Temperature measurement is the process of measuring the temperature of an object and knowing its state as a numerical value.
However, measuring the temperature itself is not the objective.
Whether you want to stabilize product quality, detect equipment malfunctions, maintain a constant temperature, or keep records, the temperature you need to know and the appropriate measurement method will vary depending on your objective.
Therefore, when measuring temperature, instead of choosing a thermometer or sensor from the start,
It's important to start by considering, "What temperature do we need to know in order to achieve what?"
Search by what you want to know or what problem you are facing.
I want to know how to measure it.
I want to solve my problem.
If you want to learn about temperature measurement itself, we'll start by reviewing the basic concepts.
Why measure temperature?
By measuring temperature, we can obtain numerical data about the state of objects, equipment, and process that were previously unknown.
"What's the temperature right now?"
"Where is the heat?"
"How is the temperature changing?"
Knowing the temperature is the starting point for subsequent decisions and actions.
Furthermore, comparing the measured temperature with target values, reference values, past conditions, and other measurement points provides information to determine whether it is normal or abnormal, and how it is changing.
We want to produce it consistently with the desired quality.
By understanding the temperatures of products, materials, and process, we reduce variations and defects, and consistently achieve the desired quality.
We want to notice abnormalities as quickly as possible and prevent problems.
By detecting unusual temperatures or changes, we can quickly identify potential problems such as equipment malfunction, overheating, product impacts, and issues related to human safety.
I want to stabilize the temperature.
Based on the measured temperature, heating and cooling are adjusted to maintain the target temperature and ensure stable operation of the equipment and process.
We want to improve process and make it more efficient.
By comparing and analyzing temperature changes, distributions, and accumulated data, we can improve temperature uniformity, yield, productivity, and energy consumption.
I want to record the temperature so I can check and explain it later.
We record temperature history and use it for verifying manufacturing and testing conditions, quality control, audits, and explaining to customers.
I want to use it for testing, evaluation, and research development
We capture temperature-related changes and phenomena, and use them for testing, evaluation, and the consideration of new products, materials, and manufacturing conditions.
There isn't just one purpose for measuring temperature. For example, temperature might be control and recorded simultaneously to monitor for anomalies and use the accumulated data for improvement.
Depending on the purpose, the temperature you need to know, the location where you measure it, and the required accuracy and responsiveness will all vary.
What temperature do you want to know?
Even within the same equipment or process, there can be a variety of temperatures.
For example, in the case of an industrial furnace, factors include the temperature of the product or material, the ambient temperature inside the furnace, and the temperature of equipment such as heaters and furnace walls.
Furthermore, the temperature of a product is not necessarily the same at the surface, inside, or in the center.
In other words, simply stating "I want to measure the temperature of the furnace" or "I want to measure the temperature of the product" doesn't always determine what needs to be measured.
What to measure
Is it a product or material, equipment or component, a medium such as a liquid or gas, or the surrounding environment?
Where exactly do you measure?
Is it the surface, the interior, the center, or a specific part?
How do you want to capture the temperature?
Do you only need to know the temperature at one point, or do you want to compare multiple points, or do you want to know the temperature distribution and how it changes over time?
For example, even if you want to check product quality, simply measuring the furnace atmosphere temperature, which is easy to measure, does not necessarily mean that the value represents the temperature inside the product.
It's important to consider the measurement location not just as "a place where it's easy to attach the sensor," but rather "what the measured values will be used for."
Furthermore, the required temperature range, accuracy, responsiveness, measurement frequency, and operating environment will vary depending on the purpose.
Measure the temperature using a method appropriate for the purpose.
Once the temperature you want to measure is clear, you can then consider a measurement method that suits your purpose and conditions.
Temperature can be broadly divided into two types: contact and non-contact.
Contact type
Temperature is measured by contacting or inserting a temperature sensor into the object. Typical sensors include thermocouples and resistance thermometer (RTDs).
This is used when you want to directly measure the temperature inside a product or liquid, or when you want to install a sensor and continuously measure the temperature.
Non-contact type
The surface temperature is measured without touching the object, primarily by utilizing infrared radiation emitted from the object.
It is used for measuring high-temperature objects, moving or rotation objects, and objects that are difficult to contact.
Neither contact-type nor non-contact-type is inherently superior.
We will consider the most suitable method based on what temperature you want to measure, whether you can touch the object, the temperature range, the required accuracy and responsiveness, and the state of the object.
You can find information on the characteristics and detailed selection methods of thermocouples, resistance thermometer, and radiation thermometer on their respective specialized pages.
To measure temperature accurately, you must consider more than just the sensor.
When measuring temperature, it's impossible to judge the quality of the measurement solely by looking at the sensor.
From the object whose temperature we want to know to the point where we actually use the temperature information, there is a series of interconnected steps, as follows:
01
Measurement target/measurement location
Is the temperature you want to measure the same as the location where you are actually taking the measurement?
02
Temperature Sensors (Japan Only)
Are you selecting the right sensor for your target and purpose?
03
Installation
Is the insertion and contact condition appropriate?
04
Wiring and signal transmission
Check if there are any problems in the wiring, connections, or signal transmission process.
05
Measuring Instrument
Can the received temperature information be display and recorded appropriately?
For example, even when using a highly accurate temperature sensor, the desired temperature may not be accurately captured if the measurement location does not match the desired temperature, the sensor is not inserted or in proper contact, heat is escaping to the surroundings, the sensor is affected by wiring or electrical noise, the sensor has changed or deteriorated due to use, or the settings or conditions on the measuring instrument side are not appropriate.
Using a high accuracy sensor is not the same as achieving high accuracy temperature measurement.
When measuring temperature, it is important to consider the entire measurement system, including not only the sensor but also the measurement location, installation, wiring, measuring instrument, and operating environment.
Can we trust and use those measurements?
When using temperature for quality assessment, control, monitoring, and recording, there's one more thing you should keep in mind.
Can we really trust the temperature that was measured?
As we have seen, temperature measurement results are influenced by various factors, including the measurement location, installation method, surrounding environment, wiring, and measuring instrument.
① Is the target temperature being measured correctly?
- Is the measurement location appropriate for the purpose?
- Is the installation condition appropriate?
- Is it being affected by the surrounding environment?
② Are the values shown by the sensors and measuring instruments reasonable?
- Are there any changes or deterioration due to use?
- How much of a difference is there compared to the baseline value?
- Does it meet the required reliability?
Temperature sensors and measuring instruments each have a certain level of accuracy and tolerance. Furthermore, the measured values may change over time due to factors such as prolonged use and the operating environment.
Therefore, when using measured values for quality assessment or control, it is important to check "how much the temperature indicated by this sensor or measuring instrument differs from the reference temperature."
Calibration is used to verify this.
Calibration involves checking the relationship between the values shown by temperature sensors and measuring instruments and the reference values.
However, even if calibration allows you to check the status of sensors and measuring instruments, that alone does not guarantee that you can accurately measure the target temperature in a real-world setting.
For example, even if there is no problem with the sensor itself, if the measurement location or installation conditions are not suitable for the purpose, it may be measuring a value different from the temperature you want to know.
It is important to consider both whether the target temperature is being measured correctly and whether the values shown by the sensors and measuring instruments used for that measurement are reasonable.
For detailed information on calibration and the reliability of measurement values, please refer to our dedicated page.
How can we make use of the measured temperature?
The measured temperature can be used not only to understand the state of things, but also in various ways depending on the purpose.
Furthermore, multiple uses may be combined to achieve a single purpose.
For example, to stabilize quality, temperature may be compared to a standard, used for control, recorded simultaneously, and the accumulated data may be analyzed later.
To judge
The measured temperature is compared to the target value, specifications, tolerance range, and past conditions to determine whether it is normal and what should be done next.
Control
The current temperature is compared to the target value, and heating or cooling is adjusted accordingly. By measuring the result again, the temperature is brought closer to the target temperature and stabilized.
Detect abnormalities and monitor them.
By continuously monitoring the temperature, you can notice when it falls outside the set range or when an unusual change occurs.
Record it and review/explain it later.
By recording temperature history, you can later verify the conditions during manufacturing and testing, and use this information for quality control, audits, and customer explanations.
Analyze and improve
We compare and analyze accumulated temperature data and multiple measurement results to improve temperature uniformity, quality, productivity, energy consumption, and equipment condition.
These tasks do not necessarily have to be performed in a specific order; they may be carried out simultaneously depending on the purpose.
From measuring temperature to utilizing temperature
Temperature isn't something you measure once and then forget about.
1
Measure and know
We measure the temperature to understand the condition of the object, equipment, and process.
2
To judge and act
Depending on the purpose, it can be used for control, monitoring, recording, analysis, and improvement.
3
Check the results and measure again.
If the condition changes, measure the temperature again to confirm the result.
By considering the entire process, from measuring the temperature to using that information and re-verifying the results, as a single continuous flow, we can consider not only individual devices but also the overall temperature management necessary to achieve our objectives.
Chino introduces the "temperature loop," a concept that integrates measurement, control, monitoring, and calibration to manage temperature.
→ What is a temperature loop?
Organize your temperature measurements.
- □ Why do we measure temperature?
- □ What temperature do we need to know for that purpose?
- □ Have you clearly defined the required temperature range, accuracy, responsiveness, etc.?
- □ Have you considered appropriate measurement methods and locations for your purpose?
- □ What will the measured temperature be used for?
When using measurement values for quality assessment or control, the entire measurement system, as well as the condition of the sensors and measuring instruments being used, should also be checked.
What I want to know next / What I'm having trouble with
I want to know how to measure it.
I want to solve my problem.
I want to know about temperature control as a whole.
INDIVIDUAL SUPPORT
I would like to discuss the specific conditions.
If the measurement method or equipment configuration needs to be determined based on individual conditions such as the object being measured or the operating environment, please consult Chino.
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