Food safety

All about calibration process | How to calibrate thermometer?

Thermometer calibration is a critical task to ensure that operations, such as cooking and low-temperature storage, are ...

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Thermometer calibration is a critical task to ensure that operations, such as cooking and low-temperature storage, are done safely. 

An accurate food thermometer plays a significant role in maintaining food safety in any food establishment. Whether for low-temperature storage or thorough cooking, accurate temperature readings are significant.

Thermometers are very common kitchen equipment where they are used almost every day during service. With frequent use, thermometers lose their accuracy over time and must be calibrated. As such, thermometer calibration must be regularly performed.

In this article, learn about the different ways how to calibrate your thermometer and why it is important to do so.

Key points covered:

  1. Thermometer calibration is an important operation that reconfigures the temperature readings of the device to become accurate after use.
  2. The two most common thermometer calibration methods are boiling point and freezing point methods.
  3. The frequent use and sudden significant changes in temperature readings affect the device and often cause mild or significant offsets.
  4. Daily calibration before the start of every shift ensures accurate readings. 
  5. Common types of thermometers include a dial, digital, probe, bimetallic, and infrared thermometers.
  6. The safety of the food being cooked or stored depends on the accuracy of your thermometer, as these operations rely on achieving or maintaining target temperatures.
  7. Inaccurate thermometer calibration and an uncalibrated thermometer can lead to significant food safety problems.
  8. Common mistakes in thermometer calibration include using unreliable standards, neglecting environmental factors, inadequate stabilization, improper insertion to water, and lack of documentation.
  9. FoodDocs' smart Food Safety Management System can generate a complete and customizable Thermometer Calibration Log with detailed instructions for the food handlers.

With an inaccurate reading, the purpose of these operations becomes insignificant and defeated. Food safety hazards, particularly pathogens, may survive and continue to grow if the target temperature reading is off by a few degrees. Such reasons make thermometer calibration an important part of food safety operations. No need to worry because this task is easy and does not take too long.


What is thermometer calibration?

Thermometer calibration refers to the process of reconfiguring a thermometer for it to produce accurate readings.

Thermometers, like other equipment, fall out of their standard specifications due to frequent use or time. Inaccurate thermometers can result in misleading results.

These results can cause over or under-processing, which can be significant for the safety or the quality of the food product. 

Food safety operations such as chilling, cooking, and holding are temperature-dependent. For example, different types of meat require a particular target internal temperature that will make the final product safe from food safety threats.

These target internal temperatures are based on the most effective temperature in eliminating pathogens and ensuring food safety. They can only be effective if reached accordingly with the help of a thermometer. A few degrees below the target temperature will increase the risk of causing foodborne illnesses. 

It is important to note that the calibration process can differ for every type of thermometer. Manufacturers and distributors often provide calibration instructions and kits to food businesses. 

Regardless of the type of thermometer, calibration is a must to produce reliable and accurate temperature readings.

Use FoodDocs' smart Food Safety Management System with a digital Calibration Log. Record all calibration readings and maintain comprehensive records as proof that your instruments are regularly maintained. Using our smart solution, you can ensure that every food handler knows how to calibrate a thermometer. Our Calibration Log comes with clear step-by-step instructions on how to perform approved calibration methods. 


Why is thermometer calibration important?

The significance of thermometer calibration in the food industry goes beyond food safety. This operation helps your food business maintain stable operations, increase efficiency, and address food-related issues.

When done regularly, thermometer calibration can save your team time and continuously grow your market by gaining consumer confidence in your food safety practices and services. 

Specifically, thermometer calibration can help you achieve the following advantages:

  • Food safety assurance. When accurate temperature measurements are achieved, food safety is secured, and the risk of causing any foodborne illness is significantly reduced. Properly calibrated thermometers help ensure that foods reach the necessary internal temperature to inactivate bacteria and other foodborne pathogens. 
  • Quality assurance. Proper calibration of the thermometer also ensures the delivery of consistent food quality. Especially for foods that can be served in a particular degree of doneness, such as steaks, a slight temperature difference can change the results. Incorrect food temperatures can lead to overcooking, drying out, or undercooking, affecting the texture, flavor, and overall quality of the food.
  • Cost-saving and produces more profit. By having a properly calibrated thermometer, store-wide shutdowns and service maintenance originating from food safety issues, are effectively prevented. Performing these corrective procedures will hinder normal operations and will affect business performance. 
  • Detection of problems with other equipment. A calibrated thermometer can help food handlers easily detect whether there is a problem with any equipment that uses it, such as an oven or a refrigerator. In case of irregular reading, reactive maintenance can be applied as an on-the-spot calibration. 
  • Data integrity. Thermometer calibration ensures that all temperature readings are accurate. This will help your team ensure that your thermometer calibration logs are reliable in case of an inspection. 
  • Traceability purposes. Proper calibration provides a clear record that can be used to track in case temperature-related issues arise. Food handlers can use the record to detect which thermometer produces faulty readings. 

Regularly monitoring thermometer calibration is an integral part of a food safety management system. Monitoring forms for this operation must be available and include information such as date, time, frequency, and results.

It can help food businesses achieve compliance with significant food safety laws concerning any thermometer calibration standard. It can also create a seamless and uninterrupted flow of work operations for everyday services.

Get all the advantages of the thermometer calibration procedure and the power of digital solutions through FoodDocs' smart Food Safety Management System. In addition to our digital Calibration Log, our smart software also features a real-time dashboard. Using this feature, you can identify areas in your establishment where thermometers require calibration with just a look.

Make food safety compliance more efficient with the help of our digital solutions!


What are the different types of thermometers?

There are different types of thermometers depending on their application. In the food industry, all thermometers are required to be food-safe and can withstand high heat or very low temperatures. This means that thermometers, such as mercury thermometers, are not allowed in the kitchen.

Digital thermometer

Digital thermometers use electronic sensors to measure temperature. The temperature reading is then displayed on a digital readout screen. Most digital thermometers used in the food industry are instant-read. This type of thermometer requires only a few seconds to stabilize and is preferred since changes to foods can occur in split seconds.

Digital thermometers can be wireless or attached to an appliance. They can be used for both hot and cold foods.

Cook preparing delicious sauce at precise temperature checking with digital thermometer

How to calibrate a digital thermometer?

Calibrating a digital thermometer may greatly vary depending on the manufacturer's instructions. Calibrating a digital thermometer involves comparing its readings to a known and accurate reference temperature.

The calibration process may either be:
  1. Freezing point method; or
  2. Boiling point method

...depending on the thermometer's intended use. You can use a designated reference thermometer to check if the readings are correct.

Calibrating a digital thermometer often involves a reset button that is set to recalibrate the temperature reading to a particular range.

How often should a digital thermometer be calibrated?

As previously mentioned, the best practice for calibrating any thermometer is to calibrate it daily before use. Use this complete guide to determine when to calibrate your digital thermometer:
  1. When used for more than 12 hours straight.
  2. When used in extreme conditions.
  3. As recommended by the manufacturer.
  4. When the thermometer is accidentally dropped.
  5. When the thermometer has not been used for days.
  6. When there is a sudden change in the environment.
  7. When the batteries are replaced.

Probe/ Meat thermometer

Probe thermometers come with a pointed probe used for inserting into foods and can determine the internal temperature. Probe thermometers are often used for measuring the internal temperatures of meat for its level of doneness. This type of thermometer is common and a conventional food thermometer in any kitchen.

The thermometer's read-out is presented by a display dial that contains the temperature reading. This thermometer is also otherwise known as the common dial food thermometer.

This type of thermometer can be used for measuring the safe temperature of meat inside the oven. As it is made of metal, it can withstand extremely high temperatures.

Taking the temperature of two seasoned chicken breasts

How to calibrate a meat thermometer?

Calibrating a regular meat thermometer involves adjusting a nut with a specialized wrench that often comes with the thermometer. This process will require a reference thermometer.

Since meat thermometers are often used for measuring the internal temperature of food during cooking, such as for hamburger patties, the best calibration method is the boiling point method.

When should a meat thermometer be calibrated?

A meat thermometer requires calibration at several key instances to ensure accurate measurements.
  1. Before first use.
  2. Regular maintenance.
  3. After impact or damage.
  4. When the thermometer produces measurement uncertainties
  5. During seasonal changes.
  6. After a long period of non-use.

Bimetal thermometer

A bimetal food thermometer uses a strip made of two different metals bonded together. The strip bends with temperature changes, causing a pointer to move on a scale to indicate the temperature.

A bimetallic stem thermometer presents the temperature reading through a dial display. Calibrating requires a wrench to turn the nut and recalibrate the reading.

What is the most accurate method for calibrating bimetallic thermometers?

Calibrating bimetallic thermometers can be a bit more challenging compared to other types of thermometers due to their mechanical nature. This type of thermometer can be calibrated using the freezing point method or the boiling point method.

During calibration, the thermometer is submerged in boiling or very cold water, and the nut is turned to recalibrate the reading, similar to the reference thermometer.

The thermometer is mounted on a stainless steel boiler. Autonomous heating of a house or apartment. Heated cold water.

When should a bimetal thermometer be calibrated?

Calibrating a bimetal thermometer is important to ensure accurate temperature measurements, especially in applications where temperature accuracy is critical, such as ensuring proper internal temperature. Here are key times when a bimetal thermometer should be calibrated:

  1. During the first use of a new bimetallic thermometer.
  2. As a regular maintenance.
  3. Before the start of operations.
  4. When unusual readings are gathered.
  5. After a long time of storage and non-use.
  6. After accidentally falling or damage.
  7. After a long hour of use.

Infrared thermometer

Infrared thermometers are non-contact appliances. This means that the thermometer will not touch the food. Temperature readings are executed by detecting the infrared radiation emitted by the food.

They are commonly used for quick, non-contact temperature measurements in industrial, medical, and culinary applications. They are very useful for big batches of food and when it is physically impossible to insert a probe into the food, such as in big production establishments.

Brewer checking temperature of water in microbrewery

How to calibrate an infrared thermometer?

Calibrating an infrared thermometer can be a bit different from the other methods. The method also uses verification of the temperature reading from a reference.

Both freezing and boiling point methods can be calibrated but with slight differences.

During calibration, the infrared thermometer must be turned on and pointed toward a boiling or very cold ice-water mixture within a specified distance. The temperature reading will then be compared with a reference thermometer submerged in boiling or very cold water.

If inaccurate, the thermometer will then be reprogrammed. Some infrared thermometers offer adjustment settings to account for calibration differences. Consult the infrared thermometer manufacturer's instructions to determine if adjustments are possible and how to perform them.

How often to calibrate an infrared thermometer?

Infrared thermometers have a very different mechanism from other manual and digital thermometers. As such, the frequency of calibration may be very different depending on the manufacturer's instructions.

In general, an infrared thermometer must be calibrated in the following cases:

  1. When the infrared thermometer is new.
  2. Before every start of a shift.
  3. Before any critical operation.
  4. When used continuously.
  5. When stored for a very long time.
  6. As suggested by the manufacturer.
  7. When there is a sudden change in the environment.
  8. When measuring extremely different temperature ranges.

Some infrared thermometers require very technical calibration. In this case, the manufacturer will request that your business send them to the unit, and they will perform the calibration for you. In this case, the calibration effect can last longer than normal.

How to calibrate a thermometer?

Thermometer calibration methods depend on the type of thermometer you use. Some thermometers come with a special kit used specifically to calibrate them, whereas some can be calibrated using general methods.

More technical calibrations are often done by thermometer manufacturers themselves. They can either send a calibration expert to perform the calibration on-site or return the thermometer to their calibration laboratory for custom thermometer calibration services. 

Here are two of the most common methods for thermometer calibration that you can perform for common thermometer types. 

Freezing point method

Otherwise known as the ice point method or ice-water method, this technique is commonly performed for thermometers that measure low temperatures. This method is performed as follows:

  1. Fill a glass or deep container large enough to accommodate the thermometer probe with crushed ice.
  2. Add distilled water or soft water into the glass and stir the ice water mixture.
  3. Submerge the thermometer probe until the immersion mark without touching the bottom of the glass. After placement in ice and water, a thermometer reading should stabilize in about 30 seconds.
  4. If the thermometer does not read 32°F (0°C), use a wrench to adjust the calibration nut until the reading is correct.
  5. Reread the temperature of the ice water solution using the calibrated thermometer at least two to three times and record the results in a thermometer calibration log. Wash the thermometer with room temperature water in between readings.

Thermometers used for refrigerated storage or cold-holding foods would require this calibration. 

Freezing point calibration method


Boiling point method

The boiling water method is used for thermometers to measure high temperatures, such as cooking and hot holding. This method is performed as follows:

  1. Fill a deep pan or a glass beaker with distilled water and heat into a rolling boil over medium heat.
  2. While the water is boiling, place a previously calibrated thermometer and allow it to read the temperature. 
  3. After 30 seconds or once stable, place the thermometer being calibrated and read the temperature measurements. Do not let both thermometers touch the bottom of the pan or container.
  4. If the temperature readings differ, ideally  212°F (100°C), adjust the calibration nut or adjustment screw until the reading is correct.
  5. Reread the temperature of the boiling water using the calibrated thermometer at least two to three times and record the results in a thermometer calibration log. Wash the thermometer with room temperature water in between readings.

Boiling point calibration method

For both calibration techniques, take note that the water to be used must be soft or distilled water. The impurities in hard water can significantly affect the accuracy of the thermometer reading. When the water is filled with impurities, the freezing and boiling point of water are relatively higher and lower, respectively. Additionally, a reference or comparison thermometer can also be used for the freezing point method.

The two calibration methods can be used along with a reference thermometer to calibrate non-adjustable thermometers. Reference thermometers are preferably NIST-certified (National Institute of Standards and Technology).

Make sure that the reference thermometer is accurately and recently calibrated. Upon comparing the temperature readings, the non-adjustable thermometer can be labeled with an offset value of the degree difference to correct any temperature reading.

That is, if the reference thermometer reads 212°F (100°C) and the thermometer being calibrated reads 209°F (98°C), all temperature readings using the non-adjustable thermometer must be offset by  3°F or 2°C. 

How do I know if my thermometer is accurate?

In addition to repeatedly recording temperatures using the calibrated thermometer, you can also use a previously calibrated thermometer as a reference.

Submerge both thermometers in either an ice bath or in boiling water. If their temperatures are almost or exactly similar, then the thermometer is accurate.

If a thermometer is used regularly to measure a particular range and it repeatedly shows readings out of this range, this may be a sign that the thermometer needs recalibration. 

How frequently should a thermometer be calibrated for accuracy?

Ideally, thermometers must be calibrated every day before starting your operations. This ensures you work with an accurate thermometer that produces correct readings.

Generally, a thermometer reading must only have a ±1°F or ±0.5°C difference from a reference thermometer. Any higher or lower reading than this calibration temperature range can significantly affect the results of food safety operations.

Ideally, calibration must be performed during these instances:

  • When dropped (especially for dial thermometers)
  • When switching its use from extreme temperature ranges (freezing to boiling or vice versa)
  • Long storage time period
  • When the thermometer is new
  • When used multiple times in a day

During calibration, recordkeeping must always be practiced.

All temperature readings during calibration must be recorded as proof of the accuracy of the performed calibration, which can be used for a thermometer calibration report. This calibration document can be used to verify whether the problem with a critical control point concerns the temperature, and proper corrective actions may be applied. 

Level up your calibration tasks with the help of FoodDocs' Food Safety Management System. Our software is compatible with major appliances with IoT sensors. Integrations with our software can help log calibration readings seamlessly. Keep all records organized and ensure proper calibration with FoodDocs. 

What are common mistakes in thermometer calibration?

Calibrating a thermometer is a technical operation that requires training. When improperly done, the calibration can be ineffective, leading to several safety problems when the thermometer is used. 

Here are some common mistakes that you should avoid when calibrating a thermometer:

  1. Using incorrect quality standards or uncalibrated references. A certified individual must calibrate the reference thermometer, which can only be used for this purpose. 
  2. Improper calibration. Improper calibration includes not using boiling water or ice-water mixture, allowing the tip of the thermometer to touch the glass, and skipping steps as described. 
  3. Neglecting environmental conditions. Temperature is affected by altitude, humidity, and ambient temperature, which can lead to a certain degree of inaccuracy. A standard conversion and effect reference, such as for altitude, must be prepared to guide food handlers on the effects of the environment on the temperature.
  4. Insufficient stabilization time. Every thermometer requires adequate exposure time to the boiling water or ice-water mixture during calibration to stabilize. Taking it out before the reading stabilizes can lead to inaccurate results. 
  5. Misinterpreting readings. Food handlers must learn to read and record readings from a dial or a digital screen. 
  6. Unclean thermometer. Leftover food particles can change the resulting temperature and cause cross-contamination. That's why cleaning the thermometer before and after the calibration process is important.
  7. Incorrect adjustment. During calibration, if the process is not done as specified by the manufacturer, inaccurate results may be achieved. Technical tasks such as using the proper wrench to turn a nut must be followed. 
  8. Lack of training. Food handlers must be familiar with boiling point and ice-point methods. This will help them become more mindful of each step and perform the thermometer calibration process more effectively.
  9. Skipping documentation. Documentation is a critical part of calibrating a thermometer. This will prove that your thermometers are working properly and achieve data integrity.

Provide proper training and clear references to your employees for thermometer calibration with the help of FoodDocs' smart Food Safety Management System. Our smart software provides clear, step-by-step instructions on thermometer calibration and our digital Calibration Log.

With the help of our intuitive digital solutions, you can ensure that all of the mentioned problems can be avoided significantly. Ensure accurate and effective food safety with FoodDocs.

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What are common factors to consider when calibrating a thermometer?

During calibration training, you must consider a few things. These factors may make a significant difference, and knowing them will prepare your kitchen staff for uncommon situations during calibration.

Below are a few factors to consider when calibrating a thermometer:

  • Purpose of the thermometer. It is suggested to use different thermometers for measuring hot and cold temperatures. The abrupt and significant changes in the temperature readings can cause significant discrepancies faster and would require calibration more often. The proper calibration method must also depend on the type of operations where the thermometer will be used.
Use the freezing point method for a thermometer to measure low temperatures and the boiling point for hot temperatures.
  • Changes in boiling temperature by elevation. The boiling point of water varies depending on the altitude of your location. The higher the elevation of your location, the lower the boiling point of water is. Below are the changes in boiling point temperatures of water depending on the level of elevation or atmospheric pressure:
    • Sea Level: 212°F (100°C)
    • 1,000 feet: 210°F (98.9°C)
    • 2,000 feet: 208°F (97.8°C)
    • 3,000 feet: 206.4°F (96.9°C)
    • 4,000 feet: 204.5°F (95.8°C)
    • 5,000 feet: 202.75°F (94.9°C)
    • 8,000 feet: 197.5°F (91.9°C)
  • Purity of water used for calibration. As previously mentioned, any impurities such as minerals, dirt, or added components in water will affect its boiling and freezing points. The boiling point will become higher, whereas the freezing point will be lower. If impure water is used, it will result in inaccurate temperature readings and incorrect calibration decisions. Use distilled water to ensure that there will be no materials to affect the temperature readings.
  • Types of food thermometers. The appropriate calibration method for a thermometer can be dependent on its type. Digital thermometers have a few different settings or calibration operations than a dial thermometer. Make sure to read the manufacturer's product instructions.

Learning to calibrate a food thermometer must be part of a food handler's training routine. This operation will need to be repeated many times to ensure food safety. In doing so, the mentioned factors and proper temperature measurement procedures must be highlighted during training.

Regarding choosing the type of thermometer to measure high or low temperatures, dial thermometers can do both low and high-temperature readings.

This type is flexible and durable, even if exposed to extreme temperatures. Digital thermometers are advisable for operations that will not expose the thermometer to high heat. You cannot leave a digital thermometer inside an oven, unlike a dial thermometer.

How to ensure accurate thermometer calibration with digital solutions?

Proper and timely calibration of a thermometer is a significant preventive step toward controlling food safety hazards.

Use FoodDocs' smart Food Safety Management System to ensure thermometer calibration is covered and well-emphasized.

Switch to our innovative solutions for recording thermometer calibration data and training employees with clear instructions.

Thermometer calibration log to help employees record efficiently

Get a digital Thermometer Calibration Log and other automatically generated monitoring logs that fit your daily operations. Using our AI-powered system, you can get this comprehensive log for a more efficient recording of thermometer calibration readings. 

You will no longer need a pen and paper to record results. In addition, the Thermometer Calibration Log is equipped with a prefill solution that shows calibration values based on your previous data entries. 

Save more time and ensure more accurate calibration records with the help of our digital solutions. Present clear and credible calibration results to inspectors as proof of your commitment to food safety.


Thermometer calibration log from the FoodDocs software

Step-by-step instructions to guide employees in the correct calibration

With the help of our smart solutions, food managers can efficiently and effectively train food handlers on how to calibrate thermometers and read temperature measurements. 

We understand how important it is to perform every calibration process step precisely. 

All monitoring logs are equipped with detailed instructions that can serve as references. Use these instructions to teach your employees the proper boiling point or ice-point method steps.

You can also upload your versions of the instructions as images of videos. Make learning more personalized to your unique operations with the help of our digital solutions. 

Customizable monitoring system for a tailor-fit monitoring

Apply improvements from inspections and customize your monitoring logs and checklists according to your business needs. All sections of our digital monitoring system can be tailored to your requirements. 

In no time, you can get a monitoring system that fits like a glove. Add monitoring parameters and recording fields to your tasks to capture more information for a more credible system. 

If you have a unique operation to monitor, you can also make monitoring tasks from scratch using our system. Make switching to a completely digital system more seamless with the help of our solutions. 


Real-time dashboard to give a clear overview of operations

Quickly identify areas that can cause problems with the help of our real-time dashboard. This feature gives you a quick overview and informative insight into areas that need more attention across your brands. 

You can quickly detect thermometers that require calibration with the help of our dashboard. In addition, you can also easily spot calibration processes with problems. Address the situation as it happens to minimize any further complications. 

Save at least 20% of your time supervising your team manually with the help of our real-time dashboard. 


Real-time dashboard from the FoodDocs software

With the help of our digital Food Safety System, you can ensure that every calibration process you perform is accurate and precise. We can help you secure temperature readings throughout your branches.

Our team of food safety experts aims to make food safety and compliance with food laws and regulations accessible to every business. With this digital FSMS with a built-in digital HACCP plan maker, food businesses can easily achieve compliance compared to the traditional process.

Book a free one-on-one call with our team to learn more about how can FoodDocs help your food business stay compliant.



Frequently Asked Questions (FAQs)

Need more information about food handlers' tests and training? Here are some frequently asked questions about the topic.

How do you calibrate a digital thermometer?

Both boiling point and freezing point methods of calibration can be used to calibrate a digital meat thermometer. The only difference is that most digital thermometers have a calibration reset button and a digital display to reenter the correct temperature reading when compared with analog thermometers. Additionally, digital thermometers need to have their batteries checked and replaced.

A set of exhausted batteries will most likely produce inaccurate or unclear temperature readings. More sophisticated digital thermometers may need to be sent to their manufacturers for a scheduled thermometer calibration.

How to test thermometer calibration?

To check the thermometer calibration, the chosen method must be performed two to three times and gain the same temperature reading. Only very small differences between calibration results are allowed to ensure the effectiveness of the calibration method.

How do I know if my thermometer is accurate?

The best way to know if your thermometer is accurate is to compare its reading with a calibrated reference thermometer.

What is one effective way to calibrate a thermometer?

One effective way to calibrate a thermometer is by using a reference standard thermometer with known and traceable accuracy. Compare the readings of the thermometer being calibrated with the reference thermometer at multiple calibration points within its intended temperature range.

What temperature should a bimetallic stemmed or digital thermometer be?

The temperature at which a bimetallic stemmed or digital thermometer should be calibrated depends on its intended use and operating range. Generally, calibration points should cover the thermometer's expected temperature range, including lower, middle, and upper values.

When should a bimetal stem or digital thermometer be calibrated?

A bimetallic stemmed, or digital thermometer should be calibrated regularly, typically based on the manufacturer's recommendations and the specific application. It's important to calibrate whenever there are significant environmental changes if accuracy is in doubt or according to a predetermined schedule to ensure accurate and reliable temperature measurements.




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