The thermocouple wire or cable is used to manufacture thermocouple probes in order to sense temperature using the point of cold junction compensation (cjc end). On the other side, as it has been explain in this other article, a thermocouple is a sensor for measuring temperature, that consists of two dissimilar metals that are joined together at the sensing end.
Different thermocouple types (e.g. J or K type thermocouple wire) use different mixtures of metals in the cable. At the cjc end, the millivolt value provided by the thermocouple represents the difference in temperature of the sensing end as compared to the cjc end (also called the reference end)...
A thermocouple is a sensor for measuring temperature. This sensor consists of two dissimilar metal wires, joined at one end, and connected to a thermocouple thermometer or other thermocouple-capable device at the other end. When properly configured, thermocouples can provide temperature measurements over wide range of temperatures.
Thermocouples are known for their versatility as temperature sensors therefore commonly used on a wide range of applications...
It is not practical to compare RTDs (Pt100 and others) and thermocouples generally. However, if we compare their performance in terms of specific criteria, we can see which is best suited for specific applications. Thermocouples are best for working at high temperatures. New manufacturing techniques have improved the measurement range of RTD probes, but more than 90% of RTDs are designed for temperatures below 400°C.
In contrast, some thermocouples can be used at up to 2500°C. Thermocouples are generally cheaper than RTDs...
Temperature can be measured via a diverse array of sensors. All of them infer temperature by sensing some change in a physical characteristic. Six types with which the engineer is likely to come into contact are: thermocouples, resistive temperature devices (RTDs Pt100 and thermistors), infrared radiators, bimetallic devices, liquid expansion devices, and change-of-state devices.
Choose the right temperature measurement instrument for your application...
Temperature measurement is possible through several means. We commonly use thermometers for measuring temperature. However, for precision measurements, where even a small spike in temperature requires to be recorded, we use advanced forms of measurement devices like thermocouples. Thermocouples are measurement devices that can read very slight temperature changes. Hence, they are widely used in applications where accuracy is of utmost importance.
However, like any measurement device, the efficiency of thermocouples will deteriorate overtime under constant use. At this point, the thermocouple needs recalibration...
Thermocouples are the most widely used temperature sensors on the planet due to their combination of wide temperature capabilities, ruggedness, and low cost. Thermocouples are used in applications that range from home appliances to industrial processes, to electric power generation, to furnace monitoring and control, to food and beverage processing, to automotive sensors, to aircraft engines, to rockets, satellites and spacecraft.
When it comes to high temperatures, small size, fast response, high vibration or shock, most times you will find thermocouples providing the temperature measurements.
RTDs or Resistance Temperature Detectors, are temperature sensors that contain a resistor that changes resistance value as its temperature changes. The most popular RTD is the Pt100. They have been used for many years to measure temperature in laboratory and industrial processes, and have developed a reputation for accuracy, repeatability, and stability.
Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it...
The same year (1821) that Thomas Seebeck made his discovery about thermoelectricity (Seebeck effect, see thermocouples), Sir Humphrey Davy announced that the resistivity of metals showed a marked temperature dependence. Fifty years later, Sir William Siemens proffered the use of platinum as the element in a resistance thermometer. His choice proved most propitious, as platinum is used to this day as the primary element in all high-accuracy resistance thermometers, Pt100, Pt1000 etc.
In fact, the Platinum Resistance Temperature Detector, or RTD Pt100, is used today as an interpolation standard from the oxygen point (-182.96°C) to the antimony point (630.74°C)...
An infrared thermometer is a sensor that consists of a lens to focus the infrared (IR) energy on to a detector, which converts the energy to an electrical signal that can be displayed in units of temperature after being compensated for ambient temperature variation. This configuration facilitates temperature measurement from a distance without contact with the object to be measured (non-contact temperature measurement).
As such, the infrared thermometer is useful for measuring temperature under circumstances where thermocouples or other probe type sensors cannot be used or do not produce accurate data for a variety of reasons...