Thermistor( Popularly known as 'Thermally Sensitive
Resistor' )
Principal
Characteristics: Thermistor
shows change in electric resistance
due to change in temperature. Like
RTD, the thermistor uses resistance
to detect the temerature. They
are classified into:
PTC
:
Devices
whose resistance increases
as their temperature increases.
NTC
:
Devices
whose resistance decreases
as their temperature increases.
NTC are manufactured
from ceramic semiconductor materials
based on the transition metal oxides
that respond inversely with temperature. Thermistor
typically works in the following range:
Temperature
Range
:
-40
to 150 oC / -40 to
302 oF
Resistance
:
Typical
use in range of kilo ohms; although
it can work in range of mega
ohms.
Stability
And Reliability Of Thermistors
The
issue of long term stability of components
is a critical one in most temperature
sensing applications. Circuitry
and thermistor sensor specifications
should assure accurate, long-term
measurement capability. It
is extremely important therefore that
the Resistance versus Temperature
characteristics of the thermistors
used in such critical applications
do not change or drift over time.
