TEMPERATURE
SENSING PRODUCTS
SELECTION GUIDE
Littelfuse.com
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Your Design
Challenges, Solved
Littelfuse offers a broad portfolio of thermistors, resistance
temperature detectors (RTDs), digital temperature indicators,
and probes and assemblies to meet a wide range of
demanding temperature sensing applications. We also
specialize in designing custom NTC thermistor and RTD
sensors to meet unique system requirements.
Standard and customized
probe assemblies offer very
precise and extremely reliable
thermal monitoring in the most
demanding applications.
Littelfuse surface mount
thermistors are available in
a variety of sizes and
configurations suitable for
mounting using solder, wire,
bond or epoxy.
Highly accurate over a wide
temperature range, our RTDs
are especially suitable for
use in extreme environmental
conditions.
Designed to meet a broad
range of applications, our
leaded thermistors include
standard precision, as well as
glass encapsulated and epoxy
coated options.
Temperature Sensing
Products Selection Guide
Recognized for their
accuracy and long-term
reliability, Littelfuse
thermistors and RTDs
are the sensor of choice
for diverse markets.
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Thermistor Probes and Assemblies
NTC and PTC Thermistors RTD Elements and Probe Assemblies
Chip and MELF Style Thermistors
Littelfuse.com
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Introduction to
Temperature Sensing
Thermistors (NTCs and PTCs)
Thermistors are thermally sensitive resistors whose prime
function is to exhibit a large, predictable, and precise change
in electrical resistance when subjected to a corresponding
change in body temperature. Negative Temperature Coefficient
(NTC) thermistors exhibit a decrease in electrical resistance
when subjected to an increase in body temperature. Positive
Temperature Coefficient (PTC) thermistors exhibit an increase
in electrical resistance when subjected to an increase in body
temperature.
Applications
Based on the predictable characteristics and their excellent
long-term stability, Thermistors are generally accepted to be
the most advantageous sensor for many applications including
temperature measurement and control.
A Temperature Sensor is a device that detects and measures the average heat or thermal energy in a medium and converts it into
an electrical signal. A wide variety of temperature sensing devices are available today. Littelfuse offers a broad range of Thermistors,
Resistance Temperature Detectors (RTDs), Digital Temperature Indicators, and probes and assemblies for temperature sensing
applications worldwide. Each has its own set of operating principles, features, benefits, considerations, and limitations for optimal use.
RTDs
Platinum Resistance Temperature Detectors (Pt-RTDs) are
temperature sensors that have a positive, predictable, and
nearly linear change in resistance when subjected to a
corresponding change in their body temperature.
Applications
The nearly linear output needed to precisely measure
temperature over a very wide range makes RTDs ideal for
digital measurement and control applications. Typical
applications include industrial controls, medical electronics,
HVAC-R, aerospace systems, white goods, small appliances,
and food handling.
Digital Temperature Indicators
Digital Temperature Indicators have a positive relationship
between resistance and temperature. The response is
very much like a digital signal; below the trip temperature,
resistance will be low, above the trip temperature, resistance
will be very high. This digital response is ideal for applications
where knowing the temperature has increased beyond a
specific value is required. With the digital response, no analog
to digital conversion is necessary, allowing designers to save
time and space.
Applications
Typical applications include USB Type-C cables, power
supplies, servers, and other similar systems where monitoring
for a specific temperature is required.
NTC Thermistors RTDs (Pt Thin Film)
Both are electrical resistors in which resistance changes with temperature
Both require excitation current
Metal oxide on ceramic substrate
Precious metal (typically Pt)
on ceramic substrate
Very good accuracy suitable for most
applications – most commonly used
cost-effective temperature sensor
For more-specialized applications requiring
very high accuracy (ex. 0.06%/0.15°C)
For applications requiring a lot of
precision
Exponential resistance-temperature curve
Nearly linear resistance-temperature
curve provides ease and consistency
of measurement
Wide operating temperature ranges
from -50°C to 300°C
Extremely wide temperature ranges,
specifically on the higher end, from -50°C
to well above 500°C
Resistance values such as 100Ω,
up to 5MΩ at 25°C
Resistance values such as 100Ω, 500Ω
and 1000Ω at 0°C
Comparing NTC Thermistors vs. RTDs. Although both
technologies sense temperature, they each exhibit different
characteristics as shown in the comparison table above.
Shown below is a comparison of the resistance-temperature
behavior.
Customizable Options
Modifications are available to existing standard product
packages, such as adding connectors or changing wire size
or length, as well as offering special resistance-temperature
(R-T) curves, R-T curve matching, and custom lead forming
and bending to discrete thermistors. In addition, the following
options and services are available.
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Complete custom sensor packages, including moisture-
resistant designs
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Custom resistance-temperature (R-T) characteristics
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Specialized resistance tolerance or temperature accuracy
within specified temperature ranges
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Sensing element design for best long-term stability
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Rapid prototyping and quick-turn concept parts including 3D
printed parts
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Prototype units using prototype tooling
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Reliability/validation testing options
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Fully designed, production-capable sensor and tooling
Quality and Reliability Testing
In addition to providing custom-designed products, we provide
options to evaluate performance and long-term stability for the
most demanding applications. Some of our testing capabilities
include:
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Salt water immersion
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Freeze/thaw temperature cycling
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Thermal shock
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Sinusoidal vibration
Design Your Custom Temperature Sensor
Littelfuse specializes in custom design packages that meet
our customers’ needs for both Thermistor and Resistance
Temperature Detector (RTD) sensor designs.If a standard
sensor style doesn’t meet your needs, contact us for further
assistance at littelfuse.com/sensorform. Our application
engineers are ready to help design the sensor you need.
Resistance (Ω)
Thermistor
(2252 Ω at 25˚C)
10 M
1 M
1100 k
10 k
1 k
100
10
-200
-150
-100
-50
0
50
100
150
200
250
300
350
400
RTD
(PT 100 Ω)
Temperature (˚C)