Special Test Services
Configure to Order Probes
YSI 400 and 700 Series Reusable Probes
YSI 4600 Precision Thermometers
YSI Precision Thermistors & Probes
Thermistors at YSI
YSI developed the first interchangeable thermistorprobes in 1955 and the first line of precisioninterchangeable thermistors in 1961. In 1982, weintroduced the first precision interchangeable glass-encapsulated thermistors. We have improved theseproducts and expanded them into a full line ofprecision thermistors.
What Are Thermistors?
The name is derived from the devices major charac-teristic its a thermally sensitive resistor. There aretwo major types: NTC, with a negative temperaturecoefficient of resistance; and PTC, with a positivetemperature coefficient. YSI manufactures NTC ther-mistors, which exhibit a steep drop in resistance astemperature increases, providing high sensitivity totemperature changes. The resistance changes approxi-mately three orders of magnitude in a 100C range.This provides a means to measure very small tempera-ture variations very accurately.
How We Manufacture Thermistors
Manufacturing precision thermistors involves ceram-ics technology, solid state chemistry, electronics andprecision temperature measurement.
Thermistors are mixed metal oxide semiconduc-tors. We prepare them by intimately mixing fine pow-ders of transition metal oxides, pressing them intodisks under high pressure, and firing the disks at hightemperature. In the high-temperature firing process,called sintering, the metal oxides undergo a solid statechemical reaction, forming an electrically activematerial called a spinel. Spinels of transition metaloxides, such as nickel, manganese and iron, exhibitlarge changes in resistance with small changes intemperature.
After sintering, we apply electrical contacts andattach leads. To protect thermistors from environmen-tal damage, we encapsulate them in epoxy or glass.
The electrical properties are controlled by compo-sition, sintering temperature and oxygen partial pres-sure. The material constant beta (or slope) and theresistivity (ohm-cm) are established by the manufac-
turing process. To achieve interchangeability over anextended temperature range, the material constantbeta must be tightly controlled. YSI maintains vari-ability in beta of less than 0.3%.
The resistance (ohm) is a function of the resistiv-ity and the physical dimensions of the device.Although the slope and resistivity are fixed by com-position and firing temperature, the resistance can beadjusted by varying the dimensions. YSI uses thisproperty in a patented process to manufacture preci-sion interchangeable thermistors.
The Advantages of Thermistors
SensitivityA thermistor is much more sensitive totemperature change than other sensors. A typicalthermistor changes 1,290 ohms per degree at 25C. InterchangeabilityYSI thermistors are availablewith interchangeabilities to 0.05C, not just at asingle point but over a temperature range from 0 to70C. This is a result of precise process control andextreme attention to quality.
Two-Wire ConnectionNo reference junctioncompensation necessary as with thermocouples. Thethermistors inherent higher resistance allows forlonger lead length without introducing significanterrors compared to platinum RTDs, which mustoperate in a 3-wire or 4-wire mode.
RuggednessThe NASA qualification programincludes numerous tests of ruggedness, which YSIthermistors continue to pass. NASA has deemed YSIthermistors worthy of qualification for extendedspace flight.
Hermetic SealYSI glass-encapsulated thermistorsachieve a hermetic seal between the environment andthe thermistor disk. This permits measurement insevere moisture environments without concern forsilver migration.
FlexibilityYSI thermistors come in a great varietyof resistances, slope characteristics, lead configura-tions and encapsulation materials. The charts thatfollow will help you determine which thermistor willperform best in your application.
Electrical ContactElectrical Contact
Lead Lead Lead
This catalog describes YSI thermistors, probes andassemblies for laboratory, medical, industrial andprocess temperature measurement, control, indicationand compensation. You may purchase YSIthermistors unmounted or as complete temperaturesensing assemblies.
YSI manufactures thermistors and thermistorprobe assemblies for use in diverse fields of tempera-ture sensing: from neonatal infant monitoring totracking the temperature of astronauts in space; frommeasurement of temperature in the ocean to main-taining critical temperature parameters of satellites;from one-time use in a disposable medical probe todecades in buried telecommunications cables.
We can provide you with the proper thermistorfor the job as well as help you design the appropriateprobe configuration for your critical temperatureapplications.
Custom ProfilesWhen standard thermistors orprobes just do not meet your requirements, YSI canhelp. We have 45 years of experience helpingengineers develop temperature measurementsolutions. Put our applications engineering staff towork for you.
The internal construction of a YSI thermistor
Special TestingWe have a special test section forthermistors requiring extraordinary or specificverification of characteristics. Our NASA qualifica-tion process includes long-term age testing, burn-in,vibration, impact, humidity, high-temperature andlow-temperature exposure.
Our precision temperature measurement capabili-ties extend past the millikelvin range. The constant-temperature baths we use for verifying thermistorcalibration have stabilities and accuracies better than5 millikelvin (0.005C). NIST TraceabilityOur thermistor temperaturemeasurements are directly traceable to the NationalInstitute of Standards and Technology (NIST). Wemaintain a world-class temperature calibrationlaboratory for thermistor reference probes andstandard platinum resistance thermometers. Its theonly laboratory outside Germany with DKD(Deutscher Kalibrierdienst) accreditation from thePTB, Germanys equivalent of our NIST.
SPRTsYSI also manufactures the worlds workingstandard of temperature, the traditional standard plati-num resistance thermometer (SPRT).
For more information,contact us at 800 747-5367 or
937 427-1231Fax 937 427-1640Info@YSI.com www.YSI.com
Comparative Sensor Table
We specialize in thermistor-based temperature mea-surement. The chart tells you how thermistors com-pare with other temperature measurement methods.When accuracy and sensitivity are important,thermistors are the best choice.
Thermistor Thermocouple Platinum Integrated100 ohms to 1 B, R, S, E, T, J, K 100, 200, 500, 1,000 Circuitmegohms at 25C ohms at 0C Temperature
Sensitivity Units 3.3 to 53K 7 to 62 V/C 0.00385 and 0.00392 1A/Cohms/C at 25C ohms/ohm/C
Standard Accuracy (C)
Interchangeability 0.05 to 0.2C 0.8 to 4.4C 0.3C 0.6 to 5.0C
Stability at 100C 0.02C/ month (epoxy) Depends on 0.05C/year (film) 0.1C/month0.02C/year (glass) environment 0.002C/year (wire)
Power Required Stable voltage Self-powered Stable voltage 4 to 30 Vor current or current
Minimum Practical Span 1C 100C 25C 25C
Temperature Range -100 to +250C -100 to +1750C -200 to +750C -55 to +150C
Reference None Cold junction None None
Ruggedness Very rugged Large wire diameter Rugged Very Ruggedvery rugged
Maximum Power (self-heat) 50 W NA (susceptible to 500 W Offset error isfor Stated Accuracy amplifier bias current supply voltage
Hysteresis over Range 1C 0.01C Not available
Repeatability over Range
Characteristics of YSI Thermistors
YSI Series 55000 46000 45000 44900 44000 Thermilinear
Coefficient Negative Negative Negative Negative Negative Negative
Resistance 23.51 to 23.51 to 23.51 to 23.51 to 11.49 to NARatio 29.26 29.26 29.26 29.26 61.9625C/125C
Maximum 200C 250C 250C 150C 150C 150COperatingTemperature(C)
Recommended -80 to +200C -80 to +200C -80 to +200C -80 to +90C -80 to + 120C -30 to + 100COperatingRange
Dissipation 6 mW/C 10 mW/C 10 mW/C 8 mW/C 8 mW/C 8 mW/CConstant in oil min in oil min in oil min in oil min in oil min in oil min
1.5 mW/C 4 mW/C 4 mW/C 1 mW/C 1 mW/C 1 mW/Cin air min in air min in air min in air typical in air typical in air typical
Thermal Time 1.5 sec 2.5 sec 2.5 sec 1.0 sec 1.0 sec 1.0 secConstant max in oil max in oil max in oil max in oil max in oil max in oil
Resistance 2252-30K 2252-30K 2252-30K 2252-30K 100 -1 meg NAAvailable@ 25C
Stability 0.12C/10 mo 0.01C/10 mo. 0.05C/10 mo.
Precision Interchangeable Thermistors YSI 44000 Series
High-Temperature Hermetic Thermistors YSI 45000 Series
Super-Stable Thermistors YSI 46000 Series
GEM (Glass-Encapsulated Material) Thermistors YSI 55000 Series
NASA Space-Qualified Thermistors YSI 44900 Series
Interchangeability Tolerance Data
YSI 44000 Series Thermistors YSI 44100 Series Thermistors withTeflon Sheath
YSI thermistors provide highly accurate and stabletemperature sensing for measurement, control,indication and compensation. The tight interchange-ability of our precision components allows precisemeasurement without calibration of circuitry tomatch individual components.
We offer two interchangeability tolerances0.2C, 0.1Cand two configurations epoxy-encapsulated and epoxy-encapsulated with Teflonsheath.