How to choose a calibration laboratory - things to consider

Things to be considered while doing calibration

What is calibration?

One of the most important steps for maintaining instrument accuracy is instrument calibration. Calibration is the process of preparing an instrument so that it can generate a consistent result for a given sample. Instrumentation design involves removing or eliminating elements that can lead to faulty measurements.

To establish the correlation at precise places within the instrument’s operational range, calibrations are performed using only a few calibrators. While using a large number of calibrators to develop the calibration relationship, or “curve,” the time and labour required to prepare and test a large number of calibrators may outweigh the level of performance achieved. In practice, a compromise must be established between the desired degree of product performance and the effort required to complete the calibration. When the intermediate points stated in the manufacturer’s performance criteria are used for calibration, the instrument will perform best; the defined technique effectively eliminates, or “zeroes out,” the inherent instrument error at these locations.

Why is calibration so important?

The precision and quality of measurements taken with a piece of equipment are defined by calibration. When using technologies or measuring characteristics like temperature and humidity, there is a propensity for results and accuracy to ‘drift’ with time. For dependable, accurate, and repeatable readings, it is necessary to maintain the calibration of equipment throughout its lifetime.

The goal of calibration is to reduce measurement uncertainty by ensuring the accuracy of test equipment. Calibration is the process of quantifying and reducing measurement errors or uncertainties to a safe level.

When to Calibrate?

A measuring device should be calibrated:

  • Based on the manufacturer’s recommendation
  • After any mechanical or electrical shock.
  • Before and after major critical measurements.
  • Periodically (annually, quarterly, monthly).
  • After any reformation of the device.

Things to be considered while doing calibration

  • Manufacturer’s laboratory
  • Accreditation
  • Calibration uncertainty
  • Calibration certificate
  • Experience & Size:
  • Adjustment
  • As Found / As Left calibration
  • Turnaround time
  • Brand and reputation
  • Price
  • Repairs, service, and maintenance
  • Warranty, Agreements and reminders

Manufacturer’s laboratory

If possible, using the calibration laboratory of the equipment maker is an excellent option to find a calibration laboratory. The manufacturer already knows everything there is to know about the equipment and can calibrate it. The manufacturer can also perform any necessary service or maintenance. Additionally, using the manufacturer’s calibration service does not void the equipment’s guarantee; in fact, they may even provide an extended warranty.

However, using the manufacturer’s calibration facility is not always viable or practical, so let’s look at some alternative options.


Specific managerial and technical requirements for running a quality operation will be followed by an accredited calibration laboratory. Compliance with today’s ever-changing standards is ensured by a recognised lab. An accreditation authority recognised by the International Laboratory Accreditation Cooperation will accredit a respectable calibration lab (ILAC)

Calibration uncertainty

Calibration certificates are difficult to understand, especially if you are unfamiliar with metrology. The calibration certificate certifies the measurement device’s quality and accuracy, thus it’s crucial that you comprehend the terminology and what the random numbers signify.

The paper contains different characteristics regarding the device, as well as information on the calibration laboratory and the standards to which they adhere. The “uncertainty” of the calibration conducted, a value required by the ISO 17025 standard, is one very important piece of information to pay attention to.

Simply expressed, the value linked with “uncertainty” represents the measurement’s reliability. Because of a multitude of circumstances, including the tools used, the person performing the calibration, and the method utilised, every measurement comes with some uncertainty or doubt. This value indicates whether or not this measurement is appropriate for use.

It’s vital to remember that “error” is not the same as “uncertainty,” and that “error” has no significance without the measurement’s “uncertainty.” The difference between the reference standard and the measurement’s “uncertainty” is called error.

Calibration certificate

A calibration certificate is a document that details the calibration of equipment. This certificate details the device’s quality and measuring accuracy. The calibration certificate is made according to the norms of the National Institute of Standards and Technology (NIST).

It’s crucial to remember that a variety of factors influence the accuracy and calibration of a gadget. On the other hand, measurement equipment used for less complex operations may not require as much precision. A device’s price is determined by its calibration.

Calibration certificate contains

  • Title: The certificate name
  • The details of the laboratory tasked with the calibration
  • Customer details
  • Calibration certificates have a unique identification code
  • The device name and details
  • It also contains the details of environmental conditions where the calibration took place
  • Calibration results with respective sign conventions
  • The person in charge of the calibration’s name, designation, identification, and signature
  • A statement stating that these test results are solely applicable to this device.
  • Evidence that the measurements are traceable

Experience & Size

Learning how long the laboratory has been undertaking calibration is a useful rule of thumb. Solid experience and a long track record can indicate that the laboratory is well-versed in its field. Consider the number of people who work in a calibration facility. Be aware that even when a specialist exists in a particular field, it is fairly rare for smaller 1 or 2 person businesses to fail.


Setting a measuring instrument, whether a reference instrument or not, to perform as precisely as feasible, or make it acceptable for its intended purpose.

Adjustment entails working on the measurement equipment in order to achieve maximum operational accuracy.

A calibration is frequently followed by an adjustment. The measuring equipment must be recalibrated after it has been adjusted. The measurement findings before and after adjustment are included in a proper calibration certificate. It also shows if the measurement values are within the acceptable tolerance.

As Found / As Left calibration

Some calibration equipment is difficult to modify and may necessitate the use of specialised tools and experience.

If the laboratory is unable to make this change, the equipment must be sent elsewhere, potentially to the manufacturer. Obviously, this will cause a delay and increase prices.

Turnaround time

Another factor to consider is the calibration laboratory’s turnaround time. This includes the time spent travelling both directions.

You don’t want your equipment to be out of commission for an extended period of time.

Brand and reputation

The brand and reputation of the calibration laboratory will also influence your decision, especially if you have no prior experience with that calibration laboratory.


Price is another thing you need to consider while selecting the calibration process. Need to check whether the product is value for money or not

Repairs, service, and maintenance

Need to consider whether the calibration company capable of performing repairs, service and maintenance if needed.

Warranty, Agreements and reminders

If your equipment is still under warranty, is the calibration laboratory allowed to provide warranty service?

If the device is serviced by someone other than the manufacturer, the warranty will very certainly be voided.

Using authorised calibration/service centres may allow you to extend the warranty of your equipment without incurring additional charges in some situations.