Calibration, certificates and turnaround
This page describes how a measurement is specified, what a certificate has to state, how long the work takes, and what to send in a first message so that the reply is a specification rather than a list of questions.
What a specification has to state
A usable specification names four figures for every measurement: the range it is taken in, the resolution it is read to, the uncertainty of the result, and the conditions — temperature above all — that uncertainty was established under. A document missing any of the four will be read differently by every person who uses it.
Where your own procedure already fixes some of these, send it with the enquiry. It is quicker to work inside an existing procedure than to specify a measurement and then discover it conflicts with one.
Resolution, tolerance and uncertainty
These three are routinely confused and they are not the same number. The tolerance is what the part is allowed. The resolution is the smallest change the instrument can show, and it should be finer than a tenth of the tolerance. The uncertainty is how far the true value may sit from the one displayed, and it is the figure that decides whether a reading near the limit means anything at all.
A reading of 0.048 mm against a limit of 0.050 mm is not inside the limit if the uncertainty is 0.004 mm; it is a result that cannot be called either way. Saying that plainly is part of the work, and it is a great deal cheaper than saying it after a batch has shipped.
Reference standards and traceability
Length is calibrated against gauge blocks, mass against a reference set of a stated class, torque against a transducer that has its own certificate. Each of those standards carries its own chain, unbroken back to a national standard, and the chain is named on the certificate we issue. Where we cannot show the chain for a quantity, we do not certify that quantity.
Reference standards are held apart from working instruments and are checked on a stated interval. A reference that lives in the same drawer as the tools it certifies stops being a reference within a year.
Turnaround, batches and soak time
Turnaround is confirmed with the quotation and is measured from written acceptance, not from the first enquiry. It depends on the quantity, on whether the work is done here or at your bench, and on soak time: an instrument arriving from a cold vehicle is left to reach reference temperature before a single reading is taken, and no amount of urgency shortens that.
Where a batch of instruments is booked together, we agree in advance which ones go first, so a production line is not waiting on the certificate for a gauge nobody uses.
Handling, storage and transport
An instrument is a certified figure only for as long as it is treated like one. Instruments travel in their cases; a caliper loose in a toolbox is measured again on arrival and often explains itself. Click-type torque wrenches are stored wound down. Gauge blocks are kept lightly oiled, handled with the tongs, and never left wrung together.
Keep the certificate number. It is the only thing that connects an instrument on the bench to the measurement record held here.
Support in use
We attend to help with setting up a measurement, agreeing where the reading is taken from, checking a bench for level and draught, and questions about what a certificate actually permits. What is measured on the day is written down as it is measured, and a copy of that record goes to you with the certificate.
Where a result looks wrong during a check, it is easier to settle on the spot than after a batch has been judged with it. A telephone call at that moment costs nothing.
Intervals and recall
An interval is a decision, not a tradition. We propose one from the use, the environment and the cost of a wrong reading, then read the next certificates against the last ones: an instrument that drifts gets a shorter interval, and one that has been stable across three cycles can usually be given a longer one, in writing, with the reasoning attached.
Due dates are held in a register and we send the recall in advance. Nothing is calibrated or invoiced on the strength of that notice alone.
How to request a quotation
Describe the measurement
The feature, its nominal value, its tolerance and the unit your drawing uses. If a print or an inspection sheet already exists, send it. A tolerance quoted from memory is the single most common reason a specification has to be redone.
Describe the conditions
Where the measurement happens — bench, machine, or out on site — the temperature range of that place, how many people take the reading, and how often. For mass, describe the bench and what shares the floor with it.
State the constraints
Any standard or procedure of your own the instrument has to satisfy, the calibration interval you are required to keep, whether the instrument can leave your site, and the accuracy class already written into your documentation.
Receive the specification and the quotation
You get a written specification with the range, resolution, uncertainty and conditions for each measurement, a turnaround time, and a price per instrument and per certificate. Nothing is supplied until that document is accepted in writing.
What cannot be handled by message
We do not take payment details in a message, and no page on this site collects them. Nobody legitimate will ask you to send a card number by email; a request of that kind claiming to come from us did not come from us.
We also cannot certify an instrument against a range, a class or a quantity it has not been measured in, however the question is phrased. Where the answer is not known, it is given as not known.
Send the enquiry
Written enquiries reach us at contact@slatemetrology.online, and by telephone at during business hours. Postal correspondence goes to the registered address shown on the contact page.