What is a PTC EGT Sensor?

1. Working Principle: The PTC EGT Sensor is based on the positive temperature coefficient (PTC) property of platinum metal. As temperature increases, the resistance of platinum metal rises significantly, allowing for accurate calculation of exhaust temperature by measuring the resistance.

2. Structural Composition: The core of the sensor consists of one or more platinum wires/films, externally encased in a high-temperature, corrosion-resistant protective sleeve to protect against the high temperatures, acidic gases, and particulate matter in engine exhaust.

3. Application Areas: Widely used in automotive engines, industrial combustion systems, and environmental monitoring systems for real-time monitoring of exhaust temperature, providing crucial data to support engine performance optimization, combustion efficiency improvement, and emissions compliance.

4. Advantages and Characteristics: It boasts high accuracy, long-term stability, fast response, and high durability, maintaining reliable operation even in extreme environments, making it the preferred temperature sensor for demanding scenarios.

How to determine whether an EGT sensor is PTC or NTC?

1. Resistance-Temperature Characteristics

Positive Temperature Coefficient (PTC): The resistance of the platinum or ceramic material inside the sensor increases with increasing temperature, exhibiting an approximately linear or predictable positive correlation curve.

Negative Temperature Coefficient (NTC): Using semiconductor or ceramic negative temperature coefficient materials, the resistance decreases rapidly with increasing temperature, showing an exponential decay trend.

Identification Method: Measure the resistance at a known temperature (e.g., room temperature 25°C) and gradually heat it, recording the resistance change trend. If the resistance increases with temperature, it is PTC; if it decreases, it is NTC.

2. Identification and Model Number

Product Model Number: Manufacturers usually indicate the coefficient attribute directly in the model number. PT200, PT500, PT2000, etc., are all PTC platinum resistance thermometers; while models marked "NTC" or "EGTS-NTC" are negative temperature coefficient models.

Technical Manual: The product manual's specification sheet will list keywords such as "Positive Temperature Coefficient" or "Negative Temperature Coefficient," which should be checked against the resistance-temperature curve.

Packaging Label: The sensor housing or packaging often bears the markings "PTC"/"NTC," or uses symbols like Rmin/xx (PTC) and R25/xx (NTC) for differentiation.

3. Circuit Connection and Signal Processing

PTC Sensor: Often used with a constant current source or voltage divider circuit, causing the output voltage to rise linearly with temperature as the resistance increases, facilitating direct reading by the ECU.

NTC Sensor: Mostly uses a bridge or voltage divider circuit; the output voltage decreases as the resistance decreases, and the signal direction is opposite to that of PTC.

Actual Testing: Connect the sensor to a known current source and measure the slope of the voltage across its terminals as a function of temperature; a positive slope corresponds to PTC, and a negative slope corresponds to NTC.

4. Temperature Range and Linearity

PTC: Wide operating temperature range, exceeding 300°C, and maintains near-linear response in high-temperature regions, suitable for high-temperature measurement scenarios such as exhaust gas temperature (EGT).

NTC: High sensitivity, suitable for the mid-to-low temperature range of -50°C to +150°C, commonly used for coolant and ambient temperature monitoring. Its resistance-temperature curve exhibits an exponential change in the low-temperature range, and sensitivity decreases as temperature increases.

Selection Tips: If the maximum temperature of the measured object exceeds 250°C, PTC is preferred; if minor temperature fluctuations are important and the operating temperature range is 0–150°C, NTC is more advantageous.