RU95849U1 - WIRELESS GAS SENSOR WITH INDEPENDENT POWER SUPPLY - Google Patents

Abstract

 1. A device for measuring the composition of the gas medium containing gas sensors, an analog measuring part, a microprocessor module for controlling the operating modes of the sensors, primary processing of the measurement data and their storage, as well as the power supply circuit of the sensor and the device as a whole, characterized in that it is composed of electronic device circuitry, an integrated hardware-software interface for transmitting data and commands over wireless networks, and the algorithm for measuring and transmitting data is optimized for the autonomous operation of the device without replacing batteries during recalibration (mezhkalibrovochnogo) interval. ! 2. The device according to claim 1, characterized in that a ZigBee modem is used for data transmission. ! 3. The device according to claim 1, characterized in that the ZigBee modem is compatible with other data transfer standards WPAN, SRD, ISM, etc.! 4. The device according to claim 1, characterized in that the data is transmitted from a transmitter made on the same chip with a microprocessor (microcontroller). ! 5. The device according to claim 1, characterized in that CH4, CO, H2 or their mixtures are detected, including in the presence of extraneous components. ! 6. The device according to claim 1, characterized in that the device is capable of transmitting through itself the commands transmitted to the dispatch console from other devices. ! 7. The device according to claim 1, characterized in that the control modes of the sensors and the device as a whole is carried out from the control panel by transmitting commands over the air. ! 8. The device according to claim 1, characterized in that the device is self-powered from batteries, chemical elements, fuel cells, solar panels, capacitors, piezoe

Description

The technical field to which the utility model relates.

The invention relates to the field of monitoring the parameters of the gas environment and is intended to automatically control the concentration of explosive, fire and toxic hazardous gases in the atmosphere of residential premises, inside and on the territory of industrial facilities, as well as in the atmosphere of mine workings and issuing not only an individual alarm when reaching the measured component of the set threshold values, but also data transmission over the wireless sensor network to the control room control (control panel).

In particular, the invention may find application:

- as autonomous wireless sensors for monitoring the concentration of methane (CH ₄ ) of gasified apartment buildings and individual houses, at oil and gas facilities; in the atmosphere of mine workings, coal mines;

- as autonomous wireless pre-fire detectors for monitoring the chemical composition of air (in particular, СО and Н ₂ ) in order to prevent a fire at an early stage preceding a fire;

- as autonomous measuring (control) devices in the construction of wireless sensor networks.

State of the art

Known multi-gas multi-channel stationary gas control system [http://www.deltapro.ru/catal_igs98_ss.aspx]. The gas control system consists of a control panel and stationary sensors. The sensors are connected to the control panel with a 4-wire cable, providing power to the sensor circuit and transmitting information to the control panel (Fig. 1).

This system allows you to:

- continuous automatic control of gas pollution through N channels;

- issue warning and emergency light and sound signals and signals to the control panel of external systems (on / off ventilation, etc.) using the built-in relay;

- display the concentration values for each channel on the built-in display (sensor and remote, only sensor, only remote);

- adjust the threshold in accordance with a given algorithm

- install a readout memory unit with the ability to output and process data on a PC;

- connect sensors of other manufacturers or other measured physical quantities (temperature, pressure, etc.) to the control panel;

- connect sensors to existing security systems.

The disadvantage of this device is that the sensors are connected to the control panel with a 4-wire cable, providing power to the sensor circuit and transmitting information to the control panel. This limits the number of sensors and the possibility of arbitrary arrangement of sensors in a controlled room. In addition, the controlled premises must be electrified.

Known gas analyzer ESSA with a radio channel [http://safeair.ru/content/view/97/51/], which is a multi-channel device with wireless data transmission. The gas analyzer is designed to control toxic gases (chlorine, ammonia, sulfur dioxide, carbon monoxide, hydrogen sulfide, nitrogen oxide and dioxide, ozone) and oxygen in the air.

Data is transmitted by a radio modem in the frequency range from 433.1 to 434.7 MHz. The communication range in open space is up to 3 km with the possibility of expansion with the help of repeaters.

There are two options for performing a gas analyzer:

1) The gas analyzer consists of one or more measuring transducers, a data acquisition and transmission unit, and a portable registration unit. The measuring transducers are connected to the data acquisition and transmission unit by cables, and the structure is no different from the usual multi-channel gas analyzer ESSA. Transmitters are powered by a data acquisition and transmission unit. The radio modem is installed in the data collection and transmission unit and operates on the same frequency. Data from each primary converter is formed into a packet and transmitted over the air to a recording unit equipped with a receiving device.

2) The gas analyzer consists of one or more measuring transducers and a portable registration unit. A radio modem is installed on each transmitter. In this case, up to 16 frequency channels can be used. The transmitters can be powered from the mains or from rechargeable batteries.

This gas analyzer is used in cases where cabling is difficult and if a stationary gas analyzer is not provided, and there is a need to control the content of toxic substances in the air (for example, during commissioning).

The disadvantages of this device is the limited number of measuring transducers (maximum 16), which is associated with the selected frequency range from 433.1 to 434.7 MHz (frequency separation 100 kHz) and the data transfer standard. In addition, the communication range of up to 3 km (in open space) requires a relatively powerful transmitter and receiver and, accordingly, external antennas and a powerful power source. This does not make the gas analyzer compact and non-volatile for a long battery life. The data frequency range is reserved for low-power radio stations, therefore, there may be problems with the imposition of signals from third-party communication systems due to the insecurity of such a data transmission channel, as well as the possibility of unauthorized access to the gas measurement system.

Known quickly deployed, wireless, multi-functional gas detector AreaRAE Responder [http: //www.cis-controls.ru/pdf/AreaRAE_Responder_Europe_RU.pdf |.

AreaRAE Responder is a multi-channel gas analyzer, with data transmission over the air, ATEX certification for explosion protection. Thanks to its welded stainless steel housing, it is a particularly rugged portable and sealed device, suitable for use in adverse environmental conditions. The gas analyzer is ideally suited for monitoring hazardous substances in the air and can be used in emergency situations, as AreaRAE Responder instruments can be used to quickly determine the perimeter of exposure to hazardous substances and allow emergency response services to be at a safe distance and monitor the situation at a distance of up to 3 kilometers.

A photoionization detector (PID), available in the AreaRAE Responder, detects the concentration of volatile organic compounds to the nearest millionths. The gas analyzer is equipped with sensors of the lower limit of explosive concentration, oxygen content, as well as for measuring the concentration of toxic gases such as hydrogen sulfide, chlorine, etc. Data on the measured gas concentration is transmitted in real time by the built-in radio modem to the base station, which consists of a standard personal computer with ProRAE Remote and Windows operating system installed on it. The base station can simultaneously monitor and display eight AreaRAE Responder and / or AreaRAE Responder Gamma instruments (or other AreaRAE compatible gas analyzers, including MultiRAE, MiniRAE 2000, ppbRAE, Smiths APD-2000®, RAE ChemSentry®, and Coastal Environmental Systems Weatherpak® ) This allows you to create a network for controlling hazardous substances and to control a large area. Using the capabilities of a cellular network created by several AreaRAE Responder instruments, gas analyzers can operate at a large distance from the receiving station and in a difficult radio environment.

This gas analyzer allows you to:

- Transmit received data in real time through the built-in radio modem

- View data received from sensors in real time and issue an alarm at headquarters or command post

- Simultaneously monitor and display information from 8 remotely installed devices

- Transmit data at a radio frequency of 869 MHz over a distance of 3 km

- Create a cellular network based on AreaRAE Responder devices that act as repeaters, contributing to a significant expansion of the radio coverage area

Applications are

- Emergency situations with the identification of hazardous substances

- Oil refineries and petrochemical plants

- Power plants

- Pulp and paper industry

- Prestarting / pre-operation operations on production and design equipment

- Oil wells on the high seas.

The disadvantages of the device are: short battery life (24 hours of continuous operation in the mode with a radio modem with a lithium-ion battery). A limited number of sensors. In addition, the frequency range of 869 MHz is intended for cellular systems of mobile and stationary radio communications, and not for sensor networks.

Known wireless gas sensor Major MR-GS01 [http://www.major-gsm.ru/photo/7/5/], which is designed to detect gas leaks in the room. In addition to the fact that the device is a GSM sensor and sends an alarm to the base, it is also equipped with its own autonomous sound and light alarm systems. The sensor can also be used both as part of a GSM security system, and as an exclusively gas sensor. The sensor has a built-in combined indicator and operates at a frequency of 433 MHz. The signal range is about 100 m.

The disadvantages of this device is that it requires 220 V mains power, there is no possibility of creating a sensor network based on such sensors and the signal can be transmitted to the base station through other sensors.

Closest to the described is a device (gas analyzer) [A.E.Senkin, B.I. Seleznev, A.I. Maksimov, V.A. Moshnikov, Microprocessor gas analysis module. Bulletin of Novgorod State University, No. 26, 2004 p.161-167], containing a semiconductor sensor for measuring the concentration of CO and CH ₄ , a microprocessor gas analysis module, a serial data transfer interface and a network adapter.

The advantages of this device is that the microprocessor gas analysis module allows you to change the temperature of the sensor element according to any law in the measurement cycle and take measurements at any point in this cycle. It combines the following functionality:

- measuring the resistance of the sensitive surface of the sensor at any time during the heating cycle;

- temperature control of the sensitive surface of the sensor with the possibility of implementing various temperature conditions (continuous, pulsating, linear scanning by temperature);

- the conversion of the resistance value of the sensitive surface to the concentration of the analyzed gas or gases;

- the ability to simultaneously determine the concentration of CO and CH ₄ ;

- the ability to programmatically automatically calibrate and reconfigure the device for a specific type of sensor;

- data transmission via a serial interface and the possibility of building, based on the device, branched networks for monitoring the gas situation;

- remote control of the operating mode and self-diagnosis.

Such an approach to the implementation of electronic control and data processing devices for semiconductor gas sensors makes it possible to increase the information content of the sensor response to the influence of the gas medium by choosing the temperature regime and the measurement algorithm that meets the physicochemical specifics of a particular sensor.

The module uses a pulse-width pulse width modulated (PWM) method of temperature control. The temperature is stabilized at the desired point by continuously measuring the resistance of the heater, calculating the deviation of this resistance from the set value (corresponding to the set temperature) and controlling the width of the voltage pulses on the heater. A quick exit to the operating mode is provided by a proportional-integral controller programmatically implemented in the microcontroller, the gain of which is selected experimentally based on the conditions of the maximum heating rate and minimum transient processes when the set temperature mode is reached. The pulse-width heating method, in addition to reducing power consumption, allows you to separate the time measurements of the resistance of the sensitive layer and the heater (to determine the temperature), which allows you to use the device for sensors made on a micro-membrane, in which the heater and the sensitive layer are electrically connected to each other. To implement the module, an ATMEL ATmega8 microcontroller was used, the periphery of which includes an 8-channel 10-bit ADC, a UART transceiver unit, and a timer with the ability to operate in pulse-width mode, which made it possible to run the entire device on almost one chip (see Fig. 1 )

To measure the concentration of CO, a pulsating temperature regime is used: heating to a temperature of 450 ° C for 1.5, followed by stabilization of the temperature at 110 ° C. The entire heating cycle period was 10 s. Measurements of the resistance of the sensitive layer and the temperature of the working surface are carried out throughout the cycle after 100 ms. Real-time data is transferred to a personal computer, where they can be saved as a text file. To exchange data with a personal computer and configure the operating mode, a special program has been developed for a microprocessor gas analysis module.

The disadvantage of this device is the use of a serial transmission interface (wired data transfer), which does not provide for the possibility of building a sensor and the presence of mains power. This limits the possibility of real practical use of this gas analyzer, which is most likely used for laboratory research, since it is required to connect cables to each of the gas analyzers used (for power supply and data transmission to the control room). In the case when the simultaneous use of a large number of gas analyzers is required, this solution is not possible. In addition, this gas analyzer is devoid of mobility.

Utility Model Disclosure

The technical task of the utility model is to create a portable wireless autonomous sensor for monitoring the composition of the gas environment, promptly informing the relevant services in case of emergency, and expanding the arsenal of technical means of gas monitoring for cases where there are no power supply systems and cable telemetry in the monitoring zone.

The technical result, which provides a solution to the problem, consists in increasing the battery life of the sensor, including in the device hardware-software interface for transmitting data and commands over wireless networks, as well as expanding the functionality due to the formation of sensor networks based on similar sensors, covering large territory and the possibility of subsequent data transfer to the cellular network (GSM) and the Internet (GPRS).

The essence of the invention lies in the fact that the gas sensor contains gas sensors, an analog measuring part, a microprocessor module for controlling the operating modes of the sensors, primary processing of the measurement data and their storage, as well as the power supply circuit of the sensor and the device as a whole, while the device electronic circuit a hardware-software interface for transmitting data and commands over wireless networks is integrated, and the algorithm for measuring, processing and transmitting data is optimized for the purpose of autonomous operation of the device without replacing batteries during the inter-calibration (inter-calibration) interval.

At the same time, refusal to transfer data over wire lines is most effective with a simultaneous refusal from mains power. The need for mains supply limits the area of use of the device, complicates and increases its cost due to the need to have a voltage converter with ~ 220 V to 3-5 V DC.

In addition, the technical result is achieved due to the ability of the sensor to transmit through itself the commands transmitted to the control panel from other sensors; the ability to control the operating modes of the sensor from the control panel by transmitting commands over the air; the use of autonomous power from batteries, chemical elements, solar panels, piezoelectric transducers, fuel cells, capacitors, or a combination thereof; the use of semiconductor, thermocatalytic, conductometric, electrochemical, optical sensors, or a combination thereof; use of a pulse (periodic) gas concentration measurement mode: measurement mode - standby mode - measurement mode; the use of sound and light alarms when the specified concentrations are exceeded, the built-in vibration signal, as well as the ability to display data on the device display; the ability to determine the location of the device in a known three-dimensional volume; monitoring capabilities of other environmental parameters (temperature, humidity, pressure, etc.); connectivity to existing security systems; the ability to send commands to the control panel of external actuators.

For the wireless transmission of measurement data, it is preferable to use the IEEE 802.15.4 standard and the ZigBee high network layer protocol, since its software and hardware interface, unlike conventional radio channels, allows you to create sensor networks from an almost unlimited number of devices. ZigBee technology has frequency channels in the ranges of 868 MHz, 915 MHz and 2.4 GHz. At the same time, the highest data transfer rates and the highest noise immunity are achieved in the 2.4 GHz band. In addition, the use of a frequency of 2.4 GHz allows you to make the antenna smaller than 1 cm and remove it inside the device. A small data transmission distance allows you to reduce the power of the transmitter and, therefore, reduce the size and increase the battery life of the entire device.

Using the ZigBee data transfer standard in the described sensor allows you to create reliable, inexpensive, low-energy wireless devices that provide information protection and the required characteristics of radio frequency performance.

Moreover, the combination of measurement functions with the technology of data exchange via radio channel and autonomous power supply makes it possible to create wireless sensor networks from such sensors for monitoring the gas atmosphere both indoors and outdoors, including in large areas, when it is necessary to carry out monitoring in large number of points. In particular, for monitoring rooms inside multi-story buildings, territories of oil and gas refineries, mining, gas pipelines, as well as forests, waste dumps, roads. A concrete example is the pre-fire detectors and methane sensors in the premises of gasified houses, installed in apartments of apartment buildings or office premises.

Moreover, ZigBee-based networks are self-forming and self-healing networks. This is a consequence of the fact that ZigBee devices, when turned on, thanks to the built-in software, can "find" each other and form a network, and if any of the nodes fails, they are able to establish new routes for sending messages.

The device’s compactness, independence from mains power and data cables, together with the ability to form self-forming sensor networks, reduce the time and cost of technical, human and financial resources for the deployment of gas monitoring systems, expand their scope and avoid the limitations associated with with data loss during disconnection (in emergency situations) of the mains supply, cable breakage and failure of some devices.

In addition, the combination of microprocessor technologies with wireless data transmission technologies allows issuing commands to executing devices that are remote over long distances, in particular, shut-off valves for gas supply systems, ventilation, power switches, etc.

To expand the functionality of the device and integrate it into security systems, global information or measurement networks, it can be additionally equipped with wireless GSM / GPRS, Wi-Fi, Bluetooth and other transmitters and devices for transmitting data using industrial RS 232 communication protocols, RS 485, CAN, etc.

Brief Description of the Drawings

Figure 1. Schematic diagram of a microprocessor module for controlling a semiconductor gas sensor operating in PWM mode.

Figure 2. Schematic diagram of a wireless sensor with a semiconductor sensor.

Figure 3. Schematic diagram of a wireless sensor when measuring using thermocatalytic sensors

Figure 4. Appearance of the device board.

Figure 5. Sensor temperature and current Ish depending on heating time

6. Voltage dependencies on the diagonal of the bridge (Um):

a) from the heating time and the concentration of CH ₄ in air: 0%, vol., 0.25%, vol. and 2%, vol .;

b) on the concentration of CH ₄

7. Schematic diagram of a wireless gas analyzer with a semiconductor sensor and two thermoelectric sensors.

Utility Model Implementation

Example. 1. Wireless sensor with a semiconductor gas sensor

The device consists of a case (83 × 53 × 30 mm in size), a board placed in it, and a battery compartment with three AA cells. The board contains a semiconductor gas sensor with an analog measuring circuit, a microprocessor module, video and audio signaling devices, a device power circuit, a wireless transmission module and ports for programming the microprocessor and modem. The wireless data transmission module is a ZigBee standard modem using a 2.4 GHz frequency channel. The device has a hardware-software interface for wireless data exchange with the dispatch console.

The microprocessor module controls the operation of the sensors and the entire device according to the algorithm laid down in it. In particular, it carries out primary processing of data received from sensors, calculates the concentration of the monitored gas, compares the obtained value with the values of the maximum permissible concentrations, and, in case the measured value exceeds the maximum permissible value, instructs the ZigBee modem to send an alarm to the control panel corresponding to the degree of danger. The memory of the microcontroller can contain one or several threshold values for each monitored gas or the corresponding functional dependence.

The device is designed to detect methane (CH ₄ ) in the atmosphere, as well as work as a pre-fire detector (in this mode, CO and H ₂ are measured). The sensor itself is a membrane with a microheater and a semiconductor sensitive layer deposited on it. The power consumed by the sensor in continuous measurement mode is ~ 60 mW.

The device is two threshold. The first warning signal is transmitted to the control panel when the methane concentration exceeds 0.25%, vol. the second - when the concentration is exceeded - 1%, vol.

Schematic diagram of a wireless gas analyzer with a semiconductor sensor is presented in figure 2.

The principle of the device’s operation is that with a period of 30 seconds, the pulse width modulation (PWM) signals of 500 ms duration are received from the Atmega168P microcontroller PC2 port line to the “gate” of the VT1 transistor, as a result of which a voltage of 500 ms is applied to the sensor element and an amplitude of 3.3 V, which heats the sensor element to a temperature of 450 ° C. Under the influence of gases of various compositions, the conductivity of the sensitive layer of the semiconductor sensor changes. Data on the changes in the conductivity of these layers are received on the port lines of the RSO and RS1, the built-in ADC of the microcontroller DD1. The microcontroller DD1 performs primary processing of the received data and transmits the result via the RXD line to the DD2 wireless data transmission module (ETRX2). This module transmits data to the control room. Direct ports IDC6M and X2 are also provided for programming the microcontroller DD1 and the wireless data transmission module DD2, respectively. Using the PD1 line, you can control the power supply of the analog part of the circuit (by supplying the corresponding signal to the “gate” of the transistor VT2), apply or de-energize the power of the operational amplifier (IC DA1) to reduce power consumption. Also, in the design of the wireless gas analytic sensor module, sound PZ1 and light HL1-HL3 information emitters are provided.

In order to save energy, gas concentration measurements are carried out in a periodic mode: measurement mode - standby mode - measurement mode. The duration of the measurement mode is determined by the type of sensor, or rather, the time the sensor goes to operating mode. The standby time is determined by the technical requirements. Typical values are in the range from 10 to 60 s.

Moreover, in the measurement mode, all elements of the device are turned on except for the ZigBee modem. In standby mode, all elements of the device are in minimum power consumption modes. The ZigBee modem is in minimum power mode all the time except when the command “send data” to the dispatch console comes from the microcontroller. At this point in time, the modem enters the transmit-receive mode, establishes communication with the dispatching console, transmits a data packet, waits for confirmation of receipt of data, and returns to the minimum power consumption mode.

This device is powered by three batteries. The battery life is 10-12 months (with 1 measurement per minute). It is also possible to use alternative sources of electrical energy, such as solar panels, to increase the operating time of the sensor.

Example 2. A wireless sensor with a semiconductor and two thermocatalytic gas sensors.

Unlike example 1, this device is supplemented by two thermocatalytic sensors included in the bridge measurement circuit, and has circuitry features

The device is designed to perform the same tasks as the device in example 1. Moreover, different types of sensors have different responses to the same gases. This allows you to more accurately determine the value of the concentration of the measured gas.

Unlike example 1, this device uses a microcontroller that has a digital-to-analog converter (DAC), which allows you to adjust the amplitude of the voltage supplied to the microheater (in contrast to the PWM feed mode, in which the applied power is adjusted by the duration and duty cycle of the pulses) . This significantly expands the ability to control the heating modes of the sensor and, accordingly, allows more accurately determine the concentration of monitored gases. In addition, the use of the DAC significantly expands the capabilities of the device as a whole, as it allows the use of other types of sensors that cannot work in the PWM mode (electrochemical, optical, etc.). Otherwise, the principle of operation of this device is similar to that described in example 1.

Consider the operation of the device in the measurement mode with thermocatalytic sensors. The functional purpose of the sensor in this measurement mode is to operate as a two-threshold wireless methane signaling device (CH ₄ ) in air in the concentration range 0-50% LEL (0-4.4%, vol.). The first threshold (warning) lies in the range of methane concentrations of 0.25-1%, vol., The second threshold (alarm) is in the range of 1-2%, vol.

The main elements of the circuit (Fig. 3) are: ADuC836 micro-converter (MK), TG-ETRX2 ZigBee modem, AD8532 operational amplifier (op-amp) and ADP3335 stabilizer.

The measuring sensor RK1 together with the compensation sensor RK2 is installed in the bridge circuit (R1-R2-RK1-RK2). The shunt R3 (C 1-4) is also installed in the circuit, the nominal value of which is 1 Ohm. The resistance of the RK1 and RK2 sensors at room temperature is 12 ohms. The nominal resistance R1 and R2 is 1000 Ohms.

The measured parameters are: the potential difference of the measuring diagonal of the bridge (Um) (inputs AIN1 and AIN2) and the voltage at the shunt R3 (Uш) (input AIN5).

The bridge circuit is controlled using the ADuC836 micro-converter (MK). This micro-converter was selected on the basis that it has sufficient speed and at the same time has low power consumption in active and sleep modes (Table 1).

Table 1. The current consumption of the main elements of the sensor in different operating modes Sensor Mode Current consumption, no more than mA ADuC836 TG-ETRX2 ADP3335 Bridge circuit Mode 2,3 0.01 one 50-90 Mode 2,3 42 0.5 0 "Sleeping" 0.02 0.01 0.08 0

The operation of the wireless sensor is optimized to ensure minimum power consumption. As can be seen from table 1, the main consumer of power are sensors. In continuous operation, when the sensors are constantly heated to operating temperature, the sensor can work from elements of type AA for no more than 50 hours. Therefore, the periodic regime of measurements of methane concentration in air was realized and studied in the work. That is, the sensor implements three modes: - data measurement mode, data transfer mode and "sleep" mode (power saving). The frequency of measurements is determined by regulatory documents [GOST R 52136-2003. Gas analyzers and signaling devices for flammable gases and vapors, electric. Part 1. General requirements and test methods] and, in particular, for monitoring methane concentration, the time for establishing the sensor readings at 50% of the volume fraction of methane with an abrupt increase in its concentration should be no more than 20 s [GOST R 52137-2003. Gas analyzers and signaling devices for flammable gases and vapors, electric. Part 2. Requirements for devices of group I with an upper limit of measurements for the volume fraction of methane in air no more than 5%]. The duration of the measurement is determined by the time the sensors reach the operating mode and is discussed below.

To control the operation of the current buffer on the basis of the ОУ AD8532, a key is used on the VT1 field-effect transistor, which is connected to the MK I / O line P2.0. In the ground state (“sleep mode”) this key is closed, the op-amp is turned off and there is no current through the bridge circuit.

Every 20 seconds, when an interrupt is triggered by the built-in on-timer, the MK switches to the active mode of operation, opens the VT1 key, supplies a voltage of 2.8 V from the output of the DAC to the input of the OA, and measures the corresponding circuit parameters. The choice of the sensor heating voltage value of 2.8 V is due to the fact that this voltage value is working for the sensors in the case of continuous operation.

The value of the bridge potential difference (Um) is converted into an equivalent digital code using a 16-bit ADC microconverter. The conversion time is 10 ms. Since the ADC is used only for measurements, the power of the ADC, as well as the power of the analog part of the circuit, is programmatically turned off after the measurement.

The obtained value of the potential difference of the diagonal of the bridge is compared with threshold values (for 0.25%, vol. And 2%, vol. CH4) stored in the micro-converter. Concentration values below the hazardous value are ignored and the sensor enters energy saving mode. If one or both thresholds has been exceeded, the MC sends to the radio modem bytes of data via the asynchronous serial UART interface, thereby switching the modem to the active state. Then, a packet with information about the measured concentration is sent to the modem via the UART interface. The modem transmits this data to the dispatch console, which in our case was a computer with a ZigBee USB modem connected to it. A program was installed in the computer that displayed measuring sensors and the concentration of methane in the air. The data transmission range inside the building was 25-30 m.

The sensor is powered by three AA batteries with a voltage of 1.5 V and a capacity of about 3000 mAh. All elements of the circuit are matched by the supply voltage, which is 3.3 V. The ADP3335 stabilizer provides the setting and maintenance of this voltage.

The appearance of the device is presented in figure 4.

Figure 5 shows the dependence of the current Ish (curve 1) flowing through the shunt R3 (in fact, this current value coincides with the current flowing through the arm of the bridge in which the sensors are located), and the dependence of the temperature of the sensors on the heating time (curve 2) with the supply voltage of 2.8. B. It is seen that the time for heating the sensors to an operating temperature of 450 ° C is about 0.9 s. This time can be considered as the time the sensors entered the operating mode. It is a voltage pulse with a duration of at least 0.9 s that must be supplied to the bridge circuit to ensure that measurements are taken.

The current flowing through the sensors in operating mode is 52 mA. Accordingly, the power consumed by each sensor was 73 mW.

Figure 6 shows the experimental dependences of Um on the heating time of the sensors (Fig.6a) and the dependence of Um on the methane concentration (Fig.6b), measured 0.9 s after applying voltage to the bridge circuit, by which it is possible to determine the concentration of methane in air .

Based on the obtained dynamic parameters of the sensor, it is possible to estimate the time of its operation on autonomous power supply. Assuming the sensors have an operating time of 0.9 s, a supply voltage of 2.8 V and calculating the average current during heating, which is ~ 60 mA, we obtain that the capacities of three AA batteries are (stored power 13.5 Wh ) is enough for ~ 320 thousand measurements (excluding consumption in "sleep mode"). At three measurements per minute, this corresponds to ~ 74 days. During the same time, the consumption in sleep mode will be about 0.65 Wh. Which is about 5% of the battery capacity.

A further increase in the operating time of the wireless sensor is possible by replacing three AA batteries with 3 D type batteries (having a reserve of 15,000 mAh). This will increase the working time to ~ 360 days.

Schematic diagram of a wireless sensor with a semiconductor sensor and two thermoelectric sensors is shown in Fig.7.

The control circuit DD1 (ADuC836) performs the initial processing of the received data and transmits the result via the RXD line to the wireless data transmission module DD2 (TG-ETRX2). Warming up the sensor element to the operating temperature is carried out by applying PWM pulses or from the DAC of the DD1 microcontroller (DAC line). The choice of heating method (PWM or DAC) for semiconductor and thermocatalytic sensors is carried out using a jumper JP2. The board directly provides the XS2 port for programming the microcontroller DD1 and the wireless data transmission module DD2, respectively. Also, programming of the DD2 wireless data transmission module and the DD1 microcontroller can be carried out from the control panel. Using the PD1 line, you can control the power supply of the analog part of the circuit (by supplying the corresponding signal to the “gate” of the transistor VT2), apply or de-energize the power of the operational amplifier (IC DA1) to reduce power consumption. The design of the wireless gas analytic sensor module provides sound PZ1 and light HL1 and HL2 signaling.

Claims (24)

1. A device for measuring the composition of the gas medium containing gas sensors, an analog measuring part, a microprocessor module for controlling the operating modes of the sensors, primary processing of the measurement data and their storage, as well as the power supply circuit of the sensor and the device as a whole, characterized in that it is composed of electronic device circuitry, an integrated hardware-software interface for transmitting data and commands over wireless networks, and the algorithm for measuring and transmitting data is optimized for the autonomous operation of the device without replacing batteries during recalibration (mezhkalibrovochnogo) interval. 2. The device according to claim 1, characterized in that a ZigBee modem is used for data transmission. 3. The device according to claim 1, characterized in that the ZigBee modem is compatible with other data transfer standards WPAN, SRD, ISM, etc. 4. The device according to claim 1, characterized in that the data is transmitted from a transmitter made on the same chip with a microprocessor (microcontroller). 5. The device according to claim 1, characterized in that CH ₄ , CO, H ₂ or mixtures thereof are detected, including in the presence of extraneous components. 6. The device according to claim 1, characterized in that the device is capable of transmitting through itself the commands transmitted to the dispatch console from other devices. 7. The device according to claim 1, characterized in that the control modes of the sensors and the device as a whole is carried out from the control panel by transmitting commands over the air. 8. The device according to claim 1, characterized in that the device is self-powered from batteries, chemical elements, fuel cells, solar panels, capacitors, piezoelectric transducers, etc., or a combination thereof. 9. The device according to claim 1, characterized in that semiconductor, thermocatalytic, conductometric, electrochemical, optical sensors or a combination thereof are used as gas sensors. 10. The device according to claim 1, characterized in that it, in order to save energy, implements a pulse (periodic) mode of measuring gas concentration. 11. The device according to claim 1, characterized in that a constant voltage generated by a digital-to-analog converter (DAC) is used to heat the semiconductor and thermocatalytic sensors to the operating temperature. 12. The device according to claim 1, characterized in that pulse-width modulation is used to heat semiconductor and thermocatalytic sensors to operating temperatures. 13. The device according to claim 1, characterized in that it has sound and light alarms when the set concentrations are exceeded, a vibration signal, as well as the ability to display data on the display of the device. 14. The device according to claim 1, characterized in that, in order to save energy, data is transmitted to the control panel (data collection point) over the air in a pulsed mode: data transfer - standby mode - data transfer. 15. The device according to claim 1, characterized in that the housing of the device is made in explosion-proof execution (in particular, with the marking "ROIaS). 16. The device according to claim 1, characterized in that it is possible to determine the location of the device in a known three-dimensional volume. 17. The device according to claim 1, characterized in that the device, in addition to measuring the concentration of gases, monitors other parameters: temperature, humidity, pressure, etc. 18. The device according to claim 1, characterized in that it has the ability to connect to existing security systems. 19. The device according to claim 1, characterized in that it has the ability to issue control commands to external actuators (valves). 20. The device according to claim 1, characterized in that it has the additional ability to transmit data in a cellular network standard. 21. The device according to claim 1, characterized in that it has the additional ability to transfer data to the Internet. 22. The device according to claim 1, characterized in that it has the additional ability to transmit data using industrial data transfer protocols RS 232, RS 485, CAN, etc. 23. The device according to claim 1, characterized in that it has the additional ability to power or charge the batteries from the mains. 24. The device according to claim 1, characterized in that it has devices for attaching to the wall.