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MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (sensing temperature changes for compensating measurements of other variables for compensating readings of instruments for variation in temperature, see G01D or relevant subclasses for variable measured; radiation pyrometry G01J; investigating or analysing materials by use of thermal means G01N 25/00; compound sensitive elements, e.g. bimetallic, G12B 1/02)
Definition statement
This subclass/group covers:

A detailed description of the subject matter appropriate for the subclass G01K is possible only at the main-group level.

Provisions that are valid at a general level (e.g. of a kind appropriate to more than one of the main groups) are provided in the sections that follow.

The user is otherwise referred to the definitions for the individual main groups of G01K which follow hereafter. The following listing is intended to assist the user:

Apparatus or methods for measuring temperature, i.e. thermometers. The following types of thermometers are therefore covered, the list being non exhaustive:

  • thermometers giving results other than momentary value of temperature;
  • thermometers based on the expansion or contraction of a material;
  • thermometers based on the use of electric or magnetic elements directly sensitive to heat;
  • thermometers based on movements caused by redistribution of weight, e.g. tilting thermometer;
  • thermometers based on other physical or chemical changes.

Testing or calibrating of thermometers.

Apparatus or methods for measuring quantity of heat, i.e. calorimeters.

Testing or calibrating of calorimeters.

Thermally-sensitive elements not otherwise provided for.

Relationship between large subject matter areas

Subclass G01K covers temperature measurements where there is direct physical contact between sensor and object and environment. Temperature sensing by radiation pyrometry (based on, e.g., infrared radiation emitted from the object) is classified in G01J.

When temperature measurements are used for the investigation of material properties (e.g. flaw detection), that subject matter falls under the scope of G01N 25/00.

For subject matter relating to sensing temperature changes for compensating measurements of other variables or for compensating readings of instruments for variations in temperature, see G01D or relevant subclass for variable measured.

References relevant to classification in this subclass
This subclass/group does not cover:
Radiation pyrometry

Examples of places where the subject matter of this class is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Measuring temperature of human body parts for diagnostic purposes
Heat-sensitive devices for control of fire-fighting equipment
Control or measuring devices, e.g. for temperature of metal, in the art of manufacture of metal sheets, wires, rods, tubes or profiles
Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass, in the art of casting of metals
Measuring, controlling or regulating of temperature in injection moulding
Heat-sensitive sheets for use in thermography
Measuring temperature specially adapted to boreholes or wells
Arrangements of temperature sensing elements for regulating or controlling in gas turbines
Indicating devices concerning coolant temperature, in the art of cooling of machines, engines, or internal-combustion engines
Use of thermally-sensitive elements in systems controlling or regulating combustion
Flow measurement by thermal means
Investigating or analysing materials by use of thermal means, e.g. by calorimetry
Meteorology; Indication of human comfort
Temperature control
Fire alarms
Structural combination of nuclear reactor elements with sensitive instruments for measuring temperature
Thermally-sensitive members for thermally-actuated switches
Temperature sensing in car batteries
Informative references
Attention is drawn to the following places, which may be of interest for search:
Thermometer holders specially adapted to veterinary purposes
Ambient temperature regulation specially adapted to passengers or goods spaces in vehicles
Heating in general
Sensing temperature changes for compensating measurements of other variables or for compensating readings of instruments for variations in temperature
Bimetallic elements
Compensating for the effects of temperature on instruments
Thermistors, i.e. thermo-resistors
Electrolytic temperature-sensitive devices
Peltier elements
Semiconductor or solid-state thermo-electric or thermo-magnetic devices
Special rules of classification within this subclass

For the following application fields, the following appropriate additional information is obligatory (also check the scheme for the groups):

Airconditioning: Indexing code G01K 2201/00

Cryogenics: Indexing code G01K 2203/00

Vehicle motors: Indexing code G01K 2205/00

Household appliances (e.g. cooking): Indexing code G01K 2207/00

Further, the following general technical details are also obligatory as additional information using the following classes:

Thermometers based on nanotechnology: Indexing code G01K 2211/00

Spatial (2D) mapping of temperature: Indexing code G01K 2213/00

Details or special adaptations concerning the sensor power supply: Indexing code G01K 2215/00

Dedicated Analog to Digital Converters for temperature sensors: Indexing code G01K 2217/00

Glossary of terms
In this subclass/group, the following terms (or expressions) are used with the meaning indicated:
Thermometer
Includes thermally-sensitive elements not provided for in other subclasses.
Synonyms and Keywords

In patent documents the following abbreviations are often used:

PTAT
Proportional To Absolute Temperature
CTAT
Complementary To Absolute Temperature
NTC/PTC
Negative/Positive Temperature Coefficient
RTD
Resistance Temperature Detector
3-wire / 4-wire RTD's
Resistive temperature detectors with additional lead wire for compensation purposes
OTDR
Optical Time Domain Reflectometry
FBG
Fiber Bragg Grating
SAW/BAW
Surface/Bulk Acoustic Wave
HVAC
Heating Ventilation Air Conditioning
TAT/SAT
Total/Static Air Temperature (in aircrafts)
Details of thermometers not specially adapted for particular types of thermometer (circuits for reducing thermal inertia G01K 7/42)
Definition statement
This subclass/group covers:

Indicating and recording of temperature.

Protective devices and casings.

Support and fastening of thermometers.

Conducting heat from an object to the sensor.

Compensation, e.g., for ambient temperature or pressure.

References relevant to classification in this group
This subclass/group does not cover:
Temperature calculation based on spatial modelling

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Remote temperature indication for medical applications
A61B5/00B4
Mounting of thermocouples for injection moulding
Informative references
Attention is drawn to the following places, which may be of interest for search:
Compensation of undesired influences per se
Sensor housings in general
Casings for pressure sensors
Remote indication per se
Indicating of human comfort
Synonyms and Keywords

In patent documents the following abbreviations are often used:

ZHF
Zero Heat Flux
ZHF Sensor
Measures core body temperature by attaching a first sensor to the body surface and a second sensor at a distance. Once the first and second temperatures are the same (i.e. there is zero heat flux), they are assumed to correspond to core temperature. Also known as ZHF sensors or "fox probes".
Thermowell
A closed-end tube designed to protect a temperature sensor from harsh process conditions as in G01K 1/08.
{arrangements for monitoring a plurality of temperatures, e.g. by multiplexing}
Special rules of classification within this group

If a temperature profile is recorded, Indexing code G01K 2213/00 is obligatory as additional information.

Protective devices, e.g. casings
Definition statement
This subclass/group covers:

Protective devices for preventing both chemical attack and heat overloading.

Protective devices that are vibration resistant.

Supports; Fastening devices; Mounting thermometers in particular locations
Relationship between large subject matter areas

To clarify difference between G01K 1/14 and G01K 13/00: In general G01K 13/00 concerns internal adaptation of the sensor, G01K 1/14 concerns mounting of an existing sensor.

{for measuring surface temperatures, e.g. of pipe walls}
Special rules of classification within this group

If pipe wall temperature is measured as a reference of flowing fluid temperature inside the pipe, also classify in G01K 13/02.

{arrangements for moving thermometers to or from a measuring position}
Definition statement
This subclass/group covers:

Automated systems moving the thermometer to and from the measurement position.

References relevant to classification in this group
This subclass/group does not cover:
If the thermometer is fixed/removed manually
Special arrangements for conducting heat from the object to the sensitive element
Definition statement
This subclass/group covers:

Preventing heat leakage.

Preventing heat from electronics to affect sensor temperature.

{ for application in zero heat flux sensors}
Special rules of classification within this group

See US 3,933,045 as an example of a ZHF probe. If heat flux is measured, and based on this measurement temperature is calculated then the document should be classified in G01K 7/427 and not in G01K 1/165.

for reducing thermal inertia
Definition statement
This subclass/group covers:

Preheating of the measurement object.

Creating additional thermal inertia.

Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
Definition statement
This subclass/group covers:

Compensation for optical radiation.

Thermometers giving results other than momentary value of temperature (G01K 7/42 takes precedence)
Definition statement
This subclass/group covers:

Thermometers that are integrating or differentiating temperature over time or over space.

Thermometers that indicate crossing of a predetermined (threshold) temperature.

References relevant to classification in this group
This subclass/group does not cover:
Threshold indicators based on material phase change (e.g. melting)
Threshold indicators based on thermochromes
Temperature difference measurement between the hot and cold junction of a thermocouple
Circuits for predicting the stationary value of temperature
Temperature calculation based on spatial modeling, e.g. spatial inter- or extrapolation

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Indication of incorrect storage conditions
Labels that change in response to external conditions
Informative references
Attention is drawn to the following places, which may be of interest for search:
Measurement of temperature profiles
Time-temperature integrators for non-biological materials
Time integrating devices
Fire detection
Thermally actuated switches
Emergency protective devices responsive to temperature
Special rules of classification within this group

Further details of subgroups:

This group is really limited to circuit arrangements.

This groups contains the Time Temperature Integrators.

If the difference of temperature values is between the hot and the cold junction of a thermocouple, G01K 7/02 is given and not G01K 3/08.

This group also comprises determination of temperature maximum and of temperature gradients. In case of determination of the location of a hotspot, Indexing Code G01K 2003/145 is obligatory as additional information.

Synonyms and Keywords

In patent documents the following abbreviations are often used:

TTI
Time Temperature Integrator: Devices used, e.g, to monitor the cold-chain of a perishable such as food, blood samples. Based on a chemical process, diffusion process, capillary process or a shape memory material that changes over time, resulting in a change of color or shape. The speed of the process underlying a TTI is temperature-dependent. The color/shape of a TTI at any moment is a measure of the integral of temperature over time.
Arrhenius curve
Curve representing the development of bacteria. TTI's are often designed to match an Arrhenius curve.
Measuring temperature based on the expansion or contraction of a material (G01K 9/00 takes precedence; giving other than momentary value of temperature G01K 3/00; of vapour arising from a liquid G01K 11/02; thermally-actuated switches H01H)
Definition statement
This subclass/group covers:

Thermometers where the expanding/contracting material is either a liquid (i.e. the traditional capillary thermometers), a gas or a solid.

References relevant to classification in this group
This subclass/group does not cover:
Tilting thermometers
Temperature based upon vapour arising from a liquid
Temperature based upon vapour arising from a liquid where liquid is contained in a hollow body having parts which are displaceable under pressure
Informative references
Attention is drawn to the following places, which may be of interest for search:
Shape Memory elements per se
Thermometers giving results other than momentary value of temperatures
Pressure measuring devices in general
Compound/bimetallic strips per se
Thermally actuated switches
Thermally actuated switches with extendable rods
Special rules of classification within this group

Further details of groups:

If the liquid is contained in a hollow body having parts which are deformable or displaceable under the pressure developed by the material, G01K 5/32 is given and not G01K 5/02.

If the liquid column is displaced for maximum or minimum indication, G01K 5/20 is given and not G01K 5/14.

G01K 5/22 takes precedence.

If the gas is contained in a hollow body having parts which are deformable or displaceable under the pressure developed by the material, G01K 5/32 is given and not G01K 5/28.

If the pressure is developed by evaporation G01K 11/04 is given and not G01K 5/32.

G01K 5/36 and G01K 5/42 take precedence.

This group contains the Shape Memory Alloys SMA's and the Shape Memory Polymers SMP's. They are sometimes used as Time-Temperature Integrators TTI's, in which case also G01K 3/04 is to be assigned.

G01K 5/62 takes precedence.

Synonyms and Keywords

In patent documents the following abbreviations are often used:

Shape memory materials
A group of materials that can return to some previously defined shape or size when subjected to the appropriate thermal procedure. That is, shape memory alloys can be plastically deformed at some relatively low temperature and, upon exposure to some higher temperature, will return to their original shape. Examples are SMA and SMP (see below).
SMA
Shape Memory Alloy
SMP
Shape Memory Polymer
Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat (giving results other than momentary value of temperature G01K 3/00; measuring electric or magnetic variables G01R) ; {Power supply, e.g. by thermoelectric elements}
Definition statement
This subclass/group covers:

Diode thermometers, thermocouples, resistive temperature sensors (such as thermistors) and capacitive temperature sensors.

Thermometers based on thermal noise, resonant frequencies, magnetic elements and gas ionization.

Circuits for predicting stationary temperature and for spatial inter- and extrapolation

References relevant to classification in this group
This subclass/group does not cover:
Surface (or Bulk) Acoustic Wave Sensors
Zero Heat Flux sensors or "fox probes"
Cooling arrangements in electronic devices using the Peltier effect
Informative references
Attention is drawn to the following places, which may be of interest for search:
Giving results other than momentary value of temperature
Measuring electric or magnetic variables
Open/short circuit determination per se
Testing or monitoring of circuits in sensors systems
Resistive elements for temperature control
Producing voltage/current as function of temperature
Bandgap reference voltage sources
Thermal management of data processing equipment
Digital storage with means to avoid temperature influence
Resistive elements per se
Terminals for resistive temperature sensors
Thermistors per se
Capacitors with temperature dependent dielectric per se
Thermoelectric devices per se
Thermomagnetic devices per se
Temperature measurement in car batteries (often done by extrapolation/modeling)
Connectors per se
Stabilizing oscillators by generating a temperature dependent oscillation signal
Ohmic resistance heating
Heating or cooling of PCB's
Sensors based on nano technology
Indexing code Y01N8/00
Special rules of classification within this subclass

If temperature is measured using electric of magnetic components already present in the system to be measured, the class Indexing code G01K 2217/00 is obligatory as additional information.

Further details of subgroups:

Temperature measurement based on the temperature dependent current through a diode or a PNP transistor with base and collector short circuited. G01K 7/02, G01K 7/16 and G01K 7/30 take precedence.

G01K 7/026, G01K 7/12 and G01K 7/14 take precedence.

This groups also contains arrangements for signalling wrong or reversed connection of thermocouples.

For thermocouples based on nanotechnology, G01K 2211/00 is obligatory as additional information.

If one of the following two elements is present, the indicated classes as additional information are obligatory (next to the appropriate group under G01K 7/16):

Specially adapted connectors for resistive temperature detectors: G01K 2007/163

Electrical time domain reflectometry (see for example DE102006022363):

G01K 7/26 takes precedence.

For RTD sensors based on nanotechnology Indexing code G01K 2211/00 is obligatory as additional information.

These groups also contain measurement of decay time, when the resistive temperature sensor is in an RC circuit.

G01K 7/203 and G01K 7/245 take precedence. G01K 7/32 also comprises:

piezoelectric oscillators

electric oscillators (e.g. ring oscillators)

tuning forks

This group comprises modelling in the time domain. Modelling in the spatial domain is for G01K 7/427.

This group comprises:

Spatial inter- and extrapolation

General modelling, where temperature is calculated based on, e.g., heat flux measurement

Dummy objects used for estimating the temperature of real objects, in which case the class Indexing Code G01K 2007/422 is obligatory as additional information

Synonyms and Keywords

In patent documents the following abbreviations are often used:

Curie temperature
the temperature at which the magnetic properties of a substance change from ferromagnetic to paramagnetic
Measuring temperature based on movements caused by redistribution of weight, e.g. tilting thermometer (not giving momentary value of temperature G01K 3/00)
Definition statement
This subclass/group covers:

The somewhat exotic "tilting thermometers"; an example can be found in FR405419.

References relevant to classification in this group
This subclass/group does not cover:
Thermometers giving results other than momentary value of temperature
Measuring temperature based upon physical or chemical changes not covered by groups G01K 3/00, G01K 5/00, G01K 7/00 or G01K 9/00
Definition statement
This subclass/group covers:

Temperature measurement based on:

  • microwaves or millimeter waves emitted by an object
  • phase change (e.g. melting) of materials
  • color change of materials (e.g. thermochromes)
  • thermoluminescence or fluorescence
  • acoustic effects
  • the effect of a material on radiation (e.g. gamma radiation)
  • changes in transmission in optical fibers
  • measuring temperature by temperature sensitive (optical) refractive index
References relevant to classification in this group
This subclass/group does not cover:

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Temperature measurement in boreholes (often by using optical fibers as in G01K 11/32)

Places in relation to which this group is residual:

Details of thermometers not specially adapted for particular types of thermometer
Measuring temperature based on the expansion or contraction of a material
Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat
Measuring temperature based on movements caused by redistribution of weight, e.g. tilting thermometer
Informative references
Attention is drawn to the following places, which may be of interest for search:
Heat sensitive sheets for use in thermography
Thermosensitive paints (relevant for G01K 11/12) per se
Tenebrescent compositions
Liquid crystal compositions
Optical fiber sensors per se
FBG's for stress measurement
Pressure sensors with optical fibers
Optical Time Domain Reflectometry (relevant for G01K 11/32) OTDR for general testing of optical fibers
G01M11/00B2A
Measuring density in general
Determining freezing or melting point (relevant for G01K 11/06) of a substance
Mm-waves (relevant for G01K 11/006) for detecting hidden objects
Bragg gratings (relevant for G01K 11/3206) per se
Electro-optic liquid crystals
Special rules of classification within this group

Further details of subgroups:

The methods in this class are mainly passive (i.e. measurement of radiation emitted by the object itself). G01K 17/003 takes precedence.

G01K 11/32 takes precedence.

This group also comprises temperature measurement by fluorescence (G01K 11/3213 takes precedence).

Bulk acoustic wave sensors are also in this group.

These methods, in the shorter wavelength region of the electromagnetic spectrum, are mostly active methods (i.e. there is an external source irradiating the measurement object).

The following additional information is obligatory to distinguish between systems based on Brillouin and Raman scattering respectively:

Brillouin: Indexing Code G01K 2011/322

Raman: Indexing Code G01K 2011/324

This group also comprises measuring temperature at the end of an optical fiber using other means than fluorescence. The sensors used in this group are often also used for pressure measurement, in which case circulation to G01L 1/246 is obligatory.

Synonyms and Keywords

In patent documents the following abbreviations are often used:

DTS
Distributed Temperature Sensor
OTDR
Optical Time Domain Reflectometry
OFDR
Optical Frequency Domain Reflectometry
FBG
Fiber Bragg Grating
Adaptations of thermometers for specific purposes
Definition statement
This subclass/group covers:

Adaption of thermometers:

  • for clinical purposes
  • for cryogenic purposes
  • for measuring moving fluids (gas or liquid)
  • for measuring moving solid bodies
  • combined with sampling devices (e.g. for molten metal)
References relevant to classification in this group
This subclass/group does not cover:
Clinical infrared (ear) thermometers
Mounting of thermometers per se

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Patient garments with monitoring equipment
Recording temperature data for clinical diagnosis
A61B5/00B4
Diagnostic temperature sensing
A61B5/00H
Temperature mapping of body parts
A61B5/00H5
Baby bottles with temperature sensors
Temperature measurement in rolling mills
Measurement of metal bath temperature
Temperature regulation for vehicle airco and HVAC
Temperature sensing elements in gas turbines
Temperature sensing in exhaust gases of combustion engines
Prevention of heat overload in bearings
Air temperature sensors in air conditioning systems
Frost detectors for fridges
Temperature monitoring in heat treatment chambers (industrial furnaces, ovens)
Flow measurement by thermal means
Temperature sensing on integrated circuits
Car battery state of charge
Temperature monitoring in nuclear reactors
Temperature monitoring of semiconductor wafers during manufacturing
H01L21/00A8A
Special rules of classification within this subclass/group

Further details of subgroups:

This group also comprises adaptations of specific objects for thermometric purposes. In general G01K 13/00 concerns internal adaptation of the sensor, G01K 1/14 concerns mounting of an existing sensor. For specific application fields there is a dedicated Indexing Code G01K "200" series that is obligatory as additional information. Reference is made to the special rules of classification at the subclass G01K level.

This group also comprises measurement of animal temperature. Temperature prediction aspects (e.g. prediction of stationary value of temperature) are found in G01K 7/42; in this case both G01K 13/002 and G01K 7/42 are obligatory. G01K 5/22 takes precedence.

If pipe wall temperature is measured as a reference of flowing fluid temperature inside the pipe, also classify in G01K 1/143. The following classes are obligatory as additional information:

This group comprises temperature measurement of bearings. When the result of the temperature measurement is used to prevent heat overload in bearings, then also circulate to F16C 17/24.

This group comprises, e.g., temperature measurement in grain containers (silos). If temperature is measured by special arrangements for conducting heat from the object to the sensitive heat element both G01K 13/10 and G01K 1/16 are obligatory.

Synonyms and Keywords

In patent documents the following abbreviations are often used:

HVAC
Heating Ventilation Air Conditioning
Total Air Temperature
Total Air Temperature (TAT) is the air temperature as measured by a temperature probe on an aircraft. It is greater than the static (ambient) air temperature because of the heating that occurs as air moving past the aircraft is slowed down
Testing or calibrating of thermometers
References relevant to classification in this group
This subclass/group does not cover:
Arrangements with respect to the cold junction of thermocouples

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Failure detection of sensors in combustion engines
Special rules of classification within this subclass/group

Further details of subgroups:

This group comprises testing or verification of the temperature sensor, to investigate whether calibration is necessary. If the document is purely about testing or purely about calibration, it should be classified in one of the groups G01K 15/007 or G01K 15/005 and not in G01K 15/00.

This group comprises verification for proper functioning (i.e. testing) and estimation of expected life-time. Testing could be either in-line (i.e. during operation) or off-line.

This group comprises the eutectics, peritectics, triple point cells, etc. defining a temperature reference point used for calibration. This class should be given together with G01K 15/00 or G01K 15/005.

Measuring quantity of heat (measuring temperature by calorimetry G01K 3/00 to G01K 11/00; specially adapted for measuring thermal properties of materials, e.g. specific heat, heat of combustion G01N)
Definition statement
This subclass/group covers:

(Micro)calorimeters.

Measuring heat in (domestic) radiation systems.

Heating cost allocation.

Testing of heat pipes.

References relevant to classification in this group
This subclass/group does not cover:

Examples of places where the subject matter of this group is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Measuring quantity of heat specially adapted for measuring thermal properties of materials
Investigating materials and chemical reactions by thermal means
Microreactors / "lab-on-a-chip" systems
Utility meters
Counting of domestic energy consumption
Same as above for domestic hot water
Same as above for combi-kettles
Informative references
Attention is drawn to the following places, which may be of interest for search:
Measuring quantity of heat in order to calculate temperature
Special rules of classification within this subclass/group

Further details of subgroups:

For classification: also circulate to G01N 25/48 if applicable (i.e. if material investigation as such is relevant). This group further also comprises testing of heat pipes.

G01K 17/06 and groups:

This group comprises measurement of domestic energy consumption. Circulate to F24D 19/00 and/or G01D 4/00 if applicable. G01K 17/02 and G01K 17/04 take precedence.

This group also comprises determination of so called U-value, R-value or K-value of a building.

Synonyms and Keywords

In patent documents the following abbreviations are often used:

U-value, K-value
Overall heat transfer coefficient. Represents a measure of thermal insulation of a building
R-value
Reciprocal of the U-value
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Last Modified: 10/11/2013