If you’re in the market for accurate temperature measurements, you’ve probably come across the PT100 sensor. A PT100 sensor is a type of resistance temperature detector (RTD) that has a resistance of 100 ohms at 0°C. It works by measuring changes in the resistance of a platinum wire as the temperature changes.
3-wire PT100 sensors are commonly used in industrial applications because they offer higher accuracy than 2-wire sensors. However, wiring a 3-wire PT100 sensor can be a bit tricky, and if done incorrectly, can lead to inaccurate temperature measurements. In this article, we’ll go over everything you need to know about wiring a 3-wire PT100 sensor correctly.
What is a 3-Wire PT100 Sensor?
A 3-wire PT100 sensor is a type of RTD that has three wires connected to it. The three wires are used to compensate for the resistance in the connecting wires, which can cause errors in temperature readings. The three wires are connected in a Wheatstone bridge configuration, which cancels out any resistance in the connecting wires.
The Wheatstone bridge configuration consists of four resistors, with the PT100 sensor acting as one of the resistors. The other three resistors are usually precision resistors of the same value, and they are connected in a diamond shape. The voltage across the bridge is measured using a voltmeter, and the temperature can be calculated based on the change in resistance of the PT100 sensor.
How to Wire a 3-Wire PT100 Sensor
Wiring a 3-wire PT100 sensor correctly is crucial for accurate temperature measurements. Here are the steps you need to follow to wire a 3-wire PT100 sensor correctly:
Step 1: Check the Wiring Configuration of the Sensor
Before you wire the sensor, you need to make sure you know the correct wiring configuration. Some sensors have the wiring diagram printed on them, while others may require you to refer to the datasheet.
Step 2: Connect the Wires
The three wires of the PT100 sensor are usually color-coded, with one wire being red, one being white, and one being blue or green. The red wire is usually connected to the positive terminal of the power supply (or the input signal), while the white wire is connected to the negative terminal of the power supply (or the input signal). The blue or green wire is connected to one of the inputs of the voltmeter.
Step 3: Connect the Precision Resistors
The three precision resistors are usually connected in a diamond shape, with one resistor at the top and two resistors at the bottom. The resistor at the top is usually connected to the positive terminal of the power supply, while the two resistors at the bottom are connected to the negative terminal of the power supply.
Step 4: Connect the Volmeter
The voltmeter is connected across the two inputs of the diamond-shaped configuration, with one input connected to the blue or green wire of the PT100 sensor and the other input connected to the other resistor at the bottom of the diamond.
FAQ
Q1: What is the difference between a 2-wire and 3-wire PT100 sensor?
A: A 2-wire PT100 sensor has two wires connected to it, while a 3-wire PT100 sensor has three wires connected to it. The extra wire in a 3-wire PT100 sensor is used to compensate for the resistance in the connecting wires, which can cause errors in temperature readings.
Q2: Can I use a 3-wire PT100 sensor with a 2-wire system?
A: No, you cannot use a 3-wire PT100 sensor with a 2-wire system. The 3-wire sensor requires a Wheatstone bridge configuration to work properly, which cannot be achieved with a 2-wire system.
Q3: How accurate are PT100 sensors?
A: PT100 sensors are very accurate, with an accuracy of up to ±0.1°C. However, the accuracy is dependent on several factors, such as the quality of the sensor, the wiring, and the measuring instrument.
Conclusion
Wiring a 3-wire PT100 sensor correctly is crucial for accurate temperature measurements in industrial applications. By following the steps outlined in this article, you should be able to wire your sensor correctly and achieve accurate temperature readings. Remember to always refer to the datasheet of your sensor for the correct wiring configuration.
