Circuit arrangement for monitoring temperature and calorimetric mass flowmeter

Abstract

A circuit arrangement (1) for monitoring the temperature of an electronic component (2), which, in particular, can be impinged with an electric current and can be connected to at least one voltage source (3). The circuit arrangement is able to guarantee safe monitoring of the temperature of an electronic component impinged with electric current by the electronic component (2) being part of at least one Wheatstone bridge (7) and by at least one switching device (8) being provided that influences the impingement of the electronic component (2) with electric current on the basis of a bridge transverse voltage of the Wheatstone bridge (7). Additionally, circuit arrangement (1) is well suited for use in a calorimetric mass flowmeter (18).

Claims

1. Circuit arrangement for monitoring the temperature of an electronic component which can be impinged with an electric current and which can be connected to at least one voltage source, comprising wherein the electronic component is part of at least one Wheatstone bridge and wherein at least one switching device is provided that influences the impingement of the electronic component with electric current based on a bridge transverse voltage of the Wheatstone bridge, wherein the electronic component is part of at least one redundant Wheatstone bridge and wherein at least one redundant switching device is provided that influences the impingement of the electronic component with electric current on the basis of a bridge transverse voltage of the redundant Wheatstone bridge.

2. Circuit arrangement according to claim 1, wherein the switching device influences an electrical connection between the voltage source and the electronic component on the basis of the bridge transverse voltage.

3. Circuit arrangement according to claim 1, wherein the electronic component has a temperature-dependent electric resistance value.

4. Circuit arrangement according to claim 3, wherein the electronic component has at least one temperature-dependent electric resistance value.

5. Circuit arrangement according to claim 1, wherein the switching device has at least one comparator and a switch, wherein the at least one comparator influences the switch, and wherein, in a switched state, the switch disconnects a connection between the voltage source and the electronic component.

6. Circuit arrangement according to claim 5, wherein the switch is a thyristor.

7. Circuit arrangement according to claim 5, wherein the bridge transverse voltage of the Wheatstone bridge is present at two inputs of the at least one comparator.

8. Calorimetric mass flowmeter having at least one electronic component which can be impinged with an electric current and which can be connected to at least one voltage source, wherein the electronic component is part of at least one Wheatstone bridge of a circuit arrangement, wherein at least one switching device is provided that influences the impingement of the electronic component with electric current based on a bridge transverse voltage of the Wheatstone bridge, wherein the electronic component is part of at least one redundant Wheatstone bridge and wherein at least one redundant switching device is provided that influences the impingement of the electronic component with electric current on the basis of a bridge transverse voltage of the redundant Wheatstone bridge.

9. Calorimetric mass flowmeter according to claim 8, wherein the switching device influences an electrical connection between the voltage source and the electronic component on the basis of the bridge transverse voltage.

10. Circuit arrangement according to claim 8, wherein the electronic component has a temperature-dependent electric resistance value.

11. Circuit arrangement according to claim 10, wherein the electronic component has at least one temperature-dependent electric resistance value.

12. Calorimetric mass flowmeter according to claim 8, wherein the switching device has at least one comparator and a switch, wherein the at least one comparator influences the switch, and wherein, in a switched state, the switch disconnects a connection between the voltage source and the electronic component.

13. Calorimetric mass flowmeter according to claim 12, wherein the switch is a thyristor.

14. Calorimetric mass flowmeter according to claim 12, wherein the bridge transverse voltage of the Wheatstone bridge is present at two inputs of the at least one comparator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of the circuit arrangement as block diagram and

(2) FIG. 2 is a schematic flowmeter in cross-section.

DETAILED DESCRIPTION OF THE INVENTION

(3) A circuit arrangement 1 is schematically represented in FIG. 1, in which the temperature of an electronic component 2 is monitored and in which it is ensured that a certain specified temperature value is not exceeded.

(4) When used in areas at risk of explosion, it is partially necessary to make sure that temperatures are not reached in a component that could lead to a medium igniting in the corresponding area.

(5) Such an increase in temperature could arise in the illustrated arrangement in that the electronic component 2, which is considered in the following to be an electric resistance element, heats up after impingement with electric current from a voltage source 3.

(6) The electronic component 2 is thus at least temporarily electrically connected to the voltage source 3 and is at least temporarily impinged with an electric current from the voltage source 3. The circuit arrangement 1 is used thereby for the purpose of interrupting the power supply in the case that the electronic component 2 reaches a temperature that is too high, in order to prevent further heating.

(7) Here, only one resistance element is shown as electronic component 2. In alternative designs (not shown here), several members or units or components are provided as electronic component 2 and are suitably connected to one another.

(8) The separation between the zone that is at risk of explosion and that, which is safe, is indicated here with a dashed line and both contacts for the electronic component 2 are indicated.

(9) Monitoring the temperature or also ensuring that the temperature does not become too high is implemented here in that the electronic component 2 forms a Wheatstone bridge 7 with three electric resistance elements 4, 5, and 6.

(10) The electronic component 2 and a resistance element 4 are switched in series between the voltage source 3 and ground, for this. The two other resistance elements 5, 6 switched in series are provided parallel thereto, they are also connected to the voltage source 3 and the ground potential.

(11) The resistance elements 4, 5 and 6 are indicated here, as an example, as discreet resistance components.

(12) The resistance element 4 switched in series with the electronic component 1 is also used here for limiting the electric current that flows through the electronic component 1. Thus, the resistance value of this resistance element 4 is also to be chosen in compliance with the protection conditions.

(13) In an unillustrated alternative embodiment, at least one resistance element 4, 5, or 6 is formed of several members or components, which can be described overall by the characteristic of the electric resistance in respect to the circuit arrangement 1 according to the invention.

(14) A switching device 8 is provided for monitoring the bridge transverse voltage of the Wheatstone bridge 7, which is formed here of a comparator 9 and a switch 10. The switch 10 lies parallel to the Wheatstone bridge 7 and is—in respect to the voltage source 3—upstream from the Wheatstone bridge 7.

(15) The switch 10 in the illustrated embodiment comprises a thyristor, which is controlled by the output of the comparator 9 and which opens and closes the electric connection between the voltage source 3 and—here as an example—ground.

(16) Depending on the switched state of the switch 10, thus, the electronic component 2 is either impinged with electric current or the electric connection between the electronic component 2 and the voltage source is interrupted.

(17) The connections between the Wheatstone bridge 7 and the comparator 9, the comparator being implemented here by an operation amplifier, are such that the bridge transverse voltage is present at the inputs of the comparator 9.

(18) In order to increase the reliability of the circuit arrangement 1, the electronic component 2 and the resistance element 4 switched in series with it and two resistance elements 11, 12 parallel thereto and switched in series with one another form a redundant Wheatstone bridge 13, whose bridge transverse voltage is monitored by a redundant switching device 14.

(19) The redundant switching device 14 is designed the same as the switching device 8 in the illustrated embodiment and thus has a comparator 15 and a thyristor as switch 16, which is arranged between the voltage source 3 and ground.

(20) The redundant Wheatstone bridge 13 and the redundancy switching device 14 function principally the same as the Wheatstone bridge 7 and the switching device 8. A certain threshold resistance value of the electronic component 2 also contributes, here, to the power supply being interrupted.

(21) Another fuse 17 is switched upstream in the direction of the electronic component 2 from the voltage source 3 in the shown design.

(22) The circuit arrangement 1 according to the invention of the illustrated embodiment functions overall as follows:

(23) The electronic component 2, which, as an example, is located in a zone at risk of explosion, is impinged with electric current by a voltage source 3, which, here, in particular, is arranged in a zone that is not at risk of explosion.

(24) For this, the electronic component 2 is arranged between the voltage source 3 and ground in the illustrated embodiment.

(25) A Wheatstone bridge 7 is formed by an electric resistance element 4 switched in series with the electronic component 2 and two resistance elements 5, 6 arranged in series with one another and parallel to the electronic component 2.

(26) Thereby, the resistance value of the electronic component 2 is dependent on the temperature of the component 2.

(27) The bridge transverse voltage of the Wheatstone bridge 7 is monitored by a switching device 8.

(28) The resistance elements 4, 5, and 6 are thereby set or chosen so that the switching device 8 interrupts the power supply when a predetermined resistance value of the electronic component 2 is reached, in that it separates the contact between the voltage source 3 and the electronic component 2 with a switch 10.

(29) Thus, if the electronic component 2 reaches a predetermined temperature, then it has an already-known electric resistance value.

(30) The Wheatstone bridge 7 allows the resistance value to be reached or to acknowledge this temperature and to react suitably to it.

(31) If this state is present, the power supply to the electronic component 2 is interrupted and the electronic component 2 can no longer heat up.

(32) If the electronic component 2 has sufficiently cooled down in the illustrated embodiment, then the Wheatstone bridge 7 is sufficiently tuned again and the power supply to the electronic component 2 is reinstated.

(33) Alternatively—not shown here—the return to the impinged state can be prevented by using appropriate designs or components.

(34) In the embodiment shown, one half of the Wheatstone bridge 7 and the switching device 8 are redundantly designed and arranged before the Wheatstone bridge 7 in respect to the voltage source 3.

(35) Thus, the electronic component 2 also forms a part of the redundant Wheatstone bridge 13, whose bridge transverse voltage influences the switch 16 of the redundancy switching device 14.

(36) Closing the electric connection into an electric circuit is implemented in the illustrated embodiment partially via contact of a ground potential.

(37) Thereby, the switching device is generally suitable for monitoring temperature of an electronic component 2 impinged with current, which can be characterized by its electric resistance. This can be relevant, in particular, in use in zones at risk of explosion, in which the exceeding of a certain temperature value is to be prevented.

(38) A particular use of the circuit arrangement 1 is shown as an example in FIG. 2.

(39) FIG. 2 shows a cross-section through a schematically depicted calorimetric mass flowmeter 18.

(40) For this, the electronic component 2, as is shown in FIG. 1, is arranged in a protective tube 19 on the inside of a measuring tube with medium 20 flowing through it—not shown.

(41) For measurement, the electronic component 2, which is, in particular, at least one resistance element here, is impinged with electric current, which leads to a heating of the component 2.

(42) This thermal energy is taken away by the flowing medium, which locally heats up.

(43) This change in temperature can be registered by a temperature sensor—not shown here—arranged downstream in the direction of flow from the electronic component 2.

(44) Finally, the mass flow of the medium can be determined using the output of the thermal component 2, the detected change in temperature, and, preferably, also data about the measuring medium.

(45) A problem arises when there is no medium flow or when the flow of the medium is so small, that the electronic component 2 heats up too much due to a lack of heat removal.

(46) The circuit device 1, which interrupts the power supply to the electronic component 2 when a given temperature value is exceeded and which prevents further heating, is provided here for this situation.