If you are looking for a reliable temperature sensor, you might have come across the term “Pt100”. It is a type of platinum resistance thermometer that is commonly used in process control and automation applications.
However, wiring a Pt100 sensor can be tricky, especially if you are not familiar with the wiring diagram. In this journal article, we will guide you through the 4 wire Pt100 wiring diagram and provide valuable tips to help you get the best results.
What is a Pt100 Sensor?
Before we dive into the wiring diagram, let’s first understand what a Pt100 sensor is. A Pt100 sensor is a temperature sensor that measures temperature changes by detecting the resistance changes of a platinum wire. The resistance of the wire changes with temperature following a predictable curve, which makes it a reliable sensor for accurate temperature measurements.
The “Pt” in Pt100 stands for “platinum,” which is the material used for the wire. The “100” refers to the resistance value of the wire at 0°C. A Pt100 sensor has a resistance of 100 ohms at 0°C and changes by approximately 0.385 ohms per °C.
Why Use a 4 Wire Pt100 Wiring Diagram?
There are two types of wiring diagrams for Pt100 sensors: 2-wire and 4-wire diagrams. The 2-wire diagram is simpler but has limitations in accuracy due to lead wire resistance. The 4-wire diagram, on the other hand, is more accurate and can compensate for lead wire resistance.
In a 4-wire Pt100 wiring diagram, two wires are used to apply a constant current to the Pt100 sensor, while the other two wires are used to measure the voltage across the sensor. By measuring the voltage drop, the resistance of the wire can be calculated accurately without being affected by lead wire resistance.
4 Wire Pt100 Wiring Diagram
The following is a step-by-step guide on how to wire a 4-wire Pt100 sensor:
Step 1: Prepare the wires and connectors
Before you start wiring, make sure you have the correct wires and connectors. You will need four wires, two for the constant current source and two for the voltage measurement. The wires should be color-coded for easy identification. The connectors should be compatible with your Pt100 sensor and measuring device.
Step 2: Connect the constant current wires
Connect the two wires for the constant current source to the Pt100 sensor. The wires should be connected to the positive and negative terminals of the constant current source. The positive wire should be connected to one end of the Pt100 sensor, while the negative wire should be connected to the other end.
Step 3: Connect the voltage measurement wires
Connect the two wires for the voltage measurement to the Pt100 sensor. The wires should be connected to the two remaining terminals of the Pt100 sensor. It does not matter which wire is connected to which terminal.
Step 4: Connect the measuring device
Connect the two wires for the voltage measurement to your measuring device. The wires should be connected to the input terminals of the measuring device. Make sure the wires are connected to the correct input terminals and follow the polarity indicated by your measuring device.
Step 5: Turn on the constant current source
Turn on the constant current source to apply a constant current to the Pt100 sensor. The current should not exceed the maximum current rating of your Pt100 sensor.
Step 6: Measure the voltage across the Pt100 sensor
Measure the voltage across the Pt100 sensor using your measuring device. The voltage should be within the range specified by your measuring device. If the voltage is too low, increase the current. If the voltage is too high, decrease the current.
Step 7: Calculate the resistance of the Pt100 sensor
Calculate the resistance of the Pt100 sensor using the following formula:
| Formula: | Rpt = (Vmeas * Rp / Vcc) – Rp |
|---|---|
| Where: | Rpt = resistance of the Pt100 sensor in ohms |
| Vmeas = measured voltage across the Pt100 sensor in volts | |
| Rp = resistance of the pre-set resistor in ohms | |
| Vcc = voltage of the constant current source in volts |
Once you have calculated the resistance, you can convert it into temperature using a Pt100 temperature conversion chart or equation.
Frequently Asked Questions (FAQs)
What is the difference between a 2-wire and 4-wire Pt100 wiring diagram?
The main difference between a 2-wire and 4-wire Pt100 wiring diagram is the number of wires used to connect the sensor to the measuring device. A 2-wire diagram uses two wires for both the constant current source and the voltage measurement. A 4-wire diagram, on the other hand, uses four wires, two for the constant current source and two for the voltage measurement. The 4-wire diagram is more accurate and can compensate for lead wire resistance, which can affect the accuracy of the measurement in a 2-wire diagram.
What is the accuracy of a Pt100 sensor?
The accuracy of a Pt100 sensor depends on various factors, such as the quality of the sensor, the stability of the constant current source, the quality of the measuring device, and the temperature range being measured. A typical Pt100 sensor can have an accuracy of ±0.1°C, but high-precision sensors can have an accuracy of up to ±0.025°C.
Can I use a Pt100 sensor for high-temperature measurements?
Yes, Pt100 sensors can measure high temperatures up to approximately 660°C. However, for higher temperatures, other types of sensors, such as thermocouples or infrared sensors, are more suitable.
Can I use a Pt100 sensor for cryogenic temperature measurements?
Yes, Pt100 sensors can measure cryogenic temperatures down to approximately -200°C. However, for lower temperatures, other types of sensors, such as thermistors or superconductive sensors, are more suitable.
What is the advantage of using a Pt100 sensor over other types of temperature sensors?
The main advantage of using a Pt100 sensor over other types of temperature sensors is its high accuracy and stability over a wide temperature range. Pt100 sensors are also highly resistant to corrosion and chemical reactions, making them suitable for harsh environments. Additionally, Pt100 sensors do not require additional signal conditioning or amplification, which simplifies the measurement setup.
Conclusion
The 4 wire Pt100 wiring diagram is a reliable and accurate way to wire a Pt100 temperature sensor. By following the steps outlined in this journal article, you can ensure that your Pt100 sensor is wired correctly and that you are obtaining accurate temperature measurements. If you have any further questions or need assistance with your Pt100 sensor, don’t hesitate to contact a professional.
