In industrial, consumer electronics and other types of scenarios, the choice of temperature sensors is critical, NTC and RTD as the most widely used two, both through the resistance change to achieve temperature measurement, the two in the principle of operation, performance and applicable scenarios on the significant differences, each has its unique advantages.
In this article, we will comprehensively dismantle the core features, key differences, application scenarios and installation and maintenance points of NTC and RTD, combined with the actual needs of different users, to provide a clear selection guide, to help you quickly lock the most suitable for their own projects of temperature sensors.
What is an NTC Thermistor?
NTC is the abbreviation of “Negative-Temperature-Coefficient Thermistor”. Its core characteristic is “Negative Temperature Coefficient”, as the temperature rises, its own resistance value will decrease, and this resistance change is predictable, is the core principle of temperature measurement.
From the material composition point of view, the core of NTC thermistor is a variety of powdered metal oxides mixed and pressed, as the core of the conductive medium, the proportion of its composition of the slightest difference, directly determines the initial resistance value, temperature coefficient and other key electrical properties, which affects the NTC’s temperature measurement accuracy and scene adaptability.
Compared with other temperature sensors, the temperature curve of NTC thermistor is non-linear, and its conventional operating temperature range is from -55℃ to +300℃, which can meet the temperature measurement needs of most civil and some industrial scenarios.
Common Types of NTC Thermistors
According to the package form and structure differences, NTC thermistors are mainly divided into the following five common types, different types of durability and applicable scenarios have their own focus, according to the actual needs of flexible choice:
- Glass encapsulated type: Adopting axial lead design, the glass shell can effectively isolate chemicals, moisture and physical shock, so it is suitable for temperature measurement in harsh environments, such as industrial wastewater treatment, chemical equipment and other scenarios.
- Glass bead type: radial lead design, the biggest advantage is the fast response speed, can quickly capture the temperature change, and at the same time has a certain degree of adaptability to harsh environments, commonly used in the need for rapid temperature measurement scenarios, such as medical equipment, environmental monitoring instruments.
- Epoxy-coated: Leads are divided into insulated and non-insulated, with excellent long-term reliability, not easy to aging, suitable for long-term stable operation of equipment, such as household appliances, automated office equipment.
- Surface Mount: Compact, with a variety of package configurations, suitable for circuit board surface mount process, but only for non-corrosive environments, widely used in consumer electronics, IoT modules and other small devices.
- Wafer and Chip: Basic design, no complex packaging, excellent thermal stability. Among them, the response speed of the round chip type is slightly slower than the chip type, both of which are suitable for the packaging volume is not strictly required, the pursuit of thermal stability of the scene, such as energy storage devices, industrial control modules.
Principle of NTC Temperature Sensing
The temperature measurement principle of NTC thermistor is based on the temperature sensitivity of resistance:
Its internal metal oxide semiconductor material, when the temperature changes, the intensity of thermal movement between the atoms will change, which in turn leads to a corresponding change in the resistance value of the material. When the temperature rises, the thermal movement of atoms intensifies, the carrier concentration increases, and the resistance value decreases; when the temperature decreases, the resistance value increases.
It should be noted that the accuracy of NTC temperature measurement is greatly affected by the calibration accuracy of the components and the material properties: the fine calibration of the internal components ensures a more stable correspondence between the resistance change and the temperature change, while factors such as the proportion of the metal oxide composition, purity, and so on, will also directly affect the accuracy of temperature measurement.
For bulk purchasing and wholesale scenarios, the precision and tolerance control of NTCs is especially critical. Tiny parameter differences may lead to significant fluctuations in the temperature measurement performance of wholesale devices, so it is necessary to focus on the specification parameters and consistency of the product at the time of procurement.
The Core Material of Thermistors NTC
The core of NTC thermistor is a semiconductor material, its main component is a mixture of various metal oxides, the type and proportion of these metal oxides, which directly determines the temperature-resistance characteristics, sensitivity and stability of the NTC. Common metal oxides include:
- Manganese Dioxide (MnO₂): It is usually the main component of NTC thermistors, and has a significant impact on the overall resistance value of the thermistor, and the subtle changes in the proportion of its addition will directly change the temperature sensitivity and temperature coefficient of the NTC.
- Nickel Oxide (NiO): The main role is to regulate the electrical characteristics of the thermistor, through the interaction with other oxides, fine calibration of the temperature-resistance curve, so that the NTC’s temperature range and sensitivity more in line with the actual application requirements.
- Cobalt Oxide (CoO): The core function is to adjust the B constant of NTC (B constant is the key parameter to define the temperature sensitivity of thermistor), and optimize the temperature response speed and stability of thermistor.
- Copper Oxide (CuO): added in some NTC formulations, used to further optimize the temperature-resistance characteristics, especially to improve the linearity and stability in a specific temperature range, suitable for the temperature measurement linearity of certain requirements of the scenario.
- Other additives: According to the performance requirements of the product, a small amount of other metal oxides or auxiliary materials will be added, mainly used to enhance the long-term stability of the NTC, to extend the service life, to reduce the noise of the temperature measurement, and to reduce the impact of aging on the accuracy of temperature measurement.
In the production process, the proportion of metal oxides is extremely strict control, a small deviation from the ratio may lead to large fluctuations in the resistance value of the NTC, temperature coefficient and other key parameters, which in turn affects the overall performance of the product and the application effect.
Application Scenarios of NTC Thermistors
With the advantages of high precision, high reliability, high sensitivity and low cost, NTC thermistors are widely used in many fields, covering new energy, consumer electronics, office equipment, energy storage, etc. The specific application scenarios are as follows:
- New Energy Vehicles (EV): mainly using grounded ring series NTC thermistors, with high reliability, high stability and high accuracy, used to monitor various core components of new energy vehicles, to achieve accurate temperature measurement, high temperature warning and safety protection, to ensure the safe operation of the vehicle.
- High-end consumer electronics: used in coffee machines, vacuum cleaners, steam ovens, smart toilets and other products. The response speed of NTC thermistor in this kind of scenario can reach 0.5 seconds, with fast temperature measurement capability and excellent waterproof performance, especially suitable for water temperature detection and other water contact scenarios.
- Automated office equipment: mainly used for temperature monitoring of printers, copiers and other equipment, through real-time monitoring of the temperature of the print head, thermal paper, to ensure the safe and efficient operation of the equipment, which can not only improve the print quality, but also extend the service life of the equipment, while reducing energy consumption.
- Energy storage and industrial control: energy storage systems with dense battery packs and closed environment are prone to heat buildup affecting performance; NTC thermistors capture temperature changes and prevent heat buildup through thermal management monitoring to ensure safe and stable operation of the system.
Negative Temperature Coefficient (NTC) thermistors are a class of highly sensitive, cost-effective and compact temperature sensors whose resistance value shows a predictable downward trend with increasing temperature. The device is suitable for rapid temperature feedback and circuit overcurrent protection scenarios, but also suffers from nonlinear resistance-temperature characteristics, limited operating temperature range and other shortcomings.
Advantages and Disadvantages of NTC Sensors
Advantages
- High sensitivity: sharp perception of temperature changes, can accurately identify the small fluctuations of 0.1 ℃ and below, resistance changes can be measured accurately and significantly, can provide stable and accurate readings in precision temperature measurement scenarios, suitable for various types of high-precision temperature measurement needs.
- Fast response speed: compact size, low thermal capacity, response time of milliseconds, can quickly capture the instantaneous changes in temperature, suitable for inrush current suppression, real-time temperature monitoring, and other demanding scenarios.
- Excellent cost performance: simple production process, low cost of raw materials, especially outstanding advantages in batch applications, and easy to install and use, without the need for complex ancillary equipment, widely used in various types of cost-sensitive areas.
- Lightweight: tiny physical size, miniaturized packaging, occupies very little space, can be seamlessly integrated into smart wearable devices, smart phones and other space-constrained electronic devices.
- Flexible selection: bare bead, glass package, industrial probe package and other types, according to the specific temperature measurement needs and use of environmental conditions, flexible selection, suitable for different application scenarios.
Disadvantages
- Characteristic non-linearity: resistance value and temperature are exponential, directly through the resistance value to calculate the temperature is prone to large errors, need to be matched with the table, fitting formula or microprocessor temperature compensation, increasing the complexity and cost of circuit design.
- Temperature measurement range is limited: conventional models effective working temperature of -50 ℃ ~ 150 ℃, beyond the range, the measurement accuracy will be significantly reduced or even lead to component damage, extreme temperature scenarios need to replace the special sensor.
- Existence of self-heating error: the temperature measurement process needs to pass into the operating current, resulting in I²R loss will lead to the sensor itself warming, resulting in temperature measurement deviation, low-power scenarios the error is more pronounced, the need to optimize the circuit design to reduce the impact.
- General environmental adaptability: without special treatment, vulnerable to water vapor, corrosive media erosion, resulting in resistance drift, component damage, use in harsh environments need additional sealing, anti-corrosion treatment.
What is a RTD Sensor?
RTD is the abbreviation of “Resistance Temperature Detector”, the full name of the Chinese resistance temperature detector, its core temperature measurement principle is based on the characteristics of the metal resistance with the change in temperature, is a high precision, strong stability of the temperature sensing equipment.
Its core working principle is: specific metal materials, the most commonly used is pure platinum resistance value will change with the temperature and show a predictable linear change, through the measurement of resistance changes, you can inverse launch the corresponding temperature value.
Unlike NTC thermistors, which have a “negative temperature coefficient”, RTD sensors have a positive temperature coefficient as the resistance value increases with temperature. The predictability and linearity of this resistance change makes RTDs extremely accurate, making them suitable for use in scenarios that require high accuracy.
Key Specifications and Characteristics of RTD Sensors
The core advantages of RTD sensors are high accuracy, high stability and wide temperature range. The key specifications and characteristics are as follows, which are also the core points that differentiate RTD sensors from other temperature sensors:
- Structural composition: mainly composed of a fine platinum wire and ceramic/glass core, the platinum wire is wrapped around the core and led out through the wire, the core plays a fixed and insulating role to ensure that the resistance change of the platinum wire is only affected by the temperature.
- Temperature range: the conventional operating temperature range of -200 ℃ to 850 ℃, the specific range can be adjusted according to the design and structure, can cover most of the industrial temperature measurement scenarios from very low to medium-high temperatures, much wider than the temperature range of NTC thermistors.
- Accuracy: With extremely high temperature measurement accuracy, especially in the narrow temperature range, the accuracy can reach ± 0.1 ℃, far more than the NTC thermistor, suitable for laboratories, medical care, high-end industrial and other demanding temperature measurement accuracy scenarios.
- Linearity: resistance value and temperature change is a good linear relationship, compared with other sensors such as thermocouples, linearity is better, in the specified temperature range, every increase of 1 ℃, the amount of change in the resistance value is basically the same, easy to data processing and calibration.
- Stability: especially platinum RTD sensors, long-term stability is excellent, resistance drift is very small, can be in the long-term continuous work to maintain stable temperature measurement performance, without frequent calibration, suitable for long-term reliability requirements of the scene.
- Wiring: 2-wire structure is the simplest, but will be affected by the lead resistance, lower accuracy; 3-wire is the most commonly used in industrial scenarios, to compensate for the error caused by the lead resistance, to improve accuracy; 4-wire has the highest accuracy, can completely eliminate the impact of the lead resistance.
Types of RTD Sensors
Categorized by Material
The material of RTD sensor directly determines its temperature measurement performance, temperature range and cost, the most commonly used materials are mainly 4 kinds, specific characteristics are as follows:
- Platinum RTD (Pt100, Pt500, Pt1000): the most commonly used, highest precision and best stability RTD type, widely used in industrial and scientific research scenarios. Among them, Pt100 is the most common specification, referring to the resistance value of 100Ω at 0°C; Pt500 and Pt1000 refer to the resistance value of 500Ω and 1000Ω at 0°C, respectively, which are suitable for different measurement circuit requirements.
- Nickel RTD: the cost is lower than platinum RTD, but the temperature measurement range is limited, up to only 300 ℃, applicable to the accuracy requirements are not high, cost-sensitive and narrow temperature range of the scene.
- Copper RTD: Excellent linear relationship between resistance value and temperature, but the copper material is easy to oxidize, and the temperature measurement range is limited to below 150°C. It is mainly used in low-temperature industrial scenarios such as electric motors, generators, turbines, etc., and is a low-cost alternative.
- Balco RTD: a nickel-iron alloy (containing 70% nickel and 30% iron), not as widely used as the first three, lower cost, resistance value similar to nickel RTDs, but the resistivity is twice as high as nickel, temperature measurement range of -40°C to 116°C, suitable for low-cost, narrow temperature range scenarios.
Classification by Structure
According to different structural designs, RTD sensors are mainly categorized into 3 types, suitable for different installation and application scenarios:
- Thin-film type RTD: Platinum film is deposited on a ceramic substrate, a circuit pattern is formed by laser etching, and the leads are connected and then covered with a glass coating for protection. Compact structure, lower cost, strong resistance to shock and vibration, flat shape, high design flexibility, suitable for industrial control, instrumentation and other scenarios.
- Wire-wound RTD: fine platinum wire wound in ceramic or glass skeleton made of precision and stability higher than the film-type RTD, but the production process is complex, high cost, suitable for industrial and scientific research scenarios that require high precision, such as high-temperature environment of precision temperature measurement.
- Coil-type RTD: the external shape is like a spring, platinum wire coil is placed in the ceramic/glass core, wrapped in a metal shell, which can reduce the temperature measurement error, improve thermal conductivity and response speed, suitable for submerged temperature measurement.
RTD Sensor Element Materials
RTD sensor temperature measurement core is the sensitive element, the material needs to meet the “temperature – resistance relationship linear, long-term stability” requirements, the material characteristics directly determine the RTD temperature measurement performance. At present, the main metal used for RTD sensitive element has four kinds, the specific characteristics are as follows:
- Platinum sensitive element: composed of pure platinum wire and copper extension leads, it is the most commonly used sensitive element material in industrial scenarios, with a wide temperature range, high accuracy and high stability, and can meet the needs of most high-end industrial and scientific research scenarios.
- Nickel sensitive element: temperature range is lower than the platinum sensitive element, more than 300 ℃ needs to be error correction, with a certain degree of corrosion resistance, the cost is lower than the platinum sensitive element, but the service life is shorter, the temperature range of -80 ℃ to 260 ℃, suitable for low-cost, low and medium-temperature scenarios.
- Copper sensitive components: excellent linear relationship between resistance value and temperature, but due to the low resistivity of copper, the need to make longer components to achieve the required resistance value; at the same time, copper is easy to oxidize, the temperature range is limited to below 150 ℃, mainly used for electric motors, generators and other low-temperature temperature measurement of industrial equipment is a low-cost option.
- Balco sensitive element: nickel-iron alloy material, low cost, resistivity is twice as much as nickel, resistance value is similar to nickel sensitive element, temperature range of -40 ℃ to 116 ℃, in the range of good linearity, suitable for low-cost, narrow temperature range of the scene.
When choosing the material of the sensitive element, you need to focus on three factors: cost budget, temperature range and accuracy requirements. It should be noted that gold, silver and other metals can not be used as RTD sensitive element materials due to low resistivity.
Application Scenarios for RTD Sensors
With the advantages of high accuracy, high stability and wide temperature range, RTD sensors are mainly used in industrial and scientific research scenarios that require high temperature measurement accuracy and reliability, covering a wide range of industries, as follows:
- Power plants: Used to monitor the temperature of boilers, turbines, exhaust ports and other core equipment to ensure that the equipment operates within a safe temperature range, prevent overheating damage, and safeguard the stable and efficient operation of the power generation system.
- Pharmaceutical industry: pharmaceutical production and storage process, the temperature control requirements are extremely strict, RTD sensors through accurate temperature measurement, to ensure that the production process in line with industry standards, to protect the safety and effectiveness of drugs.
- Food and beverage industry: used for food processing, storage process temperature monitoring, strict control of the temperature range, to ensure that the product meets the food safety standards, to prevent food spoilage, while improving production efficiency.
- Heating, ventilation and air conditioning (HVAC) systems: used in commercial buildings for temperature zoning regulation, through accurate monitoring of the temperature in each area, to realize the efficient operation of the air conditioning system, reduce energy consumption and improve indoor comfort.
- Petrochemical industry: In extreme temperature and pressure environments, RTD sensors are used to monitor the temperature of chemical reactions, pipeline transportation, and other processes with excellent durability and accuracy to ensure production safety and product quality.
Advantages and Disadvantages of RTD Sensors
Advantages
High temperature measurement accuracy: good repeatability, high precision temperature detection, especially in the narrow temperature range, can continue to output stable and reliable temperature measurement data, to ensure data consistency, suitable for all kinds of precision application scenarios.
- Wide temperature measurement range: conventional coverage of -200 ℃ to 850 ℃, breakthrough NTC in low temperature limitations, can be adapted to very low temperature to high temperature complex scenes, without the need to replace the sensor, is the first choice for a wide temperature range of temperature measurement.
- Excellent long-term stability: the core is made of platinum and other high-quality components, resistance drift is extremely small, long-term operation without significant performance degradation, without frequent calibration, can reduce downtime loss, reduce maintenance costs, improve the stability and efficiency of project operation, suitable for industrial, scientific research and other long-term continuous operation scenarios.
- Outstanding safety: no need for high-voltage power supply, low energy consumption, non-toxic and environmentally friendly core materials, no leakage and safety hazards, suitable for medical, food, mother and child and other strict requirements for safety and environmental protection scenarios, taking into account the safety and practicality.
- Excellent durability: processed through a special process, the structure is designed to be solid, can withstand various types of harsh environments in industrial production (and is not easy to damage, failure and other issues, can run stably for a long period of time, not only to enhance the reliability of the equipment’s own operation, but also effectively extend the service life of the sensor, reduce equipment replacement costs.
- Strong compatibility: the use of standardized interface design, in line with the industry’s common standards, and various types of hardware equipment, measurement systems to achieve seamless docking, without additional transformation can be quickly integrated to effectively reduce the difficulty of system integration, and at the same time can be flexibly adapted to different industries, different scenarios of the diversified needs of use, taking into account the convenience and practicality.
Disadvantages
High cost, compared with NTC thermistor, the price of RTD sensor is usually 2-5 times higher, which will directly increase the overall cost of the project, the adaptability of cost-sensitive projects is poor.
- Slow response speed, compared with the NTC thermistor, it is difficult to quickly capture the instantaneous temperature fluctuations, can not meet the high requirements for temperature measurement of the application of time-sensitive scenarios, there are limitations in the scope of adaptation.
- Relatively fragile structure, the internal platinum wire is thin, if subjected to violent collision or vibration, it is very easy to damage, which in turn affects the normal performance of the temperature measurement function and reduces the reliability of equipment operation.
- Relatively large size, especially wire-wound and coil-type RTDs, due to their own structural limitations, difficult to adapt to small consumer electronics and other small space application scenarios, installation flexibility is not enough.
- Installation and wiring process is more complex, requiring professional operation, and in order to ensure the accuracy of temperature measurement, usually need to use 3-wire or 4-wire wiring, which further increases the difficulty of operation and labor costs.
- Dependent on the power supply to work normally, can not realize the passive temperature measurement, at the same time, it is more sensitive to vibration and electrical noise, easy to trigger the temperature measurement precision deviation, affecting the accuracy of the data.
- Despite the excellent long-term stability, regular calibration is required (especially in high-precision application scenarios), which indirectly increases the maintenance cost and daily workload of the project, and enhances the difficulty of operation and maintenance.
NTC vs RTD Key Differences and Selection Guide
In order to show the differences between NTC and RTD more clearly, the following is a comparison from the core characteristics of the dimensions, to help quickly distinguish between the two applicable scenarios:
Response Speed
NTC thermistor has compact size, low heat capacity, and extremely fast temperature response speed, the fastest can reach 0.5 seconds, which can quickly capture the instantaneous change of temperature, and is suitable for electronic equipment heat dissipation monitoring, medical temperature monitoring, rapid temperature measurement instrumentation, and other scenarios with high requirements on time;
RTD sensors are affected by their own structure is relatively complex, heat capacity is large, the temperature response speed is slow, it is difficult to capture the instantaneous fluctuations in temperature, so it is more suitable for the response speed is not a strict requirement, pay more attention to the long-term stability of the temperature measurement of the application of the scene.
Temperature Measurement Accuracy
NTC thermistor belongs to medium precision temperature sensors, its conventional temperature measurement accuracy can fully meet the needs of civil, general industrial and other conventional temperature measurement scenarios, without complex calibration process can be stable and reliable data output, can be flexibly adapted to most of the application scenarios that do not have stringent requirements on temperature measurement accuracy.
RTD sensors have a very high temperature measurement accuracy, especially platinum RTD, the accuracy can reach ± 0.1 ℃, far more than NTC, very suitable for laboratory calibration, medical equipment, high-end industrial precision control and other demanding temperature measurement accuracy scenarios.
Cost
NTC thermistor production process is simple, low cost of raw materials, the cost-effective advantage of bulk purchasing, can effectively control the overall cost of the project, suitable for large-scale production and various types of cost-sensitive projects;
RTD sensors due to the high cost of the core material (eg, platinum), the complexity of the production process, the price of the NTC is usually 2-5 times, which will directly increase the project investment, and is more suitable for the cost of non-sensitive, focused on the temperature measurement accuracy and long-term stability of the project. It is more suitable for cost-insensitive projects that focus on temperature measurement accuracy and long-term stability.
Temperature Measurement Range
NTC thermistor’s regular working temperature range is -55℃ to +300℃, mainly suitable for low and medium temperature scenarios, unable to meet the needs of very low and high temperature measurement, widely used in civil and general industry and other low and medium temperature monitoring scenarios.
The RTD sensor’s regular working temperature range can cover -200℃ to 850℃, which can flexibly adapt to various complex temperature measurement scenarios from extremely low to medium-high temperatures, and its temperature measurement range is significantly better than that of NTC thermistors.
Long-term Stability
The long-term stability of NTC thermistors is at a medium level. After a long period of continuous operation, the resistance value may drift due to the aging of the material and the influence of environmental factors, which requires regular checking and calibration;
The long-term stability of RTD sensors is excellent, the resistance value drift is very small, can maintain stable temperature measurement performance in long-term continuous operation, without frequent calibration, suitable for all kinds of scenes that require long-term continuous operation.
Linearity
NTC thermistor resistance value and temperature is a non-linear relationship, the two changes follow the exponential law, directly through the resistance value to calculate the temperature is prone to large errors, need to be matched with the table, fitting formula or microprocessor temperature compensation, increasing the complexity of circuit design;
RTD sensor resistance value and temperature change is a good linear relationship, within the specified temperature range, the resistance value with the increase in temperature change is basically the same, without complex calibration, data processing is more simple and efficient.
Volume
NTC thermistors are compact and small in size, and can be miniaturized and packaged, taking up very little space, so they can be seamlessly integrated into consumer electronics, IoT modules and other equipment where space is tight, and installation flexibility is extremely high;
RTD sensors are limited by their own structure, especially wire-wound and coil-type RTDs, which are relatively large in size and require high installation space, making it difficult to adapt to small devices and narrow installation space, with poor spatial adaptability.
Comparison Based on Different User Scenarios
Different users focus on different needs, the choice of NTC or RTD sensors, need to combine their own work scene and the core needs of a comprehensive judgment, the following three types of typical users to give a specific analysis:
Electronic Engineers
The core needs of electronic engineers is usually a balance between product performance and scenario applicability, depending on the type of project, the direction of choice is also different:
- If the development of industrial control systems and precision instruments that require high temperature measurement accuracy, the core demand for long-term stability and high precision, give priority to RTD sensors, which have excellent stability and accuracy, and can work stably for a long time in harsh industrial environments.
- If the development of battery management system (BMS), processor cooling system or Internet of Things equipment, the core requirements for small size, fast response, cost control and adaptable circuit boards, give priority to the NTC thermistor, its compact structure, fast response, low cost, can effectively control the project budget.
Purchasing Manager
The core demand of procurement manager is to control the project cost, ensure the stability of the supply chain, while taking into account the reliability of the product, the specific selection recommendations are as follows:
- If the project batch size, cost-sensitive, and temperature measurement scenarios for low and medium temperatures, conventional precision needs, give priority to NTC thermistors, its low cost, easy to purchase features can significantly reduce project investment, while meeting the regular use of demand;
- If the project has higher requirements for temperature measurement accuracy and long-term stability, and low sensitivity to cost, RTD sensors can be prioritized; although the initial procurement cost is high, it can effectively reduce the maintenance cost, and effectively guarantee the long-term stability of product quality.
For IoT Developers and Technology Enthusiasts
The core needs of these users are ease of use, compatibility, and the flexibility to adapt to homemade projects, the specific choices are as follows:
- NTC thermistors are easy to operate and can be directly connected to the ADC pins of Arduino, Raspberry Pi and other development boards without the need for additional electronic components, which is ideal for homemade projects, smart home devices and other scenarios, and is the first choice for most enthusiasts.
- RTD sensors, on the other hand, need to be paired with additional electronic components in order to work properly, the operation is relatively complex, but its high precision and stability are more suitable for industrial IoT scenarios, not suitable for ordinary homemade projects.
Combining the above core factors, the following simple checklist can be used to quickly determine the direction of choice and improve decision-making efficiency:
Prioritize NTC thermistors If you meet the following conditions:
- If you need to respond quickly to temperature changes, strict cost control, and limited space for sensor installation, and at the same time, the temperature measurement range is between -55 ℃ and +300 ℃, you can give priority to NTC thermistors, suitable for consumer electronics, Internet of Things, general industrial control and other conventional temperature measurement scenarios.
Prioritize RTD sensors If you meet the following conditions:
- If you need high-precision temperature measurement, wide temperature range and long-term stable operation, and can accept higher procurement costs and complex installation process, the sensor is suitable for scientific research, medical, high-end industry, extreme temperature environment and other types of precision temperature measurement scenarios.
Installation and Maintenance Tips
Although both NTC thermistors and RTD sensors realize temperature measurement through resistance changes, their installation specifications and maintenance methods differ due to different structures and core characteristics. Correct installation and regular maintenance can effectively protect the sensor’s temperature measurement accuracy and extend its service life, specific tips are as follows:
Installation Tips
NTC thermistor installation points
- Welding and fixation: NTC thermistor is more sensitive to mechanical stress, welding needs to control the amount of solder, to avoid high temperature and mechanical pressure resulting in ceramic components produce micro-cracks, which affects the accuracy of temperature measurement; fixed to avoid squeezing the sensor body to prevent damage to the internal structure.
- Installation location: should be far away from the motor, resistance and other heating elements, to avoid environmental heat interference with the temperature measurement results; at the same time to ensure that the installation location has sufficient air circulation, to ensure that the sensor can sense the ambient temperature changes in a timely manner, to avoid the accumulation of heat resulting in temperature measurement deviation.
RTD sensor installation points
- Sensor protection: In chemical, humid, corrosive and other harsh environments, RTD sensors need to be inserted into the protective sleeve, not only to effectively protect the sensor from media erosion, but also does not affect the temperature conduction, and without interrupting the operation of the equipment to complete the sensor replacement.
- Optimization of thermal conduction: For surface mount or clamp-on RTD sensors, a thermally conductive paste should be applied between the sensor and the object under test to maximize the efficiency of thermal conduction and ensure that the sensor can accurately sense the actual temperature of the object under test.
- Wiring specification: If you need to ensure high temperature measurement accuracy, you should avoid using 2-wire wiring, as it is susceptible to errors caused by the resistance of the lead wires; give preference to 3-wire or 4-wire wiring, which can effectively compensate for the deviation caused by the resistance of the lead wires, and significantly improve the accuracy of temperature measurement.
Maintenance and Troubleshooting
Whether it is NTC thermistor or RTD sensor, regular maintenance and timely troubleshooting are the key to prolong the service life and guarantee the accuracy of temperature measurement, the specific operations are as follows:
- Appearance Inspection: Regularly check the sensor terminals, leads and sensor head to see if there is corrosion, cracks, moisture intrusion and other anomalies, if there is any abnormality need to be replaced in a timely manner to avoid affecting the performance of temperature measurement.
- Multimeter test: standard multimeter can be used for resistance testing, to determine whether the sensor is working properly. For example, the standard Pt100 RTD sensor at 0 ℃, the resistance value should be accurate for 100 Ω; if the resistance value is infinite, indicating that the circuit is open, the sensor has been damaged; if the resistance value deviation is too large, indicating that the sensor drift or failure.
- Calibration and maintenance: RTD sensors are recommended to be NIST-certified calibrated once every five years to ensure that the accuracy meets the requirements of use; NTC thermistors do not require frequent calibration, but if the temperature measurement deviation is found to be large after long-term use, it is also necessary to calibrate or replace them in a timely manner.
- Prevent self-heating: When the sensor is working, if the excitation current is too large, it will lead to internal heat generation and false temperature rise, which will affect the accuracy of temperature measurement. Therefore, it is necessary to control the excitation current within a reasonable range to avoid self-heating phenomenon.
Conclusion
The selection of NTC and RTD temperature sensors should be combined with the application scenarios, taking into account the temperature measurement range, accuracy and other core elements, NTC is suitable for conventional low and medium temperature scenarios, RTD is suitable for precision temperature measurement and harsh environments, the two types of sensors have their own advantages, and need to be selected in accordance with the needs of the project in order to take into account the performance and cost.
Our company supplies both NTC and RTD series temperature sensors, which can be customized for industrial manufacturing, HVACR and other fields to meet the needs of different customers in terms of temperature measurement accuracy, response rate and weathering performance.
