DE102010003125A1 - Device for temperature measurement of heater in automobile industry, has sensor consisting of hybrids, where hybrids consist of temperature-dependent resistor i.e. platinum resistor, and thermo-couples - Google Patents

Abstract

The device (100) has a sensor (21) consisting of hybrids (21a), where the hybrids consist of a temperature-dependent resistor (23) i.e. platinum resistor, and thermo-couples (23a, 23b) i.e. accumulators. Metals or metal alloys (24, 25) are contacted at both ends of the resistor and possess the form of a wire or a strip guard. The sensor is electrically connected with a measuring input (26) of a circuitry (22) of the device by a 2-wire connection, where the circuitry has a passive component (31) and/or an analog digital converter (ADC) (28) and/or a microprocessor (33). An independent claim is also included for a method for determination of temperature values.

Description

The invention relates to a device for measuring temperature, comprising at least one sensor.

The invention further relates to a method for determining temperature values.

Devices for measuring the temperature of the specified type win in heaters for the automotive industry, eg. As parking heaters, increasingly important. The temperature measurement in heaters such. B. Parking heaters is primarily for the purpose of temperature control. Due to high requirements of the legislator for electronic circuits in the automotive industry, such temperature measurements are safety-relevant measuring processes with high requirements for protective measures. It is Z. B. required, in addition to the temperature measurement, which takes place for the purpose of temperature control of a heating circuit, as an independent protective measure to ensure the provision of overheating protection. In addition, with regard to the EMC (Electromagnetic Compatibility) strength in the automotive industry very high demands are placed on electronic assemblies. In auxiliary heaters for the automotive industry, the use of electromechanically acting thermal circuit breakers is known. Usually, such auxiliary heaters are equipped with at least two mechanical components, which have a secure thermal contact with the medium and are electrically effectively integrated, so that they react independently of temperature changes. Such a measuring device is integrated by at least two connectors and four contact points in a heater. Such a measuring device can be implemented only with very high mechanical effort.

The DE 10 2006 012 957 C5 describes a method of providing overheat protection for a heater using two temperature sensors. The temperature measurement takes place by means of two temperature sensors, wherein both temperature sensors have a different thermal inertia from each other. The method described already reduces the effort compared to the structure of electromechanically acting thermal circuit breakers already considerably. The disadvantage, however, is that external influences affect both sensors equally and thus could go undetected. So there is a risk that parasitic resistances occur. Another problem is the aging of the probes, since both probes are exposed to the same temperature stress and age the same. Another disadvantage is the relatively high circuit complexity, since the two temperature sensors must be routed to two separate measuring inputs of the circuit. An arrangement for the described temperature measuring method could thus be realized only with at least three contact points and a relatively high circuit complexity.

The invention has for its object to provide a device for measuring temperature and a method for the determination of temperature values are available, wherein the temperature data can be determined by two different and independent measurement methods and the device with minimal circuit complexity is feasible.

This object is achieved with a device for measuring temperature according to the features of claim 1 and a method for determining temperature values according to the features of claim 18.

After that, the device for temperature measurement described at the beginning has at least one temperature sensor. Furthermore, the sensor is constructed of a hybrid, which consists of at least one temperature-dependent resistor and at least one thermocouple. Thus, based on the device according to the invention, it is possible to carry out a temperature measurement in two completely different ways. On the one hand, the temperature with the aid of the temperature-dependent resistor can be determined by measuring the voltage drop across the temperature-dependent resistor and correspondingly evaluating it. In a second temperature measurement, the voltage resulting from the influence of temperature on the thermocouple can be measured and evaluated accordingly. This ensures that different temperature measurement materials are used in both temperature measurements. Thus, the device according to the invention has a very high safety standard. A decisive advantage of this device is that the aging behavior of both temperature measurements is directed against each other, so that this can be detected safely and early depending on approved tolerances. In addition, it is possible to reliably detect parasitic resistances on the way from the sensor to the measuring input both against ground and against plus. Furthermore, the device according to the invention has the advantage of checking the thermal contact and thus reliably determining insufficient contact with the medium. Such a test is of great importance especially when used in a parking heater. In practice, it often happens that the cooling medium is not or not sufficiently available and thus the removal of heat or not insufficiently possible. In such cases, it overheats and thus damage to equipment or individual components. Another important advantage of the device according to the invention is the simple and inexpensive construction of the probe, since it consists of only one temperature-dependent resistor and thus requires only a single connection for the evaluation of the two measurement results.

It is preferred that the sensor is constructed of a hybrid consisting of at least one temperature-dependent resistor and at least two thermocouples.

Preferably, a typical platinum resistance is chosen for the temperature-dependent resistor. In this case, the platinum resistance known from the prior art resistance rating such. PT100, PT500, PT1000, PT2000 or other resistance ratings at 0 ° C. In principle, the temperature-dependent resistance could also consist of any other temperature-dependent material.

It is also preferable to contact at the ends of the temperature-dependent resistor in each case a metal or a metal alloy. Thereby, the contact point between the temperature-dependent resistor and the contacted metal or metal alloy is fixed.

It is also preferable to contact the metals or metal alloys in the form of a wire or wire-like form at the ends of the temperature-dependent resistor. Furthermore, it is possible to contact the metals or metal alloys in the form of a conductor or a track-like shape. In principle, however, the metals or metal alloys could also have a completely different shape.

In order to be able to use as simple a circuit as possible, it is preferable to connect the sensor with only two lines to a reference point and a single measuring input of the circuit. This has the considerable advantage that the plug connection between the measuring sensor and the circuit, in contrast to the measuring devices known from the prior art with three-wire or multi-core connections, is reduced to a two-core connection only. Thus, it is sufficient to use a circuit with only one measuring input. The reduction of the connectors to a two-wire connection and the associated reduction of the measuring inputs of the circuit to only one measuring input lead to a decisive cost advantage. In addition, thus, the size of the measuring device is reduced considerably.

To create an element which generates an electrical voltage under the influence of temperature, it is preferred that the two metals or metal alloys are selected and contacted at the two ends of the temperature-dependent resistor so that in each case a thermocouple is formed.

Furthermore, it is preferred that the two metals or metal alloys are chosen such that a thermocouple generates a positive electrical voltage when heated.

Preferably, the two metals or metal alloys are selected such that the two forming at the contact points thermoelements equivalent but opposite to each other behave. This ensures that the resulting voltage between the two thermocouples reaches as high a value as possible. As a result, the resolution and the measurement accuracy of the temperature measurement can be increased.

Similarly, it is further preferred that the sensor with its two thermocouples behave like a battery. In this case, the sensor on a Urspannungswiderstand in the amount of a temperature-dependent resistor. Thus, the sensor generates an electrical voltage which depends on the temperature.

According to a further preferred embodiment of the invention, the circuit components such. As passive components, integrated circuits, analog-to-digital converters and microprocessors. Ideally, the circuit consists of at least one passive component such. As a resistor, an analog-to-digital converter and a microprocessor. Alternatively, the analog-to-digital converter can be saved and a microprocessor with corresponding analog input and internal analog-to-digital converter can be used. The measurement accuracy of a measurement depends essentially on the absolute accuracy of the passive components, eg. As the resistance, its temperature coefficient, and the offset behavior of the analog-to-digital converter. In contrast, the temperature resolution is essentially dependent on the resolution of the analog-to-digital converter. Thus, it is possible to determine the resolution and the measurement accuracy by selecting the corresponding components. In addition, such a circuit provides the ability to detect any errors before operation. It is Z. B. possible to detect an insufficient or missing contact of the measuring device with the medium early.

Preferably, the circuit has a switch or a device equivalent to the behavior of a switch. Thus it is It is possible to choose or switch between the two measuring methods and to activate the desired measuring method. It is also possible to continuously switch between these two measuring methods with an automatic control.

In another alternative embodiment, a circuit is provided which has only a single measuring input and is connected via this to the measuring sensor.

Furthermore, an advantageous embodiment of the invention, as an internal voltage source to use the reference voltage of the analog-to-digital converter. Thus, it can be avoided that voltage fluctuations of the reference voltage source lead to falsification of the measurement results.

It is preferred that an analog-to-digital converter with a resolution of at least 16-bit be used for the circuit. Thus, in the temperature measurement based on the resistance measurement method, temperature resolutions below 0.1 ° K can be made possible. Since the thermocouples generate relatively small voltages in the voltage measurement method, the choice of an analog-to-digital converter with such a high resolution ensures that these small voltages can be detected with the required accuracy.

It is particularly useful to use two or more microprocessors for the circuit. It should be mentioned that more than one microprocessor is not necessary for the function and the execution of the two measuring methods, but the use of a further microprocessor has the advantage of taking into account additional functions as well as other safety-relevant features. It is Z. B. conceivable that the calculation of the temperatures from the two measurement methods and the corresponding integrity check by both microprocessors is done separately, the control of the temperature supply or temperature dissipation, z. B. by a solenoid valve for the release of a fuel flow, by an electrical or logical combination of the two independently determined temperatures. Also conceivable are far more complex procedures. Under the influence of strong electromagnetic fields, the temperature detection could still work by one of the two methods, while the other method already fails. In this case, to allow trouble-free operation, the temperature control could be performed for a limited time based on the still functioning measurement method. In this case, a corresponding error offset could also be taken into account in order to ensure the accuracy based on only one measurement method. Such an error offset can be obtained for the respective measurement method during the time, while both measurement methods function without error. Continuous comparison of the two independently determined temperature values as well as continuous plausibility checks allow the determination of such error offsets and the reliable detection of possible problems of one of the two measuring methods.

Furthermore, if two or more microprocessors are used, it is useful to connect them together and allow communication among each other.

When using a plurality of microprocessors, it is also preferred to carry out the activation of the switch or of an equivalent component by one of the two microprocessors. Such control leads to further increase the security. The selection of the measuring method or the duration of the measurement could be determined by the microprocessor depending on certain conditions or factors. Thus, more complex links of several conditions or factors are conceivable. Furthermore, a timer could be realized by the use of timers in the microprocessor. By such a timing z. For example, ensure that both measurement methods are activated at scheduled intervals and for a defined measurement duration. This also has the advantage that z. For example, the temperature measurement based on the resistance method is performed with a much shorter measurement time as compared with the temperature measurement based on the voltage measurement method. Thus, the platinum resistance is traversed over a much shorter period of time than in known by the prior art method with current. This, in turn, allows a much larger current to be passed through the platinum resistor over this shorter time to produce the same self-heating. As a result, the measurement accuracy and the resolution of the temperature measurement can be increased.

• a) Messung eines Widerstandswertes eines temperaturabhängigen Widerstandes nach Anlegen einer Referenzspannung und Ermittlung eines daraus resultierenden Temperaturwertes.
• b) Messung einer Spannung an Thermoelementen unter Ermittlung eines daraus resultierenden Temperaturwertes.

The method according to the invention for determining temperature values is carried out as follows:

• a) Measurement of a resistance value of a temperature-dependent resistor after application of a reference voltage and determination of a resulting temperature value.
• b) Measurement of a voltage on thermocouples with determination of a resulting temperature value.

• c) Generierung eines oder mehrerer Signale durch elektrische/logische Verknüpfung der ermittelten Temperaturwerte.
• d) Steuerung einer Temperaturzufuhr oder Temperaturabfuhr durch das oder die generierten Signale.
• e) Ansteuerung einer sicherheitsrelevanten Schaltung.

Preferably, the method for the determination of temperature values is followed by a generation of one or more signals for the purpose of temperature control and / or activation of safety-relevant circuits, for example Legs Overheat protection circuit, on. This procedure could be performed with the following steps, whereby the order of the individual steps can be changed:

• c) Generation of one or more signals by electrical / logical combination of the determined temperature values.
• d) controlling a temperature supply or temperature dissipation by the generated signal (s).
• e) control of a safety-related circuit.

In the described method for determining the temperature values, the order of the individual measuring steps is not important. In particular, the measuring steps a and b described above could also be carried out in the reverse order. In addition, it would be possible to perform only one of the two measurements a or b and to control the temperature supply or the removal of temperature depending on the determined temperature value based on the selected method. In order to carry out the two measurements a and b, the same device is used in each case, the corresponding measuring method being selected with a switch or an equivalent component. The design of the sensor and the choice of measuring method ensures that both measurements are based on different methods and that different materials are used to determine the temperature values. This has the advantage that signals for the purpose of temperature control and signals to provide overheating protection are generated by independent methods. In addition, the safety of the process is increased by linking the two results of the different measurement methods. Furthermore, it is possible to reliably detect any errors in one of the two measuring methods.

Preferably, the two independently determined temperature values are compared with one another after measurement a and b for the purpose of a plausibility check. Thus, measurement errors that have occurred in one of the two methods can be detected. Since both measurements are based on different methods and use specially selected different materials, a plausibility check can detect measuring errors even if both measurements have errors at the same time.

It is particularly useful to control the two measurements a and b by a time control. It is thus possible to repeat the two measurements at specific intervals and to individually control the duration of the individual measuring processes. This has the advantage that z. B. the duration of the load of the temperature-dependent resistor during the resistance measurement can be minimized. In addition, it is thus possible to perform the voltage measurement on the thermocouple with sufficient duration, so z. B. ensures that the voltage in practice strongly filtered measuring input in an e-function can approach the actual voltage of the thermocouple.

In order to take into account the different properties of the two methods and the corresponding materials, it is advantageous to carry out the measurement a with a shorter duration compared to measurement b.

It is particularly advantageous if the duration of the measurement a is chosen to be only in the order of magnitude of 1% in relation to the total measurement duration of the measurements a and b. This minimizes the duration of the current load on the temperature dependent resistor and thus allows up to a 100 times higher current to maximize the accuracy and resolution of the temperature measurement.

In another, alternative embodiment it is provided that one of the two measurements a or b is used to determine the temperature in the circuit itself. This has the advantage that in addition to the actual temperature measurement, the temperature within the circuit can be monitored. Based on this additional information obtained, any measures, such. B. shutdown of a function or system or switching on a cooling introduced.

The invention will now be described by way of example with reference to the accompanying drawings by way of particularly preferred embodiments.

Show it:

1 a block diagram of a conventional device for temperature measurement;

2 a block diagram of a device according to the invention for temperature measurement;

3 a schematic representation of the temperature sensor according to the invention;

4 a block diagram of the device according to the invention for resistance measurement; and

5 a block diagram of the device according to the invention for voltage measurement.

1 shows a block diagram of a device known from the prior art for Temperature measurement, as z. B. is used in parking heaters. Such a device usually consists of two platinum resistance sensors 13 . 14 that has three separate lines 10 . 11 . 12 at a reference point 10a as well as two measuring entrances 15 . 16 with a circuit 14a are electrically connected. The two measurement input signals of the circuit are each connected via a separate analog input to a microprocessor 17 guided. Alternatively, both measurement input signals via upstream analog-to-digital converters to a microprocessor 17 be guided. The microprocessor 17 serves for further processing or evaluation of the two temperature values. Bypassing the microprocessor 17 evaluates a comparator 18 also the temperature at a platinum resistance sensor 14 out. That through the comparator 18 determined signal 20 can z. B. be used to implement an overheating protection signal. The microprocessor 17 assumes the tasks of further data processing for the purpose of temperature control. In addition, it is possible that the microprocessor 17 a signal 20 generated for controlling a safety-relevant switch for the purpose of overheating protection and via an output amplifier 19 outputs.

2 shows a block diagram of a device according to the invention 100 for temperature measurement. The measuring arrangement according to the invention consists of a measuring sensor 21 and a circuit 22 , which is used for further processing and evaluation of the measured values.

The sensor 21 consists of a typical platinum resistor 23 as well as two thermocouples 23a . 23b , The two thermocouples 23a . 23b arise by contacting special metal alloys 24 . 25 with the two electrodes of the platinum resistor 23 , The contacting with the platinum electrodes is not carried out as usual by means of copper wires.

The temperature sensor 21 comes with a two-wire connection 26 . 27 with a reference point 29 , z. B. ground and a single measuring input 26 the circuit 22 with the input of an analog-to-digital converter 28 connected. Such an analog-to-digital converter 28 has a high-impedance measuring input. A reference voltage 30 goes to the analog-to-digital converter 28 placed, which also serves as a voltage source for the resistance measurement. The resistance 31 is needed for resistance measurement. With the switch 32 You can choose between two different measuring methods. With the switch closed 32 the temperature is determined by means of resistance measurement. When the switch is open 32 the temperature is determined by means of voltage measurement. The two different measuring methods, resistance measurement and voltage measurement, for determining the temperature become the 4 and 5 described in more detail. The output of the analog-to-digital converter 28 is with the microprocessor 33 connected. The microprocessor 33 is used for evaluation or further processing of the measured values. Depending on the chosen measuring method, the microprocessor evaluates 33 the measured value and thus determines the current temperature. The determined temperature value is used to control the desired temperature as well as to generate a signal 34 for overheating protection. That through the microprocessor 33 depending on the measured temperature determined control signal 34 used to release a safety-relevant actuator, eg. B. a solenoid valve for the release of a fuel flow. With the help of in 2 Thus, the temperature data are determined based on two different methods by the use of different materials.

3 shows a schematic representation of a sensor according to the invention 21 ,

The sensor 21 consists of a typical platinum resistor 23 , z. Pt100, Pt500, Pt1000, Pt2000 or other resistance values at 0 ° C, as well as two thermocouples 23a . 23b , The contacting of the platinum electrodes is not carried out as usual by means of copper wires, but with special metal alloys 24 . 25 , The two contact points between platinum resistance 23 and metal alloy 24 . 25 each form a thermocouple 23a . 23b , The choice of metals 24 . 25 takes place in such a way that the metal A 24 at the contact point with the platinum resistor 23 a thermocouple 23a forms, which generates a positive voltage when heated compared to a reference junction. Metal B 25 is chosen such that it is at the point of contact with the platinum resistor 23 a thermocouple 23b forms, which generates a negative voltage when heated and is equivalent to the thermocouple 23a between the platinum resistance 23 and the metal A 24 behaves. In total, you get a battery of two thermocouples 23a . 23b with an additional primary resistance equal to the platinum resistance 23 ,

4 shows a block diagram of an inventive arrangement for measuring the resistance of the temperature sensor 21 , A typical platinum resistor 23 will have a connection 25 with a reference point 29 , z. B. mass, as well as via a line 24 with a measuring input of a circuit 22 connected. Through a closed switch 32 becomes a voltage divider from the series resistors 23 . 31 educated. For this serves as a voltage source, the reference voltage 30 of the analog-to-digital converter 28 , The resistance of the platinum resistor 23 depends on the Temperature. The determination of this resistance value is made by a typical ratio equation of the voltage drops across the resistors 23 . 31 , The voltage drop across the known resistor 31 behaves proportionally to the unknown resistance 23 , The voltage drop across the platinum resistor 23 is from the measuring circuit via line 24 connected to a high-impedance input of the analog-to-digital converter 28 connected, tapped. To achieve the highest possible temperature resolutions, an analog-to-digital converter is used 28 with at least 16-bit resolution selected. Temperature resolutions within 0.1 ° K are possible with such a 16-bit converter. The determined value is used for evaluation, for checking the signal integrity and for further processing to a microprocessor 33 passed. In order to perform the described resistance measurement correctly, the switch must 32 be turned on for each measurement only for a very short time. Due to the short duty cycle, it is possible higher currents due to the platinum resistance 23 to conduct as these by the manufacturer of platinum resistance 23 in the data sheet. Thus, the self-heating of the platinum resistance 23 be kept low and a good resolution of the measured values can be achieved. As voltage source for the resistance measurement, the reference voltage source of the analog-to-digital converter 28 voltage fluctuations of the reference voltage source do not lead to falsification of the measurement results. The measurement accuracy based on the described method and the described arrangement becomes substantially of the absolute accuracy of resistance 31 , its temperature coefficient, as well as the offset behavior of the analog-to-digital converter 28 certainly.

5 shows a block diagram of an inventive arrangement for measuring the voltage of the thermocouple 36 , The two thermocouples 23a . 23b , which are formed at the contact points between platinum electrode and metal alloy, are summarized in the diagram and as a thermocouple 36 shown. As in 3 already described results from the two thermocouples 23a . 23b a behavior of a battery whose voltage depends on the temperature. The thermocouple 36 is over a line 25 with a reference point 29 , z. B. mass, and a line 24 connected to the input of a measuring circuit. When the switch is open 32 is at the high-impedance input of the analog-to-digital converter 28 that of the thermocouple 36 generated voltage measured. In this arrangement, the resistor has 31 no meaning. To also very small voltages of the thermocouple 36 becomes an analog-to-digital converter 28 with high resolution (16-bit and higher) selected. The analog-to-digital converter 28 has a high-impedance measuring input. For this reason, during the voltage measurement, the internal resistance of the thermocouple 36 neglected and does not contribute to the falsification of the measurement results. For evaluation of the measured values, for checking the signal integrity and for further processing, the determined value is sent to a microprocessor 33 forwarded.

The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

100

Device for temperature measurement

10

connecting line

10a

reference point

11, 12

connecting line

13, 14

Platinum RTD

14a

circuit

15

Trade fair entrance 1

16

Fair entrance 2

17

microprocessor

18

comparator

19

output amplifier

20

control signal

21

probe

21a

Hybrid

22

circuit

23

temperature-dependent resistance / platinum resistance

23a, 23b

thermocouple

24

Metal A / pipe / connection

25

Metal B / wire / connection

26, 27

Connecting line / measurement input / two-wire connection

28

Analog to digital converter

29

reference point

30

reference voltage

31

resistance

32

switch

33

microprocessor

34

control signal

35

CJC

36

thermocouple

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006012957 C5 [0004]

Claims (28)

Contraption ( 100 ) for temperature measurement, comprising at least one sensor ( 21 ), characterized in that the sensor ( 21 ) from a hybrid ( 21a ) and the hybrid ( 21a ) of at least one temperature-dependent resistor ( 23 ) and at least one thermocouple ( 23a . 23b ) consists. Device according to claim 1, characterized in that the hybrid ( 21a ) of at least one temperature-dependent resistor ( 23 ) and at least two thermocouples ( 23a . 23b ) consists. Device according to one of claims 1 or 2, characterized in that the resistor is a platinum resistor ( 23 ). Device according to one of claims 1 to 3, characterized in that at both ends of the resistor ( 23 ) each metal or a metal alloy ( 24 . 25 ) is contacted. Device according to one of claims 3 or 4, characterized in that the metals or metal alloys ( 24 . 25 ) have the form of a wire or a conductor track or have a wire-like or conductor track-like shape. Device according to one of the preceding claims, characterized in that the measuring sensor ( 21 ) by means of a 2-wire connection with a measuring input ( 26 ) a circuit ( 22 ) of the device ( 100 ) and a reference point ( 29 ) is electrically connected. Device according to one of claims 3 to 6, characterized in that the two metals or metal alloys ( 24 . 25 ) at their contact points with the temperature-dependent resistor ( 23 ) a first and a second thermocouple ( 23a . 23b ) form, each generating an electrical voltage under the influence of temperature. Apparatus according to claim 7, characterized in that the first thermocouple ( 23a ) generates a positive electrical voltage when heated. Device according to one of claims 7 or 8, characterized in that both thermocouples ( 23a . 23b ) behave equivalently but opposite to each other under the influence of temperature. Device according to one of claims 7 to 9, characterized in that the sensor ( 21 ) with its two thermocouples ( 23a . 23b ) how a battery behaves, the sensor ( 21 ) has an additional original resistance, the height of the height of the temperature-dependent resistance ( 23 ) corresponds. Device according to one of claims 6 to 10, characterized in that the circuit ( 22 ) at least one passive component ( 31 ) and / or at least one integrated circuit and / or at least one ADC (Analog Digital Converter) ( 28 ) and / or at least one microprocessor ( 33 ) having. Device according to one of claims 6 to 11, characterized in that the circuit ( 22 ) a switch ( 32 ) or the behavior of a switch ( 32 ) has equivalent component selected with the between two different measurement methods and / or can be changed. Device according to one of claims 6 to 12, characterized in that the circuit ( 22 ) only a single measuring input ( 26 ) with the sensor ( 21 ) connected is. Device according to one of claims 11 to 13, characterized in that the circuit ( 22 ) a reference voltage ( 30 ) provides the ADC ( 28 ) is removable. Device according to one of claims 11 to 14, characterized in that the circuit ( 22 ) an ADC ( 28 ) with at least 16-bit resolution. Device according to one of claims 11 to 15, characterized in that the circuit ( 22 ) two or more microprocessors ( 33 ) having. Device according to one of claims 11 to 14, characterized in that the circuit ( 22 ) two or more microprocessors ( 33 ) which communicate with each other. Device according to one of claims 12 to 17, characterized in that the control of the switch ( 32 ) or the equivalent component by the microprocessor ( 33 ) is feasible. Method for determining temperature values, comprising the steps of: a) measuring a resistance value of a temperature-dependent resistor ( 23 ) after applying a reference voltage ( 30 ) and determination of a resulting temperature value, b) measurement of a voltage at thermocouples ( 23a . 23b ) and determination of a resulting temperature value. A method according to claim 19, characterized in that at least one signal for the purpose of temperature control and / or the control of safety-relevant circuits is generated and the following steps are performed: c) generating one or more signals ( 34 ) by electrical / logical combination of the determined temperature values, d) control of a temperature supply or temperature discharge by the generated signal or signals ( 34 ), e) control of a safety-relevant circuit. A method according to claim 19, characterized in that the independently determined temperature values for the purpose of a plausibility check are compared. Method according to one of claims 19 to 21, characterized in that the measurements in steps a) and b) are repeated by a time control in previously defined intervals. Method according to one of claims 19 to 22, characterized in that the duration of the measurement in step b) is longer than in step a). Method according to one of claims 19 to 23, characterized in that the duration of the measurement in step b) is at least 10 times longer than in step a). Method according to one of claims 19 to 24, characterized in that the duration of the measurement in step b) is at least 50 times longer than in step a) Method according to one of claims 19 to 25, characterized in that the duration of the measurement in step b) by at least 99 times longer than in step a). Method according to one of claims 19 to 26, characterized in that one of the two measurements a or b for determining the temperature of the circuit ( 22 ) is used. Use of a device according to claims 1 to 19 for a heater.

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