How to determine the quality of a PT100 temperature sensor

The core of determining the quality of a PT100 temperature sensor is to measure its resistance, insulation performance, and temperature response characteristics, and compare these measurements with standard parameters to confirm its accuracy, stability, and reliability.

As a high-precision temperature sensing element, the PT100 is widely used in industrial control, medical equipment, and new energy systems. Its quality directly affects the accuracy of temperature measurement and system safety. A qualified PT100 sensor should have a resistance of 100.00Ω at 0℃, and the resistance should increase approximately linearly with temperature (temperature coefficient approximately 0.385Ω/℃). The following are specific methods for judging its quality from multiple dimensions:

I.Room Temperature Resistance Measurement (Basic Judgment)

Measuring the sensor's resistance at room temperature using a digital multimeter is the simplest and most effective preliminary judgment method.

Standard Reference Values:

0℃ → 100.00Ω

20℃ → Approx. 107.8Ω

50℃ → Approx. 119.4Ω

100℃ → Approx. 138.5Ω

Operating Procedures:

Place the sensor in a stable room temperature environment (avoid handling to prevent temperature fluctuations).

Set the multimeter to the resistance range (200Ω range).

Measure the resistance between the two leads.

Check the deviation against the PT100 calibration table.

Acceptance Criteria:

Measured value vs. theoretical value deviation ≤ ±1Ω (Industrial Class B) or ≤ ±0.5Ω (High Precision Class A).

If the display shows "OL" (infinity), it indicates an internal open circuit; if it is close to 0Ω, it may be a short circuit.

II. Temperature Response Test (Dynamic Verification)

Verify whether the sensor can output a corresponding resistance value with temperature changes to determine its dynamic performance.

Hot Water Test Method:

Prepare a basin of hot water at a known temperature (e.g., 50℃). Confirm the water temperature using a standard thermometer.

Completely immerse the sensor in the water and wait 3-5 minutes for thermal equilibrium.

Measure the resistance value at this point; it should be close to 119.4Ω. Repeat the test with water baths of different temperatures, observing the trend of resistance change.

Heating Verification: Gently heat the probe using a hot air gun. The multimeter reading should rise steadily without any jumps or pauses.

III. Insulation Resistance Test (Safety Assessment)

Test the insulation performance between the sensor housing and the leads to prevent leakage or interference.

Test Method:

Use a megohmmeter (or a multimeter with insulation testing function).

Connect one end to the sensor's metal sheath and the other end to the signal line.

Apply a DC 500V voltage and measure the insulation resistance.

Acceptance Criteria:

Insulation resistance > 100MΩ (Ambient temperature 15~35℃, humidity <80%). Values ​​below this may indicate signal drift or safety hazards due to moisture or aging.

IV. Lead Wire and Wiring Method Inspection (Interference Resistance)

Wiring method affects measurement accuracy, especially in long-distance transmission.

It is recommended to prioritize three-wire or four-wire sensors to improve system stability.

V. Appearance and Structural Inspection (Physical Reliability)

Check for deformation, corrosion, or coking of the protective tube.

Check for damage, oxidation, or loosening of the lead wires.

Check for secure connections, poor welding, or seal failure.

While these issues do not directly affect the resistance value, they reduce long-term reliability, especially in high-temperature and vibration environments, easily leading to malfunctions.

VI. Comprehensive Quality Judgment Standards