WO2015159107A1

WO2015159107A1 - Adjustment and control of the temperature of any conductive, semi-conductive, superconductive material

Info

Publication number: WO2015159107A1
Application number: PCT/GR2015/000016
Authority: WO
Inventors: Athanasios RAPTIS
Original assignee: Raptis Athanasios
Priority date: 2014-04-16
Filing date: 2015-03-31
Publication date: 2015-10-22
Also published as: GR20140100215A

Abstract

The invention relates to a method for controlling the temperature of the resistance of electric and electronic resistors, where the control is effected by changing the output voltage by an electronic circuit (1). The change in the power supplied to the resistor (2) causes changes to the resistance value (2), allowing the integrated circuit (1), which monitors the resistance continuously, to know the temperature to which each resistance value corresponds. When the desired temperature is achieved, the electronic circuit changes the supplied power so that the resistance value (2), and thus the temperature value, is kept at the desired levels.

Description

DESCRIPTION

"ADJUSTMENT AND CONTROL OF THE TEMPERATURE OF ANY CONDUCTIVE. SEMI-CONDUCTIVE, SUPERCONDUCTIVE MATERIAL" FIELD OF THE INVENTION

The present invention relates to the field of controlling the temperature of a material by electronic devices, as well as a method of achieving the same. STATE OF THE ART

The temperature adjustment method and the temperature control of disclosed herein have been disclosed in the prior art.

Until now, the control of the temperature of various devices is achieved either by the use of thermostats, or by the use of a thermocouple, or a thermistor. This means that, additionally to the operation circuit of a device, there is also a control circuit which has a sensing element and control the temperature, switching the respective circuit on or off depending on the conditions.

In case of a thermostat, when the temperature reaches a user- defined value, the thermostat activates or deactivates the circuit mechanically, by a bimetallic strip, or electromechanically.

Thermoelectric couples or thermocouples are low-cost, high- accuracy temperature detectors. They consist of two wires made of different materials, which are connected at two points.

The operation of the thermocouples is based on thermoelectric effect, or Seebeck effect. In particular, when two different metals are connected at a point, then at this point voltage arises, the thermoelectric voltage or contact potential, and is due to the different extraction work of the metals. However this voltage depends on the temperature, thus, if the two metals are connected at two points which are at different temperature, two different thermoelectric voltages will arise. The difference of the two values is proportional to the temperature difference of the two points. A problem that arises is that the thermoelectric voltage in general is not proportional to the temperature difference at all the temperature ranges, but this is true only for specific narrow temperature ranges. In the specific ranges, it is considered proportional to the temperature difference. Usually, we look up at the respective tables in order to find which temperature corresponds to a specific voltage difference, under consideration of the manufacturing material of the thermocouple also.

Thermistors are also resistors, the resistance of which varies with the temperature, however they present large variations in the value of the resistance. The thermistors are made of oxides of the transition metals of the iron row, such as chromium, manganese, iron, cobalt and nickel. Their resistance varies strongly with temperature but has high tolerance limits - thus temperature measurements are not as accurate as other methods. On the other side, the strong variation of the resistance allows use of the thermistors as switches or current limiters. Thermistors constitute a widely used and cost-effective choice for measuring temperatures.

There are two kinds of thermistors, NTCs i.e. of Negative Temperature Coefficient, and PTCs, i.e. of Positive Temperature Coefficient. In NTCs, resistance decreases as temperature increases, while in PTCs resistance increases as temperature increases. Based on the thermistors, portable temperature detectors have been manufactured.

NTC thermistors present large resistance variations when subjected to small temperature variations. They are used for measuring temperatures between - 00 and 300 °C. The variation of their resistance is determined by the ratio of their resistance at 25 °C to their resistance at 125 °C and is, depending on the model, of the order of 20 to 40. This means that the resistance at 125 °C becomes 20 to 40 times smaller than that at room temperature. The tolerances of the thermistors, ranging ca. 5% depending on the temperature, are much higher than those of the thermoelectric resistances. Thermistors present high stability over time and their resistance at 100 °C varies after 1000 hours of operation by 0,1%. Thermistors present a self-heating effect, i.e. their temperature increases when current passes through them, an increase of the order of 1 °C per 7 mW electric power in their interior.

The disadvantage of the non-linearity of the NTC thermistor resistance versus temperature frequently prevents the use of the thermistors in applications.

The PTC-type thermistors on the side have a resistance that increases with temperature, and in particular they pass from a low- resistance state to a high-resistance state when the temperature reaches a specific value. Thus, they are widely used as current limiters at temperatures between 50 and 250 °C. The resistance of the PTC thermistors range from 0,5 Ω to 20 kQ at room temperature. Since the resistance increases sharply, these thermistors are not suitable for measuring continuous temperature values but for interrupting the power supply to circuits. Thus, they constitute thermosensitive electronic switches. They do not have mechanical parts, contrary to other switches, and therefore they present minimal mechanical wear and a long lifetime. Additionally, they do not present hysteresis and have an extremely low cost. The PTC thermistors are self-heated when electric current passes through them, and this effect is exploited in various applications.

Thermoelectric resistances, thermistors and thermocouples present a non-linear behavior. Thermocouples and thermistors respond rapidly, while thermoelectric resistances respond slowly. Thermocouples do not require an external supply, while thermoelectric resistances and thermistors do require. Thermocouples measure temperatures in a wide range, while thermistors in a narrow one up to 300°C. Thermoelectric resistances have a high cost and the thermocouples a low one. Thermocouples connected in parallel provide at the output low voltages, which are noise-sensitive. In general, they present low sensitivity and lower stability than the other types of sensors.

Thermoelectric resistances provide readings of high accuracy and stability, however the resistance of their connecting wires damages them and should be compensated. Finally, thermistors provice extremely reproducible readings, have a high resolution and require low supply currents. However they present considerable non-linearity.

It is thus an object of the present invention to provide a method for measuring temperatures, which will be performed by the resistor itself without needing any other sensing element.

It is a further object of the present invention to provide a method for measuring temperatures without delays, with direct response to changes and preservation of the temperature at constant and desired levels.

It is a further advantage of the specific invention which can be applied on any electric or electronic device exhibiting resistance, independently of its size. Thus, the method may be applied in ovens, toasters, water heaters, electronic cigarettes, or anywhere else where temperature control is required and a resistance is used.

It is a further advantage of the invention that it allows controlling of the temperature of any conductive or semi-conductive material including, but not limited to, metals, alloys, semi-conductive materials, titanium or even carbon.

These and further objects, features and advantages of the invention will be apparent by the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES AND TABLES

Figure 1 shows an exemplary embodiment of the method with the use of the relevant circuit.

Table 1 shows data of a conductive material, titanium. This table shows the percentage increase in the resistance value depending on the temperature of the material.

DETAILED DESCRIPTION OF THE PROPOSED EMBODIMENT

Referring now to the temperature control method without an external sensing element, we describe exemplary, non-limiting embodiments of the specific method.

By the present invention, the temperature control on a circuit with electric resistance, of any conductive or semi-conductive material, does not require the use of an additional sensing element, but it is achieved by monitoring and control of the resistance itself.

As it is known, any conductive, semi-conductive or superconductive material exhibits a characteristic curve, which shows the variation of the resistance of the material vs. its temperature. Thus, we can derive the resistance of a material from its temperature. For example, in the commercially available electronic cigarettes, the preservation of the supplied power, i.e. of the product of voltage and current, at constant levels, is achieved by increasing or decreasing the voltage on the resistor, monitoring the current passing through it. A problem however arises when there is no combustion liquid to be heated by the resistor. The temperature increases uncontrollably, thus the use will not know the actual temperature at which he smokes. Also, he does not know if the gases produced by the combustion of the liquid in contact with the resistor of the cigarette have been converted to toxic compounds harmful for the human body.

According to the present invention, there is a temperature sensing element which is the resistor itself. Given that a conductive, superconductive or semi-conductive material is used for the resistor, its characteristic curve is known and thus the resistance value is known for each respective temperature. According to the present invention, the continuous measurement of the resistance allows complete control of the temperature of the resistor.

For the application of the method, the output voltage of the integrated circuit (1) is substantially influenced, by the use of a voltage increase/decrease converter, or any other suitable circuit, figure 1, and the current flowing to the resistance (2) from the power source (3) is adjusted. In this way, both the power consumed on the resistor (2) and the temperature of the resistor (2) are substantially determined -since as it was mentioned above, if the manufacturing material of the resistor is known, the characteristic resistance-temperature of the material is known, and thus we know the temperature developed on the resistor (2) itself.

In this way, the user may pre-set the temperature at which the resistor (2) of the circuit will operate, and without the use of a temperature sensing element, the control is effected simply by supplying the suitable current on the resistor (2). In this way, the temperature may be kept constant without consuming more power than the required, thereby ensuring reduced consumption of the power source (3).

Exemplarily, in an embodiment, we supply a reference voltage from the battery (3) and by means of the current we obtain the resistance value (2) at room temperature. In this way, we obtain a reference value. Suppose that as material for the resistor titanium has been used, table 1, without being limited to it for the use of any other suitable material. If the user intends to achieve a temperature of 150°C on the resistor, an increase of 49.40% must be achieved on the resistance, in relation to the reference value. The integrated circuit (1) supplies voltage increasing the value until a resistance value is measured that corresponds to the temperature of 150°C. Thereafter, it keeps the value of the supplied voltage constant, so that the resistance value and the temperature value are kept constant respectively. In order to keep this variation, the system increases or decreases the voltage suitably, depending on the load, i.e. of the combustion liquid, imposed on the resistor. If for example the electronic circuit has been set to keep the temperature of the resistor constant at 100°C, and then the resistor is immersed in water of 20°C, the electronic circuit will sense immediately the start of the temperature drop, and will supply large power to the resistor, in an attempt to keep the temperature it had before being immersed in water. When, after a time period of power supply, the water reaches the temperature of the resistor, the electronic circuit undertakes to keep the temperature constant, reducing the supplied power, since as it is known the maintenance of the temperature requires much smaller power than for its increase. When finally the water starts to evaporate (and thus its quantity is reduced), the electronic circuit starts to reduce the supplied power even further, since as it is also known, the smaller the volume of the water (or any other material in general), the less energy required for keeping at the same temperature. In this way, as it is apparent, the electronic circuit adjusts the power supplied to the resistor continuously and always according to the needs of the load, so that in any case only the necessary power required to keep the preset temperature is consumed. As it is apparent from the specific method, the consumption of current and power by a circuit is significantly reduced, given that only current required to achieve the individually necessary temperature is supplied to the circuit, while in parallel it is ensured accurately that this will be kept at the desirable levels.

It should be noted that the description of the invention was made with reference to an exemplary, non-limiting embodiment. Any variation or modification as regards shape, dimensions, morphology, type of power energy, manufacturing and assembling materials and components used, as long as they do not constitute a new inventive step and do not contribute to the technical progress of the already known, are considered as encompassed in the scope of the present invention, as summarized in the following claims.

Table 1

Claims

1. Adjustment and control of the temperature of any conductive, semi-conductive, superconductive material, characterized in that a device consisting of the said material (2) achieves the desired temperature by means of an integrated circuit (1), by the use of a voltage increase- decrease converter, which varies the value of the voltage supplied from a power source (3), so that a temperature value is achieved that corresponds to an individual resistance value of the material (2).