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:

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.

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

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.

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

Protective devices for preventing both chemical attack and heat overloading.

Protective devices that are vibration resistant.

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.

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.

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

Thermometers fixed or removed manually are placed in G01K 1/14.

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.

Preheating of the measurement object.

Creating additional thermal inertia.

Compensation for optical radiation.

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

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

G01K 3/005:

This group is really limited to circuit arrangements.

G01K 3/04:

This groups contains the Time Temperature Integrators.

G01K 3/08:

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.

G01K 3/14:

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.

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

Further details of groups:

G01K 5/02:

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.

G01K 5/14:

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

G01K 5/20:

G01K 5/22 takes precedence.

G01K 5/28:

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.

G01K 5/32:

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

G01K 5/32:

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

G01K 5/486:

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 5/486:

G01K 5/62 takes precedence.

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

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.

G01K 7/01:

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 7/021:

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

G01K 7/026:

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

G01K 7/028:

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

G01K 7/16:

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 2007/166.

G01K 7/18, G01K 7/22:

G01K 7/26 takes precedence.

G01K 7/186; G01K 7/226:

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

G01K 7/203, G01K 7/245:

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

G01K 7/32:

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

piezoelectric oscillators

electric oscillators (e.g. ring oscillators)

tuning forks

G01K 7/42:

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

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

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

Temperature measurement based on:

G01K 11/006:

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

G01K 11/20:

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

G01K 11/265:

Bulk acoustic wave sensors are also in this group.

G01K 11/30:

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).

G01K 11/32:

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

G01K 11/3206:

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.

Adaption of thermometers:

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.

G01K 13/00:

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.

G01K 13/02

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:

G01K 13/08:

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.

G01K 13/10:

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.

G01K 13/20:

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.

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.

G01K 15/00:

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.

G01K 15/007:

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.

G01K 15/002:

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.

(Micro)calorimeters.

Measuring heat in (domestic) radiation systems.

Heating cost allocation.

Testing of heat pipes.

G01K 17/00:

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.

G01K 17/20:

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