What is NTC Sensor?
An NTC (Negative Temperature Coefficient) sensor is a type of temperature sensor that uses a resistor whose resistance decreases as the temperature increases. NTC sensors are commonly used to measure temperature in various applications, such as automotive engines, HVAC systems, and household appliances.
NTC sensors work by using the principle that the resistance of a conductor decreases as its temperature increases. The resistance of the NTC sensor is typically measured using a Wheatstone bridge circuit, which allows the temperature to be determined based on the resistance of the sensor.
NTC sensors are often used in applications where precise temperature measurement is required, such as in temperature control systems. They are also used in systems where temperature monitoring is critical, like in automotive engines where coolant temperature must be tracked to avoid overheating.
There are several types of NTC sensors, including bead, disc, and chip sensors. Each type has its own advantages and limitations, and the best choice depends on the specific application requirements.
Types of NTC sensor
There are several types of NTC (Negative Temperature Coefficient) sensors, including:
- Bead sensors: Small, cylindrical, usually made of ceramic or glass. Ideal for tight spaces.
- Disc sensors: Flat, round, often ceramic or metal. Good for applications needing a larger sensing surface.
- Chip sensors: Silicon-based rectangular sensors, known for low cost and compact size.
- Probe sensors: Designed to be inserted into substances for localized temperature detection.
- Thermistors: Made of ceramic or polymer, fast response, widely used in dynamic systems.
- Infrared sensors: Measure temperature via IR radiation, great for non-contact measurement.
- RTDs (Resistance Temperature Detectors): More accurate than NTCs but slower and costlier.
NTC vs PTC
NTC and PTC sensors are both resistor-based temperature sensors. The core difference lies in the direction of resistance change with temperature.
In an NTC sensor, resistance decreases as temperature increases. This property is useful in a range of systems like automotive, HVAC, and appliances.
In contrast, a PTC sensor exhibits an increase in resistance as temperature rises. It’s often used in current-limiting applications like fuses and circuit protection.
To summarize: NTC sensors have a negative coefficient, while PTC sensors have a positive coefficient. Their usage depends on whether you need decreasing or increasing resistance behavior with heat.
NTC tables
NTC tables show the relationship between temperature and resistance of a sensor. These are usually found in datasheets and help you calculate temperature based on resistance, or vice versa.
Example NTC table:
Temperature (°C) Resistance (Ω)
-40 10000
-20 5000
0 2500
20 1000
40 500
This table shows typical resistance values for certain temperatures. For instance, a reading of 1000 Ω would indicate around 20°C.
Note: Always check the specific NTC sensor’s datasheet for exact values, as different models have unique characteristics.
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