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How to choose ntc thermistor

Selecting the right NTC thermistor involves careful consideration of the maximum working current, nominal resistance value, ntc thermistor beta value and thermal characteristics. Understanding these factors ensures optimal performance and longevity of the NTC thermistor in various applications. By considering additional factors like maximum rated voltage, filter capacitor value, allowable startup current, and environmental conditions, engineers can make informed decisions to enhance the reliability and efficiency of their electronic designs.

Table of Contents

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What is NTC?
How NTC thermistor works
NTC thermistor applications
How to choose a NTC thermistor
Factor 1: Maximum Working Current
Calculation Example
Key Points:
Factor 2: Nominal Resistance Value
Example Calculation:
Key Points:
Factor 3: NTC thermistor B value and Thermal Characteristics
Thermal Characteristics:
Additional Considerations
Maximum Rated Voltage and Filter Capacitor Value
Allowable Startup Current and Long-Term Load
Environmental Factors
Conclusion

What is NTC?

An NTC thermistor, or Negative Temperature Coefficient thermistor, is a type of resistor whose resistance decreases as temperature increases. This characteristic makes NTC thermistors ideal for temperature sensing and control applications. Widely used in various industries, these thermistors are valued for their precision, reliability, and fast response time.

How NTC thermistor works

NTC thermistors are made from ceramic materials that exhibit significant changes in resistance with temperature variations. As the temperature rises, the semiconductor material's resistance drops, allowing more current to flow through the circuit. This predictable change in resistance with temperature makes thermistors NTC a critical component in many electronic devices.

NTC thermistor applications

NTC thermistors are used in a broad range of applications. Common uses include temperature monitoring in HVAC systems, battery packs, and medical devices. Additionally, they are essential in automotive temperature sensors, household appliances, and industrial equipment, where precise temperature control is crucial.

How to choose a NTC thermistor

Table: Summary of Key Factors for Selecting NTC Thermistors

Factor	Description	Example Calculation
Maximum Working Current	Must exceed the circuit's operating current	If operating current is 5A, select > 5A
Nominal Resistance Value	Determines inrush current limiting capability	For 220V line, 50A inrush: ≥ 6.2Ω
ntc thermistor b value	higher b value of thermistor results in lower residual resistance and smaller temperature rise	B-value selection based on application
Maximum Rated Voltage	Affects the allowable filter capacitor value; inverse relationship between voltage and capacitance	For higher voltage, use smaller capacitance
Allowable Startup Current	Must handle the maximum startup current and continuous load	For 60A startup, minimum resistance = 4.2Ω
Environmental Factors	Consider ambient temperature, humidity, and mechanical stress	High humidity accelerates aging

Factor 1: Maximum Working Current

The maximum working current of an NTC thermistor must be greater than the actual operating current of the circuit. This ensures the NTC thermistor can handle the electrical load without overheating or failing.

When selecting a power type NTC thermistor, the maximum operating current is a critical factor. The NTC thermistor's maximum operating current must be greater than the actual operating current of the power circuit to prevent overheating and ensure reliable performance.

Calculation Example

For instance, consider a power circuit with an operating current of 10 A. The selected NTC thermistor should have a maximum operating current significantly higher than 10A to handle potential current surges without degradation.

Key Points:

Ensure the NTC thermistor's maximum current rating exceeds the circuit's operating current.
Account for potential inrush currents which can be significantly higher than steady-state currents.

Factor 2: Nominal Resistance Value

The nominal resistance value of the NTC thermistor, denoted as , is another crucial factor. This value should be selected based on the line voltage and the expected inrush current

Key Factors in Selecting Power Type NTC Thermistors-1

Where:

· R: Nominal resistance

· E: Line voltage

· Im: Inrush current

For conversion power supply, inverter power supply, switching power supply, UPS power supply, Im=100 times the operating current
For filament, heater and other circuits Im=30 times the operating current

Example Calculation:

For a power supply with a line voltage of 220V and an inrush current of 60A:

Key Factors in Selecting Power Type NTC Thermistors-2

This calculation helps determine the minimum resistance required to manage the inrush current effectively.

Key Points:

Calculate the minimum resistance based on line voltage and inrush current.
Ensure the selected NTC thermistor's resistance value meets or exceeds this minimum requirement.

Factor 3: NTC thermistor B value and Thermal Characteristics

The B value of thermistor indicates its sensitivity to temperature changes. A higher B value means a greater change in resistance with temperature, which can be beneficial for certain applications.

Thermal Characteristics:

· Thermal Dissipation Coefficient (δ): Indicates how much power the thermistors ntc can dissipate per degree of temperature rise.

· Time Constant (τ): Represents the ntc thermistor's thermal response time.

The product of the time constant and the thermal dissipation coefficient gives an indication of the NTC thermistor's thermal capacity and its ability to suppress inrush currents.

Additional Considerations

Maximum Rated Voltage and Filter Capacitor Value

The maximum rated voltage and the value of the filter capacitor are crucial for selecting the appropriate NTC thermistor. The size of the filter capacitor determines the size of the NTC thermistor needed. In power applications, the inrush current results from the capacitor charging, and the NTC thermistor must handle this current.

Allowable Startup Current and Long-Term Load

The maximum startup current and the continuous current load on the NTC thermistor must be within the specified limits. For example, if an electronic device allows a maximum startup current of 60A and the thermistor has a minimum resistance of 4.2 ohms at startup, it must be selected to handle these conditions.

Environmental Factors

The operating environment significantly affects the performance of NTC thermistors. Factors such as ambient temperature, humidity, and mechanical stress must be considered. For instance, high humidity can accelerate the aging process of the thermistor, reducing its effectiveness over time.

Ensure the NTC thermistor operates within the specified temperature , humidity, and mechanical stress range to avoid accelerated aging or failure.

Conclusion

Selecting the right NTC thermistor involves careful consideration of the maximum working current, nominal resistance value, ntc thermistor beta value and thermal characteristics. Understanding these factors ensures optimal performance and longevity of the NTC thermistor in various applications. By considering additional factors like maximum rated voltage, filter capacitor value, allowable startup current, and environmental conditions, engineers can make informed decisions to enhance the reliability and efficiency of their electronic designs.

NTC Thermistor Inrush Current limiter MF72

Introducing the DXM NTC Thermistor Inrush Current Limiter MF72, a high-performance solution designed to protect your electronic devices from surge currents.

Key Features of MF72 Thermistor:

● Hight Durability: This reliable NTC Thermistor ensures optimal performance by strong surge suppression,enhancing device longevity.

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NTC Thermistor Inrush Current limiter MF72

Negative Temperature Coefficient Thermistor for temperature compensation (MF11 series)

Introducing the DXM MF11 Series Negative Temperature Coefficient Thermistor, designed for precise temperature compensation.

Key Features of MF11 Precision NTC Thermistor:
● High Accuracy: Offers precision up to ±5% resistance accuracy.
● Wide Operating Temperature Range: Functions effectively from -55°C to +125°C.
● Versatile Applications: Ideal for measuring equipment, electronic circuits, and more.
● Durable Construction, Compact Design: Resin-coated, small size design ensures longevity.
●Economical Solution: Cost-effective for maintaining stable semiconductor and IC performance.

Trust DXM's MF11 NTC Thermistors for precise and durable thermal management. Perfect for industries requiring accuracy and stability. Enhance your system's efficiency with our leading-edge technology today.

Negative Temperature Coefficient Thermistor for temperature compensation (MF11 series)

Glass Thermistor MF58 NTC for temperature control

Introducing the DXM Glass Thermistor MF58 NTC, your reliable solution for precise temperature control.

Key Features of MF58 thermistor:

● High Precision and Sensitivity: Designed for high accuracy and durability.

● Wide Temperature Range: Thermistors NTC operate effectively between -55℃ and +300℃.

● Durable and Compact: Glass encapsulated resistants to heat and moisture.

● Wide Applications : MF58 Thermistor perfect in electronics, automotive, and industrial use.

● Cost-Effective, RoHS Compliance: Offers a practical, economical choice for temperature control.

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Glass Thermistor MF58 NTC for temperature control

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