RTD full form & What is RTD? – Full form of rtd sensor

In today’s article, we will tell you what is RTD? What is the full form of RTD? Where is it used, how RTD works, from which material (metal) it is made. Why is platinum used in RTD? And how many types are there.

Friends, if you study electrician in ITI, then you must have heard about the word RTD at least once. As well as, even if you work in a big company or industry, you must have heard about RTD. If you have come to this article, then you must need to know about RTD. You will know the full form of RTD and what is its meaning?

Let us tell you that RTD is the most advanced type of thermocouple, that is, it is more advanced than thermocouple. Right now, as the industry and factory are becoming modern, RTD devices are used instead of thermocouples.

For your information, let us tell you that the design of the thermocouple is such that it measures the temperature in milli volts, the yellow wire in the chamber of this device represents positive and the red wire negative. Thermocouple works on the principle of Seebeck effect. Let us tell you that Seebeck is one of the three effects under the thermoelectric effect.

What is RTD?

RTD is a type of device which is also called Resistance Thermometer. It is a temperature sensor and this device is often used to measure temperature in industries and factories. With increase in temperature, the resistance of TRD also increases and the output of temperature is also obtained in resistance and it works on Positive temperature Coefficient (PTC). Talking about the structure of RTD, there are elements of RTD at its lower end.

There is a lead support in the middle to support these elements. These elements can be made of platinum, nickel, copper and tungsten metals. There is a special type of sheath on its edge which protects the RTD from high temperature. After this, there is a mounting thread on one side of its head, which is used to hang it somewhere. 2, 3 or 4 connecting leads come out from the head of RTD. The accuracy of temperature is determined by the number of connecting leads, meaning the more leads, the more accurate the temperature.

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Full Form Of RTD – What is the full form of RTD?

In RTD full form, R stands for Resistance, T stands for Temperature and D stands for Detector. In this way the full form of RTD in English is Resistance Temperature Detector.

Its full form means ‘resistance temperature sensor’.

R Resistance resistance
T Temperature temperature
D Detector detector

RTD = Resistance Temperature Detector

Types Of RTD

There are many types of RTD which are being told to you today. We divide the Resistance Temperature Detector into two categories, first on the basis of connection and second on the basis of wire.

In the first category of connection, we also get to see two subcategories, the first is RTD simplex and the second is duplex.

Now there are three types of RTD in the second category i.e. wire, first two wire, second 3 wire and 3rd 4 wire RTD. Know all these one by one below.

Simplex RTD

In which the output circuit of temperature is sent to one place, it is known as Simplex RTD. It has a maximum of 3 strings.

Duplex RTD

Duplex RTDs are mainly used in the Pharmaceuticals, Textiles, Chemical and Food industries.

Duplex RTD is used where the signal has to be sent to 2 places, for example distributed control system (DCS) or Programmable Logic Controller (PLC) and the other is sent to the location indicator where the temperature is observed. .

What is Two Wire RTD?

As its name suggests, it has two wires. This RTD is used for short distance like 3 to 4 meters. If the distance is more than this, the accuracy of the temperature decreases.

3 (Three) Wire RTD

Let us tell you that as the length of the wires increases in the RTD, the resistance of the wires itself also gets added to the output, due to which the measurement of temperature becomes more.

Three wire RTD has three wires and the third wire reduces or eliminates the resistance (resistance) arising from the longer length of the wire, so that the temperature output is accurate.

Which metal is used in RTD?

Four metals are used in Resistance Temperature Detector which are Platinum, Nickel, Copper, Tungsten. RTD made of Platinum wire comes in the name of PT100, PT500, PT1000.


PT100 uses platinum wire because it gives stable and accurate results. Platinum provides excellent repeatability and is capable of providing a sufficiently large resistance range per degree of change.

Its linearization equation is:

Rt = R0 * (1 + A* t + Bt2 + C(t-100)* t3)

where Rt is the resistance at temperature t and R0 is the resistance at 0°C and

A = 3.9083 E–3
B = –5.775 E–7
C = –4.183 E–12 (below 0 °C), or
C = 0 (above 0 °C)

The PT100 gives a resistance output of 100Ω at 0°C and a change of 0.384 Ω (ohm) in its resistance is observed for a temperature change of 1°C.

The formula to solve PT100 numerically is:

Rt = Ro(1+αot)

where Rt is the resistance of the RTD at temperature t Ω

  • Ro = resistance of rtd at 0°C (ohm) and
  • αo = temperature coefficient of resistance at 0°C (per °C)


Here PT means platinum and 500 means that this RTD gives a resistance output of 500 Ω (ohms) at 0°C. The PT500 is rarely used.


The PT1000 is used over the PT100 sensor in two wire applications. This is because the PT 1000 is a sensor which makes the resistance of the lead less significant.

What is the temperature range of RTD?

The temperature range of RTD depends on its metal. RTD made of four different metals have the following temperature range.

Platinum Wire RTD (PT100) −260 °C to 110 °C
Copper Wire 0°C to 180°C
Nickel Can sense −220 °C to 300+ °C
Tungsten Senses from −200 °C to 1000 °C

Working Principal Of RTD

  1. Every metal has an atom and it has its own energy, due to which there is a slight vibration in them. When a battery is connected to a conductor, current flows in it.
  2. This flow of current is due to the electron and the electron collides with the atom present in the metal.
  3. Due to this collision the speed of electron decreases and it is a material property. Due to this property, the metal opposes the flow of current and this is the resistance of the material.
  4. When the conductor is heated, the atoms present in the metal start vibrating more and the electron flow that is happening starts colliding more.
  5. Due to this collision, its speed decreases further, as a result of which the output of current also decreases.
  6. The metal used in RTD has resistance to temperature and as the temperature increases the resistance of metal used in RTD’s element like Platinum, copper Nickel and tungsten also increases.


Generally RTD comes in three types of configuration which are Thin Film, Wire Wound RTD and coil element.

Thin Film


In this, there is a thin layer of platinum on the flat ceramic plate and glass is coated on top of it, this is called Thin Film type Rtd.

Wire Wound


In Wire Wound RTD, platinum or any other metal is wrapped around a glass or ceramic bobbin (oscillating) like a round spring and a layer of molten glass is given on top of it.

coil elements

The resistance wire is rolled into a small coil which is loosely fitted in the ceramic form, after which non-conductive (non-conductive) powder is filled and it is called coil element rtd.

What is the accuracy of RTD?

RTD is more accurate than thermocouple. It works more accurately in low temperature range and its accuracy is 0.1 to 1°C.

What is the response time of RTD?

The response time of RTD is fast, it responds in 0.5 seconds to 5 seconds.


By reading this article, you came to know what is RTD, what is the full form of RTD. With this, you know about the metal used in RTD and what is the temperature range of Resistance temperature detector. You must have also known the working principal of RTD and how many types of RTDs are there. Hope you have understood this article about RTD. If you have any question then you can ask by commenting.

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