Measuring and testing – Gas analysis – Detector detail
Reexamination Certificate
2003-03-10
2004-05-25
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
Detector detail
C073S023200
Reexamination Certificate
active
06739180
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intelligent gas identification system and a method of gas identification for gas or volatile chemical matters in a specific environment.
2. Description of the Related Art
Conventionally, a gas concentration sensor is used for obtaining concentration for a specific gas. An example of a conventional gas concentration sensor
500
is described in detail with reference to
FIG. 1
a
and
FIG. 1
b.
The conventional gas concentration sensor
500
, as shown in
FIG. 1
a
, has a body
510
, voltage input elements
520
, and output elements
530
. The body
510
, as shown in
FIG. 1
b
, has a substrate
512
, electrodes
514
, a sensing element
516
, and a heater
518
. Generally, the sensing element
516
is a membrane of metallic oxide, such as a membrane of tin dioxide (SnO
2
), which reacts to a specific gas in the vicinity of the gas concentration sensor
500
. When the conventional gas concentration sensor
500
is applied in a specific environment to perform gas concentration measurement, a fixed voltage is input to the sensor
500
through the voltage input element
520
to activate the heater
518
, so that the membrane of the sensing element
516
is heated to a predetermined temperature, such as 400° C. Thus, the membrane of the sensing element
516
reacts to the specific gas to be measured in the specific environment, and the resistance of the sensing element
516
is changed due to the reaction. Then, an outgoing voltage, determined by the resistance of the sensing element
516
, is obtained through the output element
530
as an outgoing signal.
It is obvious that the concentration of the specific gas in the specific environment affects the reaction, and the relation between the concentration of the specific gas and the resistance of the sensing element
516
can be established by experiment as a reference of the gas concentration sensor
500
.
FIG. 2
is a chart showing an example of the gas concentration measurement with the conventional gas concentration sensor
500
, in which the curves L
1
and L
2
respectively refer to different concentrations of the specific gas. When the voltage is input to the sensor
500
through the voltage input element
520
to activate the heater
518
, the membrane of the sensing element
516
is heated to a predetermined temperature, such as 400° C. In both cases, the resistance of the sensing element
516
is changed due to the reaction, which induced to the outgoing voltages shown as point A to concentration L
1
and point B to concentration L
2
. It should be noted that the predetermined temperature of the conventional gas concentration sensor
500
is generally set to a preferred temperature, in which the outgoing voltage is significant, so that responses of the gas concentration sensor
500
are obvious. Fox example, the preferred temperature shown in
FIG. 2
is approximately 400° C.
The conventional gas concentration sensor
500
has a membrane-type structure, which has a relatively low cost. Further, the conventional gas concentration sensor
500
reacts to the gas to be measured in a short time and can be used effectively for a long period of time. As a result, the gas concentration sensor is widely used in various situations. For example, U.S. Pat. No. 6,336,354 discloses a gas concentration measuring apparatus, in which a gas concentration sensor is applied, that uses a heat control circuit to supply power to the heater of the sensor cyclically using a pulse-amplitude-modulated (PAM) signal. In this case, the apparatus corrects errors contained in the gas concentration signal, so that the signal is regulated, and the outgoing signal of the gas concentration sensor is significant.
However, the conventional gas concentration sensor
500
is used mainly to measure the concentration of a specific gas. It is obvious that the conventional gas concentration sensor
500
can be used in a specific environment when the specific gas exists in the specific environment. However, the membrane of gas concentration sensor
500
may react to a plurality of gases. Thus, when more than one of the gases exists in the specific environment, the conventional gas concentration sensor
500
does not distinguish between each gas, so that the outgoing signal of the gas concentration sensor
500
does not correspond exactly to a specific gas among the multiple gases, and concentrations are not obtained accurately. Additionally, when the composition of the gas in the specific environment is completely unidentified, the conventional gas concentration sensor
500
does not distinguish the composition of the gas.
SUMMARY OF THE INVENTION
In view of this, the present invention relates to an intelligent gas identification system and method thereof, in which a pulse-amplitude-modulated (PAM) signal is used as the input voltage to the conventional gas concentration sensor so that the outgoing signals corresponding to various gases differ. Thus, a chemical matter characteristics database can be established by experiment, and the chemical matter characteristics can be used as a reference fingerprint of composition and/or concentration of the gases.
The present invention discloses an intelligent gas identification system. The intelligent gas identification system has a sensor, a pulse power supply module, and a processing device. The sensor has a voltage input element, an output element and a sensing element and is disposed in a specific environment to perform gas identification. The pulse power supply module is connected to the voltage input element to send a variable pulse-amplitude-modulated voltage to the sensor through the voltage input element, so that the sensor outputs an outgoing signal through the output element. The processing device stores a plurality of chemical matter characteristics signals and receives the outgoing signal from the output element of the sensor, then compares the outgoing signal with the chemical matter characteristics signals to determine an identification result for the gas.
Further, the present invention discloses a method of gas identification. First, a sensor is provided in a specific environment. The sensor is provided with a variable pulse-amplitude-modulated voltage, so that the sensor outputs an outgoing signal corresponding to gas in the specific environment. Then, the outgoing signal is compared with a plurality of chemical matter characteristics signals to determine an identification result for the gas in the specific environment.
In the method of gas identification, the chemical matter characteristics signals can be obtained by exsposing the sensor to a plurality of predetermined chemical matters and sending a variable pulse-amplitude-modulated voltage to the sensor respectively, so that the sensor outputs each of the chemical matter characteristics signals corresponding to each of the predetermined chemical matters. Then, the chemical matter characteristics signals can be stored in a database.
In the system and method of the present invention, the outgoing signal can be a pulse amplitude voltage signal. Further, the sensing element can be a membrane of a metallic oxide, such as tin dioxide (SnO
2
). Further, the identification result for the gas can be composition and/or concentration of the respective constituents of the gas.
REFERENCES:
patent: 5987963 (1999-11-01), Stormbom
patent: 6029090 (2000-02-01), Herbst
patent: 2001/0032054 (2001-10-01), Kimoto et al.
patent: 2369730 (2002-06-01), None
patent: 406082407 (1994-03-01), None
patent: 406130017 (1994-05-01), None
Chen I-Cherng
Huang Yi-Shiao
Tai Chien-Hsiung
Tsai Wen-Yuan
Birch & Stewart Kolasch & Birch, LLP
Industrial Technology Research Institute
Larkin Daniel S.
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