Applications by Market:  

       NTC Thermistor temperature sensors are widely used in the following general markets.  Within each market there are many different sensing applications and each one has its own unique design considerations.  We stand ready to help you come up with a solution that meets or exceeds all critical requirements of your application.

 

· High Reliability - sensors for precision temperature measurement of liquids, gases or solid/semi-solid surfaces.

· Medical Instrumentation - sensors for continuous or intermittent patient temperature monitoring; temperature control and compensation for analytical test instrumentation.

· Industrial / OEM - sensors for control and/or monitoring of furnaces, ovens and baths; sensors for production line instrumentation systems.

· Laboratory / Calibration - titration, calorimetry, chromatography and chemical analysis sensors; temperature standards.

· HVAC - thermostats for energy management and building automation; compressor, generator and motor protection.

· Automotive / Transportation - engine management and emission control sensors; fire protection and safety sensors.

· Marine / Atmospheric - remote meteorological and oceanographic sensors; submersible and towed array sensors.

· Processing Industry - petro-chemical processing, plastic molding, food and beverage processing, handling and storage.

· Appliance / Consumer - circuit protection, current limiting, power management, small appliances and office equipment.

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NTC THERMISTORS ---  APPLICATIONS  and  SUPPORT

Applications by Characteristic:  

       There are three fundamental characteristics of NTC Thermistors that are derived from the thermal and electrical properties of the device.   The NTC thermistors are first connected in an electrical circuit and then the various applications are grouped according to the characteristic employed.

 

· Resistance-Temperature Characterisitic - In applications based upon this characteristic the NTC thermistor is operated at very low power levels (ideally as close to a “zero-power” condition as possible).  The zero-power resistance of the thermistor is calibrated (or else R-T tables are previously published) such that data can be used to determine the temperature of the sensor in its ambient environment.  The majority of temperature control, temperature compensation and resistance thermometry applications using NTC thermistors are based on the R-T characteristic.  A few examples of resistance thermometry applications (and also the control of the measured temperature) would be the temperature measurement of liquids (beverage brewing, calorimetry, oceanography, laboratory standards); the temperature measurement of surfaces of solids or semi-solids (soils, engine blocks, plastic molding, copy machines, printers); and, the temperature measurement of gases (oven control, meteorolgy, refrigeration, emission controls).   Some examples of temperature compensation applications include thermistors for motor windings, instrument windings, transistor circuits and gain stabilization.  NTC thermistors are sometimes used in conjunction with an external heater element (a resistor, filament or even another thermistor) such that they are indirectly heated by power applied to the element.  However, these are just special application cases utilizing the basic R-T characteristic. 

· Voltage-Current Characterisitic - In applications based upon this characteristic the NTC thermistor is deliberately  operated in a circuit to achieve a “self-heated”, “steady-state” condition.  Care must be taken to design the circuit such that maximum power levels of the thermistor are not exceeded.  Once the thermistor reaches equilibrium, the rate at which heat is lost to the ambient environment (through conduction, convection and radiation) is equal to the energy supplied and an operating point is established on the voltage-current (E-I) characterisitic curve or a family of such curves.  The operating point is changed by varying either the environmental conditions or the electrical circuit parameters and the effects can be calibrated to provide useful data for control or compensation.  Such “self-heated” applications are grouped according to the way the operating point on the E-I curve is changed.  One major group of applications involve changing the dissipation constant of the sensor by changing the thermal conductivity of the medium, the relative velocity of the medium or the heat transfer from the thermistor.  Examples of  these applications would include sensors for anemometers, liquid level detectors, flow meters and gas analyzers.  A second major group of applications involve changing the elctrical circuit parameters (Thevenin source voltage or source resistance).  Examples of these applications would include voltage regulation, amplitude control and switching devices.  Changing the ambient temperature of the medium creates a third group of applications that involve over-temperature alarm indication and temperature control.  Lastly, there is a group of applications based upon changing the absorbed radiation where the thermistor is utilized to measure RF or Microwave power.

· Current-Time Characterisitic - In applications based upon this characteristic the NTC thermistor is intended to be operated in an electrical circuit that produces a “self-heated” condition.  Here too, care must be taken to design the circuit such that maximum power levels are not exceeded.  When power is first applied to the circuit, the energy is dissipated as heat and the thermistor begins warm and its resistance will decrease as a function of time.  The rate at which the energy is absorbed to produce a given rise in body temperature depends upon the specific heat (a function of the materials used to create the thermistor) and the mass of the device.  The time from initial turn-on until an equilibrium condition is achieved is the “transient” condition.  Applications based upon the current-time characteristic are meant to operate during this transient period.  Examples of these applications include in-rush current limiting, time delay, surge suppression and sequential switching. 

Applications Support:  

Do you have a custom temperature sensing application --- or a problem that you can’t quite solve?

If so, then please feel free to contact us with your specific requirements and let our application engineering staff put their experience to work for you.  We will be happy to work with you in any of the following areas in order to arrive at the best solution for your specific application or problem.   

 

· Engineering - We can provide you with applications engineering support to reverse engineer a current design; to assess the reliability and maintainability of your design; and, to insure that your temperature sensor meets or exceeds all your design requirements.

· R&D - We can work with you to create prototypes and first-article samples as needed.  We can also help you to create the documents necessary for procurement.  

· Production - We can help you develop the processing steps and assembly instructions that insures the successful incorporation of the sensor into your product line.  We can also use our troubleshooting and problem solving expertise if you find that are not getting the performance you desire out of your next level assembly.  

· Supply Chain - We can help you with overall component selection for your next level assembly.  We have a number of trusted partners and vendors who can supply you with such items as hardware, materials, encapsulants, wires/cables and terminations.  We can also help you with cost analysis, supplier evaluation and vendor audits as needed.

· Quality - Our engineering staff has considerable experience with quality control plans, inspection procedures, acceptance test plans as well as validation and verification procedures.  Contact us with your specific application requirements and we will be happy to share our knowledge to help you comply with all national and international standards for quality conformance and product performance.  Our knowledge and experience encompasses the following key documents:

Document #                             Title of document

ISO 9001:2008                       Quality Management System - Requirements

AS-9100                                    Quality Management System - Aerospace Requirements

ISO/TS 16949:2002              Automotive Quality Standard - Technical Specifications

ISO/EN 13485:2003              Medical Devices - Quality Management System - Requirements for Regulatory Purposes

ISO/TR 14969:2004              Medical Devices - Quality Management System - Guidance

MIL-PRF-23648                      Performance Specification - Resistors, Thermal (Thermistors)

ESA/SCC 4006                       Generic Specification for Thermistors (Resistors, Thermally Sensitive)

MIL-T-24388                           Thermocouple and Resistance Temperature Detector Assemblies

DIN IEC 751                            Industrial Platinum Resistance Thermometer Sensors