Temperature measurement involves measuring the temperature of an object using a method appropriate for the purpose, and treating the obtained value as information that can be used for judgment and management.

Measuring temperature is not the objective itself. For example, in a manufacturing plant, temperature is measured to determine whether the product is at the appropriate temperature, whether process conditions are being maintained, and whether any abnormal temperature changes are occurring.

Measuring temperature is a way to understand the conditions on site.

By quantifying temperature, it becomes possible to perform comparisons, recordings, monitoring, and judgments that would be difficult to do based solely on intuition.

For example, instead of just noticing that the equipment temperature has "become a little higher," recording the temperature changes over time allows you to compare them with past conditions and identify the changes.

About "measurement" and "measurement"

"Measurement" (測) often refers to the act of measuring a quantity and obtaining a value. On the other hand, "conductive measurement" (測) can also include considering measurement methods and conditions according to the purpose, and evaluating and utilizing the obtained results.

However, in practice, the two are not always strictly distinguished. In this article, "temperature measurement" will be explained not only as obtaining a numerical value of the temperature, but also as capturing a temperature that is appropriate for the purpose and using that value for decision-making and management.

When considering temperature measurement, the first thing to decide isn't the measuring instrument. The starting point is clearly defining what temperature you want to measure.

Even with the same equipment, the temperature you want to know isn't necessarily just one thing.

For example, in an industrial furnace, multiple temperatures can be considered, such as the ambient temperature inside the furnace, the heater temperature, the surface temperature of the product, and the internal temperature of the product.

These are temperatures present in the same equipment, but they are not necessarily the same value.

The temperature obtained will vary depending on the measurement location.

If the object has a temperature distribution, the value obtained will vary depending on where the measurement is taken.

Therefore, it is important to determine the measurement location not just based on "a place where it is easy to attach the sensor," but by considering what the measured values will be used for.

Once you've determined the temperature you want to measure, the next step is to consider how to capture that temperature.

There are various methods for measuring temperature, but they can be broadly categorized into contact and non-contact methods.

Contact temperature measurement

In contact thermometers, temperature sensors such as thermocouples and resistance thermometer are used. The sensor detects temperature through heat exchange with the object being measured, and the change in temperature is treated as an electrical signal.

In contact-type sensors, it is necessary to position the sensor so that it has an appropriate thermal relationship with the object being measured. Therefore, not only the type of sensor, but also the measurement location and mounting method are important.

View the temperature sensor guide.

Non-contact temperature measurement

Non-contact methods primarily measure surface temperature by utilizing infrared radiation emitted from the object.

Non-contact measurement can be effective for high-temperature objects, moving objects, and objects that are difficult to touch. However, it is necessary to confirm that the measurement conditions differ from those of contact measurement.

What is infrared measurement?

When measuring temperature, you shouldn't just look at the sensor.

In this article, we will refer to all the elements involved in capturing temperature and using that information for display, recording, and other purposes as a "measurement system."

Measurement accuracy is not determined solely by the sensor.

Even if you select a high-precision temperature sensor, you may not obtain the desired temperature if the measurement location is not suitable for the purpose, the installation is inappropriate, the measurement is affected by wiring, or the conditions on the measuring instrument side are not appropriate.

In other words, using a high accuracy sensor is not the same as achieving high accuracy temperature measurement.

You don't need to memorize all the technical terms.

Temperature measurement involves various specialized elements, such as thermocouple compensation wires and 3-wire and 4-wire resistance thermometer.

The important thing here is not to memorize every single term. Temperature measurement is not something that can be completed with just one sensor; it's about having the perspective to consider everything from the object being measured to the measuring instrument.

Even if you select the appropriate temperature sensor, if the actual measurement conditions are not suitable, it may not be able to accurately capture the temperature you want to measure.

Measurement location

The first thing to check is whether the measurement point is positioned correctly to measure the temperature you actually want to know. If the object being measured has a temperature distribution, the results will vary depending on the measurement point.

Installation Method

With contact-type temperature sensors, the measured values may be affected by the mounting position and insertion state.

The appropriate installation method varies depending on the target, such as piping, tanks, furnaces, or surfaces.

See how to properly install the temperature sensor.

responsiveness

When the temperature changes, the sensor indicated value may not change instantaneously. The sensor's ability to respond to temperature changes varies depending on structure and mounting conditions.

In process that require tracking rapid temperature changes, it is crucial to consider the necessary responsiveness in advance.

Operating environment

When measuring temperature, we check not only the object being measured, but also the environment in which the sensor, wiring, and measuring instrument are placed.

• High temperature / Low temperature
• vibration and shock
• Humidity and dew condensation
• corrosive atmosphere
• dust
• Electrical noise
• thermal radiation from the surroundings

Required accuracy

Temperature sensors and measuring instruments each have their own specifications accuracy and tolerances. However, the reliability of actual measurements is not determined solely by the instrument's specifications.

The required accuracy must be considered in conjunction with the object being measured, the tolerance range of process, the installation conditions, the measuring instrument, and other factors.

Up to this point, we have considered "what temperature to measure," "how to measure it," and "how to configuration the measurement system."

So, there's another important question.

It's not determined solely by the precision specifications of the equipment.

Temperature sensors and measuring instruments have specifications accuracy requirements. However, using equipment that meets those specifications does not automatically guarantee that the measurements obtained in the field will have the same reliability.

Actual measurements involve various factors, including the measurement location, installation, surrounding environment, wiring, measuring instrument, and changes over time.

Calibration is the process of checking against a standard.

Calibration is one method of verifying the values that sensors and measuring instruments are showing, after configuration an appropriate measurement system.

Calibration involves comparing the values shown by measuring instruments or sensors with reference values and checking the difference.

However, simply being calibrated does not guarantee that the device will accurately measure the target temperature in a real-world setting.

Calibration is performed by comparing the measurement to a standard under specific conditions, so in actual field settings, it is necessary to consider factors such as the measurement location, installation conditions, and surrounding environment.

Temperature measurement doesn't end with display the temperature. The obtained temperature information is used for a variety of purposes, including recording, monitoring, and control.

CHINO 's "temperature loop" is a concept that considers measuring, recording, monitoring, control, and maintaining the reliability of temperature measurements as a continuous process.

What is a temperature loop?

When considering new temperature measurement methods or reviewing existing ones, try organizing the following points in order.

• Why measure temperature?
• What temperature do you really want to know?
• Where should we measure to capture that temperature?
• Which is more suitable, contact or non-contact?
• Which temperature sensor/measuring instrument should I use?
• Is the measurement system, including the object being measured, sensors, wiring, and measuring instruments, appropriate?
• What level of accuracy and responsiveness is required?
• What kind of influences are there from the surrounding environment?
• Is it necessary to record, monitor, and control the measured values?
• How to verify the reliability of measurement values

See how to choose a temperature measuring device.