Resistance temperature sensor or thermocouple? Make a wise choice
Resistance temperature sensors (RTD) and thermocouples are the two most common types of temperature sensors in industrial processes. Sometimes it is difficult to evaluate all the facts and choose the facts that better fit your application needs.
Resistance temperature sensor
A resistance temperature sensor is a thin wire wound inside the probe. The resistance of a wire varies with temperature. The relationship between resistance change and temperature is known and can be used to determine temperature. The common materials of resistance temperature sensor elements are metals, such as platinum, nickel or copper. Platinum is preferred because it is chemically inert and has a very linear resistance temperature relationship over a wide temperature range. The resistance temperature sensor is divided into three types: film, wound wire and coiled wire.
The thin film resistance temperature sensor has a very thin metal layer deposited on a ceramic substrate.
The coil of the winding element is wound on the insulating core.
The coiled resistance temperature sensor is like a bulb - the wire is held in place by some mechanical supports, but it coils itself.
Which type is more suitable for a particular application depends mainly on the required stability, temperature range and durability.
| advantage | shortcoming |
| Good precision | Limited temperature range (- 200 ° to+850 ° C) (- 328 ° F to+1562 ° F) |
| Long term stability | Slow reaction |
| Repeatable | Current source required |
| No extension cord required | Self heating error |
| Not so strong | |
| More expensive |
Thermocouple
The thermocouple temperature sensor consists of two different conductors or semiconductors in contact with each other. The difference in temperature between the two contact points produces a voltage. The relationship between temperature and voltage is known and used to determine temperature. Nickel, chromium, aluminum and copper alloys are some of the most popular materials. The choice of materials depends on such factors as cost, melting point, chemical properties and stability.
| advantage | shortcoming |
| Wide temperature range (- 200 ° C to+2300 ° C) (- 328 ° F to+4172 ° F) | Accuracy decreases with time |
| high quality and inexpensive | Not very stable |
| Quick reaction | Nonlinear |
| strong | Low voltage output |
| Prompt sensitive | Need reference |
| Self powered | Extension cord required |
| Small bore | |
| Multipoint sensing |
Resistance temperature sensor or thermocouple: which one to use
The choice between resistance temperature sensors or thermocouples depends on your application requirements. In general, thermocouples are more suitable for high temperature processes, applications requiring fast response time, and applications with limited space. The resistance temperature sensor provides better accuracy, repeatability and stability. The first step is to determine your application requirements based on:
● Temperature range
● Pressure range
● Humidity
● Shock and vibration
● Medium (solid, liquid or gas; corrosive; dangerous)
● Flow
In many cases, you will find more than one choice. Eliminate speculation with the help of the maintenance experts. They have rich knowledge and years of on-site experience. They can help you analyze your application and find the best product in the market for your specific needs. Call the maintenance expert hotline/WeChat 18717811268 Huang Gong immediately.
