Method for controlling a thermometer

Abstract

The present invention relates to a control method comprising the following steps: a) triggering a temperature reading, b) performing N measurements, where N is a natural number greater than or equal to 2, c) calculating a dispersion index of the N measurements by the control unit (16), d) if the dispersion index is less than a predetermined threshold value (σ0), then the thermometer provides temperature information (I), and if the dispersion index is greater than or equal to a predetermined threshold value (σ0), then the thermometer provides information representative of insufficient reliability (E). Figure for the abstract: 1

Description

Title of the invention: Method for controlling a thermometer Technical field of the invention

[0001] The present invention relates to a method of controlling a thermometer for medical use.

[0002] The invention relates more particularly to a method for detecting insufficient reliability of the temperature measurement. Technical background

[0003] To facilitate taking a patient's temperature, it has become common to use so-called "contactless" electronic thermometers, for example in the form of a housing equipped with a handle and a sensor capable of measuring the patient's temperature at a distance from the skin, in particular by aiming at a part of the body, for example the patient's temple or forehead.

[0004] Standards (ISO 80601-2-56) require high reliability of measurements provided by thermometers for medical use. In particular, test protocols are becoming increasingly strict.

[0005] The protocols test in particular the reliability of the measurement in a disturbed electromagnetic environment.

[0006] For cost reduction reasons, thermometer manufacturers use electronic components that may be sufficiently accurate for medical use but sensitive to magnetic disturbances, particularly in an environment disturbed by a strong electromagnetic field.

[0007] Furthermore, the conditions of use of the medical thermometer are not always optimal, for example in the event of improper handling or trembling of the operator, and can impact the reliability of the measurement. In this case, the temperature measurements may be unstable.

[0008] Therefore, there is a need to detect these instabilities to ensure the reliability of the temperature measurement. Summary of the invention

[0009] The invention proposes a method for controlling a “contactless” thermometer for medical use comprising a body temperature measurement mode capable of providing temperature information, the thermometer comprising: - a case, - a sensor capable of providing an electrical signal representative of a measured temperature, and - a control unit capable of interrogating the sensor and processing the signal received from the sensor to provide a temperature measurement, the process comprising the following steps: a) triggering a temperature measurement, b) carrying out N measurements, N being a natural whole number greater than or equal to 2, c) calculating a dispersion index of the N measurements by the control unit, d) if the dispersion index is less than a predetermined threshold value, then the thermometer provides temperature information, and If the dispersion index is greater than or equal to a predetermined threshold value, then the thermometer provides representative information of insufficient reliability.

[0010] According to other characteristics of the invention:

[0011] - the dispersion index of the N measurements is a Pearson standard deviation;

[0012] - the dispersion index of the N measurements is a standard deviation, a normalization or a normalized median;

[0013] - the temperature information provided corresponds to the average of the N measurements;

[0014] - the method is implemented during a period of time less than or equal to 400ms ;

[0015] - N is greater than or equal to 20;

[0016] - the sensor having at least two measurement modes, the method comprises a initial step of selecting the measurement mode from among the following measurement modes: - a so-called “body” mode to measure body temperature, and / or - a so-called “surface” mode to measure the temperature of an inert body;

[0017] - the method of determining the temperature by the control unit depends on the selected mode: - for the “body” mode: the determination process corresponds to a mathematical algorithm which takes into account the emissivity of the skin, a surface temperature measurement as well as an ambient temperature measurement, - for the “surface” mode: the determination process corresponds to a mathematical algorithm which takes into account the emissivity of the water and a measurement of surface temperature;

[0018] - the temperature measurement is given with an accuracy of 0.1°C;

[0019] - the thermometer is an infrared thermometer. Brief description of the figures

[0020] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0021] [Fig. 1] is a general perspective view of a thermometer capable of implementing a method according to the invention;

[0022] [Fig.2] is a block diagram showing the elements of the thermometer of [Fig.l] involved in the method according to the invention;

[0023] [Fig.3] is a flowchart showing the different steps of a method according to the invention. Detailed description of the invention

[0024] For the description of the invention and the understanding of the claims, the vertical, longitudinal and transverse orientations according to the reference V, L, T indicated in the figures, the longitudinal L and transverse T axes of which extend in a horizontal plane, will be adopted as a non-limiting example and without limiting reference to Earth's gravity. By convention, the longitudinal axis L is oriented from the rear to the front and the vertical axis V is oriented from the bottom to the top.

[0025] In the following description, identical, similar or analogous elements will be designated by the same reference numbers.

[0026] Figures 1 and 2 represent a contactless thermometer 11 for medical use capable of implementing a method according to the invention.

[0027] In the example shown, the thermometer 11 is an infrared thermometer allowing a temperature measurement by quantification of the radiative energy emitted in the infrared spectral band by a body. The body can be that of a person (body mode) or an inert body (liquid or solid in surface mode). The thermometer 11 takes temperature measurements at a distance from the body, the optimal distance for a measurement being of the order of 2 to 5 cm.

[0028] Alternatively, the thermometer 11 could use a technology other than infrared.

[0029] The thermometer 11 comprises: - a 10 case, - a temperature sensor 12, - a control unit 16, and - a 24-hour power supply.

[0030] The housing 10 has the general shape of a pistol grip with a handle 28 surmounted by a head 30. The head 30 of the housing 10 extends along a principal longitudinal direction between a rear end and a front end. The front end of the head 30 has a sighting aperture 26 allowing infrared radiation to reach the sensor 12. The rear end of the head 30 has a display screen 20.

[0031] The handle 28 of the housing 10 extends in a main direction of substantially vertical elongation between a lower end capable of resting on a base 22 and an upper end connected to the head 30.

[0032] The handle 28 has a substantially cylindrical shape and includes a lateral face 38 delimited by the generatrices of the cylinder. In a preferred mode of use, the user grips the handle by clenching the fist around the lateral face 38 of the handle 28. The handle 28 includes a trigger 18 on a front lateral portion located under the index finger of a user in the preferred mode of use.

[0033] The base 22 has a general L shape, the base of the L comprises a base 32 for receiving the handle 28. The upper end of the L comprises a support 34 for receiving the front end of the head 30.

[0034] The sensor 12 is capable of providing an electrical signal 14 representative of a measured temperature. The sensor 12 is for example an infrared sensor one of whose electrical characteristics is modified as a function of the radiative energy received, the electrical characteristics impacting the output electrical signal 14. The signal 14 is for example a voltage. The electrical signal provided by the sensor is for example in a voltage range of -2 to 10 millivolts.

[0035] The sensor may be a thermopile coupled to an 8-14 pm bandwidth filter. The sensor is for example mounted in a metal cone improving the thermal stability of the sensor. It is possible to envisage another mounting of the sensor.

[0036] The control unit 16 is capable of interrogating the sensor 12 and processing the signal 14 received from the sensor 12 to provide a temperature measurement. The control unit 16 comprises, for example, a microcontroller and a CAN (acronym for “analog digital converter”) for digitizing the voltage provided by the sensor. The information processing time by the microcontroller is designed not to exceed 400 ms.

[0037] The electrical power supply 24 comprises, for example, a battery (not visible) present in the housing 10 and a wired power supply 36 present in the base 22. When the housing 10 is placed on the base 22, the housing is electrically connected to the wired power supply 36 by an electrical contact in the lower end of the handle 28 allowing the battery to be charged.

[0038] The thermometer 11 is portable. The battery has a battery life of several hours, allowing in particular a healthcare worker to take the thermometer 11 with them for a round of visits to patients.

[0039] A method of controlling the thermometer 11 according to an embodiment of the invention will be described more specifically with reference to [Fig.3].

[0040] The method mainly comprises four steps a) to d).

[0041] In a first step a) of the method, the user triggers a temperature measurement. The temperature measurement is conventionally triggered by pressing a button. The temperature measurement is triggered, for example, when a user presses the trigger 18.

[0042] In a second step b) of the method, the control unit 16 controls the performance of N measurements by the temperature sensor 12. The performance of a measurement typically consists of digitizing and then recording the voltage value at the output of the temperature sensor 12. The N temperature measurements are performed over a time period defined by the control unit 16. This period is chosen so as to be able to make the electromagnetic disturbance detectable. N is a natural whole number greater than or equal to 2. Advantageously, N is greater than or equal to 20. In the preferred embodiment, the microcontroller is capable of performing a maximum of 20 measurements in a time period of 400 ms.

[0043] In a third step c) of the method of the invention, the control unit 16 calculates a dispersion index of the N measurements. The calculation of the dispersion index is carried out in the current period. It results from the execution of a calculation algorithm specific to the chosen dispersion index and which will be detailed in the following for different examples of dispersion indices.

[0044] In a fourth step d) of the method of the invention, the control unit 16 sends to the display screen information to be displayed which depends on the value of the dispersion index. In a first case, if the dispersion index is lower than a predetermined threshold value o0, then the thermometer 11 displays temperature information I. The temperature information I displayed comes from the N measurements. For example, in order to obtain a temperature measurement closer to the actual temperature, the temperature information I provided corresponds to the average of the N measurements calculated by the control unit 16. [Fig. 2] shows an example of temperature display 19 on the display screen 20.

[0045] In a second case, if the dispersion index is greater than or equal to a predetermined threshold value o0, then the thermometer 11 displays information indicating insufficient reliability E. Figure 2 shows an example of an error display 21 indicating insufficient reliability to the right of the display screen 20. The display screen may, for example, have three horizontal lines to signify insufficient reliability. Alternatively, the screen could display an error code or remain black, and the thermometer 11 could sound an alarm.

[0046] According to different exemplary embodiments, the dispersion index of the N measurements can be: - a Pearson standard deviation oP, - a standard deviation os, - a normalization oN, or - a normalized median oM.

[0047] The Pearson standard deviation op is the dispersion index adopted in a preferred embodiment of the invention. It is calculated by the following equation 1: ï V-1 '7 Nl

[0048] [Equation 1]

[0049]

[0050] In equation 1: - op is the Pearson standard deviation, - Tl, T2, ..Tn, .. .TN are the values ​​of the N measurements taken, and - T is the average value of the N measurements taken.

[0051] The standard deviation is calculated by the following equation 2:

[0052] [Equation 2]

[0053] CL =

[0054] In equation 2: - os is the standard deviation, - Tl, T2, ..., Ti, ...TN are the values ​​of the N measurements taken, and - T is the average value of the N measurements taken.

[0055] The normalization is calculated by the following equation 3:

[0056] [Equation 3]

[0057] _ Max(TiyMi^Ti} GN ~ t

[0058] In equation 3: - we are the normalization, - Max(Ti) is the maximum value of the N measurements taken, - Min(Ti) is the minimum value of the N measurements taken, and - T is the average value of the N measurements taken.

[0059] The normalized median is calculated by the following equation 4:

[0060] [Equation 4]

[0061] MedianiTi)

[0062] In equation 4: - oM is the normalized median, - Min(Ti) is the minimum value of the N measurements taken, and - Median(Ti) is the median value of the N measurements taken.

[0063] The temperature measurement is given with an accuracy of 0.1°C. This is a typical accuracy for the type of medical device.

[0064] The threshold value o0 is set to be consistent with the temperature accuracy. This accuracy is required by current standards.

[0065] According to a particular embodiment, the sensor has the following measurement modes:

[0066] - a so-called “body” mode for measuring body temperature, and / or

[0067] - a so-called “surface” mode for measuring the temperature of an inert body.

[0068] The user can select a mode for example by clicking on a button positioned on a side face of the head 30 of the housing 10.

[0069] When a measurement mode is selected, the method for determining the temperature from the signal 14 of the sensor is adapted according to the mode:

[0070] - for the “body” mode: the determination method corresponds to an algorithm mathematics which takes into account the emissivity of the skin (0.99), a measurement of surface temperature as well as a measurement of ambient temperature,

[0071] - for the “surface” mode: the determination method corresponds to an algorithm mathematics which takes into account the emissivity of water (0.95) and a measurement of surface temperature.

[0072] The method of the invention has the advantage of being able to be easily implemented in a thermometer comprising a low-cost control unit with limited computing performance.

[0073] The method is easy and inexpensive to implement. It does not impact the architecture of the thermometer.

[0074] The method efficiently detects insufficient reliability of measurements. It can be adapted to any level of reliability by adjusting the threshold value of the dispersion index.

[0075] Legend

[0076] 10 case 11 thermometer 12 sensor 14 signal 16 control unit 18 trigger 19 temperature display 20 screen 21 error display 22 base 24 power supply 26 sighting hole 28 handle 30 head 32 base 34 support

[0077] 36 wired power supply 38 side face I temperature information E information representative of insufficient reliability

Claims

Claims

1. Method for controlling a “contactless” thermometer for medical use comprising a body temperature measurement mode capable of providing temperature information, the thermometer comprising: - a housing (10), - a sensor (12) capable of providing an electrical signal (14) representative of a measured temperature, and - a control unit (16) capable of interrogating the sensor (12) and processing the signal (14) received from the sensor (12) to provide a temperature measurement, the method being characterized in that it comprises the following steps: a) triggering a temperature measurement, b) carrying out N measurements, N being a natural whole number greater than or equal to 2, c) calculating a dispersion index of the N measurements by the control unit (16), d) if the dispersion index is less than a predetermined threshold value (o0), then the thermometer provides temperature information (I),and if the dispersion index is greater than or equal to a predetermined threshold value (o0), then the thermometer provides information representative of insufficient reliability (E).,

2. Method for controlling a thermometer according to claim 1, characterized in that the dispersion index of the N measurements is a Pearson standard deviation (o).

3. Method for controlling a thermometer according to claim 1, characterized in that the dispersion index of the N measurements is a standard deviation, a normalization or a normalized median.

4. Method for controlling a thermometer according to any one of the preceding claims, characterized in that the temperature information (I) provided corresponds to the average of the N measurements.

5. Method for controlling a thermometer according to any one of the preceding claims, characterized in that it is implemented during a time period less than or equal to 400ms.

6. Method for controlling a thermometer according to any one of the preceding claims, characterized in that N is greater than or equal to 20.

7. Method for controlling a thermometer according to any one of the preceding claims, characterized in that, the sensor having at least two measurement modes, the method comprises an initial step of selecting the measurement mode from among the following measurement modes: - a so-called "body" mode for measuring a body temperature, and / or - a so-called "surface" mode for measuring a temperature of an inert body.

8. Method for controlling a thermometer according to claim 7, characterized in that the method for determining the temperature by the control unit (16) depends on the selected mode: - for the “body” mode: the determination method corresponds to a mathematical algorithm which takes into account the emissivity of the skin, a surface temperature measurement as well as an ambient temperature measurement, - for the “surface” mode: the determination method corresponds to a mathematical algorithm which takes into account the emissivity of the water and a surface temperature measurement.

9. A method of controlling a thermometer according to any one of the preceding claims, characterized in that the temperature measurement is given with an accuracy of 0.1°C.

10. A method of controlling a thermometer according to any one of the preceding claims, characterized in that the thermometer is an infrared thermometer.

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