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You can find the relevant section in the article by searching for terms such as Pt100, JPt100, 3-wire type, self-heating, thermocouple, calibration, etc.
Key points to understand when learning about resistance thermometer
resistance thermometer is a temperature sensor that utilizes the change in electrical resistance due to temperature. In industrial applications, the Pt100 is typical, and it has temperature measurement characteristics that differ from thermocouples, such as a 3-wire design to suppress the influence of lead wire resistance.
- Measurement principle: This method utilizes the property that the electrical resistance of metals changes with temperature.
- Pt100: A platinum resistance thermometer with a nominal resistance of 100Ω at 0℃.
- 3-wire system: Widely used in industrial applications to minimize the influence of lead wire resistance on measurement values.
- Self-heating: The sensor itself may generate a small amount of heat due to current used to measure resistance.
- Selection: Check the temperature range, required accuracy, wiring method, structure, operating environment, and the measuring instruments to be connected.
- Reliability of measurement values: This includes not only the sensor itself, but also the installation, wiring, and measuring instrument.
Which should you choose: resistance thermometer or a thermocouple?
Neither method is always superior. The most suitable method depends on factors such as the measurement temperature, required accuracy, responsiveness, operating environment, and installation conditions.
1. What is resistance thermometer (RTD)? How does it measure temperature?
resistance thermometer (RTD) is a contact-type temperature sensor that measures temperature by utilizing the property that the electrical resistance of a metal changes with temperature.
Electrical resistance also changes with temperature.
Metals have the property that their electrical resistance changes with temperature. resistance thermometer measures this resistance value, and the temperature is determined from the relationship between resistance value and the temperature.
Temperature changes → Metal's resistance changes → Measure resistance → Convert it to temperature.
It's not directly reading the temperature itself.
resistance thermometer do not directly measure temperature itself, but rather measure "electrical resistance," which changes in relation to temperature.
This is a different measurement principle from thermocouples, which utilize the thermoelectric power generated by the combination of different metals.
Why is platinum used?
In industrial applications, platinum resistance thermometer resistance thermometer which use platinum, are typical.
Platinum resistance thermometer allow for the handling of the relationship between resistance and temperature according to standards, and are widely used in industrial temperature measurement.
2. What is Pt100? Also, check the difference between Pt100 and JPt100.
When researching platinum resistance thermometer, you'll often come across the name "Pt100." Pt100 is a representative platinum resistance thermometer widely used in industrial temperature measurement.
What does the "100" in Pt100 mean?
The "100" in Pt100 indicates that the nominal resistance value at 0°C is 100Ω.
Pt = Platinum
100 = Nominal resistance value at 0°C is 100Ω
This doesn't mean "100Ω at 100℃." resistance changes with temperature, and this relationship is used to determine temperature.
Pt100 and JPt100 are not the same.
You may sometimes see the notation "JPt100" in existing equipment or older specifications.
Although Pt100 and JPt100 have similar names, the relationship between resistance and temperature is not the same. Therefore, when replacing an existing JPt100, it is necessary to check not only the sensor but also the input settings of connected display, recorders, controllers, etc.
For existing equipment, do not assume that "it's the same because it's 100Ω"; please check the type of sensor and the input settings on the measuring instrument side.
There are also options like Pt500 and Pt1000.
Platinum resistance thermometer also come with nominal resistance values other than Pt100.
However, CHINO 's industrial temperature sensors primarily use the Pt100. If you are using Pt500 or Pt1000 sensors, be sure to check the compatibility between the sensor and the connected equipment.
What are Class A and Class B?
Platinum resistance thermometer have tolerance classifications based on standards. Class A and Class B are typical examples of these classifications.
However, the class refers to the tolerance of the sensor itself and is not the same as the overall accuracy of the temperature measurement.
In addition to sensor tolerances, wiring, measuring instruments, and installation conditions also affect the measured values.
3. What are the differences between 2-wire, 3-wire, and 4-wire systems?
resistance thermometer have connection methods known as 2-wire, 3-wire, and 4-wire.
You might wonder, "Why does a temperature sensor need three or four wires?" The key to understanding this is that lead wires also have electrical resistance.
resistance of the lead wires is also included in the measurement.
resistance thermometer determine temperature by measuring the resistance of the sensor. However, the lead wires connecting the sensor and the measuring instrument also have resistance.
resistance visible from the measuring instrument = resistance of resistance thermometer + the influence of lead wires, etc.
Depending on how this effect is handled, there are two-wire, three-wire, and four-wire connection methods.
| Method | Way of thinking | Major features |
|---|---|---|
| 2 wire system | resistance value is measured using two lead wires. | configuration is simple, but it is susceptible to the effects of lead wire resistance. |
| 3 wire system | Using three lead wires makes it easier to compensate for the effects of lead wire resistance. | It is widely used in industrial temperature measurement. |
| 4-wire | Separate the line that runs through the current and the line that measures the voltage, and measure the resistance. | It is used for precise measurements where the influence of lead wire resistance is minimized. |
The 3-wire system is widely used in industrial applications.
The 3-wire system allows for measurements that minimize the influence of lead wire resistance, and is therefore widely used in industrial applications such as Pt100.
However, this does not mean that "the effect of lead wire resistance is completely eliminated with a 3-wire system." The condition of the lead wires and the type of measuring instrument also play a role.
The 4-wire system is used for more precise resistance measurements.
In a four-wire system, the wire for carrying the measurement current and the wire for measuring the voltage are separated.
This allows for more accurate measurement of the sensor's resistance value while minimizing the influence of lead wire resistance.
Which equation should I choose?
The choice isn't based solely on the number of wires; it's based on factors such as required precision, wiring distance, connecting measuring instruments, and ease of installation.
4. What types and structure are there for resistance thermometer?
"Pt100" is a name that describes characteristic of the temperature sensing element, and does not mean that there is only one type of shape or structure for the actual temperature sensor.
Even with resistance thermometer using the same Pt100 core, the sensor structure will vary depending on what, where, and how it is being measured.
Sheath type
structure houses the temperature-sensing element and other components within a metal sheath. It is used in a variety of industrial applications, such as in equipment and piping.
General industrial use
This is the basic structure of an industrial temperature measuring device that is attached to pipes, tanks, equipment, etc.
For surface temperature
This device is structure to measure the surface temperature of pipes, equipment, and components, taking into account thermal contact with the measurement surface.
For gases
We will consider structure of the temperature-sensing element to make it easier to detect temperature changes in air and gases.
structure by use
There are structure to suit different measurement targets and usage environments, such as food, pharmaceuticals, chemicals, and low-temperature environments.
Simply choosing a Pt100 sensor is not enough to complete the selection process. You need to consider the overall structure of the sensor based on factors such as the object being measured, the mounting method, the environment, and the desired response time.
5. What is "self-heating" in resistance thermometer?
In resistance thermometer, current is passed through the sensor to measure resistance.
Therefore, the sensor itself may generate a small amount of heat due to current used to measure temperature. This is called self-heating.
current used for measurement heats the sensor.
Measurement: Run current → Measure the value at resistance → resistance: Heat is generated in the system → This affects the measured value depending on the conditions
If the temperature of the temperature-sensing element rises above the target temperature due to self-heating, it can cause measurement errors.
The effect of self-heating varies depending on the conditions.
The effect of self-heating is not determined solely by the measured current.
- Measurement current
- Sensor structure and dimensions
- Thermal contact with the object being measured
- How easily heat escapes to the surroundings
- Differences in the substances being measured, such as gases, liquids, and solids.
Also check the specified current.
specifications for resistance thermometer may include a specified current.
The specified current is not merely an electrical specifications; it's also an item that should be checked when considering the relationship between resistance measurement and self-heating.
6. How do you choose between resistance thermometer and thermocouples?
Both resistance thermometer and thermocouples are contact-type temperature sensors widely used in industrial temperature measurement.
However, because the measurement principles differ, the optimal temperature range, accuracy, responsiveness, wiring, and operating environment also vary.
| Item | Resistance thermometer | Thermocouple |
|---|---|---|
| Measurement principle | Change in electrical resistance due to temperature | Thermoelectric power generated by temperature difference |
| Typical example | Pt100 | K, J, T, R, S, B, etc. |
| Features | This method is a viable option for measurements that require relatively high accuracy and stability. | This is a suitable candidate for applications involving a wide temperature range or high-temperature measurements. |
| Check the wiring. | 2-wire, 3-wire, 4-wire, lead resistance, current measurement | Thermocouple type, polarity, compensating wire, cold contact compensation |
| Main points to note | Lead resistance, self-heating, installation, usage environment | Degradation, drift, compensating wire, cold contact compensation, operating atmosphere |
When resistance thermometer is likely to be a candidate
When relatively high measurement accuracy and stability are important within the temperature range to be used, resistance thermometer are a suitable option.
When thermocouples are likely to be the candidate
If you need a wide temperature range, including high temperatures, or if you want to choose from various types and structure depending on the application, thermocouples are a good option.
Choose based on the conditions, not on which is superior.
Instead of simply deciding that "resistance thermometer are high accuracy than thermocouples" or "thermocouples are always necessary for high temperatures," the decision should be made based on a combination of factors including the object being measured, the temperature range, required accuracy, responsiveness, operating environment, installation, and maintenance.
Learn more about thermocouples
Select from all temperature sensors
7. Key points for correctly using resistance thermometer
Simply selecting the appropriate Pt100 resistance thermometer.
It is necessary to consider factors such as the measurement location, mounting, wiring, the measuring instruments to be connected, and the operating environment.
| Check items | Confirm |
|---|---|
| What to measure | Please clarify what temperature you want to know. |
| Measurement location | We will check if the measurement is being taken at a location that represents the target temperature. |
| attachment | We check whether the insertion state and thermal contact with the target are appropriate. |
| wiring | Check the wiring type, wiring distance, connection status, noise, etc. |
| Measuring Instrument | Check if the input settings and line diagrams for Pt100, JPt100, etc. are correct. |
| Operating environment | We check for vibration, moisture, corrosion, pressure, thermal cycling, and other factors. |
Think in terms of the "measurement system," not just the sensors.
The measurement value of resistance thermometer is not determined solely by the temperature sensing element.
It is important to consider the sensor, wiring, measuring instrument, and installation conditions as a single measurement system.
What is temperature measurement? Basic principles and concepts for accurately measuring temperature.
8. How do you choose resistance thermometer?
When choosing resistance thermometer, don't assume that "any Pt100 thermometer will do," but rather organize the actual measurement conditions.
| Selection item | Contents to be confirmed |
|---|---|
| What to measure | Gases, liquids, solids, pipes, tanks, surfaces, etc. |
| Temperature range | room temperature, maximum and minimum temperatures, temperature changes. |
| Required accuracy | Precision required for process control, quality control, testing, etc. |
| element | We will primarily check Pt100, but also JPt100 and other types in existing equipment. |
| Wiring method | Supports 2-wire, 3-wire, and 4-wire connections and compatible devices. |
| structure and dimensions | Sheath, protective tube, outer diameter, length, insertion length, etc. |
| attachment | Methods of connecting equipment, such as screws, flanges, and nipples. |
| Operating environment | vibration, moisture, corrosion, pressure, etc. |
| Connected devices | display, recorders, controllers, converters, etc. |
| maintenance | Methods and frequency of replacement, inspection, and calibration. |
Simply choosing "Pt100" is not enough to complete the selection process.
resistance thermometer, when combined with its elements, wire configuration, structure, dimensions, mounting, environment, and measuring instrument, forms a complete temperature measurement system.
9. How can we trust the readings from resistance thermometer?
The fact that resistance thermometer display a temperature is not the same as being able to use that value with the required accuracy.
Check the condition during inspection.
During routine and periodic inspections, we check the appearance, wiring, installation status, abnormal values, and past measurement trends.
We also want to check for things like insulation degradation due to moisture and dew condensation, and the impact of vibration on wiring and temperature sensing components.
Calibration checks for differences from the standard.
In applications where the reliability of the measurement is required, the value shown by resistance thermometer is compared to a reference value, and the difference is checked.
This is calibration.
Being calibrated and being able to accurately measure the temperature you truly need in the field are not the same thing. In addition to calibration, we also check the measurement location, mounting, wiring, and the measuring instrument itself.
Learn more about calibration
Frequently Asked Questions about resistance thermometer
This document summarizes common information about resistance thermometer, including Pt100, JPt100, 3-wire type, self-heating, and differences from thermocouples.
Pt100 wiring
FAQ text
Q. What is Pt100?
This is a platinum-based resistance thermometer with a nominal resistance of 100Ω at 0°C. It is widely used as an industrial resistance thermometer.
Q. Are JPt100 and Pt100 the same?
They are not the same. Because the relationship between resistance and temperature differs, it is necessary to check specifications of the sensor and connected equipment when replacing existing equipment.
Q. Why is a three-wire system used in Pt100?
This is because there is resistance in the lead wires connecting the sensor and the measuring instrument. With a 3-wire system, the influence of lead wire resistance on the measurement value can be minimized.
Q. What is a 4-wire system used for?
By separating the wire carrying the measurement current from the wire measuring the voltage, this method is used to reduce the influence of lead wire resistance and measure resistance values more accurately.
Q. What is Pt1000?
This is a platinum resistance thermometer with a nominal resistance of 1000Ω at 0°C. While platinum resistance thermometer come in multiple nominal resistance values, CHINO 's industrial temperature sensors primarily use Pt100. Please check the compatibility with your connected equipment before use.
Q. What is self-heating in resistance thermometer?
This phenomenon occurs when resistance itself generates a small amount of heat due to current used to measure resistance. The effect on the measured value varies depending on the measurement current, sensor structure, and thermal contact with the object being measured.
Q. How do you choose between resistance thermometer and thermocouples?
The decision is based on factors such as temperature range, required accuracy, responsiveness, operating environment, wiring, and installation conditions. Neither option is always superior.
Q. Can resistance thermometer be used at high temperatures?
The usable temperature range depends not only on the temperature sensing element but also on structure and material of the sensor. Thermocouples may be a suitable option in high-temperature ranges, so the selection should be based on the actual operating temperature and environment.
Q. Can resistance thermometer also be calibrated?
Yes, we can. When reliability of measurement values is required for quality control, research and development, audits, etc., we perform inspections and calibrations according to working conditions and control standards.
Next
What I want to know next about resistance thermometer
resistance thermometer Once you understand the basics, moving on to how to select and install temperature sensors, the differences between them and thermocouples, and calibration will make it easier to grasp the big picture of temperature measurement.
Select from all temperature sensors
This document explains the differences between thermocouples and resistance thermometer, and outlines how to choose the appropriate temperature sensor based on the measurement target and conditions.
Learn more about thermocouples
This book provides a systematic explanation of thermocouples, covering everything from thermoelectric power, types, structure, compensating wires, degradation, and calibration.
Install the temperature sensor correctly.
This document provides a detailed explanation of how to install a contact-type temperature sensor, including measurement points, insertion depth, heat dissipation, protective tubes, and surface temperature measurement.
Verify the reliability of the measurement values.
This section will organize the concepts necessary for reliably using measured values, including calibration, traceability, uncertainty, and JCSS.
Reference information
- The operating temperature, tolerance, rated current, structure, material, and dimensions of resistance thermometer vary depending on the product. Please refer to the latest specifications, catalog, and instruction manual when making your selection.
- Temperature Sensor General Catalog
- Product knowledge of temperature sensors
- Temperature Sensor FAQ
