The invention relates to an intelligent meat thermometer that is designed to measure the temperature at three or more points in the meat by means of at least one temperature sensor at each point so as to estimate the centre temperature of the meat.

The invention relates to an intelligent meat thermometer that is designed to measure the temperature at three or more separate points in meat. It comprises a probe with at least three sensors, said probe being a stainless steel tube, and the sensors are located on the inner side of the steel tube in the longitudinal direction.

If at least one temperature is measured on the far side of the centre of the meat opposite the point of insertion, so that the centre is between two measurements, it will be possible to estimate the centre temperature of the meat with the meat thermometer.

The measured temperatures are sent to an external unit for showing on a display or another external unit via cable or wirelessly.

The internal or external unit is designed to perform a calculation with received measurement data together with displaying of for instance the centre temperature, possibly as a function of time, and can also be designed to setting of parameters for use at the calculations, so that any remaining cooking time can be estimated.

The state of the art is described in EP2741061 A1 , in which a meat thermometer and a method for determining the centre temperature of the meat are described. The meat thermometer comprises a probe with at least three temperature sensors for measurement at at least three points in the meat. If at least one temperature sensor, after insertion, is on the far side of the centre of the meat opposite the point of insertion, so that the centre is located at a point between the two temperature sensors, it is not necessary with extrapolation from an estimated polynomial as the closest descriptive mathematical function. In the Figures, parabolas are shown. The at least three measurement values, one from each of the at least three sensors, is used to find a lowest value by interpolation. This lowest value is the centre temperature. According to the document, it is also possible to find polynomials of lowest order, so called Lagrange polynomials, from which the centre temperature can be estimated. It is also stated that Newtonian algorithms can be used. The meat thermometer can also comprise a unit for calculating of received data.

The probe is described in such a way that it can be a steel tube, within which the sensors can be distributed evenly in the longitudinal direction. In Fig. 1 in the document, a conductor from the sensors and back to the top of the probe is shown. Measurement inaccuracies of the meat thermometer and means in the construction to minimize sources of erroneous readings are not mentioned.

Another meat thermometer is described in WO2006035005 and DE102004047756. The probe consists of a stainless steel tube with a diameter that is chosen to be so small that heat conduction along the walls of the probe is minimized. A number of sensors are located inside the probe, and each sensor has an energy saving unit manufactured in quartz to collect vibrational energy.

It is essential to ensure the correct centre temperature of meat for the culinary quality and hygiene, and tests have shown that down to a centimetre from the centre of the meat, the temperature can be up to 10 °C higher when cooking at oven temperatures of above 160 °C. Furthermore, tests have shown that the variety of the centre temperature of the meat is generally quite large (> 20 °C) when cooking, which results in a very variant culinary quality. It is yet another problem that the meat shrinks with higher centre temperature. Finally, it can constitute a hygienic problem, if the centre temperature is too low.

Therefore, it would be optimal to be able to estimate the centre temperature as well as possible, without it leading too large costs of manufacturing the probe for measurement of the centre temperature.

It is the object of the present invention to devise an intelligent meat thermometer that estimates the centre temperature with higher accuracy than meat thermometers according to the state of the art, when, at the same time, the meat thermometer is cheap to manufacture.

Short description of the invention

The object of the invention is met by means of an intelligent meat thermometer of the type according to the introductory part of claim 1 and being characterized in that the probe comprises a tube of a stainless, heat conducting material such as steel, said heat conducting material having a material thickness of between 0.05 and 0.30 mm, preferably between 0.05 mm and 0.25 mm and most preferably 0.25 mm, and that the probe is also designed with a distance between the temperature sensors in the steel tube, of less than 15 mm and preferably less than 10 mm at a material thickness of 0.05 mm, and with a distance of between 15 mm and 20 mm at a material thickness of between 0.05 and 0.25 mm, and with a distance of more than 20 mm at a material thickness of 0.25 mm and above.

A meat thermometer according to claim 1 will not give rise to inaccurate measurements. Advantageous embodiments of the invention are described in claims 2 to 7.

In the following, the invention will be described in further detail referring to the drawings, in which:

Fig. 1 shows a meat thermometer according to the invention,

Fig. 2 shows insertion of a meat thermometer,

Fig. 3 shows a sectional view of a meat thermometer according to the invention,

Fig. 4 shows a screen dump of an app for controlling roasting using a meat thermometer according to the invention, while

Fig. 5 and 6 show other screen dumps of the app according to the invention. App is short for an application or program that is downloaded to a smartphone or a tablet.

Fig.1 , 2 and 3 show an example of a meat thermometer according to the invention for measuring the temperature of a piece of meat. It comprises a probe 1 for inserting into a piece of meat 2. There is a handle 3 that is manufactured in a heat insulating material and is connected by means of a cord 15 or wirelessly (not shown) to a unit that is adapted to receive collected measurement data, calculate, set and show settings and measurement results, whether these are calculated or read directly.

The probe 1 of the meat thermometer is adapted to be inserted longer than to the centre of meat 2 that is roasting or is to be roasted on a grill, in an oven or in a casserole or is to be heat treated in any other way. The probe 1 is manufactured as a tube that is pointed and reinforced at the end 16 (Fig. 2) that is to be inserted into the meat 2. The tube 1 is manufactured in a thin walled stainless steel material (see Fig. 3) so as to obtain least possible heat conduction, but at the same time ensure a fairly accurate temperature measurement at the sensors 5 and 14 that are placed with equal spacing 4 in the steel tube 1 .

The probe 1 of the meat thermometer could also comprise a transmitter for wireless communication (not shown) with a custom designed proprietary external unit or an app on an external unit, such as a smartphone or a tablet or any other means being capable of receiving, processing and displaying processed and measured data, etc. The unit can be a proprietary part of the thermometer or an app that is installed on a smartphone, a tablet or other similar means for showing real temperature, calculate and show centre temperature, show estimated remaining cooking time 8 calculated from the measured or calculated data for centre temperature 7 and heat gradient that can be measured, calculated or chosen as an empirical value that only depends on the type and age of the meat.

The probe 1 on the meat thermometer according to the invention is provided with a number of at least three and advantageously four or more sensors 5, 14, at least three of which are intended to measure the temperature inside the meat 2. The sensors 5 can advantageously be of the thermistor or the thermocouple type. The sensors 5 are in direct contact with the inside of the steel tube of the probe 1 so as to obtain the best and most reliable measurement at each sensor 5, 14.

The embodiment of the meat thermometer of Fig. 1 has a probe 1 that comprises five sensors 5 and 14, one A 14 for measuring the temperature outside the meat 2, and four B, C, D and E 5 for measuring temperatures at several positions through the meat. It has been demonstrated experimentally that when measuring of at least three and advantageously more separate points in a solid piece of meat 2, at least one of said points being on the far side of the centre of the meat 2 in relation to the point of insertion (see Fig. 1 ), it is possible to deduct a temperature curve through the meat 2, from which the coldest point in the meat 2, the centre temperature, is estimated. In this way, the meat thermometer can be placed easily and comfortably and the desired result is insured every time. At the same time, the meat thermometer is cheap to manufacture. It has shown that it is important to use for instance a stainless steel tube 1 with as little material thickness as possible, so that the heat resistance is as high as possible. The reason is that heat conduction from the heat conducting material at an adjacent sensor causes an erroneous reading due to heat transmitted from another place in the meat via heating of the tube of the probe 1. All things being equal, a small material thickness will therefore mean that only the temperature of the meat around the sensor concerned is measured with no or only a minimal erroneous reading. Tests have shown that with a material thickness of the stainless steel tube of 0.25 mm, a distance between the sensors 5 of 20 mm or more reduces the heat effect of the sensors 5 from the surrounding heat source to a minimal level that will be negligible, while, at the same time, the control of the cooking temperature of the meat 2 is still fairly accurate. Consequently, a heat source at an adjacent sensor cannot give rise to an erroneous reading.

If one wants to further reduce the material thickness of the probe 1 , so that the heat resistance is further increased, high requirements are put on the manufacturing process of the probe 1 , and 0.25 mm has shown to be a good compromise. However, tests have shown that by a material thickness of 0.05 mm, the distance between the sensors 5 can be reduced to below 15 mm, with the precision and the measurement accuracy still being fairly good. If the distance is reduced below 10 mm, the measurement accuracy becomes too bad.

When the tube of the probe is provided with said material thicknesses and with the appertaining distances between the sensors 5, it is possible to manufacture the probe 1 very cheaply, as no other detailed manufacturing processes must be performed. At the same time, the probe 1 can be used to estimate the centre temperature with high precision.

It is possible to do an estimate, as the measuring data that are results of the temperature measurements, advantageously, as stated in claim 2, are used to determine a temperature curve and therefrom deduct the minimum temperature that is the centre temperature of the meat, by using a Lagrange polynomial or Newtonian algorithms. In this way, it is possible to estimate the centre temperature of the meat very precisely, whereby the drawbacks of insufficient precision of an estimated centre temperature are largely avoided.

Tests have shown that the use of a Lagrange polynomial compared with other algorithms is optimal for calculation and deduction of the centre temperature of the meat from this temperature curve, and hence calculate it very precisely. As stated, at least one measuring point must be located at the far side of the centre of the meat 2. With a design of the meat thermometer, as it is devised by this invention, a user will not be in doubt whether he has hit the centre om the meat, and in this way have had the opportunity to obtain an even very precise centre temperature measurement, whereby the basis for achieving the highest possible culinary quality is likely to be present. When cooking a piece of meat, the meat is put on a heat source (directly or indirectly) so that the surrounding heat heats the cold piece of meat up, until it has reach the desired cooking temperature, followed by removal of the meat from the heat source. As stated in claim 3, the meat thermometer can comprise an external unit for calculating such as an app for use on smartphones or tablets, etc., or another similar unit that is capable of receiving input and perform calculations and display results therefrom. This provides the advantage that the integration of the mathematical calculations of the centre temperature and cooking time in the app entails that the processor power in smartphones and tablets is used, whereby the manufacturing price of the electronics for the meat thermometer is reduced significantly.

Further advantageous embodiments of the invention are indicated in claims 4 to 7.

Among further advantages of the present invention are:

When slow cooking, one wishes to keep all juices and flavour within the meat. This is done by keeping the oven or grill temperature low.

To ensure an optimal slow cooking, the temperature difference between the centre temperature and the surface of the meat must be as small as possible. A useful technology must guarantee the measuring of the centre temperature and the temperature difference through the meat so as to guarantee the correct slow cooking. Said invention solves this problem, as the temperature difference through the meat is measured from the surrounding temperature that in the example of Fig. 1 is A (14), which in an oven is the oven temperature, and measurement data on temperatures from the sensors BCDE (5). The temperature difference, when cooking in an oven, can be adjusted to a preferred level by adjusting the oven temperature.

Another advantage of the invention is that it is possible to calculate the cooking time. When one knows the centre temperature of the meat, it is possible to calculate the remaining cooking time until the sought centre temperature is achieved with the relevant surrounding temperature. It is also possible to display which surrounding temperature the oven or grill must be adjusted to at a given cooking time.

Especially when barbecuing, tests have shown that the accuracy of the calculated cooking time depends on the time expired. In the beginning of the barbecuing, the calculated cooking time is very inaccurate, but after approximately 5-7 minutes it is possible, within a couple of minutes, to calculate when the cooking is finished. Calculation of the cooking time becomes more and more precise with time. Calculation of the cooking time takes place continuously, so that changes in the surrounding temperature are taken into consideration. Fig. 4 shows an example of a wireless unit that can communicate with the intelligent meat thermometer. An app is shown that is installed on a smartphone or tablet. The principle can without further ado be transferred to any unit which is capable of communication - whether wirelessly or not - with the meat thermometer, and which, in this way, is capable of receiving measurement data, calculate, adjust and display settings and measurement results, whether these are calculated or read directly. The app that is shown in Fig. 4 to 6 is provided with means for visualizing centre temperature 7, cooking time 8 and alarms through the whole cooking process.

The shown unit is designed with user friendliness in mind and comprises, apart from said means for visualizing of centre temperatures 7, etc., also means for setting of alarms 9 and not least means for adjusting settings of the cooking process. For example, the app is provided with several possibilities for choosing cooking parameters, primarily centre temperature. They can for example be reached by means of the possibilities that are shown in Fig. 5 for manually choosing the cooking process. Here, a setting of a cooking temperature can be performed by "Meat temp", which is a manual setting of the sought centre temperature, but it is also possible to choose cooking process by choosing between shown "visuals" of meat that is cooked at different temperatures (se Fig. 6). When using the slide 13, it is possible to change between the five overall types of cooking of a piece of beef: the categories being - Rare, Medium Rare, Medium, Medium Done and Well Done.

When just browsing between these categories, the app shows pictures of the current category, so that one, by choosing, can decide for the wanted result on the background of a visual impression, whereby the app sets the necessary parameters and shows pictures of the current category at the same time. It can also be contemplated that said invention can be integrated with a control for an oven or burner (barbecue) so that sought parameters can be controlled through all of the cooking period without manual adjustment of heat or cooking time. It can possibly be automatic control of an oven or burner (barbecue) so as to obtain the cooking of the meat defined by centre temperature, cooking time and temperature difference through the meat, primarily during slow cooking.