CPC Definition - Subclass G01K
This place 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.
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.
This place does not cover:
Radiation pyrometry |
Examples of places where the subject matter of this place 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 | |
Temperature sensing in car batteries | |
Thermally-sensitive members for thermally-actuated switches |
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 thermoelectric or thermomagnetic devices |
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
In this place, the following terms or expressions are used with the meaning indicated:
Thermometer | Includes thermally-sensitive elements not provided for in other subclasses. |
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) |
This place 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.
This place does not cover:
Temperature calculation based on spatial modelling |
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:
Remote temperature indication for medical applications | |
Mounting of thermocouples for injection moulding |
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 | |
Indicating of human comfort | |
Remote indication per se |
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. |
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:
Temperature indicating arrangements in hand irons internally heated by electricity | |
Displaying temperature data in connection with air-conditioning, air-humidification, ventilation or use of air currents for screening |
Attention is drawn to the following places, which may be of interest for search:
Indicating measured values, in general |
Attention is drawn to the following places, which may be of interest for search:
Recording measured values, in general |
If a temperature profile is recorded, Indexing code G01K 2213/00 is obligatory as additional information.
This place covers:
Protective devices for preventing both chemical attack and heat overloading.
Protective devices that are vibration resistant.
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:
Arrangements for detecting or measuring washing liquid temperature for washing machines |
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.
This place covers:
The measurement of a representative temperature of solid, extended objects, e.g. pipes, vessels, containers, requiring that the geometry of the temperature sensor be suitably matched to the solid, extended object to be measured.
For example, an apparatus for measuring the temperature of a fluid flowing in a tube by measuring the temperature of the outer surface of the tube would be classified in this group.
Another example would be the geometric adaptation of a temperature sensor to measure the temperature of an electric cable carrying current.
Classification in this group requires that the geometry of the temperature sensor assembly be compatible with the object being measured. Instead, the subject matter of G01K 1/16 is rather directed at arrangements that can optimise the heat conduction between the probe part of the temperature sensor and the temperature transducer part of that sensor, without the need to take into account the geometry of the object that is being measured.
If a pipe wall temperature is measured as a reference of flowing fluid temperature inside the pipe, also classify in G01K 13/02.
This place covers:
Automated systems moving the thermometer to and from the measurement position.
Thermometers fixed or removed manually are placed in G01K 1/14.
This place covers:
Preventing heat leakage.
Preventing heat from electronics to affect sensor temperature.
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.
This place covers:
Preheating of the measurement object.
Creating additional thermal inertia.
This place covers:
Compensation for optical radiation.
This place covers:
Thermometers that are integrating or differentiating temperature over time or over space.
Thermometers that indicate crossing of a predetermined (threshold) temperature.
This place does not cover:
Circuits for predicting the stationary value of temperature | |
Temperature calculation based on spatial modeling, e.g. spatial inter- or extrapolation | |
Threshold indicators based on material phase change (e.g. melting) | |
Threshold indicators based on thermochromes |
Examples of places where the subject matter of this place 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 |
Attention is drawn to the following places, which may be of interest for search:
Measurement of temperature profiles | |
Measuring temperature using thermoelectric elements | |
Time-temperature integrators for non-biological materials | |
Time integrating devices | |
Fire detection | |
Emergency protective devices responsive to temperature | |
Thermally actuated switches |
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.
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. |
This place covers:
Thermometers where the expanding/contracting material is either a liquid (i.e. the traditional capillary thermometers), a gas or a solid.
This place does not cover:
Attention is drawn to the following places, which may be of interest for search:
Thermometers giving results other than momentary value of temperatures | |
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 | |
Shape Memory elements per se | |
Pressure measuring devices in general | |
Compound/bimetallic strips per se | |
Thermally actuated switches | |
Thermally actuated switches with extendable rods |
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.
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.
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 |
This place 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
This place does not cover:
Giving results other than momentary value of temperature |
Attention is drawn to the following places, which may be of interest for search:
Zero Heat Flux sensors or "fox probes" | |
Surface (or Bulk) Acoustic Wave Sensors | |
Measuring electric or magnetic variables | |
Testing or monitoring of circuits in sensors systems | |
Open/short circuit determination per se | |
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 | |
Cooling arrangements in electronic devices using the Peltier effect | |
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 | |
Thermoelectric devices per se | |
Thermomagnetic devices per se |
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
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 |
Attention is drawn to the following places, which may be of interest for search:
Thermoelectric or thermomagnetic devices per se |
This place covers:
The somewhat exotic "tilting thermometers"; an example can be found in FR405419.
This place does not cover:
Thermometers giving results other than momentary value of temperature |
This place 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
Examples of places where the subject matter of this place 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) |
Examples of places in relation to which this place 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 |
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 | |
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 |
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.
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 symbols should be used to distinguish between systems based on Brillouin and Raman scattering respectively:
Brillouin: G01K 11/322
Raman: G01K 11/324
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.
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 |
Attention is drawn to the following places, which may be of interest for search:
Liquid crystal materials |
This place 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)
When temperature is measured in order to provide compensation for the impact of a temperature or a variation of temperature on a measurement, variable, signal or technological effect, classification is made in the place that is applicable to that measurement, variable, signal or technological effect, e.g. G01D 3/028, G01G 23/48, G01L 19/04, G12B 7/00, H01G 5/017, H03F 1/30. Additional classification in G01K would be justifiable if such compensation required that a temperature-measuring instrument or circuit be modified or that temperature measurements be processed in a new way.
Examples of places where the subject matter of this place 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 | |
Diagnostic temperature sensing | |
Temperature mapping of body parts | |
Baby bottles with temperature sensors | |
Temperature measurement in rolling mills | |
Measurement of metal bath temperature | |
Temperature regulation for vehicle airco and HVAC | |
Determining when the hardening temperature has been reached by measurement of magnetic or electrical properties in the treatment of metals or alloys | |
Measuring temperature in boreholes or wells | |
Temperature sensing elements in gas turbines | |
Temperature sensing in exhaust gases of combustion engines | |
Sensors specially adapted for exhaust gas recirculation systems, for determining temperature | |
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 |
Attention is drawn to the following places, which may be of interest for search:
Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of temperature or ambient temperature |
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 and G01K 1/14 concerns mounting of an existing sensor. For specific application fields there is a dedicated Indexing Code G01K "2000" series that is obligatory as additional information. Reference is made to the special rules of classification at the subclass G01K level.
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:
- Moving gas: G01K 13/024
- Moving liquid: G01K 13/026
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.
This group comprises measurement of human or animal temperature. Temperature prediction aspects (e.g. prediction of stationary value of temperature) are found in G01K 7/42, and in this case both G01K 13/20 and G01K 7/42 are obligatory.
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 |
This place covers:
Instruments, including their constructional details, that measure the temperature of human beings or animals and that operate in direct contact with the human being or animal. These instruments are specially adapted to measure the temperature around the point of homeostasis of the human being or animal. Therefore, they could be operable only for a single species or a small number of species. In addition, a clinical thermometer may be adapted to suit the morphology of a given species or small number of species.
For example, the normal human body temperature is around 37 °C, and the medically dangerous condition of hyperpyrexia occurs around 41.5 °C, so that clinical thermometers need not be capable of measuring temperatures above 45 °C. A lower limit for the applicability of clinical thermometers in human beings would be set by medically-induced hypothermia, which is kept above 30 °C to avoid serious complications. Therefore, a clinical thermometer for use on human beings would not be designed to operate out of the range 30 °C-45 °C.
A61B 5/01 covers the medical-diagnosis aspect of temperature measurements of human beings or animals, like mapping the temperature of a body part, whereas G01K 13/20 covers hardware, circuits and processes that improve the suitability of temperature-measuring technology for use on humans or animals, but that do not provide per se a medical diagnosis. That is, what is covered in G01K 13/20 is ultimately destined to be used for medical diagnosis, but does not per se determine a specific medical condition, this latter type of improvement belonging to A61B 5/01. Stated differently, G01K 13/20 covers adaptations that make temperature measuring more suited to human beings or animals, whereas A61B 5/01 provides a precise medical answer that is inferred from temperature measurements.
In this place, the following terms or expressions are used with the meaning indicated:
clinical thermometer | Temperature-measuring instrument designed to operate around the homeostasis point of a human being or animal |
This place does not cover:
Arrangements with respect to the cold junction of thermocouples |
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:
Failure detection of sensors in combustion engines |
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.
This place covers:
(Micro)calorimeters.
Measuring heat in (domestic) radiation systems.
Heating cost allocation.
Testing of heat pipes.
Examples of places where the subject matter of this place is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:
Microreactors / "lab-on-a-chip" systems | |
Counting of domestic energy consumption | |
Same as above for domestic hot water | |
Same as above for combi-kettles | |
Utility meters | |
Measuring quantity of heat specially adapted for measuring thermal properties of materials | |
Investigating materials and chemical reactions by thermal means |
Attention is drawn to the following places, which may be of interest for search:
Measuring quantity of heat in order to calculate temperature |
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.
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 |