Your guide to temperature (and humidity) calibration in GxP

Temperature calibration is an important process within temperature compliance in GxP-regulated sectors like pharma, biotech, and pharmaceutical logistics. In this guide, we will go through everything you need to know about the art of calibration – from standards to procedures, methods, and pitfalls.

What is temperature calibration?

First things first: Temperature calibration involves comparing the readings from a temperature measuring device – often a sensor in a data logger – to a known standard and adjusting the sensor to align with that standard.

This process ensures that temperature measurements are accurate and reliable.

Why is temperature calibration needed?

Calibration of temperature and humidity measurement devices is necessary to ensure the accuracy of the data logger sensors used for monitoring. In highly-regulated industries, this process is crucial for:

  • Product quality: Maintaining the correct temperature prevents the degradation of pharmaceuticals and other temperature-sensitive products.
  • Compliance: Adhering to standards and regulations set by bodies like the FDA and EMA.
  • Operational efficiency and reputation: Avoiding costly recalls and maintaining trust with customers and other stakeholders.

Also read: Why is temperature calibration important?

7 key terms of temperature calibration

Before we dive into the different methods of temperature calibration, let us clarify a few of the field’s fundamental terms.

1. What is the reference temperature and sensor?

The reference temperature is the temperature measured by a reference sensor, which is more precise than the sensor under calibration. The reference temperature is used as a benchmark during the calibration. It ensures the accuracy and traceability of measurements by providing a fixed point of comparison.

2. What is calibration uncertainty?

Calibration uncertainty refers to the inherent error that cannot be eliminated when comparing the output from a data logger sensor to a reference temperature. This uncertainty is a recognized part of the calibration process and a fixed part of a given calibration method.

3. What is Maximum Permissible Errors (MPE)?

Governmental and industry standards typically set forth Maximum Permissible Errors (MPE), which defines the extent of deviation, including calibration uncertainty, that can be tolerated for a sensor’s operation.

4. What does accuracy mean within temperature calibration?

Accuracy refers to the closeness of a temperature measurement to the true value – the actual, precise temperature being measured. It indicates how correct the measurement is. While uncertainty quantifies the range within which the measurement is expected to lie, accuracy indicates how close the measurement is to this true value.

5. What is traceability in temperature calibration?

Traceability in temperature calibration refers to the ability to link measurement results back to national or international standards through an unbroken chain of comparisons. This ensures that measurements are accurate and consistent across different contexts and locations. For instance, it means that 0 degrees should be the same in any country. Each step in the chain is documented, which allows the calibration to be verified and validated, providing confidence in the accuracy and reliability of the temperature data logger's readings.

6. What are temperature calibration standards?

Temperature calibration standards are benchmark temperatures that provide fixed reference points to ensure the accuracy and traceability of measurements.

Examples of temperature calibration standards are:

  • Triple point of water (0.01°C): A primary calibration standard known for its precise and reproducible temperature point.
  • Melting point of gallium (29.7646°C): Used in laboratories for calibrating thermometers and other temperature measurement devices.
  • Boiling point of water (100°C at 1 atm): A widely recognized standard for basic calibration.
  • Fixed points in the International Temperature Scale of 1990 (ITS-90): Includes freezing points of metals like tin (231.928°C), zinc (419.527°C), and aluminum (660.323°C) for high-precision calibration.
  • NIST traceable standards: These standards are provided by the National Institute of Standards and Technology to ensure traceability and accuracy in measurements.
  • Ice point (0°C): A basic calibration point for verifying the accuracy of temperature sensors at the freezing point.

7. What is a calibration certificate?

A calibration certificate is an official document issued by a calibration laboratory that verifies a temperature and humidity sensor has been calibrated according to specific standards. It details the calibration procedure, the measurement results, etc. The certificate serves as proof that the device has been accurately calibrated and meets the required specifications. It also indicates whether a performed calibration was accredited.

2 common temperature calibration methods – the technique

Temperature calibration methods are the techniques used to compare a temperature measurement device to align with the known standards, ensuring its accuracy.

Here are two different methods of calibrating temperature measurement equipment:

1. Fixed point method

Using substances with well-known phase change temperatures (e.g., ice point at 0°C).

  • Advantage: Highly accurate.
  • Disadvantage: More time-consuming and requires specific conditions.

2. Dry block calibrators

Providing a stable temperature source to immerse the sensor, ensuring precise calibration.

  • Advantage: Provides a controlled environment.
  • Disadvantage: Can be expensive and require regular maintenance.

The temperature calibration procedure – the process

A calibration procedure is a systematic process used to carry out the calibration. Unlike calibration standards, which are the fixed reference points, and calibration methods, which are the techniques used, a calibration procedure outlines the specific steps and protocol followed to ensure the device is accurately calibrated.

This will often look something like this:

Step-by-step calibration guide

1. Preparation and setup:

  • Ensure the calibration environment is stable and free from temperature fluctuations.
  • Gather all necessary equipment, including the sensor and calibration reference.

2. Initial check:

  • Compare the sensor readings against the calibration standard without making adjustments.
  • Document any deviations.

3. Adjustment:

  • Adjust the data logger settings to match the calibration standard.
  • Repeat the measurements to confirm accuracy.

4. Verification:

  • Verify that the data logger maintains accuracy across the specified range.
  • Perform additional tests if necessary to ensure consistency.

5. Documentation:

  • Record the calibration process, results, and any adjustments made.
  • Provide calibration certificates as proof of compliance.

6. Post-calibration review:

  • Review the calibration certificate to ensure it meets all internal and regulatory requirements.
  • Store the certificate and related documentation for future reference and audits.

What about adjustments?

If the measurements are outside the accepted criteria, adjustments are typically not part of the calibration process, and a failed calibration will require the purchase of a new sensor.

At Eupry, however, our service makes this headache obsolete since:


Traceable or ISO 17025-accredited calibration is included and carried out in our in-house calibration laboratory – whether you are doing temperature monitoring, mapping, or all of the above.


Should a calibration fail, we simply switch the sensor for another to be easily clicked on to your data logger and have you up and running in seconds.

  • Frequency

    Perform regular calibration intervals based on usage and manufacturer recommendations.

  • Environment

    Conduct calibration in controlled environments to avoid external influences.

  • Equipment

    Use high-precision calibration tools and maintain them according to manufacturer guidelines.

Who handles calibration? And can you do it yourself?

Calibration is typically handled by specialized calibration technicians or engineers. Although some large-scale organizations have their own calibration laboratories, for most, the calibration procedure is purchased at an external calibration laboratory by sending in the data logger or having external technicians visit the site – or it can be part of the service associated with the monitoring system.

The responsibility of keeping track of calibration schedules and overseeing that the process comply with regulatory standards often fall to quality assurance specialists/engineers, validation engineers, or laboratory managers.

Make calibration a non-issue with Eupry

Psst... With Eupry’s temperature and humidity monitoring solution you won’t have to worry about keeping track of or carrying out calibration.

It includes automated – ISO17025-accredited or traceable – calibration and the most efficient (patented) process you will find:

  1. When due, we provide you with newly calibrated, external sensors.
  2. You switch them in only seconds.

Your data stream is automatically maintained without gaps, and certificates are stored digitally. Handle all calibrations in seconds, directly at your location, and without changing data loggers.

Choosing the right calibration service: The difference between accredited and traceable

When it comes to calibration services, the terms "accredited" and "traceable" are helpful in understanding the level of assurance and compliance offered by different calibration processes.

Here is a breakdown of each term to clarify their differences:

Accredited calibration:

  • Certification: Accredited calibration means that the service is performed by a laboratory that has been formally recognized by an accreditation body. This recognition is based on the laboratory's adherence to international standards, such as ISO 17025.

Psst.. Did you know that, at Eupry, we have our own ISO17025-accredited calibration lab?

  • Audit and oversight: Accredited laboratories undergo regular audits to ensure they meet stringent standards for their technical competence and quality management systems.
  • Higher assurance: This type of calibration provides a higher level of assurance in the accuracy and reliability of the equipment calibration, along with detailed reporting that aids in regulatory compliance.

Traceable calibration:

  • Standard compliance: Traceable calibration refers to a calibration service that can directly relate its measurements back to recognized standards through an unbroken chain of comparisons. This is typically documented to demonstrate that the measurements are consistent with national or international standards.
  • Documentation: Traceability requires detailed records that document each step of the calibration process and the corresponding results.
  • Broad applicability: While it ensures accuracy and consistency, traceable calibration does not imply the rigorous oversight or formal quality system compliance that comes with accreditation.

Is traceable and NIST calibration the same?

No, traceable and NIST calibration are not the same. Traceable calibration means that the calibration can be traced back to a recognized standard, which can be either national or international. This ensures that measurements are consistent with others that follow the same standards.

NIST calibration specifically refers to calibration that is traceable to standards maintained by the National Institute of Standards and Technology (NIST) in the United States. This type of calibration provides a direct assurance of accuracy and compliance with NIST standards, often required in specific regulatory environments within the U.S.

So, while all NIST calibrations are traceable, not all traceable calibrations meet the specific standards set by NIST.

Choosing the right calibration type for you

The choice between accredited and traceable calibration often depends on your regulatory requirements and the specific needs of your business.

  • Accredited calibration is essential for industries such as pharmaceuticals and biotechnology, where compliance with standards is strictly monitored.
  • Traceable calibration might suffice for internal standards and less regulated tasks where formal accreditation is not a necessity. Typically, you would opt for NIST calibration if your industry requires traceable calibration in adherence to U.S. standards.

Rid your work of calibration blockers

Calibration without manual overviews (the system keeps track for you), physical certificate chaos (all is digital), and switching data loggers (simply switch the sensor) with the fastest calibration process on the market.

Common calibration challenges and their solutions

  • Managing large-scale calibration

    In large facilities with numerous data loggers, managing the calibration process can be complex and time-consuming. A streamlined approach, such as using calibration service providers (like Eupry), can reduce downtime and ensure consistent calibration across all devices.

  • Calibration intervals and drift

    Defining appropriate calibration intervals based on the estimated drift of sensors is essential. Some sensors may require more frequent calibration due to higher drift rates. Using tables from standards to define maximum permissible errors helps in determining these intervals.

  • Interpreting calibration certificates

    Understanding and reviewing calibration certificates can be challenging, and ensuring that all results meet the defined acceptance criteria before using the calibrated equipment is vital. This reduces the risk of using out-of-specification devices, which can lead to compliance issues.

FAQ about temperature calibration

You can find many more questions about temperature compliance earlier on the page.

What is temperature calibration?

Temperature calibration is the process of adjusting a temperature measurement device to align with a known standard.

Why is calibration important in pharmaceuticals?

It ensures the accuracy and reliability of temperature readings, which is crucial for maintaining the integrity of pharmaceutical products.

How often should calibration be performed?

Calibration frequency depends on the device usage, manufacturer recommendations, and regulatory requirements.

Easy and (extremely) quick calibration with a click

Audit-ready and wireless temperature monitoring built for GxP – with the smartest calibration process you will come across as part of the package.

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Client Testimonials

  • “The automated calibration process where external calibrated sensors are replaced with new calibrated ones automatically is particularly convenient.”

    Eric Clausen

    Distribution Manager at Freja

  • The calibration of the Eupry temperature loggers is easy and quick. I received a box with the new sensors (…) It took me under an hour to calibrate 40 loggers – including the time it took to find the refrigerators.”

    Kasper H. Christophersen

    Research Associate at Novozymes