RESISTENCE OF ANY METAL CHANGES
WITH ITS TEMPERATURE CHANGE.
POSITIVE TEMPERATURE COEFFICIENT DEVICES
i.e. THEIR EFFECTIVE RESISTENCE
INCREASES WITH THE INCREASE IN
Pt 100 RESISTANCE VALUE
AT 0 DEGREE CELCIUS
IS 100 OHMS
200 degree Celsius
850 degree Celsius
Detectors / RTD / RTDs
Resistance Temperature Detectors (RTD) are
sensors used to measure temperature by correlating
the resistance of the RTD element with temperature.
Most RTD elements consist of a length of fine coiled
wire wrapped around a ceramic or glass core. The
element is usually quite fragile, so it is often placed
inside a sheathed probe to protect it. The RTD
element is made from a pure material whose
resistance at various temperatures has been
documented. The material has a predictable change
in resistance as the temperature changes; it is this
predictable change that is used to determine
The RTD is one of the most accurate
temperature sensors. Not only does it provide
good accuracy, it also provides excellent
stability and repeatability.
RTDs are also relatively immune to electrical
noise and therefore well suited for temperature
measurement in industrial environments,
especially around motors, generators and other
high voltage equipment.
Common Resistance Materials
for RTDs :
Platinum (most popular and accurate)
The RTD element is the simplest form of RTD. It
consists of a piece of wire wrapped around a
ceramic or glass core. Because of their compact
size, RTD elements are commonly used when
space is very limited.
A surface element is a special type
of RTD element. It is designed to be as
thin as possible thus providing good
contact for temperature measurement
of flat surfaces.
The RTD probe is the most rugged
form of RTD. A probe consists of an
RTD element mounted inside a
metal tube, also known as a sheath.
The sheath protects the element
from the environment.