ITMI20120628A1 - STATIC GAS COUNTER WITH BATTERY ALARM SYSTEM - Google Patents

Description

STATIC GAS METER WITH BATTERY ALARM SYSTEM

DESCRIPTION

TECHNICAL FIELD

The present invention relates to gas meters of the static type, and in particular to static gas meters of the type comprising a radio transmitter for communication with an external communications network.

The invention relates in particular to a static gas meter according to the preamble of claim 1.

STATE OF THE ART

In recent years, static gas meters have been developed (typically using a mass flow meter), in which the flow is measured through an electronic sensor, for example ultrasonic or solid state (MEMS type), placed on the inside a measuring chamber which connects the national distribution network with the utility branch via an appropriate valve. While in traditional (or diaphragm) meters the measurement took place mechanically (Volumetric Measurement), and also the reading of consumption took place through a mechanical system that did not require a power supply (at least for small calibers), static meters require a power supply battery capable of powering the measurement sensor (and the relative management electronics) for a high number of years, as necessary consequently to the legal duration of the metric stamp.

This required considerable attention in the development of technical solutions (electronic, circuit, management) with low energy consumption that were compatible with the use of chemical batteries, the ideal solution to guarantee long periods of operation and permanence in the field.

The problem of energy consumption is even more felt in those gas meters (whether they are mass or volumetric) which must communicate the measurement of consumption to a remote central system. In Italy, for example, the Italian Gas Committee (CIG), entity responsible for technical standards, has established that communication can be carried out either with public radio networks in point-to-point installations (GPRS / GSM) or through RF-MBus communication. wireless at 169MHz; this therefore requires that the meter is equipped with a transmitter and that the battery (s) is / are sized to power both the transmitter and all the electronic control, management and data collection on board the meter, for a adequate number of years.

In addition to that of energy consumption, another problem felt in the sector is that of tampering with static gas meters. Removing the battery could, in fact, compromise the functioning of the meter, and therefore the need is felt to ensure that any tampering is readily detected.

PURPOSE AND SUMMARY OF THE INVENTION

The purpose of the present invention is to present an innovative static gas meter which allows a prompt detection of tampering with the battery of the meter itself.

The object of the present invention is also to detect tampering with the meter by means of a reliable and low-cost system.

This and other purposes of the present invention are achieved by means of a static gas meter incorporating the characteristics of the attached claims, which form an integral part of the present invention.

The idea behind the present invention is to connect a pole of the battery both to a ground line of the meter and to an alarm input of the meter control unit. By monitoring the voltage on the alarm input, it is possible to detect the removal of the battery, which results, in fact, in a variation of the monitored voltage beyond a certain threshold.

This solution allows to detect the removal of the battery without the need for anti-tampering buttons or other expensive devices that could break with aging.

In one embodiment, the meter comprising an auxiliary battery which is connected, upon command of the control unit, to the metrological components of the meter if the voltage at the alarm input varies beyond a predetermined threshold. Advantageously, then, the battery is connected to the printed circuit on which the control unit is mounted by means of a connector; an electrostatic discharge protection system includes a discharger drawn on the printed circuit board and includes a preferential discharge path for energy.

This solution avoids the use of discrete component arresters that have to be mounted on the printed circuit, therefore improves reliability and reduces system costs.

Advantageously, the discharger comprises a plurality of discharge elements, in particular triangles, which have a vertex in a remote position with respect to the connector and connected to a ground line of the meter. In particular, the arrester comprises a number of discharge elements equal to the number of pins of the meter.

This arrester design is effective and preferred.

Further objects and advantages of the present invention will become clearer from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described hereafter with reference to non-limiting examples, provided for explanatory and non-limiting purposes in the annexed drawings. These drawings illustrate different aspects and embodiments of the present invention and, where appropriate, reference numerals illustrating similar structures, components, materials and / or elements in different figures are indicated by similar reference numerals. Figure 1 schematically illustrates a gas meter of the static type;

Figure 2 is a block diagram of the counter of Figure 1 according to a second embodiment of the present invention;

Figure 3 illustrates the charging cycles of the charging unit of the counter of Figure 2 according to an embodiment;

Figure 4 illustrates a block diagram of a gas meter of the static type according to a second embodiment of the present invention;

Figure 5 illustrates a block diagram of a gas meter of the static type according to a third embodiment of the present invention;

Figure 6 illustrates a current limiter for the gas meter;

Figure 7 illustrates the consumption measured by a static gas meter;

Figure 8 schematically illustrates the architecture of the gas meter of the static type according to an embodiment;

Figure 9 schematically illustrates the architecture of the static gas meter according to a further embodiment;

Figure 10 schematically illustrates a static gas meter placed inside a housing and in communication with a telecommunication network;

Figure 11 illustrates an alternative solution to that of Figure 10 to allow the communication of the gas meter of the static type.

Figure 12 illustrates the detail of the connection between the battery and the power supply circuit of a static gas meter.

Figure 13 illustrates an electrostatic discharge protection system of the static gas meter according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible of various modifications and alternative constructions, some preferred embodiments are shown in the accompanying drawings and will be described in detail below. It must be understood, however, that there is no intention to limit the invention to the specific embodiment illustrated, but, on the contrary, the invention intends to cover all modifications, alternative constructions, and equivalents that fall within the scope of the Scope of the invention as defined in the claims.

The use of â € œfor exampleâ €, â € œeccâ €, â € œorâ € indicates non-exclusive alternatives without limitation unless otherwise indicated.

Figure 1 schematically shows a gas meter 1 of the static type.

The meter 1 comprises, in a known way, a hollow body 2 which defines a measurement compartment 3 provided with an inlet 4 and an outlet duct 5 for the passage of gas (represented by the arrows in fig. 1) which, from the distribution network, must be brought to users.

A sensor 6, placed inside the measurement compartment, detects the gas flow that is required by the user. Sensor 6 is connected to a control unit 7 which processes the sensor readings, stores the measured value and transmits it by activating a transmitter 8.

By means of an appropriate actuator 90, the control unit then controls a valve 9, inside the meter, which opens or closes the passage of gas from the distribution network to the utility branch.

The meter is then equipped with an LCD display 10 for reading the consumption measurement by an operator.

Figure 2 shows a block diagram of the counter 1, according to a first embodiment of the present invention.

The meter 1 comprises a battery 11 sized to power all the electric / electronic components of the meter. In the preferred embodiment example, battery 11 is a lithium battery with a capacity of 19Ah (type D) capable of maintaining a voltage of 3.6V at its ends for its entire useful life if the current is required. it is limited to low and constant values.

Battery 11 is chosen so that it can operate in a wide range of temperatures, preferably between -25 ° C and 55 ° C, this is because the same meter must be able to be installed in places with very different environmental conditions (mountains and sea) and support significant temperature excursions (day / night, summer / winter). Batteries of this type are usually not able to satisfy, without significant degradation of the intrinsic characteristics of duration over time, the instantaneous current requirements required by the transmitter 8 (and by the on-board electronics, indicated as a whole with reference 12) to transmit via radio. the measures of the meter to generally allow remote access to it by the service managers. For this reason, in parallel with the transmitter 8, a charging unit 13 is provided which is capable of delivering to the transmitter 8 the current it needs for the maximum time established to transmit the quantity of data defined by the specific connection.

In the preferred solution, the charging group 13 is replaced by a plurality of capacitors in series, and in particular a plurality of supercapacitors (known by the English term supercapacitor or supercap), capable of storing enough energy to operate the transmitter 8 for the time sufficient to communicate the measurement of gas consumption and all data relating to user management over time. In the hypothesis that the transmitter 8 is of the GPRS type, and to allow an adequate communication time, two supercapacitors placed in series are used in the preferred embodiment.

The voltage supplied by the battery 11 is supplied to the ends of the transmitter 8 and of the charging unit 13 through a voltage regulation circuit 14 controlled by the control unit 7 comprising a microcontroller.

In one embodiment, the regulation circuit 14 is an electronic switch (for example a transistor) which opens or closes the connection between the battery 11 and the charging unit 13. In this way the control unit 7 controls the charging cycles of the charging group 13 and keeps energy consumption under control as shown in figure 3.

The control unit 7 is programmed to activate the transmitter and transmit the sensor measurements every t1 seconds, for example every 12 hours. The transmission lasts Î ”2, for example 30s, depending on the amount of data to be transmitted and the response time of the network to which the gas meter is connected, and requires an average energy E1. The control unit 7 controls the regulation circuit 14 and therefore connects the charging unit 13 to the battery 11 at an instant t0, prior to the transmission start time t1. The time t0 is calculated by the control unit in such a way that in the time t0-t1 (Î ”1), the charging group 13 charges and accumulates an energy greater than or equal to E1.

With this solution, when the charging unit 13 and the transmitter 8 are connected directly to the battery 11, the latter has to suddenly deliver (high current peaks) many hundreds of milliamps of current. This type of operation in the long run can damage the battery, which must therefore be suitably sized both in terms of its energy and its intrinsic duration.

This problem is solved by a different control of the charging and discharging cycles of the charging unit carried out by the gas meter in figure 4.

In the solution of Figure 4, the voltage control circuit 14 of Figure 2 is replaced by two blocks, indicated by the reference numbers 15 and 16, placed upstream and downstream of the charging unit 13.

Block 15 represents a controlled booster, capable of performing two functions: supplying an output voltage higher than the input voltage and limiting the output current, ie the charging current of the charging group 13 itself.

When the control unit 7 activates the booster, the voltage supplied by the battery (3.6V) is raised to 4.8V, so that the charging unit 13 charges faster until it accumulates more energy than a charge with a voltage of 3.6V, the accumulated energy being proportional to the square of the voltage itself. The choice of the 4.8V voltage depends on the intrinsic parameters of the supercapacitors of the charge group 13, in particular, the booster 15 is controlled by the control unit 7 in order to supply an output voltage Voutpari to NVMAX, where VMAXÃ ̈ the maximum voltage that, according to specifications, can be supported by the supercapacitor without being damaged, while N is the number of supercapacitors placed in series in the charging group 13. The choice of 4.8V is therefore optimal for a charging group comprising two supercapacitors placed in series and capable of supporting a maximum voltage of 2.4V, guaranteeing the functional profile in terms of electrical characteristics and quality over time.

In a preferred embodiment, the booster 15 is controlled in such a way as to gradually raise the output voltage from a minimum value (in the example described here 3.6V) to a maximum (in the example here described 4.8V); in this way the control unit can be configured in such a way as to raise the voltage across the charging group 13 according to a rise curve that depends on the choice of capacitors. In a preferred form, the curve is chosen in such a way that 4.8V is maintained for a relatively short time throughout the day (and typically only in anticipation of a scheduled transmission) in order to optimize the life of the capacitors.

The booster 15 is preferably controlled in such a way that the voltage at node n2 is always greater than or equal to the working voltage of the transmitter 8, which in the example described here is equal to 3.6V.

The booster 15, in addition to raising the voltage, limits the current drawn by the battery, and necessary to charge the supercapacitors, to a value suitable for optimizing the average life of the latter. In the preferred embodiment, the current is limited to a value comprised between 3 and 5mA, more preferably equal to 4 mA.

A reading circuit, schematized by line 17, reports the voltage at node n2 to the control unit 7, in this way the control unit knows at any moment the voltage present at the ends of the charging unit and blocks the booster when it detects a voltage of 4.8V. The frequency of this control over time is a programmable parameter.

In one embodiment, the transmitter 8 operates at 3.6V (with a minimum operating limit also lower and equivalent to 3.2V), therefore a DC / DC converter is provided between the charging group 13 and the transmitter 8 (Buck converter) which returns the voltage from 4.8V to a value useful for the operation of the transmitter, for example between 3.3V and 3.6V.

In a preferred embodiment, the control unit 7 controls the buck converter 16 by interrupting the connection between the charging group 13 and the transmitter 8 during the charging phases of the charging group 13 in order to optimize them and reduce consumption (and losses) of the system.

As for the example described above with reference to figures 2 and 3, the control unit 7 interrupts the connection between the battery 11 and the charging unit 13 during the transmission of the consumption measurements (or any data them correlated and stored in the memory of the electronics) by the transmitter 8 and more preferably for all the time in which the charging unit 13 must not be charged; this is done by controlling the booster 15. The control unit is programmed to transmit data using the transmission module at a predetermined instant of time TTR (eg at a certain day and time of the day); before data transmission, the control unit disconnects the booster circuit from the battery, so that the transmission takes place using only the energy stored in the charging group 13. After the transmission has taken place, the unit control 7 calculates the charging time ï „T necessary to bring the voltage on the charging unit from the value detected following the transmission up to the 4.8V necessary to accumulate the energy necessary for a subsequent transmission. Once the charging time is known, the control unit reactivates the connection with the battery at a time calculated according to the charging time and the transmission time, in particular the connection is restored and charging starts at a TIN time. = TTR-ï „T.

The use of the booster 15 and the buck converter 16, controllable by the control unit 7, allows to completely isolate the charging group 13 and keep the sensor reading stable. In fact, if the measurement and control electronics were directly connected to the charging unit, the current peaks absorbed by the communication circuit during transmission would inevitably generate significant voltage drops on them, disturbing or preventing their operation. In particular, the use of a booster 15 which limits the current that can be recalled by the battery, avoids, in fact, that the sudden request for current from the transmitter 8 when it has to transmit causes oscillations on the supply voltage of the sensor, thus altering its measurement unpredictable.

In an embodiment, shown in Figure 5, the sensor 6 and the actuators 90 which control the valve 9 are powered by means of a line provided by a current limiter 18 which starts from node n3, this node being the node closest to the battery 11. In other words, all the other devices of the meter take power downstream of the sensor 6 and the valve actuators 90.

The limiter 18 is necessary as a protection to limit the energy flow towards the part of the circuits located in the gas environment (sensor 6 and valve 9) which, even following faults that lead to short circuits, could potentially dissipate such energy as to be able to trigger an explosion of the gas mixture itself.

In another preferred embodiment, the valve actuators 90 are powered by the charging unit 13 and are therefore connected to these by means of a buck converter controllable by the control unit so as not to absorb or lose current when inoperative. . In one embodiment, the actuators 90 are therefore connected downstream of the buck converter 16. This choice optimizes the average life of the battery 11, as such actuators (e.g. the valve motor 9) may require a few tens of milliampà re. and therefore stress the battery.

In a preferred embodiment the limiter 18 is a limiter controllable through an enable input, for example the limiter 18 comprises an integrated limiter circuit of the type used in HDMI connections. However, this type of circuit has some losses (leakage current) which can be reduced by sending a limiter shutdown signal to the enable input which, in fact, sends the limiter output voltage to zero.

In the solution of Figure 6, the limiter 18 comprises an integrated limiter circuit 180, of the type used in HDMI solutions, which has, between the input and output pins, a bypass resistor R sized so as to pass a current just sufficient to maintain in standby the sensor (which otherwise would switch off and require a restart at each measurement step); preferably this current is of a few microamps, preferably 1µA.

This solution offers the advantage that the control unit 7 can be configured to efficiently perform discrete flow measurements over time and at the same time minimize the power dissipated in the phases between one measurement and another.

In one embodiment, the control unit 7 disables the limiter 18 and goes into a standby state, reducing energy consumption. After a predetermined time, eg. 2s, a clock inside the control unit 7 reactivates it and this in turn activates the limiter 18 allowing a rapid exit from the standby of the sensor, which can thus measure the gas flow in a few µs. This would not be possible without the bypass resistor that powers the sensor when it does not measure and is in a state of low absorption, since by completely disabling the sensor, its awakening would be longer and, as a consequence, would lead to a greater waste of energy associated with each awakening.

In an alternative solution, the measurements are not made regularly on the basis of a predetermined time, but following a prediction algorithm that calculates, based on the previous measurements, if there is a current gas consumption and it is therefore better perform closer measurements over time and / or measurements with different precision and consequent different energy balance.

By way of example, when a user turns on a stove to cook, the control unit detects a gas flow greater than the previous measurements and therefore decides that the next measurement, instead of after 2s, must be performed after a time inferior. The time interval is preferably chosen on the basis of the measurement value or, even better, on the basis of the differential with the previous measurement.

In a preferred embodiment, the sensor 6 is capable of carrying out measurements of two types: a QUICK measurement and an ACCURATE measurement. The latter is very precise, but requires a lot of energy, while the former is less precise and requires less energy. In this case, alternatively or in combination with the adjustment of the measurement intervals, it is possible to configure the control unit to require ACCURATE measurements when a derivative (positive or negative) higher than a threshold value in the curve of the consumption. This is better illustrated with reference to the consumption curve shown in figure 7: at time T0 the hot water is on and therefore the sensor detects regular consumption every 2s; the control unit then commands the sensor to perform QUICK measurements. Subsequently, at time T1 the user lights the fire and therefore consumption rises until it reaches the final value reached at time T2. Between T1 and T2 the control unit detects an increase in consumption and therefore performs ACCURATE measurements. Once consumption returns to be constant, between T2 and T3, QUICK measurements are resumed. Subsequently at time T3 the user turns off the stove and then at time T5 also the hot water. In the time intervals T3-T4 and from T5 onwards, ACCURATE measurements are required, while QUICK measurements are made between T4 and T5.

In a preferred embodiment, the choice between QUICK and ACCURATE measures depends not only on the derivative of consumption, but also on historical data used to reduce the number of ACCURATE measures, with the highest energy consumption, to the strictly necessary. For example, it is known that the distribution of gas occurs in a way that is not always constant, but has a non-linear trend. Historical data can help to understand the periodicity of this trend and decide that any increases in the value of the measured flow are dependent on the trend of gas distribution and not on an actual additional demand for gas by the user; in this case the control unit will order the sensor to perform QUICK measurements despite an increase in consumption detected between two successive measurements.

Figure 8 shows a preferred embodiment of the control unit 7. In this embodiment, the control unit comprises two microcontrollers, one (70) dedicated to communication devices (e.g. transmitter 8) and one (71) dedicated to the metrological part of the gas meter (eg sensor 6) and to the other most frequently used devices (eg display) and related to the so-called â € œLegally Relevantâ € part of the measuring instrument.

Preferably the microcontrollers 70 and 71 are made with different architectures, in particular the microcontroller 71 which controls the measurement circuit (sensor 6), being more frequently used, is made with an architecture optimized for low power (eg. 8 bit) and therefore uses a smaller silicon area than the other microcontroller 70, eg. a 32-bit microcontroller.

The two microcontrollers 70 and 71 are placed in communication, but the microcontroller 71 is equipped with a firmware identified by an identification code, for example a CRC code (Cyclic Redundancy Check) or digital signature. This solution allows you to remotely update the microcontroller 70 always guaranteeing the possibility to check the integrity of the microcontroller 71 and its firmware. Preferably both microcontrollers are provided with such an identification code.

In a particularly advantageous embodiment, shown in figure 9, the control unit is provided with a dual port RFID receiver 72 comprising a rewritable non-volatile memory, for example a flash memory, a memory reading and writing circuit in able to allow the reading and writing of the memory by a microprocessor external to the receiver and connected to the same through a data line, in particular a serial data line.

Once the production of the meters has been completed, to avoid subsequent manipulations of the meter, and in particular of its metrological software, the RFID receiver 72 is hit by an appropriate modulated RF signal from which it extracts, in a known way, the energy required to activate a small microprocessor 73 dedicated to data storage. The RFID interface of each meter is protected with a 32bit password, so that by irradiating several meters simultaneously with a signal provided with a specific password, only one of these meters recognizes the password as valid and is activated by loading the data. transmitted with the radiated signal. In particular, the transmitted data includes specific meter data (sensor calibration coefficient, various meter IDs such as meter serial number, valve serial number, etc.) and a (sealing) code that tells the meter that from this moment onwards it can no longer be re-calibrated. The data thus received are stored in a non-volatile memory, eg. a flash, of the RFID receiver.

In the preferred embodiment, the RFID receiver directly feeds, with the energy obtained from the RF irradiation, a small dedicated microcontroller 73, which sends a LOCK signal to the receiver blocking the rewriting mechanism of the non-volatile memory. This prevents the possibility of altering calibration parameters that are important for the functioning of the meter.

In an alternative embodiment, which does not require the use of a dedicated microcontroller, the blocking of the writing of the non-volatile memory of the RFID receiver occurs when the meter is first turned on. When the meter is powered up for the first time, the control unit 7 reads the data present in the memory of the RFID receiver and sends the Lock command to the RFID receiver to prevent future rewriting of its memory. In this embodiment, the data written in the memory of the RFID interface is encrypted to prevent its rewriting during the transport phase or in any case before the first switching on of the meter. This protection serves to cover the time that elapses between the meter leaving the factory and the first installation of the same.

Although in the example of figure 9 the meter uses a single microcontroller 7, it is clear that the RFID system can also be used using an architecture with two microcontrollers as in the example of figure 8.

As previously mentioned, the gas meter is equipped with a transceiver 8 which receives and transmits data from / to a remote server, directly (GPRS connection) or through a concentration apparatus that manages several meters and, in turn, connects with the remote server through a GPRS connection.

The gas meters may have to be installed in environments not covered by the radio network to which they must be connected to transmit data (e.g. in a cellar), or they can be installed inside a metal cabinet which, by shielding the meters, prevents them from being radio reachability.

In one embodiment, therefore, the meter is provided with a transmission kit consisting of a passive repeater system consisting of two calibrated antennas connected by a cable.

Figure 10 shows the meter 1 installed inside a cabinet 100 which has a metal shield that would prevent communication between the meter transmitter 8 and an access apparatus 111 of a communications network 110.

The passive repeater system 19 is mounted 100 by passing the cable 190 connecting the two antennas 191 and 192 through an opening (possibly obtained during the installation phase by making a hole in the cabinet 100). To facilitate the assembly of the passive repeater system 19, at least one of the antennas 191, 192 is fixed to the cable 190 by means of a removable connector, more preferably both antennas are provided with such a connector, so that, depending on the applications, it is possible to use cables of different lengths or, alternatively to the cable, other means of antenna connection, such as rigid connectors, which allow the two antennas to be put in direct contact.

The passive repeater system is supplied with a mounting kit which includes, for example, brackets for attaching the cable and / or antennas to different surfaces. Operationally, the antenna of the transmitter 8 emits radio waves which are received by the antenna 191 of the passive repeater located inside the cabinet 100; the radio signal is then converted into an electrical signal which, through the cable, reaches the antenna 192 located outside the cabinet. This last antenna, in turn, generates a radio signal due to the signal in the cable 190. The data transmitted by the antenna of the counter 1, in this way, reaches the access system of the network 110 and consequently a remote server.

In a preferred embodiment, shown in Figure 11, the counter 1 is not provided with an autonomous antenna for transmitting.

The passive repeater 19, on the other hand, comprises an antenna 193 embedded in a plastic case suitably shaped to hook onto the body of the meter 1. This case, in addition to removable hooking means, is equipped with electrical connectors for the electrical connection of the Antenna to the transceiver system (modulator, demodulator, and antenna amplifier) of meter 1.

Alternatively, instead of providing for the attachment of the antenna 193 to the body of the meter, it is possible to integrate this antenna to the body of the meter and provide a connector for connection to the cable 190. In this embodiment, a part of the system passive repeater is integrated into the meter body.

Figure 12 shows a detail of the battery 11 and its connection to the PCB 700 which houses the control unit 7.

It is required by the regulations to be able to detect the removal of the battery by any unauthorized users. The conventional solution to be used in similar cases would provide an anti-tamper button that is activated if the battery compartment cover is removed with consequent mechanical complications and

and cost increase.

In the embodiment of figure 12 the two poles of the battery 11 are wired to a connector 701 intended to be inserted into a corresponding connector 702 placed on the PCB 700. The battery wiring provides two ground wires 703 and 704 connected to the negative and individually carried to the power supply connector 701, and a single cable 705 which goes from the positive pole of the battery 11 to the connector 701.

Once the 701 connector is connected to the 702 connector, the 703 cable is actually used to perform the ground connection function, while the 704 cable returns (by means of a line not shown in the figure) the ground itself to an input of the microprocessor which in this way can detect the presence of the signal relating to the ground connection.

This configuration makes it possible to detect the removal of the battery itself in the absence of a microswitch set up for the purpose and therefore saving costs on the mechanics.

When the battery is removed, the system is in fact still powered by the charging unit 13, the control unit 7 detects a voltage variation at the input connected to the cable 704 which determines an alarm state. The control unit then uses the energy of the charging group 13 to power the transmitter 8 and send an alarm signal, for example a text message such as an SMS.

In a preferred embodiment, the meter is provided with a backup battery, normally not connected to the electrical / electronic system, and capable of allowing the meter to operate for a predetermined time, for example two years.

When the control unit 7 detects a supply voltage (for example at node n1) that falls below a threshold value, it connects (for example by commanding the closure of a switch) the backup battery instead of the battery 11, in such a way as to allow the operation of all components: from the sensor to the transmitter. Alternatively, the control unit can be arranged to transmit an alarm signal or to show such a signal on the display.

Still, in a further embodiment the meter can be equipped with two batteries, one (for example a 19A D type battery) dedicated to powering the metrological components of the meter, and a smaller one (for example a battery B or D type) dedicated to powering the components of the meter responsible for communication. In this embodiment the power supply circuits of the metrological part and of the communication part are separated, therefore there are no measurement problems described above and dependent on the oscillation of the power supply voltage of the metrological sensor when the meter communicates data or when you need to recharge the charging group 13.

Given the energy needs of the system, in an embodiment schematically shown in figure 13, an electrostatic discharge (ESD) protection system is implemented by designing an integrated 706 arrester on the printed circuit (PCB, 700) and drawing a discharge path preferential for the energy that in the example of figure 13 is represented by a plurality of triangles whose upper vertex (opposite to the base) is facing the connector 702, and in which the base of the triangle is connected to a ground line 707. In this way, the negative effects of electrostatic discharges are neutralized by diverting the energy towards ground (ie the system casing) and saving the electronic circuits normally used to make arresters (eg Zener diodes, Varistors, etc.) which, in addition to being a cost, dissipate current. Preferably, a triangle is provided for each pin of the connector 702.

As an alternative to the triangles, the 706 arrester can have different shapes, as long as there are tips facing the connector 702 so as to collect and convey any electrostatic discharges towards the ground.

In the light of the detailed description above, it is clear how the static gas meter described solves the drawbacks of the prior art and achieves the set objectives.

It is also clear that many variations can be made to the static meter described above and that different functions and elements of the meter described with reference to different embodiments, can be differently combined and used to form further embodiments of the meter. Thus elements and circuit blocks can be divided or grouped differently.

Claims (6)

CLAIMS 1. Static gas meter comprising: - a control unit (7), - a measuring circuit (6) for measuring gas consumption, - a wireless transmission system (8) for the transmission of the measurements made by the measuring circuit, - a charging unit (13) to store energy to be released if necessary to the transmission system, -a battery capable of generating a power supply voltage to power the control unit, the measuring circuit and the transmission system, characterized by the fact that one pole of the battery is connected both to a ground line of the meter and to an alarm input of the control unit (7) and that the control unit (7) is configured to send an alarm signal through the transmission system (8), when the voltage at the alarm input varies beyond a predetermined threshold. 2. Meter according to claim 1, further comprising an auxiliary battery and in which the control unit (7) is adapted to connect said auxiliary battery to the metrological components of the meter if the voltage at the alarm input varies beyond a pre-established threshold. 3. Counter according to claim 1, in which the battery (11) is connected to a printed circuit (700), on which the control unit (7) is mounted, by means of a connector (701,702), and in wherein an electrostatic discharge protection system comprises a discharger (706) drawn on the printed circuit board (700) and includes a preferential discharge path for energy. 4. A meter according to claim 3, wherein the arrester comprises a plurality of discharge elements, in particular triangles, which have a vertex in a remote position with respect to the connector (701, 702) and connected to a ground line (707) of the counter. Counter according to claim 4, wherein the arrester (706) comprises a number of discharge elements equal to the number of pins of the counter (702). 6. Counter according to claim 4 or 5, wherein at least one of the discharge elements has a triangular shape.