All You Need to Know About

Temperature Sensor Calibration

Temperature sensor calibration is becoming more and more important as the number of temperature sensors deployed increases every year.

It will be closely related to our life, such as Wearable thermometer, infrared temperature measurement during the new crown pneumonia epidemic, home air conditioning thermometer, smart home, smart building, smart city.

Temperature measurement has been applied in various scenarios to bring more convenience to people’s comfortable life.

Let’s dive right in.

Temperature Sensor Calibration Knowledge 1

CHAPTER 1

Temperature Sensor Definition

Temperature Sensor Calibration Knowledge 2

CHAPTER 2

Temperature Calibration

Temperature Sensor Calibration Knowledge 3

CHAPTER 3

Why Need Temperature Calibration

Temperature Sensor Calibration Knowledge 4

CHAPTER 4

How to Calibrate

Temperature Sensor Calibration Knowledge 5

CHAPTER 5

Find More

Temperature Sensor Calibration Knowledge 6

CHAPTER 6

How To Buy

Temperature Sensor Calibration Knowledge 7

CHAPTER 7

Future About It

Temperature Sensor Calibration Knowledge 8

CHAPTER 8

FAQs

CHAPTER 1:

Temperature Sensor Definition

What is a temperature sensor? I’m sure no one is unfamiliar with this issue, so let’s learn more about it together.

A temperature sensor is a sensor that senses temperature and converts it into a usable output signal.

A temperature sensor is the core part of the temperature measurement instrument, a wide variety.

According to the measurement method can be divided into contact and non-contact two categories, according to the sensor material and electronic components characteristics into two categories of RTD and thermocouple.

CHAPTER 2:

Temperature Calibration

The temperature calibration process is a reliable, reproducible, and documented comparison of one piece of equipment under test with another piece of equipment that has been temperature calibrated and referenced to a set of known parameters.

The equipment referenced is a high-precision instrument that has been regularly checked by an accredited laboratory.

Temperature calibration is typically performed at one or several defined measurement points. In order to perform the calibration, equipments/machines are needed to maintain a stable environment.

CHAPTER 3:

Why Need Temperature Calibration

The following will describe three aspects of the importance of temperature calibration that will come to the fore as we deploy more sensors each year.

Meaning Of Temperature Calibration

(1) Regulatory requirements such as calibrated thermometers and data loggers are commonly used in the GDP environment where packaged pharmaceuticals are stored and transported. Regardless of which guidance document you refer to in the GDP environment (FDA, EU, PDA, ISPE, WHO, USP or ICH), most of them require the use of “calibrated sensors”. For cold chain transport, some of the more extreme interpretations also require ISO 17025 calibration.
(2) Scientific research requirements, in a scientific research process, even 0.1 degrees of error on the final experimental data have a fatal impact, so the need to regularly calibrate the instrument calibration, so that it maintains the “best” working condition.
(3) The instrument will be affected by external influences to produce a certain degree of data drift, which may be related to the environment, but also may be related to their own characteristics or life. The calibration criteria is to keep the output value “correct” by external intervention.

CHAPTER 4:

How to Calibrate a Temperature Sensor

The temperature sensor calibration can be seen everywhere. They can be found in every corner of our lives and play a huge role.

Different Types of Temperature Sensors
Different sensors have different mechanical structures and different mechanical strengths. Some are waterproof, some are not, and can be divided into the following cases.
(1) waterproof sensor and the length of the digital thermometer that meets the insertion depth requirements (insertion depth > 10cm). The sensor can be directly inserted into the thermostat tank for calibration.
(2). Waterproof sensor length ≤ 5cm digital thermometer. In order to meet the insertion depth requirements, the sensor needs to be placed in a glass test tube for calibration, according to the temperature zone, divided into two cases in Table 2 for processing:
(3) Non-waterproof digital temperature sensors, these sensors need to be placed in an air test tube when calibrating, and should not be in direct contact with liquid.
Pre-test Preparation
There is usually not a lot of preparation, but there are a few things to consider.
First, perform a visual inspection to make sure the sensor looks normal and that it is not bent or damaged.
External contamination can be a problem, so it is a good idea to know where the sensor is being used and what type of media is being measured.
You may need to clean the sensor prior to calibration.
The insulation resistance of the RTD sensor can be measured prior to calibration. A drop in insulation resistance can cause a measurement error and indicate a damaged sensor.
Temperature Source
You need a temperature source to calibrate the temperature sensor. For industrial purposes, a temperature drying block is most often used. It is convenient and portable, and usually accurate enough.
For higher accuracy requirements, a liquid bath can be used. For zero degrees Celsius, a stirred ice bath is usually used. It is very simple and affordable but has a high zero-point accuracy.
To obtain the most accurate temperature, fixed-point sensors are used. These are very accurate, but also expensive. These are typically used inaccurate (and accredited) temperature calibration laboratories.
Reference Temperature Sensor
Obviously, you need to know the temperature of the heat source with very high precision.
The dry block and liquid bath provide an internal reference sensor for measuring the temperature.
However, for more accurate results, you should use a separate accurate reference temperature sensor that is inserted at the same temperature as the sensor to be calibrated.
This reference sensor will more accurately measure the temperature being measured by the sensor to be calibrated.
Output Signal of a Temperature Sensor
The electrical output (resistance or voltage) of most temperature sensors needs to be measured and converted to temperature. Therefore, you need to have some device for the measurement.
If you measure the signal output, you will need to convert it to temperature using international standards. In most industrial situations, you will use a measurement device that can do the conversion for you, so you can easily view the signal in temperature units (degrees Celsius or Fahrenheit).
Immersion Depth
Immersion depth (how deep you insert the sensor into temperature source) is one important consideration when calibrating temperature sensors.
Our temperature calibration lab people gave this rule of thumb when using a stirred liquid bath:
- 1% accuracy – immerse 5 diameters + length of the sensing element
- 0.01% accuracy – immerse 10 diameters + length of the sensing element
- 0.0001% accuracy – immerse 15 diameters + length of the sensing element
Heat conduction in a stirred liquid bath is better than in a dry-block and the required immersion depth is smaller.
For dry-blocks, there is a recommendation that you should immerse 15 times the diameter of the sensor added with the length of the sensor element. So, if you have a 6 mm diameter sensor, which has a 40 mm element inside, you immerse it (6 mm x 15 + 40 mm) 130 mm.
Sometimes it is difficult to know how long the actual element is inside the sensor, but it should be mentioned in the sensor specifications.
Also, you should be aware of where the sensor element is located (it is not always in the very tip of the sensor).
The sensor to be calibrated and the reference sensor should be immersed into the same depth so that the middle points of the actual sensor elements are in the same depth.
Naturally with very short sensors, it is not possible to immerse them very deep. That is one reason for the high uncertainty when calibrating short sensors.
Maintaining Stability
Remember, the temperature sensor will always measure its own temperature!
The temperature changes very slowly and you should always wait long enough for all parts to stabilize at the target temperature.
When you insert a sensor into a temperature, it will always take a while for the sensor to reach that temperature and stabilize.
Often, one of the biggest uncertainties associated with temperature calibration can be that the calibration is performed too quickly.
Temperature Calibration Range
With temperature sensors, it is very common that you do not calibrate the sensor for the entire temperature range.
You should be careful when calibrating at the highest point of the range. For example, if you calibrate at too high a temperature, the RTD sensor may drift permanently.
Similarly, the coldest point of the sensor’s temperature range may be difficult/expensive to calibrate.
Therefore, it is recommended to calibrate the temperature range in which the sensor will be used.
Calibration Points
In industrial calibration, you need to select enough calibration points to see that the sensor is linear. Typically, 3 to 5 points over the entire range is sufficient for calibration.
If you know that the sensor may not be linear, depending on the type of sensor, more points may need to be acquired.
If you calibrate a platinum sensor and plan to calculate coefficients based on the calibration results, you will need to calibrate at the appropriate temperature points in order to calculate coefficients.
The most common coefficients used for platinum sensors are the ITS-90 and Callendar van Dusen coefficients.
For thermistors, Steinhart-Hart coefficients can be used.
Adjusting the Temperature Sensor
Unfortunately, most temperature sensors cannot be adjusted or tuned.
Therefore, if a calibration error is found, no adjustment can be made.
Instead, you will need to use coefficients to correct the sensor’s reading.

CHAPTER 5:

Find More About Temperature Sensor Calibration

Temperature Sensor Calibration is already a trend in our current life. I hope the audience can learn more from other aspects. Including Wikimedia/Patent/Video and so on.

WikiPedia

Calibration
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy.^[1] Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler.
Resistance Thermometer
Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a ceramic or glass core but other constructions are also used. The RTD wire is a pure material, typically platinum, nickel, or copper. The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes.
RTDs, which have higher accuracy and repeatability, are slowly replacing thermocouples in industrial applications below 600 °C.^[1]

Patents

US10018520B2:Temperature calibration for a measuring apparatus
InventorMartin Ostermeyer Thomas Brandl
Current Assignee Anton Paar Optotec GmbH
US10648870B2:Temperature sensor and calibration method thereof having high accuracy
InventorBirama Goumballa Didier Salle Olivier Doare Cristian Pavao Moreira
Current Assignee NXP USA Inc
US9810589B2:System and method for automatically calibrating a temperature sensor
InventorManoj Sinha Sujeet Ayyapureddi Brandon Roth
Current Assignee Micron Technology Inc

Videos

How to calibrate a temperature sensor
What is Sensor Calibration and Why is it Important?

CHAPTER 6:

Buy Temperature Calibrator

The RTC reference temperature calibrator is very important. How can we choose the most suitable one?

When you come to this page, ZATA RTC Temperature Calibrator has appeared in front of you. ZATA is a main temperature calibration equipment manufacturer in China.

I believe that when you finish reading the introduction below, you will make the right purchase decision.

ZTC100 RTD Temperature Calibrator

	ZTC100
Measure Range	-60-199°C
Resolution	0.01°C
Accuracy	±0.05°C
Power In	AC220V or DC12/24 <2W
Environment
Operation Temperature	0-40°C
Operation Humidity	<80%RH
Interface	RS485/RS232
Weight	<2Kg

Learn More Request A Quote

CHAPTER 7:

Future of Temperature Sensor Calibration

Although you have read the detailed introduction above, you have a general understanding of the temperature sensor calibration. Next, I will make the following guesses about future temperature calibration.

The future temperature sensor mainly are digital temperature sensors, easy to use. No need additional datalogger.
calibration should move towards on-line calibration, where there is no additional need to send back to the laboratory for special metrology, but rather to obtain real-time temperature data from the work site for calibration through the authorization of an intelligent terminal.
In the future, instead of regular passive calibration (i.e., now mainly taking one year as the calibration cycle), the state will be automatically detected online through the cloud and actively calibrated.
The current third-party temperature calibrator price is too high, and future calibration institutions will become more and more cost-effective, at least one-tenth of the current cost.

CHAPTER 8:

Temperature Sensor Calibration FAQs

Here are some common questions about temperature sensor calibration. We will update them regularly through customer feedback.

I hope you can find the answers here. If you have more questions, please email to us.

How do you calibrate a temperature sensor

There are three common methods for calibrating temperature sensors:

Calibrating just the electronics with a simulator.
Calibrating both the electronics and the sensor in a dry-well.
Calibrating both the electronics and the sensor in a dry-well with a reference thermometer.

Why do sensors need to be calibrated

But in order to achieve the best possible accuracy, a sensor should be calibrated in the system where it will be used. This is because: No sensor is perfect. … Differences in sensor design mean two different sensors may respond differently in similar conditions.

What is the most accurate method for calibrating

Fill a large container with crushed ice. Add clean tap water until the container is full. Stir the mixture well. The ice-point method is the most widely used method to calibrate a thermometer.

How do you calibrate a temperature

Method 1: Ice Water

Fill a glass with ice cubes, then top off with cold water.
Stir the water and let sit for 3 minutes.
Stir again, then insert your thermometer into the glass, making sure not to touch the sides.
The temperature should read 32°F (0°C). Record the difference and offset your thermometer as appropriate.

What is the best temperature to calibrate to

The thermometer should read between 30° and 34° F. If it doesn’t, adjust the dial 32° F. To calibrate a thermometer used to measure higher temperatures, you might prefer the boiling method. Again, use distilled water and bring it to a rolling boil in a pot or beaker if you have one handy.

How does temperature affect calibration

Components, such as electronics, used in an instrument may be affected by changes in operating temperature. If an instrument is calibrated at one temperature and then operated at a significantly different temperature, the temperature-induced error can also degrade the results’ accuracy.

Now It’s Your Turn

I hope you enjoyed this application article.

Now I’d like to hear from you: Do you have anything else about temperature sensor calibration?

Could you make the right purchase decision?

Either way, let me know by leaving a quick comment below.

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Temperature Sensor Calibration

Contents

Temperature Sensor Definition

Temperature Calibration

Why Need Temperature Calibration

How to Calibrate

Find More

How To Buy

Future About It

FAQs

Temperature Sensor Definition

Temperature Calibration

Why Need Temperature Calibration

Meaning Of Temperature Calibration

How to Calibrate a Temperature Sensor

Different Types of Temperature Sensors

Pre-test Preparation

Temperature Source

Reference Temperature Sensor

Output Signal of a Temperature Sensor

Immersion Depth

Maintaining Stability

Temperature Calibration Range

Calibration Points

Adjusting the Temperature Sensor

Find More About Temperature Sensor Calibration

WikiPedia

Patents

Videos

Buy Temperature Calibrator

Future of Temperature Sensor Calibration

Temperature Sensor Calibration FAQs

Now It’s Your Turn

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