WO2006131152A1

WO2006131152A1 - A combined set comprising a fluid meter and a pulse generator

Info

Publication number: WO2006131152A1
Application number: PCT/EP2005/055113
Authority: WO
Inventors: Stefan Grosjean
Original assignee: Energy Ict
Priority date: 2005-06-09
Filing date: 2005-10-07
Publication date: 2006-12-14

Abstract

A combined set comprising a fluid meter and a pulse generator for a confined environment, said fluid meter having an interrupt contact, which is provided for having an electric current flowing through it when said interrupt contact is in a closed state, said pulse generator having an electrical input connected to said interrupt contact, said pulse generator comprises an electrical charging-discharging module provided to operate at a power of less than 20μW, said module being connected to said electrical input, said module being provided to be electrically charged when said interrupt contact is an open state and to be electrically discharged upon switching off said interrupt contact from said open state to said closed state, said pulse generator further comprises a detector connected to said module and provided for detecting said electrical discharging of said module and generating a low power control pulse upon detection of said electrical discharging, said generator being connected to a low power light generator provided to generate a light pulse under control of said control pulse, said light pulse having a power less than 1 mW and a pulse duration of less than 10 milliseconds.

Description

A combined set comprising a fluid meter and a pulse generator.

The invention relates to a combined set comprising a fluid meter and a pulse generator for a confined environment, said fluid meter having an interrupt contact, which is provided for having an electric current flowing through it when said interrupt contact is in a closed state, said pulse generator having an electrical input connected to said interrupt contact.

Such a combined set is known and used for example for a gas meter. In a confined environment, electric power may only be used under severe constraints in order to minimise the risks of an explosion. Electric power is however required if remote monitoring of a gas or other fluid meter has to be performed. The data measured by the meter have to be read and transmitted to a monitor station. The fluid meter has an interrupt contact connected to a rotor driven by the fluid. Upon each rotation of the rotor, the interrupt contact is switched from an open to a closed state, thereby closing and opening an electrical circuit so that during the closed state of the interrupt contact, electric current can flow through it. This current flow then triggers the pulse generator, which moreover generates a pulse and supplies the latter to for example a counter situated outside the confined environment. As the amount of current flowing through the interrupt contact has to remain low and as only low voltages may be used, Zener barriers or galvanic isolators are used as a protection against an energy overload.

A drawback of the known solution is that it is expensive due to the relative high costs of Zener barriers. Moreover, their installation is cumbersome. Finally, the known pulse generators are not protected against a longer closed state period. Indeed, it could happen that, for example due to a voluntary or non-voluntary interruption of the fluid supply, the interrupt contact of the fluid meter remains in its closed state. As electric current flows through the interrupt contact in the closed state, the fact that the contact remains in its closed state will have as a consequence that the electric current continues to flow, thereby emptying the battery, which powers the device.

The object of the invention is to realise a combined set comprising a fluid meter and a pulse generator for a confined environment which is not expensive, consumes substantial less electrical power and is protected against longer closed state periods of the interrupt contact.

A combined set according to the present invention is therefor characterised in that said pulse generator comprises an electrical charging-discharging module provided to operate at a power of less than 20μW, said module being connected to said electrical input, said module being provided to be electrically charged when said interrupt contact is in an open state and to be electrically discharged upon switching off said interrupt contact from said open state to said closed state, said pulse generator further comprises a detector connected to said module and is provided for detecting said electrical discharging of said module and generating a low power control pulse upon detection of said electrical discharging, said generator being connected to a low power light generator provided to generate a light pulse under control of said control pulse, said light pulse having a power less than 1 mW and a pulse duration of less than 10 milliseconds. The use of an electrical charging-discharging module provided to operate at a power of less than 20 μW, which module is, via the electrical input, connected to the interrupt contact, enables to limit the power used by the interrupt contact and thus to satisfy with the confined environment constraints. Moreover, as the charging and discharging of the module is controlled by the interrupt contact, and as the module is connected to the detector, it is the combined operation of the module and the interrupt contact which is detected by the detector. As the power is limited by the module not only the constraints are complied with, but also a low energy consumption is provided. Finally, since the module can only be charged when the interrupt contact is in its open state, the fact that the latter would remain in its closed state will not adversely affect the energy consumption as no charging can occur in this closed state. The use of a low power light generator controlled by the pulse generator also contributes to low energy consumption as the pulse duration is less than 10 msec with a power not exceeding 1 Mw.

A first preferred embodiment of a combined set according to the invention is characterised in that said module comprises an RLC circuit of which a solenoid is connected to said interrupt contact. The use of an RLC circuit for the module enables to create a discharge pulse having a short time period and sufficient power to trigger the pulse generator. A second preferred embodiment of a combined set according to the invention is characterised in that a resistor and a capacitor of said RLC circuit are serially connected, said solenoid having one contact point connected to said interrupt contact and another contact point connected to the connection between said resistor and said capacitor. In such a manner, a controlled charging of the module is provided.

A third preferred embodiment of a combined set according to the invention is characterised in that said pulse generator comprises a microprocessor having a signal input connected to said module. The microprocessor enables a cheap and reliable realisation of the pulse generator.

Preferably said light generator comprises a LED connected in series with a transistor, said transistor having a control gate connected to said pulse generator for receiving said control pulse. The use of a LED and a transistor enables to generate a reliable light pulse at low power consumption.

The invention will now be described in more details with reference to the annexed drawings showing a preferred embodiment of a combined set according to the invention. In the drawings : figure 1 illustrates schematically a combined set according to the invention; figure 2 illustrates a decoder to be used as an additional component of the combined set according to the invention; figure 3 illustrates a preferred embodiment of an electronic circuit implementation for the combined set according to the invention; figure 4 illustrates the generation of the control pulse; and figure 5 illustrates the situation which would occur in case that the interrupt contact would remain in its closed state. In the drawings, a same reference sign has been allocated to a same or analogous element.

The combined set according to the invention and illustrated in figure 1 comprises a fluid meter 1 , for example formed by a gas meter.

The latter constitutes what is generally called a confined environment subjected to particular constraints for what concerns the use of electricity and electrical power. So, for example only a low voltage source of at the most 6V can be used and the formation of sparks has to be avoided. As there is however a need to remotely monitor such a fluid meter, in order to reduce personnel costs, solutions are needed for enabling such a remote monitoring while satisfying the constraints prescribed for a confined environment. In this context, the use of light and optical transmission are well known. The problem is however the generation within the confined environment of the optical signal carrying the data to be transferred from the fluid meter to be monitored towards the monitoring station. Usually, fluid meters such as gas meters, comprise a blade wheel (not shown) driven by the gas supplied at a gas input 13. The gas supplied at gas input 13 is directed towards the blade wheel in order to bring the latter into rotation. The gas is afterwards exhausted via a gas output 12 in order to be consumed. The blade wheel is equipped with an interrupt contact 2, which switches from an open to a closed state at each revolution of the blade wheel. The interrupt contact is for example formed by a read contact comprising a stationary magnetic contact and a further magnetic contact mounted on one of the blades of the blade wheel. So, during each complete rotation of the blade wheel, the further magnetic contact passes the stationary magnetic contact thereby switching the interrupt contact from its open to its closed state. The rotation of the blade wheel then causes the further magnetic contact to leave again the stationary magnetic contact, thereby switching the interrupt contact back to its open state. Every rotation of the blade wheel thus corresponds to the consumption of a well defined amount of fluid. By counting the total number of revolutions during a well defined period of time i.e. by counting the number of times the interrupt contact switches from its open to its closed state and back, the total consumption during that period of time can be determined.

It can happen that the blade wheel stops at a point where the interrupt contact is switched in its closed state. This can for example happen when the gas supply is interrupted, be it voluntary by the user or due to a failure in the gas supply net. If the interrupt contact is directly linked to an electrical power source, such as a battery, the fact that the interrupt contact remains in its closed state generally has as a consequence that the battery discharges to a level that the monitoring is no longer possible. As only low power batteries can be used, such a complete discharge could rapidly occur. The present invention proposes a combined set comprising a fluid meter and a pulse generator for a confined environment, which is not only capable to operate at low power but also provides a solution which avoids a discharge of the power source when the switch remains in its closed state.

As illustrated in figure 1 , the interrupt contact 2 of the fluid meter 1 is connected to an electrical input of a pulse generator 3 powered by a power source 4. The latter is preferably formed by a battery operating at a voltage of less than 6 Volt. In the embodiment illustrated in figure 1 , the pulse generator 3 has two electrical inputs (2-1 and 2-2) and is therefor provided to be connected to two interrupt contacts. The presence of more than one electrical input for the pulse generator is however not necessary for the realisation of the present invention. An output of the pulse generator is connected to a low power light generator 5 whose output is connected to an optical fibre 6. In such a manner, an optical signal is output from the confined environment, thereby satisfying the constraints imposed by such a confined environment. The optical fibre connects the pulse generator, which is situated inside the confined environment to a decoder 7, situated outside the latter environment as illustrated in figure 2. The decoder 7 comprises an optical receiver 8, for example formed by a diode, provided for receiving the light signal and convert it into an electrical signal. The optical receiver is connected to an input of a decoding unit 9 provided for decoding the received electrical signal. Of course, the decoder is provided to operate according to the same process as the one used in the pulse generator 3 to encode the signal. An output of the decoding unit 9 is connected to transmitters 10 and 11 provided for transmitting the decoded signal to a monitoring station (not shown). The transmitters are for example formed by radio or telephone transmitters.

Figure 3 shows an example of an electronic circuit forming the pulse generator 3 and the light source 5. The pulse generator 3 comprises an electrical charging-discharging module 23. In the present example this module is formed by an RLC circuit having a resistor 16, a capacitor 17 and a solenoid 15. The resistor 16 and the capacitor are connected in series while the solenoid has one contact point connected to the interrupt contact 2 and another contact point connected to the connection between the resistor and the capacitor. Preferably the resistor 16 has a value situated between 600 and 760 KΩ, in particular 680 KΩ. The capacitor 17 preferably has a value situated between 0.40 and 0.55 μF, in particular 0.47 μF. The resistor is connected to a low power source 18, preferably of 2 Volt in order to comply with the confined environment constraints. The solenoid 15 has a value situated between 120 and 170 μH in particular 150 μH.

The connection point between the resistor 16 and the capacitor 17 is further connected to an electrical input of a detector 19 formed by a microprocessor. The latter being provided to operate at a clock frequency of 32 KHz also in order to reduce as much as possible the power consumption. In order to supply such a clock frequency, a clock input of the microprocessor 19 is connected to an output of a crystal oscillator 20. The 32 KHz clock frequency enables an operation for over ten years for detecting two pulsed inputs at a 1 Hz frequency. A power input of the microprocessor 19 is connected to the low power source 18, which is formed by a battery. Instead of using a microprocessor it could also be possible to use an electronic counter. The use of a microprocessor however has the advantage that error corrections can be applied on the supplied input signal. A signal output of the detector 19 is connected to an input of the low power light generator 5. The latter comprises a resistor 24 serially mounted in the connection line 29 connecting the signal output of the detector 19 to the basis of a transistor 25. The emitter of transistor 25 is connected to earth whereas its collector is connected to the cathode of a LED 16 whose anode is connected to resistor 27 to a power source 28. The latter power source is preferably a 3.6 Volt battery power source. The resistor 27 has preferably a value of 680Ω.

The operation of the pulse generator will now be described with reference to the figures 3 and 4. When the interrupt contact 2-1 switches from its open to its closed state, the electrical circuit in which the electrical charging-discharging module (15, 16, 17) is mounted also switches to its closed state. Consequently, the electrical charge stored in capacitor 17 will discharge over the solenoid 15 (see figure 4 a). But since the connection point between the resistor 16 and the capacitor 17 is also connected to the signal input of the detector 19, the discharging of capacitor 17 will cause an input pulse (see figure 4 b) to be supplied to this signal input. By receiving this input pulse, the detector thus detects the electrical discharging of the charging-discharging module. As illustrated in figure 4 b, the input pulse is of a short time duration (+/- 10 ms) due to the rapid discharging of the capacitor 17. Due to the choice of the components forming the electrical charging-discharging module, the power consumed by this discharging is less than 20 μW. A very low power consumption is thus obtained which is not only of interest for the lifetime of the power source 18 but also for the power consumption within the confined environment.

The supply of an input pulse to the detector 19 will cause the latter to generate a low power control pulse at its signal output. The latter control pulse preferably has a time duration of less than 1 msec. If the detector is formed by a microprocessor, the latter could be programmed in order to analyse the time duration and/or the voltage level of the input pulse. In such a manner, the microprocessor would be capable to distinguish valid input signals from noise peaks.

The output low power control pulse is supplied via the connection line 29 and the resistor 24 to the basis of the transistor 25. The latter will therefor become conductive and open the electrical circuit formed by the voltage source 28, resistor 27, LED 26 and transistor 25. The opening of this latter circuit will cause current to flow through the LED 26, thereby emitting a light pulse. The choice of the components of the latter circuit enables the generation of a light pulse having a power less than 1 Mw with a pulse duration less than 10msec, in particular 500 μs, thereby again limiting the power consumption.

When the interrupt contact 2-1 now switches back to its open state, the electric circuit comprising the electrical charging- discharging module will also switch to its open state. This will cause electrical current to flow from the source 18 via resistor 16 towards the capacitor 17 in order to charge the latter again.

Suppose now that the interrupt contact 2-1 would remain in its open state, as illustrated in figure 5, then only a very low electric current could flow through resistor 16 and solenoid 15 towards the interrupt contact 2-1 , due to the chosen high value of the resistor 16. This current can however not charge capacitor 17. As the level of the signal of figure 5 b i.e. the signal at the connection point between capacitor 17 and resistor 16 remains high, the detector will not receive an input signal pulse and thus not generate an output pulse. As no output pulse is generated, the LED 26 will not be activated and no power of power source 28 will be consumed, thereby thus protecting the circuit against the situation where the interrupt contact remains in its open state.

Claims

1. A combined set comprising a fluid meter and a pulse generator for a confined environment, said fluid meter having an interrupt contact, which is provided for having an electric current flowing through it when said interrupt contact is in a closed state, said pulse generator having an electrical input connected to said interrupt contact, characterised in that said pulse generator comprises an electrical charging-discharging module provided to operate at a power of less than 20μW, said module being connected to said electrical input, said module being provided to be electrically charged when said interrupt contact is an open state and to be electrically discharged upon switching off said interrupt contact from said open state to said closed state, said pulse generator further comprises a detector connected to said module and provided for detecting said electrical discharging of said module and generating a low power control pulse upon detection of said electrical discharging, said generator being connected to a low power light generator provided to generate a light pulse under control of said control pulse, said light pulse having a power less than 1 mW and a pulse duration of less than 10 milliseconds.

2. The combined set as claimed in claim 1 , characterised in that said module comprises an RLC circuit of which a solenoid is connected to said interrupt contact.

3. The combined set as claimed in claim 2, characterised in that a resistor and a capacitor of said RLC circuit are serially connected, said solenoid having one contact point connected to said interrupt contact and another contact point connected at the connection between said resistor and said capacitor.

4. The combined set as claimed in claim 3, characterised in that said capacitor has a value situated between 0.40 and 0.55 μF, in particular 0.47 μF, said resistor having a value situated between 600 and 750 KΩ, in particular 680 KΩ, said solenoid having a value situated between 120 and 170 μH, in particular 150 μH.

5. The combined set as claimed in any one of the claims 1 to 4, characterised in that said pulse generator comprises a microprocessor having a signal input connected to said module.

6. The combined set as claimed in claim 5, characterised in that said microprocessor is provided to operate at a clock frequency of 32 KHz.

7. The combined set as claimed in any one of the claims 1 to 6, characterised in that said light generator comprises a LED connected in series with a transistor, said transistor having a control gate connected to said pulse generator for receiving said control pulse.

8. The combined set as claimed in any one of the claims 1 to 7, characterised in that said module is provided to be powered by a 3.6 Volt source.

9. A pulse generator for a confined environment as a component of the combined set according to any one of the claims 1 to 8, said pulse generator having an electrical input provided to be connected to said interrupt contact, characterised in that said pulse generator comprises an electrical charging-discharging module provided to operate at a power of less than 20μW, said module being connected to said electrical input, said module being provided to be electrically charged when said interrupt contact is in an open state and to be electrically discharged upon switching off said interrupt contact from said open state to said closed state, said pulse generator further comprises a detector connected to said module and provided for detecting said electrical discharging of said module and generating a low power control pulse upon detection of said electrical discharging, said generator being connected to a low power light generator provided to generate a light pulse under control of said control pulse, said light pulse having a power less than 1 mW and a pulse duration of less than 10 milliseconds.