Temperature Measurement


A thermocouple is an electrical device used as a sensor for temperature measurement. This device senses low to high temperatures in the form of voltage changes and displays the temperature digitally by calculating the voltage changes. It was discovered in 1821 by Thomas Seeback and thus have been serving the function since then. The self-powered thermocouple can measure temperature between -300 and 4000F. However, this range varies according to different types of thermocouple. The advanced digital thermocouple comes up in different styles. This styling varies from simple wires to thermocouple with probes and beaded wire thermocouple. Thermocouple differs from other temperature sensing devices in their constituency and applications. They are used mostly for high-temperature measurements in industries whereas other sensors like a thermometer are rarely used commercially.

Thermocouple Principle

This temperature device works on basis of Seeback phenomena named for the German physicist who discovered it. According to this phenomenon, when two metals that are different from each other are connected at one end, a voltage is created in the metallic wires. This voltage is largely affected by external temperature. Therefore the sensor senses the temperature in the form of voltage change and then calculates the temperature in the Celsius scale. This is the general basis of a thermocouple.

Thermocouple Types

On the basis of their constituency, a thermocouple is divided into two principal types.

1- Base metal thermocouple

They are the most commonly used thermocouple. The metallic wires of these thermocouples are formed of base metals and the connector used consists of Nickel alloy. As there are a number of known base metals, a thermocouple is further subdivided according to the type of base metal wire. Type J,K type thermocouple, T, E, and N are subclasses of the base metal thermocouple. These subtype also differ from one another in the temperature range that they can measure. Type K thermocouple consists of nickel and chromium metals and it can measure temperature up to 2300F. Similarly, Type J is a combination of iron- constantan that can measure up to 1400F of temperature. Similarly, all other subtypes differ in the mentioned fields.

2- Nobel metal thermocouple

They are used less commonly because of the high cost of noble metals. However, these thermocouples provide greater accuracy for increased lifespan. Their constituent metals belong to the group of noble elements. They are also divided further into subtypes on the basis of the type of noble metal. The subclasses include type B, type R, and type S. They are Platinum and Rhodium mixtures that differ on the base of the percentage of these metals. Type R and S thermocouples can measure temperature up to 2700F whereas type B can measure till 3100F.

Thermocouple Applications

Thermocouple has a wide range of commercial and industrial applications due to its high accuracy and wide operating range of temperatures. They are used commonly in the following fields.

  • 1- They are used as a thermostat for home and office use.
  • 2- Used in gas industries for measuring gas temperature.
  • 3- Used in some industries as heat pumps.
  • 4- Food industries use it for low-temperature applications.
  • 5- Cement industry, chemical plants, and other oil and petrochemical industries use thermocouples for keeping the temperature in check.

Resistance temperature detector(RTD)

RTD is a sensing device that measures the temperature on the basis of resistance of the electrical wires. Three different metals including copper, nickel, and platinum are used for the manufacture of RTDs. The construction of this device consists of a wire wound around a frame such that it allows thermal conductivity. A stainless steel sheath is applied externally to provide insulation.

RTD Working principle

An RTD works on the principle that the resistance of a material change according to its temperature. In short resistance and temperature of some metals is related to each other either directly or indirectly. When a constant amount of current a voltage change takes place that can be measured as a voltage drop across the resistor. Similarly, RTD's resistance can be measured which can give the value to temperature.


Based on the shape the RTD's are categorized into the following three basic types.

1- Thin filmed RTD

This consists of a thin film of platinum-coated or plated on a ceramic plate. They are used for temperature measurement up to 300C.

2- Wire-wound RTD

This assembly consists of a wire winded around an insulating core. They possess higher accuracy and can measure the temperature of up to 660C.

3- Coiled RTD

This setting contains a wire that has multiple coiling along with some mechanical support. They are high power devices for a temperature of 850C.

Resistance temperature detector(RTD) Application

RTDs possess a very high accuracy in temperature measurements therefore they are used commonly for engine, oil, and air temperature sensing. They are used in fields of medical, pharmaceutics, food processing, military, electronics, and aeronautics.

We are a China Temperature sensor manufacturer; provide fast delivery, reasonable price and robust RTD (Resistance temperature detectors), thermocouples, bimetal thermometer &temperature transmitters.

Custom thermocouple, RTD temperature sensor, bimetal thermometer according to different customers’ applications with still so fast delivery time and low price is our advantages.

We can manufacture industrial temperature sensor according to your approved drawings or we can design the thermocouples or RTD sensors for your specific application.

PT100 is a kind of normally used RTD temperature sensor; it has good accuracy and can be used repeatedly. Thermocouple is durable and has broad temperature range; it can be used as high temperature sensor. We cannot say which is more superior choice, and we just choose and fabricate the temperature sensors based on the specific demands from our valued customers.

We also provide cheap bimetal thermometer, we source robust bimetal thermometer from China reliable factory, and thermometers can be used in vessels and pipelines. Bimetal thermometers can read the temperature directly; available dial size is 60mm, 100mm, 150mm. we can also make thermowell combing together with bimetallic stem thermometer to have more applications.

Temperature Transmitters is converting temperature sensor (RTD and thermocouple) signals to analog signals. We provide head mount temperature transmitters which can also have Hart Protocol or digital display temperature transmitter upon request.

Product Category

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  • K type thermocouple
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  • S type thermocouple
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  • Spring-loaded thermocouple
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