Platinum temperature sensors - Functional basics
The function of platinum temperature sensor elements and platinum temperature sensors is based on the temperature dependence of the electrical resistance of platinum. Platinum temperature sensor elements and Platin temperature sensors are usually partly characterized by the name, e.g.:
- Pt100... nominal resistance R0 = 100Ω at temperature t = 0°C
- Pt200... nominal resistance R0 = 200Ω at temperature t = 0°C
- Pt500... nominal resistance R0 = 500Ω at temperature t = 0°C
- Pt1000... nominal resistance R0 = 1000Ω at temperature t = 0°C
- Pt2000... nominal resistance R0 = 2000Ω at temperature t = 0°C
- Pt10000... nominal resistance R0 = 10000Ω at temperature t = 0°C
- ...
Valid standard: DIN EN 60751:2009
- Industrial platinum resistance thermometers and platinum temperature sensors (IEC 60751:2008); German version EN 60751:2008
- Valid from: 01/05/2009
This standard is valid for platinum sensors with a temperature coefficient (TC) α:
α = 3,851·10-3 °C-1.
Temperature coefficient (TC) α:
α = (R100 - R0) / (R0 · 100°C)
(R100… resistance [Ω] at temperature t = 100°C, R0… resistance [Ω] at temperature t = 0°C)
General characteristics - Temperature / resistance relationships (DIN EN 60751:2009)
Temperature range from -200°C up to 0°C:
Rt = R0 · (1 + A · t + B · t2 + C · (t - 100°C) · t3)
Temperature range from 0°C up to +850°C:
Rt = R0 · (1 + A · t + B · t2)
(Rt… resistance [Ω] at temperature t [°C], R0… resistance [Ω] at temperature t = 0°C, t… temperature [°C], constants / coefficients: A = 3,9083·10-3 °C-1, B = -5,775·10-7 °C-2, C = -4,183·10-12 °C-4)
Classes of accuracy - Platinum thin-film temperature sensor elements
... according DIN EN 60751:2009 - Film sensors (temperature-related validity):
F 0,1 (0°C - +150°C)… Δt = ± (0,1 + 0,0017 · | t |)
F 0,15 (-30°C - +300°C)… Δt = ± (0,15 + 0,002 · | t |)
F 0,3 (-50°C - +500°C)… Δt = ± (0,3 + 0,005 · | t |)
F 0,6 (-50°C - +600°C)… Δt = ± (0,6 + 0,01 · | t |)
(Δt… permissible temperature deviation at temperature t [°C], t… temperature [°C])
Classes of accuracy - Semi-finished temperature sensors (Temperature probes) - based on Platinum-thinfilm temperature sensor elements (Film sensors):
... according DIN EN 60751:2009 (temperature-related validity):
AA (0°C - +150°C)… Δt = ± (0,1 + 0,0017 · | t |)
A (-30°C - +300°C)… Δt = ± (0,15 + 0,002 · | t |)
B (-50°C - +500°C)… Δt = ± (0,3 + 0,005 · | t |)
C (-50°C - +600°C)… Δt = ± (0,6 + 0,01 · | t |)
(Δt… permissible temperature deviation at temperature t [°C], t… temperature [°C])
Thermal response time
Time required for a temperature sensor to reach a defined percentage of the temperature full scale:
- T0,5… time to reach 50% of temperature full scale
- T0,9… time to reach 90% of temperature full scale
(DIN EN 60751:2009).
The response time is depending on the design, the dimensions and the thermal contact resistance of the temperature sensor, the measuring medium and its flow rate as well as the heat capacity of the materials.
Self heating
As is normal with any resistance charged with current, temperature sensor elements heat up slightly in use.
This is described as heating up error and is dependent on:
- the applied electric power (P = I2 · R)
- the dissipated amount of heat
- the constant E (self heating coefficient).
Calculation of self heating:
Δt = P / E
(Δt... self heating [K], P... applied electric power [mW], E... self heating coefficient [mW/K])
Source:
DIN EN 60751:2009-05: Industrielle Platin-Widerstandsthermometer und Platin-Temperatursensoren (IEC 60751:2008); Deutsche Fassung EN 60751:2008, Beuth Verlag GmbH, 2009
To top