What is the coefficient factor of RTD?
- Resistance Temperature Detectors (RTDs), also known as platinum resistance thermometers (PRTs), are widely used temperature sensors that rely on the principle that the resistance of a metal, in this case, platinum, increases with temperature.
- RTDs functions according to the theory that the resistance of a metal will increase as temperatures increase.
- The Temperature Coefficient of Resistance (TCR), denoted by αo, is a crucial parameter for RTDs.
- It represents the average resistance change per degree Celsius over a specified temperature range, usually 0°C to 100°C, divided by the resistance of the RTD, Ro, at 0°C.
How is RTD coefficient calculated?
Here’s a step-by-step explanation of how to calculate the TCR for a PT100 RTD, along with an example calculation:
αo = (R100−R0) / (R0 X 100oC) – Equation no. 1
R0 is the resistance of the RTD at zero degrees Celsius (ohm).
R100 is the resistance (ohm) of the RTD at 100 °C.
Note: For the purpose of this conversation, we will only be referring to RTD PT100.
The relationship between resistance (Rt) and temperature (t) for a PT100 RTD is described by the following formula:
Rt= R0(1+αo.t) – Equation no. 2
Rt is the RTD‘s output resistance in Ohms at temperature t.
R0 is the resistance of the RTD at 0°C (ohms).
αo is the temperature coefficient of resistance (TCR) at 0°C (per °C).
t is the temperature in degrees Celsius.
Platinum RTD PT100 has a resistance of 100 ohms at 0 degrees Celsius and 139.1 ohms at 100 degrees Celsius.
- Find out how much resistance the RTD has at a temperature of 60 degrees Celsius.
- Perform the TCR (Temperature Coefficient of Resistance) calculation for platinum.
- Determine the temperature at which the resistance is 120 degrees Celsius.
What is temperature coefficient of Pt100?
Perform the Temperature Coefficient Calculation on the RTD PT100.
From Equation no.1:
αo = (R100−R0) / (R0 X 100oC)
αo = (139.1 -100) / (100 X 100)
αo = 0.00391 per degrees Celsius
Determine the RTD’s resistance at 60°C
From Equation no.2:
R60 = Ro(1 + αt)
R60 = 100(1 + 0.00391×60)
R60 = 123.46Ω
Determine the temperature at which the resistance is 120
From Equation no.2 :
R120 = Ro(1 + αt)
120 = 100(1 + 0.00391t)
1 + 0.00391t =120/100
0.00391t = 1.2-1
t = 0.2/0.00392
t = 51.02 degrees Celsius
Click here for more Instrumentation Calculators