FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
"A SMART SENSOR"
We , UNITED PHOSPHORUS LIMITED,
a company incorporated under the Companies Act,
1956 and having its corporate office Uniphos House,
11th Road, C. D Marg, Khar (West),
Mumbai - 400 052,
State of Maharashtra
INDIAN.
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:-
A Smart Sensor
Field of Invention:
The present invention relates to smart sensors. More particularly, the present invention relates to a hot swappable smart sensor having the provision of auto calibration. The smart sensor is incorporated with an EEPROM in which the full calibration data is stored making the smart sensor module an independent sensor unit containing the full sensor signature.
Background of the Invention:
The sensors are widely used in instruments used to detect the presence of combustible and toxic gases and vapors in the industrial environment for the purpose of safety. The sensors are also used on instruments which give a warning of potentially hazardous conditions in the environment before these gases or vapors reach explosive levels.
However, these instruments need periodic calibration. The calibration of an instrument relates the target gas concentration to the physical or chemical change occurring as a result of the exposure of the sensor to the gas. This change is directly proportional or is related to the gas concentration. Practically, the sensor of an instrument is exposed to a known concentration of target gas and the instrument is made to read this concentration. If the relation is linear, when exposed to other gas concentrations, the sensor should read the exposed concentration on its display.
However, the necessity of periodic calibration arises because the amount of physical or chemical change which occurs per ppm of target gas concentration does not remain constant with time. The amount of change per ppm depends upon the nature of the sensor. Hence the instrument has to be calibrated periodically to again correlate the gas concentration to the concentration displayed on the monitor. The frequency of calibration required depends upon how fast the signal per ppm changes with time.
These sensors are typically used on handheld or portable instruments and may be carried to the manufacturer's location in order to carry out the periodic calibration. However, the use of fixed gas monitoring devices is also prevalent in the art, which also require frequent calibration. These fixed monitoring devices are often meant for continuous monitoring. Therefore, dismantling the fixed monitoring device set up, transporting the same for calibration and reinstalling the same at the desired location is not only inconvenient but also risky since the affected portion of the industrial set up remains without any real time monitoring during the calibration procedure. These fixed devices may also be installed at inconvenient places making it harder to dismantle and re-install the same during the calibration procedure. Accordingly, there exists a need in the art for a smart sensor that is portable as well as stores the calibration information on the sensor itself which can be used on any field transmitter.
The on-site calibration of the fixed monitoring devices is cumbersome. Many a time, the existing sensor in a monitoring device needs to be replaced altogether, which further needs to be calibrated subsequent to being replaced. It is difficult to carry out these activities at the monitoring site especially when the device is located at an inconvenient place or wherein the risk of accidental gaseous exposure runs very high.
In certain other industries, a number of such monitoring devices are installed at separate locations. This makes the calibration procedure more time consuming as each of these installations need to be individually checked and calibrated differently depending on the extent to which the sensor reading has drifted from the standard. This problem is compounded when the individual monitoring devices are situated at different places and are fabricated to detect different gases. Therefore, it is required to arrange for transporting all the standard gas calibration cylinders to the industrial site and calibrating different devices individually.
It is therefore desirable to provide a smart sensor which is pre calibrated and is capable of being hot swapped. It could be unplugged from the monitoring device, plugged into a calibrator for calibration and plugged back into the device again after calibration.
It is further preferred to provide a smart sensor which is hot swappable i.e. which can be unplugged and plugged back into the monitoring device with a little interruption in the functioning of the monitoring device. In any industrial setting that deals with toxic chemicals and fumes, hot swapping is a necessity as the monitoring device is required to be constantly available.
In some other circumstances, these smart sensors need to be capable of triggering an alarm event when a chosen concentration of the monitored gas is reached or exceeded. Conventionally, a pellistor has been used for detection of toxic or combustible gases within an enclosure. However, a major problem associated with the use of the presently known pellistors when used on instruments is the baseline shift which requires frequent corrections or setting. This problem does not pose a serious impediment when these sensors are used on hand held and portable instruments used for occasional measurements of combustible gases. This is because before making measurement it is possible to adjust the baseline to zero in clean air. However when these pellistors are used on fixed systems for continuous measurement it is not practicable to adjust the zero in clean air. Measurements made with a drifted baseline lead to erroneous readings.
Moreover, in all prefabricated pellistors, the ratio of resistances of the compensator and detector arms of the Wheatstone bridge changes to different degree and zero drift is inevitable during prolonged operation of the pellistor. The zero drifts as described above can be as high as or even cross the alarm set point leading to false alarms. In such a scenario, the zero-drifted pellistor sensors remain electrically operational and display a reading even when pellistor has not encountered any gas. It is also seen that when combustible gas is present, the reading which it shows is higher or lower by the amount of zero drift. The conventional prefabricated pellistor bead pairs further display a tendency because of which their resistance ratio changes quite erratically and also by a large amount with the passage of time. Thus, these catalytic bead sensors require frequent adjustment of zero particularly during the initial stage of their life and even later the drift can continue although at a slower rate.
These and the other advantages of the present invention are realized by an invention described hereinafter.
Objects of the invention:
Thus, an object of the present invention is to provide a hot swappable smart sensor module carrying the full information about the calibration of the sensor.
Another object of the present invention is to provide a hot swappable smart sensor module that enables the swapping of the sensor module on the monitoring device.
Yet another object of the present invention is to provide a hot swappable smart sensor module which when plugged to a monitoring device is capable of directly displaying the . gas concentration on the monitoring device without needing any further calibration.
Another object of the present invention is to provide a smart sensor module which could be externally unplugged from a monitoring device, plugged into a calibrator for calibration and plugged back into the monitoring device subsequent to calibration with least interruption of the functioning of the monitoring device.
Yet another object of the present invention is to provide a smart sensor module that is capable of being used on any monitoring device.
Another object of the present invention is to provide a smart sensor module that triggers an alarm event every time a chosen concentration of a monitored gas is exceeded.
These and the other advantages of the present invention are realized by an invention described hereinafter.
Summary of the invention
A hot swappable smart sensor module comprising:
(a) a selected sensor; and
(b) an electronic module connected to said sensor, said electronic module comprising at least one signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device with information stored therein; wherein said information stored on said non-volatile storage device includes information identifying said selected sensor and a plurality of parameters related to said sensor.
A smart monitoring device for monitoring a selected gas within a selected enclosure, said monitoring device comprising:
(a) a selected sensor;
(b) an electronic module connected to said sensor, said electronic module comprising at least one signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device having information stored therein, said information stored on said non-volatile storage device includes a plurality of parameters related to the identification of said selected sensor; and
(c) a processing module electronically connected to said sensor module, and said processing module comprising a plurality of signal processing devices, at least a microcontroller and at least one output device, said processing module being additionally capable of calibrating said smart sensor module by accessing information stored on said non-volatile storage device and modifying it to match the applied gas concentration.
A method for calibrating a smart sensor module comprising:
(a) providing a smart sensor module comprising a chosen sensor and an electronic module, said electronic module comprising at least signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device having information stored therein, wherein said information stored on said non-volatile storage device includes a plurality of parameters related to the identification of said chosen sensor;
(b) providing a processing module electronically connected to said sensor module, and said processing module comprising a plurality of signal processing devices, at least a microcontroller and at least one output device,
(c) plugging said smart sensor module into said processor module;
(d) applying clean atmospheric air to pass over the smart sensor module, noting the corresponding output of said sensor and storing it on the non-volatile memory of the smart sensor module as the zero output; and
(e) applying a known calibration gas to pass over the said smart sensor module, noting the digital output of said sensor and storing it on the non-volatile memory of the smart sensor module as the digital output for the applied gas concentration.
An improved method for measuring the concentration of a chosen gas in the environment of a chosen enclosure, said method comprising:
(a) calibrating a smart sensor;
(b) applying a chosen gas of unknown concentration to circulate over the said smart sensor; and
(c) measuring the unknown concentration of said gas using the stored calibration data on smart sensor.
Brief description of the drawings
Fig.l is a schematic representation of a smart sensor module according to the present invention.
Fig 2 demonstrates the interfacing of the smart sensor with the processor module. Detailed description of the invention:
Accordingly, in one aspect, the present invention provides a hot swappable smart sensor. The hot swappable smart sensor according to the present invention comprises a chosen sensor and an electronic module.
It should be understood that the term "chosen" in the context of a sensor is to be construed same as the sensor being "selected" or "predetermined" such that the terms "chosen", "selected" and "predetermined" should be deemed to be synonymous with each other.
In an embodiment, the selection of the particular sensor is not particularly limiting and may be selected based on the nature of the target gas to be selected or measured and the expected concentration of the target gas in which it is to be measured or detected.
In another embodiment, the sensor may be selected from an electro-chemical sensor, solid state sensor, pellistor, infra-red sensor or a photo ionization detector.
In this aspect of the present invention, the smart sensor is preferably connected to an electronic module. The electronic module comprises at least one signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device.
The presence of a target gas over the smart sensor according to the present invention triggers the generation of an electronic signal. The generated electronic signal may be an electric current, voltage or a change in resistance and it depends on the particular sensor selected. The signal conditioning circuit converts the sensor signal into a preferred electrical signal output such as voltage. The generated sensor signal and the corresponding voltage signal are proportional to the target gas concentration.
In an embodiment, the preferred sensor is a pellistor while the corresponding signal conditioning circuit preferably employed is a bridge-circuit which is adapted to measure small changes in one of the resistances of the bridge resistors.
The smart sensor of the present invention further comprises a sensor power circuit. The sensor power circuit provides power to the selected sensor and other modules within the smart sensor. In a preferred embodiment, the sensor power circuit receives an incoming voltage supply, converts the same into suitable voltages and transmits the converted voltages to the selected sensor and the signal conditioning circuit.
In another embodiment, the smart sensor of the present invention comprises a temperature sensor. The temperature sensor measures the ambient temperature, converts the measured ambient temperature into a corresponding voltage signal and transmits the generated voltage signal to a processor module wherein it is converted to a digital signal using an analog-to-digital converter. The converted digital signal is used to apply as temperature correction to the measured sensor signal.
The smart sensor of the present invention further comprises a non-volatile storage device having information stored therein. The stored information includes information identifying said selected sensor to a plurality of parameters corresponding to said sensor.
In a preferred embodiment, said non-volatile storage device is an EEPROM although other non-volatile memory are not excluded. Preferably, the information stored in said storage device includes information identifying the target gas to be measured, the concentration range in which said target gas can be measured, resolution of the concentration measurement, calibration data,, information identifying the selected sensor such as, but not limited to, serial number, manufacturer, manufacturing date and last calibration date.
In a preferred embodiment, the information identifying the selected sensor and its calibration data additionally includes the span drift values and the zero drift values corresponding to a selected sensor.
In an alternate embodiment, the sensor calibration data may be downloaded using a wireless interface incorporated on the processor module.
In other embodiments, the processor module may include further application utilities to communicate the measured concentration data to a plurality of pre-defined locations over a communication network such as internet, GSM communication network, Bluetooth or via Ethernet to a pre-defined computer monitoring point.
In another aspect, the smart sensor of the present invention is calibrated by plugging the said processing module. The said processing module comprises a plurality of signal converters, at least a microcontroller and at least one output device. The smart sensor and the processing module may be connected using a suitable connector.
The preferred connector may be selected from electrical connectors those are prevalent in the art. In a most preferred embodiment, a USB connector may be used although connectors such as Ethernet crossover cables, radio frequency connectors, RS-232 connector, 8P8C and the like.
In another aspect, the present invention provides a method for calibrating the smart sensor. The method comprises plugging the smart sensor into the processing device and allowing the microprocessor existing within the processing module to download the stored information from the non-volatile storage device on the smart sensor. The downloaded information includes the sensor identification data and stored calibration data. The downloaded sensor identification data and calibration data are converted into a digital signal by the processor module and the generated digital signal determines whether a calibration of the sensor is warranted.
In an exemplary embodiment, the downloaded data may include the last calibration date. The processor module may determine that a calibration is needed existing the last calibration was done more than three months or six months back.
In yet another aspect, the present invention provides a smart monitoring device for monitoring a chosen gas in a chosen enclosure. The monitoring device comprises a sensor, an electronic module and a processor module.
In a preferred embodiment, the sensor and an electronic module are as described in the preceding aspects of the present invention or in any embodiment thereof. The monitoring device further includes a processor module.
In this embodiment, the processor module comprises a plurality of signal converters, at least one microcontroller and at least one output device. The processor module is capable of calibrating the smart sensor by referring and comparing the calibration information stored on the non-volatile storage device.
In another embodiment, the processor module additionally comprises a relay module and a display module.
In an embodiment, the processor module comprises at least two signal converters. Preferably, the two signal converters include at least one analog to digital converter and at least one digital to analog converter. Preferably, the processor module comprises at least one RS-485 output port, at least one 4-20 mA output port and at least one relay output.
In another embodiment, the smart sensor module provides at least three output signals viz. from the chosen sensor, from the temperature sensor and a third from the said non¬volatile storage device. Preferably, the sensor provides a milliVolt output, which is received by the incorporated analog-to-digital converter on the processor module and the resulting digital signal is transmitted to the microcontroller on the processor module.
In an embodiment, the temperature sensor also provides a milliVolt output, which is also received by the incorporated analog-to-digital converter and the resulting digital signal is further transmitted to the microcontroller on the processor module.
The microcontroller, depending upon the measured temperature and the corresponding digital output, applies the temperature correction and modifies the digital output received from the chosen sensor. The resultant corrected sensor signal is correlated to the stored calibration data received from the non-volatile storage device and the gas concentration is inferred which may be displayed on the digital display of the processor module.
In an alternate embodiment, the corrected gas concentration reading may be transmitted using RS-485 protocol from a incorporated RS-485 port.
Alternately, the digital concentration data may be converted into an analog signal by an existing digital to analog converter and may be transmitted to any location as a 4-20 mA analog output.
In yet another embodiment, the existing microcontroller receives the voltage signals from chosen sensor and calibrates it using a temperature-compensation curve that is pre-fed into the microprocessor and gives a digital output of the measured concentration to an existing communication bus, from where it can be digitally relayed to any desired location.
In an embodiment, the existing processor module is capable of comparing the sensed digital concentration with a stored digital concentration value, stored in its memory and is capable of sending a signal to activate an external device when the detected gas concentration exceeds the predefined threshold concentration.
In a preferred embodiment, the digital transmission of the signals is preferred over an analog transmission. A digital signal traveling over a communication bus is less susceptible to electrical noise whereas an analog signal traveling through a wire is susceptible to picking up additional voltage upon nearing certain conducive environments such as electrical lines or overheated power lines.
In another preferred embodiment, the smart sensor of the present invention is capable of being plugged with any processor module described hereinabove in any aspect of embodiments thereof to provide a smart monitoring device for monitoring a chosen gas in its environment. Thus, in this embodiment, the smart sensor of the present invention is plug-and-play with other compliant processor module such as herein described.
In yet another aspect, the present invention provides an improved method for measuring the concentration of a chosen gas in the environment of the sensor.
The step of calibration of a smart sensor is performed as described in any previous aspect or embodiment thereof. This step of calibrating a smart sensor is preferably carried out by plugging the said smart sensor module in an existing processor module and carrying out the said calibration-
Detailed Description of the accompanying drawings
Fig.l is a schematic representation of a smart sensor module according to the present invention. The smart sensor (1) comprises a chosen sensor (2) and an electronic module (3). The electronic module (3) comprises at least one signal conditioning circuit (4), at least one sensor power circuit (5), at least one temperature sensor (6) and at least one non-volatile storage device (7). The presence of a target gas in the vicinity of a smart sensor according to the present invention triggers the generation of an electronic signal. The generated electronic signal may be an electric current, voltage or a change in resistance and depends on the particular sensor selected. The signal conditioning circuit receives the generated electronic signal and converts the same into a preferred signal such as a voltage signal. The generated electronic signal and correspondingly the calculated voltage signal are proportional to the target gas concentration.
Fig 2 demonstrates the interfacing between the smart sensor (1) with the processor module (8). The processor module comprises a plurality of signal converter (9, 10), at least one microcontroller (11) and at least one output device. The output device may comprise a digital display module (12), and optionally a communication bus such as RS- 485 (13) and optionally further comprises a relay module (14). The two signal converters include at least one analog to digital converter and at least one digital to analog converter. Preferably, the processor module comprises at least one RS-485 output port, at least one 4-20 mA output port and at least one relay output. Preferably, the sensor provides a milliVolt output, which is received by the existing analog-to-digital converter and the resulting digital signal is transmitted to the existing microcontroller. The temperature sensor also provides a milliVolt output, which is also received by the existing analog-to- digital converter and the resulting digital signal is further transmitted to the existing microcontroller.
The microcontroller applies the temperature correction, depending upon the digital signal received from said temperature sensor, to the digital signal received from the said selected sensor. The resultant corrected sensor signal is correlated to the stored calibration data received from the non-volatile storage device and the received calibration data is applied to the sensor signal. The corrected sensor signal thus represents the actual gas concentration signal, which may be displayed on an existing digital display.
Wherein the aforegoing reference has been made to integers or components having known equivalents, then such equivalents are herein incorporated as if individually set forth. Accordingly, it will be appreciated that changes may be made to the above described embodiments of the invention without departing from the principles taught herein. Thus, it will be understood that the invention is not limited to the particular embodiments described or illustrated, but is intended to cover all alterations or modifications which are within the scope of the present invention.
WE CLAIM:
1. A hot swappable smart sensor comprising:
a. a chosen sensor; and
b. an electronic module connected to said sensor, said electronic module comprising at least one signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device having the capability to store information therein;
wherein the said information stored on said non-volatile storage device includes information identifying said chosen sensor and a plurality of parameters related to said sensor.
2. A smart sensor as claimed in claim 1, wherein said chosen sensor is selected from an electrochemical sensor, solid state sensor, pellistor, infra red sensor and a photo ionization detector.
3. A smart sensor as claimed in claim 1 or claim 2, wherein said signal conditioning circuit receives an electronic signal generated in response to the detection of a target gas above the said sensor and converts the received electronic signal to a voltage signal.
4. A smart sensor as claimed in claim 3, wherein said electronic signal generated in response to the detection of a target gas above the sensor is an electric current, voltage or change in resistance.
5. A smart sensor as claimed in any preceding claim, wherein said chosen sensor is a pellistor, said signal conditioning circuit is a bridge circuit and wherein said electronic signal is the change in resistance of one of the bridge resistors.
6. A smart sensor as claimed in any preceding claim, wherein the sensor power circuit receives an incoming voltage supply, converts the received supply into a plurality of voltages and supplies the desired voltages to said sensor and said signal conditioning circuit.
7. A smart sensor as claimed in any preceding claim, wherein said temperature sensor measures the ambient temperature, converts the measured ambient temperature into a corresponding voltage signal and transmits said voltage signal to an existing processor module.
8. A smart sensor as claimed in claim 7, wherein said processor module receives the voltage signal generated by said temperature sensor, converts the received voltage signal to a digital signal in an existing digital to analog converter and applies said generated digital signal as temperature correction to the sensor signal.
9. A smart sensor as claimed in any preceding claim, wherein said information stored in the non-volatile storage device includes information identifying the target gas to be measured, the concentration range in which said target gas can be measured, resolution of the concentration measurement, calibration data and information identifying the selected sensor.
10. A smart sensor as claimed in claim 9, wherein the information identifying the selected sensor includes the serial number, manufacturer, manufacturing date, last calibration date, span drift and zero drift of the selected sensor.
11. A smart sensor as claimed in any preceding claim, wherein the non-volatile storage device is an EEPROM.
12. A monitoring device for monitoring the presence of a chosen gas in the environment of a chosen enclosure, said monitoring device comprising:
(a) a chosen sensor;
(b) an electronic module connected to said Sensor, said electronic module comprising at least one signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device having information stored therein, said information stored on said non-volatile storage device includes information identifying said chosen sensor having a plurality of parameters related to said sensor; and (e) a processor module electronically connected to said sensor and said electronic module, said processor module comprising a plurality of signal converter, at least a microcontroller and at least one output device, said processor module being additionally capable of calibrating said smart sensor by accessing information stored on said non-volatile storage device.
13. The monitoring device as claimed in claim 12 comprising at least two signal converters including at least analog-to-digital converter and at least one digital-to- analog converter.
14. The monitoring device as claimed in claim 12 or claim 13 additionally comprising a display module and optionally comprising a plurality of output devices including at least one RS-485 output port, at least one 4-20 mA output port and at least one relay output.
15. The monitoring device as claimed in claims 12-14, wherein said smart sensor is plug-and-play with a processor module.
16. A method for calibrating a smart sensor comprising:
(a) providing a smart sensor comprising a chosen sensor and an electronic module, said electronic module comprising at least signal conditioning circuit, at least one sensor power circuit, at least one temperature sensor and at least one non-volatile storage device capable of storing information therein, wherein said information stored on said non-volatile storage device includes information identifying said chosen sensor having a plurality of parameters related to said sensor;
(b) providing a processor module electronically connected to said sensor and said electronic module wherein said processor module comprises a plurality of signal converter, at least a microcontroller and at least one output device;
(c) plugging said smart sensor into said processor module;
(d) applying clean atmospheric air to pass over the smart sensor module and noting the corresponding output of said sensor and store it on the non¬volatile memory of the smart sensor module as the zero output; and
(e) applying a known calibration gas to pass over the said smart sensor module and noting the digital output of said sensor and store it on the non¬volatile memory of the smart sensor module as the digital output for the applied gas concentration.
17. A method for calibrating a smart sensor as claimed in claim 16 additionally comprising receiving voltage signals from the selected sensor at the microcontroller, correcting the received voltage signal using a temperature compensation curve pre-fed into the microcontroller, digitally outputting the measured concentration to a communication bus and digitally relaying the corrected digital signal to a desired location.
18. The method as claimed in claim 16 further comprising, subsequent to plugging the smart sensor into the processor module, allowing the microcontroller existing within the processor module to download the stored information including at least sensor identification data and calibration data from the non-volatile memory existing on the smart sensor.
19. The method as claimed in claim 18, wherein said processor module is plugged into the smart sensor using an electrical connector selected from USB connector, Ethernet crossover cable, radio frequency connector, RS - 232 connector and 8P8C.
20. An improved method for measuring the concentration of a chosen gas in the environment of a chosen enclosure, said method comprising:
a. calibrating a smart sensor;
b. applying a chosen gas of unknown concentration to pass over the said smart sensor; and
c. measuring the concentration of said gas using said calibrated smart sensor.
21. The method of measuring the concentration of a chosen gas in the environment of a chosen enclosure as claimed in claim 20 wherein said step of calibrating a smart sensor is carried out using a method as claimed in any of the claims 16-19.
22. A self calibrating and hot swappable smart sensor substantially as described herein with reference to the accompanying drawings.
23. A smart monitoring device for monitoring a chosen gas in the environment of a chosen enclosure substantially as described herein with reference to the accompanying drawings.
24. A method for calibrating a smart sensor substantially as described herein with reference to the accompanying drawings.
25. An improved method for measuring the concentration of a chosen gas in the environment of a chosen enclosure substantially as described herein with reference to the accompanying drawings.