Mathematical Equations
It is known that RTD shows linear behaviour over a large range of temperature . The linear relation between resistance and temperature can be shown by
RT=R0[1+α(t-t0) +β(t-t0)2+…………….]
RT : resistance values at t0C temperature
R0: resistance values at t00C temperature.
α and β are the constants depends on the metals.
For small range of temperature, we can simplify the above expression as
RT=R0[1+α(t-t0)]
From this nature it is evident that resistance of resistance thermometers at a temperature t varies linearly from original temperature at t0 C.
Expressions for a Three Wires RTD Circuit
RTD can be combined with a circuit which helps to calculate voltage drop across RTD. In 3 wire configuration, two wires connect the sensor element to a device like voltmeter on one side of the sensory element, and one connects it to the other side. Note that the all the wires should be made up of same material.
Three wires RTD
Three lead wires L1, L2, and L3. Here note that there will be individual resistances of the wires and different voltages across corresponding resistances.
R1 R2 R3 : Resistances of the three wires
V1 V2 V3 : Voltages measured across the corresponding resistances
E: Excitation voltage
The voltage is then measured across R1 and R2. The voltage drop in the lead wires is compensated by the use of the third wire. Therefore ,we can write the voltage as
VRTD = Vmeter(A) − Vmeter(B)
Resistance Temperature Detector or RTD
In the electronics industry, we often need to deal with measuring certain quantities with precision and accuracy. One such quantity is temperature. There are different methods that can be used for measuring temperature depending on the operation range, sensitivity, frequency response, ruggedness, and other electrical parameters. In this article we will study what is an RTD, and how it works. We will also study the characteristics of an RTD.
In addition to that, we will study the advantages and disadvantages of an RTD. To study the real-life use of RTDs, we will study the applications of an RTD. In the end, some solved examples and some practice questions are provided for a better understanding of concepts. The article concludes with a summary in the end and some frequently asked questions.
Table of Content
- RTD
- Construction
- Working
- Signal Conditioning
- Mathematical Equations
- Graph
- Characteristics
- Advantages of an RTD
- Disadvantages of an RTD
- Applications of an RTD