DE102007047309A1 - Device for determining and / or monitoring a process variable - Google Patents

Abstract

The invention relates to a device for determining and / or monitoring at least one process variable, with at least one electronic unit (1) which is supplied with electrical energy at least at times via at least one current / voltage input (2), wherein for the operation of the electronic unit (1) a minimum voltage value for a voltage present at the current / voltage input (2) voltage is specified, wherein at least one voltage regulator (5) is provided, which is subjected to at least a feedback voltage and which in the case that the feedback voltage to the voltage regulator (5) predetermined voltage threshold falls below, which is dependent on the for the operation of the electronic unit (1) predetermined minimum voltage value, a shut-down of at least a part of the electronic unit (1) performed and / or which in this case the starting of at least a part of Electronic unit (1) prevents at least a circuit (6) is provided which influences the magnitude of the feedback voltage, and wherein the magnitude of the feedback voltage is adjustable as a function of the energy requirement of the electronic unit (1).

Description

The The invention relates to a device for determination and / or monitoring at least one process variable. at the process variable is For example, it is level, Pressure, density, viscosity, Flow or pH of a medium. The medium is, for example a liquid, a gas or a bulk material. The process size is in this case, for example, in a container or in a pipe system measured.

In process measuring technology are known as two-wire measuring devices, in which the signaling of the measured value and the power supply of the measuring device over the same interface takes place. The measuring signal is at least on the amperage coded. 4 to 20 mA signals are known here. Error conditions of the meter are For example, this indicates that the stream has a value outside the signaling interval of 4 to 20 mA. Preferably the current value is below the lower limit, so for example at 3.6 mA.

A such linkage between the signaling of the measured value or of error states and The energy supply brings with it that even when present of the lowest current value, operating the measuring device or especially its electronics possible have to be. Because the lowest current given by regulation is, therefore, for the meter defines a minimum voltage value when exceeded the meter only completely can work. This minimum voltage value usually refers to this to the maximum power requirement available to the meter can, d. H. at more complete Use of for the meter provided power consuming peripherals and in the application under all conditions related to energy consumption.

Vice versa is it for the user or for the Use case may be advantageous if already a lower voltage sufficient.

Of the Invention is based on the object, a measuring device with a Electronic unit to propose, which allows the required for the electronic unit minimal voltage depending on application decrease.

The Invention solves the task with a device for determining and / or monitoring at least a process variable, with at least one electronic unit, which at least temporarily over at least a current / voltage input with electrical energy is supplied, wherein for the operation of the electronic unit a minimum voltage value for a voltage applied to the current / voltage input is specified, wherein at least one voltage regulator is provided, which at least is applied with a feedback voltage, and which in the Case that the feedback voltage is a predetermined voltage regulator Voltage limit falls below, which depends on the for the operation the electronic unit is predetermined minimum voltage value, performs a shutdown of at least a portion of the electronics unit and / or which in this case starting at least a part of the electronic unit prevented, wherein at least one circuit is provided, which the size of the feedback voltage influenced, and where the size of the feedback voltage dependent on is adjustable by the power requirement of the electronic unit. In the electronic unit according to the invention There is thus a voltage regulator which monitors whether at least part of the electronics unit with the required Voltage is supplied. Therefore the voltage regulator compares a feedback voltage with a voltage value, which with the for the electronics unit as minimum specified voltage value in Relationship stands. If the feedback voltage falls below this value, so leads the voltage regulator does a shut-down prevents or prevents that at least a part of the electronic unit started becomes. This feedback voltage according to the invention according to the energy requirements the electronics unit is adjusted, d. H. depending on what voltages are required learns the voltage regulator another feedback voltage and thus leads, for example the shutdown at another voltage applied to the electronics unit voltage than at the tension, for the voltage regulator has a comparison value. It will thus the voltage regulator is supplied with such a feedback voltage, that, for example, fewer consumers the operation of the electronics unit even at a lower voltage applied to the electronics unit voltage takes place.

A Embodiment provides that the electronic unit designed in such a way is that over the power / voltage input both the power supply of the electronics unit as well as the output of a measurement signal for the process variable. At the meter or the electronic unit is thus a so-called. Two-wire device.

An embodiment includes that at least one control unit is provided which adjusts the feedback voltage as a function of the energy requirement of the electronics unit. Thus, for example, if the electronics unit requires less energy than is associated with the minimum voltage value, then the feedback voltage may be increased so that the voltage regulator assumes a higher voltage and therefore already begins operation at least a part of the electronic unit with a low effective voltage allows or does not shutdown executes. If it is thus recognized that a lower voltage is sufficient for the operation of the electronics unit, then the voltage regulator is adjusted in such a way that it only performs the shutdown at a lower voltage or allows the electronic unit to be operated even at a lower voltage.

A Embodiment provides that the control unit designed such is that the control unit in the event that the power requirement the electronics unit is below the value, which with the predetermined minimum voltage value is connected, the feedback voltage elevated. In other words, according to the invention, the voltage regulator becomes a feedback voltage which is above the feedback voltage, which actually associated with the voltage applied to the electronics unit voltage would. Consequently causes a comparison of the feedback voltage with the value at which Falls below the voltage regulator executes a shut-down or if it is exceeded at least the part of the electronics unit connected to the voltage regulator work, not that the voltage regulator intervenes, d. H. He reacts only at a significantly lower voltage than actually considering all peripherals and full scope for the Electronic unit was meant.

A Embodiment includes providing at least one voltage divider is, wherein the voltage divider ratio of the voltage divider the feedback voltage depends, and wherein the voltage divider ratio of the voltage divider dependent on is adjustable by the power requirement of the electronic unit.

A Embodiment provides that the control unit in dependence from the energy requirement of the electronic unit, the voltage divider ratio of the voltage divider established.

A Embodiment includes providing at least one consumer is that and that the consumer is designed in such a way that the Consumers are either active or inactive State, wherein the active state is that the Consumer through the electronics unit with electrical energy is supplied. For example, consumers are an LED display to an external display or even to the actual Sensor unit for measurement or monitoring the process size.

A Embodiment provides that the control unit designed such is that the control unit queries whether the at least one consumer is in the activated or deactivated state.

A Embodiment includes that the control unit in dependence of whether the at least one consumer is in the activated or in the inactivated state and / or depending on the working conditions, under which at least a part of the electronic unit works, the Adjusts feedback voltage. Is at least one consumer inactive, d. H. if it does not consume power, then the required Reduce tension.

A Embodiment provides that at least one working condition refers to the temperature, which in at least part of the electronics unit prevails.

A Embodiment includes that at least one temperature sensor provided is that the control unit is connected to the temperature sensor, and that the control unit based on the measured value of the temperature sensor adjusts the feedback voltage.

A Embodiment provides that the control unit in the event that the at least one consumer is in the inactivated state, the Feedback voltage increased.

A Embodiment includes that it at the control unit to a microcontroller acts.

A Embodiment provides that the control unit, the voltage divider ratio of Voltage divider over adjusts a resistance, which with a port of the microcontroller connected is.

A Embodiment includes that the at least one consumer via a Adjustable resistance, which depending of whether the at least one consumer is activated or inactive State is, the feedback voltage sets. In this embodiment takes over the consumer is self-acting the adjustment of the feedback voltage and thus independently Voltage at which the electronic unit is operable. This embodiment also relates in particular to pluggable consumers such as B. external displays which are connected to the electronics unit or be deducted from this.

A Embodiment provides that the adjustment designed in such a way is that the adjustment resistance in the case that the at least one Consumers in the activated state is the feedback voltage lowers.

An embodiment includes that Control unit is essentially directly connected to the power / voltage input.

A Embodiment provides that the control unit designed such is that for operating the control unit requires a voltage which is below the predetermined minimum voltage value.

The The invention will be explained in more detail with reference to the following drawings. It shows:

1 1 is a block diagram of the electronic unit of a measuring device according to the invention in a first variant,

2 : an extension of the first variant of 1 .

3 a second variant of the electronics unit,

4 : a third variant, and

5 : an extension of the third variant of the 4 ,

1 shows a first embodiment of the measuring device according to the invention. In particular, it is a so-called. 2-wire measuring device, in which the power supply of the measuring device and the signaling of the measuring signals via the same two lines is made. The measuring signals are usually transmitted as 4 to 20 mA signals, so that depending on the measured value, different powers are available to the measuring device. Furthermore, losses usually occur through measures that serve explosion protection. At the same time, however, there is also a desire on the user side to have to provide the lowest possible voltages. The electronics unit 1 of the measuring device is fed via an external power supply (not shown here).

in the The state of the art is a minimum power consumption in 2-conductor devices below 3.6 mA for the Device required. Such a current allows the device to go into an alarm state and can indicate this condition by a fault current (<= 3.6 mA). For the possibility battery operation, for example in wireless applications, be possible small minimum terminal voltages required, z. B. 10 V. This results a maximum power consumption of the device of 36 mW, often for action in the context of explosion protection of this performance already a good part is consumed. The minimum power is the product the minimum power consumption of the meter or especially the electronic unit and the clamping voltage available at the input of the electronics unit.

Shown in the 1 only the components essential for the explanation of the invention, ie it is only the electronic unit 1 shown. As examples of consumers 2 Here are, for example, a display, an LED display or the actual measurement serving sensor unit to call.

With energy or electric power is the electronics unit 1 via the current / voltage input 3 from an - not shown - supplied external power source. At this entrance 3 drops a terminal voltage Uklemme. For the electronics unit 1 usually a minimum voltage value is provided, when it reaches or exceeds the electronics unit 1 or so that the meter takes up its work. The minimum voltage value for the terminal voltage Uklemme is designed for the maximum consumption situation, ie, for example, for the application in the entire permitted for the meter temperature range and full functionality, ie in the event that all peripherals are operated.

The invention is based on the fact that in the case that the power consuming peripherals, ie that consumers 2 are not active or switched off, the power consumption decreases and thus that with constant power consumption, the required minimum clamping voltage can be reduced.

The at the current / voltage input 3 applied current is via a measuring resistor 9 - also characterized by R4 - measured. Behind the current / voltage input 3 is a voltage regulator 5 intended. Such a voltage regulator 5 or more precisely, a voltage stabilization circuit provides the supply voltages for the device and is here particularly provided with a shut-down mechanism. The voltage regulator 5 causes the electronics unit 1 falls below a predetermined voltage value, which is applied to its in-input, a shut-down undergoes, so that the device 1 is converted into a well-defined state in such a case of energy shortage. The shut-down mechanism is, for example, a voltage divider 6 at a feedback input of the voltage regulator 5 realized. The voltage divider 6 consists of two feedback resistors R1 and R2. The voltage regulator 5 Thus, at an input with the feedback voltage is applied, which is compared with a voltage value with that for the electronics unit 1 predetermined minimum voltage value is connected. If this voltage value is undershot, this is associated with the fact that at the current / voltage input 3 applied voltage below the minimum voltage value for the electronic unit 1 is that and thus either the part of the electronics unit 1 , which with the voltage regulator 5 is not yet working or that this part is being shut down, ie that its shutdown is triggered. According to the invention, this feedback voltage is set appropriately.

The output ("Out") of the voltage regulator 5 is with the control unit 4 connected, which is here for example, a microprocessor 12 is. The control unit 4 has contacts to the consumers shown here 2 - as an example display, LED display or sensor unit - on. Furthermore, the control unit receives 4 also the measuring signal of a temperature sensor 7 which monitors, for example, the temperature of the process, of which at least one process variable or measured variable is measured or monitored by the sensor unit. In the variant shown here, the temperature sensor measures 7 the temperature of the electronics unit 1 the device.

The control unit 4 is designed in the variant shown here such that the voltage value at which the control unit 4 can take their function below that for the entire electronics unit 1 predetermined minimum voltage value is. Ie. the control unit 4 becomes active before the whole meter 1 goes into the active state. He starts in an initialization phase, in which no larger power consumers such as display, LED display or measuring arrangement are energized. In the initialization phase, the control unit checks or tests 4 which consumers 2 are connected or which consumers 2 are activated or whether the temperature of the electronics unit 1 is in a moderate or critical range.

The two consumers 2 are here via switches 10 switched on or off. It is also possible that consumers 2 , z. B. plugged external display units or deducted. Represents the control unit 4 within an initialization time, that it is consumer 2 There are, which are not connected or not activated, it is based on the minimum voltage value, which for the electronic unit 1 is required, reduced. This is possible because the minimum voltage value for the application of all consumers 2 is designed. It is at the current / voltage input 3 voltage may already be above that for the electronics unit 1 increased specified minimum voltage value.

The reduction of the minimum voltage happens here in that the control unit 4 a port on which an electrical resistance as detuning resistor 8th is connected, controls such that over this resistor 8th the voltage divider ratio of the voltage divider 6 is so detuned that the voltage regulator 5 sees a voltage which does not match that at the current / voltage input 3 voltage applied matches. The voltage divider 6 is connected to ground and the signal for the shut-down mechanism is tapped here between the two resistors R1 and R2. Also at this tapping point is the detuning resistance 8th appropriate. The control unit 4 thus generates such detuning that the voltage regulator 5 only at a voltage which is below that for the electronics unit 1 specified minimum voltage value, a shut-down of the device 1 causes. The detuning resistance 8th at the one port of the microcontroller 12 is switched either to low level, high level or to IRIS (tri-state, ie the port is switched off). The detuning resistance 8th depends on the power requirements of the electronics unit 1 by controlling the port of the control unit 4 switched on or off.

• 1. Die Stromverbraucher sind vorhanden bzw. aktiviert. Die anliegende Klemmenspannung liegt oberhalb des minimalen Spannungswerts. In diesem Fall beginnt die Elektronikeinheit 1 zu arbeiten.
• 2. Die Stromverbraucher sind vorhanden bzw. aktiviert. Die anliegende Klemmenspannung liegt unterhalb des minimalen Spannungswerts. In diesem Fall schaltet sich die Elektronikeinheit 1 über den Shut-Down-Mechanismus selbst ab.
• 3. Die Stromverbraucher sind nicht vorhanden bzw. nicht aktiviert. Daher setzt die Steuereinheit 4 die Spannung herab, bei welcher der Spannungsregler 5 den Shut-Down-Mechanismus ausführt. Hat gleichzeitig die anliegende Klemmenspannung den minimalen Spannungswert überschritten, so beginnt die Elektronikeinheit 1 zu arbeiten.
• 4. Die Stromverbraucher sind nicht vorhanden bzw. nicht aktiviert. Daher setzt die Steuereinheit 4 die Spannung herab, bei welcher der Spannungsregler 5 den Shut-Down-Mechanismus ausführt. Hat gleichzeitig die anliegende Klemmenspannung den minimalen Spannungswert nicht, aber einen reduzierten Spannungswert überschritten, so beginnt die Elektronikeinheit 1 zu arbeiten.

There are four constellations imaginable:

• 1. The power consumers are present or activated. The applied terminal voltage is above the minimum voltage value. In this case, the electronics unit starts 1 to work.
• 2. The power consumers are present or activated. The applied terminal voltage is below the minimum voltage value. In this case, the electronics unit turns off 1 via the shut-down mechanism itself.
• 3. The electricity consumers are not available or not activated. Therefore, the control unit continues 4 the voltage down, at which the voltage regulator 5 executes the shut-down mechanism. If at the same time the applied terminal voltage has exceeded the minimum voltage value, the electronic unit begins 1 to work.
• 4. The electricity consumers are not available or not activated. Therefore, the control unit continues 4 the voltage down, at which the voltage regulator 5 executes the shut-down mechanism. If, at the same time, the applied terminal voltage has not exceeded the minimum voltage value but has exceeded a reduced voltage value, then the electronics unit begins 1 to work.

The control unit 4 also gets over the temperature sensor 7 Information about the in the electronics unit 1 prevailing temperature. If the temperature is within one for the electronics unit 1 specific temperature range, wel As a result, the required voltage can also be supplied by the control unit 4 be reduced.

The control of the required voltage thus builds on the fact that the minimum power consumption is always designed for the maximum consumption situation, ie over the entire temperature range and at full functionality (display, LED display, etc.). Become a consumer 2 switched off or simply removed, for example, in the case of an external display, it is possible, this status information a microcontroller 12 or microprocessor as a control unit 4 in the measuring instrument or in the electronics unit 1 to provide. The same applies to the current ambient temperature. With the information is then in the control unit 4 estimated the current consumption of electricity depending on the application of the consumer. Starting from this estimate then becomes the voltage divider 6 influenced such that the voltage regulator 5 to another, especially lower voltage than the original for the electronics unit 1 defined voltage value. Thus, the supplied clamping voltage can be reduced by the external power supply and the meter continues to operate. Thus, a consumer-dependent minimum terminal voltage can be realized, which is actively controlled by a control unit or especially a microcontroller.

When the adjacent terminal voltage is shut down by the external power supply, the threshold value set by the status of the consumer or by the prevailing temperature determines at which terminal voltage the voltage regulator 5 executes the shutdown and thus the electronics unit 1 and the meter shuts off again.

The 2 shows two extensions of the embodiment of 1 , wherein it is provided in the dashed version that the control unit 4 directly with the current / voltage input 3 connected is. This allows in particular that the control unit 4 already at a low value at the current / voltage input 3 applied voltage begins to work. Furthermore, also the feedback voltage, which is the voltage regulator 5 for the shut-down mechanism, via an analog to digital converter 11 directly to the control unit 4 or the microprocessor or microcontroller 12 fed. As a result, the second case discussed above can not occur and the self-shutdown of the electronics unit 1 will be prevented. If the voltage is below the minimum voltage value, the control unit remains 4 in the initialization phase. Only when the terminal voltage exceeds the upper threshold, the power consumers 2 switched on and the feedback voltage depends on the connected consumers 2 set. The other cases behave as described.

In the 3 a further embodiment is shown, in which the control unit 4 and the two power consumers shown here 2 with different supply voltages via individual voltage regulators 5 are supplied. This relatively easily allows the control unit 4 already begins to work at a low voltage and then only then the voltage requirement as a function of the presence or Aktiviertsein the consumer 2 regulates.

4 shows a further embodiment in which the control unit 4 directly by consumers 2 is realized. The consumers 2 each have an electrical resistance, which by the mechanical connection of the consumer 2 with the electronics unit 1 , z. B. here by the switch 10 or by the direct plugging or by the activation of consumers 2 in the voltage divider 6 be introduced. Due to the additional resistance of consumers 2 The feedback voltage on the voltage regulator also changes 5 , This is the result of every consumer 2 two thresholds for those at the entrance 3 required clamping voltage. The microprocessor 12 thus serves only for the usual tasks within the meter.

The 5 showed another version of the variant of the 4 , Here is in every consumer 2 a detuning resistance 8th provided which changes the threshold voltage depending on its respective maximum power consumption.

1

electronics unit

2

consumer

3

Current / voltage input

4

control unit

5

voltage regulators

6

voltage divider

7

temperature sensor

8th

upset resistance

9

Current sense resistor

10

switch

11

Analog / digital converter

12

microcontroller

13

port of the microcontroller

Claims (18)

Device for determining and / or monitoring at least one process variable, having at least one electronic unit ( 1 ), which at least temporarily via at least one current / voltage input ( 2 ) with electrical energy provided for the operation of the electronic unit ( 1 ) a minimum voltage value for one at the current / voltage input ( 2 ) voltage is predetermined, wherein at least one voltage regulator ( 5 ), which is subjected to at least one feedback voltage, and which, in the event that the feedback voltage is applied to the voltage regulator ( 5 ) falls below predetermined voltage threshold, which depends on the for the operation of the electronics unit ( 1 ) predetermined minimum voltage value, a shut-down of at least a part of the electronic unit ( 1 ) and / or in which case the starting of at least a part of the electronic unit ( 1 ), wherein at least one circuit ( 6 ), which influences the magnitude of the feedback voltage, and wherein the magnitude of the feedback voltage depends on the energy requirement of the electronics unit ( 1 ) is adjustable. Device according to claim 1, characterized in that the electronic unit ( 1 ) is configured such that via the current / voltage input ( 2 ) both the power supply of the electronics unit ( 1 ) as well as the output of a measurement signal for the process variable. Device according to claim 1 or 2, characterized in that at least one control unit ( 4 ) is provided, which depends on the energy requirements of the electronics unit ( 1 ) adjusts the feedback voltage. Device according to claim 3, characterized in that the control unit ( 4 ) is configured such that the control unit ( 4 ) in the event that the power requirement of the electronics unit ( 1 ) is below the value associated with the predetermined minimum voltage value, increasing the feedback voltage. Device according to one of claims 1 to 4, characterized in that at least one voltage divider ( 6 ) is provided, wherein of the voltage divider ratio of the voltage divider ( 6 ) the feedback voltage depends, and wherein the voltage divider ratio of the voltage divider ( 6 ) depending on the energy requirement of the electronic unit ( 1 ) is adjustable. Device according to claim 5, characterized in that the control unit ( 4 ) depending on the energy requirement of the electronic unit ( 1 ) the voltage divider ratio of the voltage divider ( 6 ). Device according to one of claims 1 to 6, characterized in that at least one consumer ( 2 ) and that the consumer ( 2 ) is designed in such a way that the consumer ( 2 ) is either in an active or in an inactive state, the active state being that the consumer ( 2 ) through the electronics unit ( 1 ) is supplied with electrical energy. Device according to claim 7, characterized in that the control unit ( 4 ) is configured such that the control unit ( 4 ) asks whether the at least one consumer ( 2 ) is in the activated or deactivated state. Device according to one of claims 3 to 7, characterized in that the control unit ( 4 ) depending on whether the at least one consumer ( 2 ) in the activated or inactivated state and / or depending on the working conditions under which at least a part of the electronics unit ( 1 ) which adjusts feedback voltage. Apparatus according to claim 9, characterized in that at least one working condition refers to the temperature which in at least a part of the electronic unit ( 1 ) prevails. Apparatus according to claim 10, characterized in that at least one temperature sensor ( 7 ) is provided that the control unit ( 4 ) with the temperature sensor ( 7 ) and that the control unit ( 4 ) based on the measured value of the temperature sensor ( 7 ) adjusts the feedback voltage. Device according to one of claims 8 to 11, characterized in that the control unit ( 4 ) in the case that the at least one consumer ( 2 ) in the inactivated state, increases the feedback voltage. Device according to one of Claims 3 to 12, characterized in that the control unit ( 4 ) to a microcontroller ( 12 ). Device according to claim 13, characterized in that the control unit ( 4 ) the voltage divider ratio of the voltage divider ( 6 ) above an adjustment resistor ( 8th ), which has a port ( 13 ) of the microcontroller ( 12 ) connected is. Apparatus according to claim 7, characterized in that the at least one consumer ( 2 ) via an adjusting resistor ( 8th ), which depends on whether the at least one consumer ( 2 ) is in the activated or deactivated state, sets the feedback voltage. Device according to claim 15, characterized in that the adjustment resistance ( 8th ) is designed such that the adjustment resistance ( 8th ) in the case that the at least one consumer ( 2 ) in the activated state, reduces the feedback voltage. Device according to at least one of claims 1 to 16, characterized in that the control unit ( 4 ) substantially directly with the current / voltage input ( 3 ) connected is. Device according to at least one of claims 1 to 17, characterized in that the control unit ( 4 ) is designed such that for the operation of the control unit ( 4 ) a voltage is needed which is below the predetermined minimum voltage value.