratory is at 92.5% utilisation with 3.72 spare hours a day, which sounds comfortable and is not: a single technician absent removes 6.24 h and puts the load at 106%, and from that day the backlog compounds. Utilisation above roughly 85% in a laboratory with variable intake behaves like a queue at saturation, where turnaround grows without any change in demand.

How to use it

1. Work through the input groups in order — Intake and Capacity & Custody. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Technician Utilisation in the dark results panel — that is the headline figure, expressed in %.
4. Check the supporting rows underneath (Turnaround per Sample, Test Hours Demanded, Productive Hours Available, Surplus or Shortfall, Samples Registered, Tests Performed, Custody Records Generated and Retained Sample Mass) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Technician Utilisation before a trial is booked, so machine time and material in Fiber Testing, Bale Management & Laboratory Sampling are committed against a calculated figure rather than an estimate.
• Costing and quotation — Technician Utilisation is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Lots Received per Day) shows how much of the gap in Technician Utilisation each variable explains.
• Teaching and study — the accepted ranges bracket normal Fiber Testing, Bale Management & Laboratory Sampling practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• Utilisation here is against productive hours, not shift hours, so it is directly comparable between laboratories only if the productive fraction is measured the same way. The turnaround figure assumes the day's work is shared evenly across technicians and that no test is a blocking dependency for another; where a sequence is mandatory - conditioning, then dimensional stability, then wash testing on the same specimen - the true turnaround is the sum of the chain, not the divided total. The queue term only accumulates a single day of backlog; a laboratory persistently over 100% compounds day on day and this model will understate turnaround badly after the first week. Retained mass assumes a constant retention policy across all sample types, which is rarely true: fibre and yarn retentions are small, garment retentions are not.
• Every input is bounded to the range normal practice occupies (Lots Received per Day 1 to 500, Samples Drawn per Lot 1 to 30 and Tests per Sample 1 to 40, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Standards and further reading

• ISO/IEC 17025:2017 - general requirements for the competence of testing and calibration laboratories.
• ISO 139 - textiles, standard atmospheres for conditioning and testing.
• ASTM D1776/D1776M - conditioning and testing textiles.
• ISO 5725 - accuracy, trueness and precision of measurement methods and results.

Questions people ask