CN115931752A - Wavelength scanning multipoint gas detection method - Google Patents
Wavelength scanning multipoint gas detection method Download PDFInfo
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Abstract
A multi-point gas detection method of wavelength scanning comprises a semiconductor laser, a pulse generation circuit, a circulator, a wavelength calibration element, a gas absorption chamber, a reflector, a first coupler, a delay optical fiber, a photoelectric detector and a signal acquisition system; the pulse generating circuit drives a semiconductor laser which is connected with the input end of the circulator; the number of the couplers and the number of the delay optical fibers are multiple; the input end of the first coupler is connected to the first output end of the circulator, one output end of the first coupler is connected to the wavelength calibration element, and the first coupler is connected with the subsequent couplers through delay optical fibers; the gas absorption chambers and the reflectors are provided in plurality and are arranged corresponding to the number of the couplers and the delay optical fibers; each gas absorption chamber is connected with the corresponding coupler, and each reflector is connected with the corresponding gas absorption chamber; the second output end of the circulator is connected with the photoelectric detector; and the photoelectric detector is connected with the signal acquisition system.
Description
Technical Field
The invention relates to the field of multipoint gas detection, in particular to a wavelength scanning multipoint gas detection method.
Background
The multipoint (quasi-distributed) or distributed gas detection method can accurately measure the gas concentration at different positions in a large range. The method has important significance in long-distance pipeline gas transmission [1,2], large-area underground mine gas monitoring [3] and urban road gas pollution detection [ 4-6 ]. Currently, multi-point gas detection is mainly based on fiber optic multiplexing technology [7], including Space Division Multiplexing (SDM) [3,8,9], time Division Multiplexing (TDM) [10 to 12], frequency Division Multiplexing (FDM) [13,14] and Wavelength Division Multiplexing (WDM) [15 to 17]. However, the multiplexing method mainly using SDM and WDM reported at present requires very redundant devices, for example, multiple photodetectors are required to detect multiple signals or multiple FBGs matching the gas absorption peak, and the structure is complex and has poor stability. While the FDM-based method generally requires complex signal processing and has limitations on the layout distance, although TDM is generally simple for processing multipoint gas signals, the signal-to-noise ratio is often not high, and the detection accuracy is still low, thereby limiting the application.
The method of achieving spectral absorption by pulsed wavelength scanning was first used by k.namjou et al in 1998 to measure nitrous oxide and methane, a mid-infrared quantum cascade laser with a central wavelength around 8 μm, driven at a pulse current of 2.6A and a pulse width modulation of 11ns, effectively observing the absorption peak of the gas molecule [18]. In 2003, measurements were performed on 1, 1-difluoroethylene by e.normand et al using a mid-infrared quantum cascade laser with a pulsed current drive wavelength of 10.26 μm, with too high a pulse current (peak current up to 20A) resulting in a nonlinear broadening of the laser wavelength [19]. Subsequently, it was widely used in the detection of mid-infrared gases, for example, in 2009 Bruno Grouiez et al reported that ammonia gas measurement was achieved using a mid-infrared quantum cascade laser with a center wavelength of 10 μm at a pulse width of 500-800ns [19], and carbon monoxide measurement was achieved using a laser with a center wavelength of 4.85 μm at a pulse width of 500ns in 2014 Robin s.m. et al [20]. This method is very effective for mid-infrared detection because many gas molecules have higher absorption cross-sections in the mid-infrared [21 ]. However, when multi-point measurement is realized by using an optical fiber multiplexing technology, since a low loss window of a common single-mode optical fiber is 0.8-1.8 um, and a medium-infrared optical fiber such as fluorine-doped or chalcogenide-doped medium-infrared optical fiber is not suitable for long-distance multi-point distributed use due to high price, at present, in near infrared, no report is made on the method for realizing multi-point gas detection based on a pulse internal spectrum scanning absorption.
In the near infrared band, commercial Tunable Diode Laser Absorption Spectroscopy (TDLAS) has the advantages of non-contact measurement, high measurement accuracy, high gas identification rate, simple operation, fast response speed and the like, and is widely reported to be used for gas detection of various bands [22-25]. Direct detection and wavelength/frequency modulation techniques are commonly used in conventional TDLAS. The direct absorption spectrum technology is simple, and the concentration of the gas to be measured can be obtained without carrying out concentration calibration. However, this method has low sensitivity and is easily affected by external factors such as external environment, electrical devices for detection, optical devices, and the like. In order to improve the detection sensitivity, TDLAS is generally combined with a Wavelength Modulation Spectrum (WMS) or a Frequency Modulation Spectrum (FMS), and the fundamental principle is to generate a harmonic signal proportional to the target gas concentration, which is different from a weak signal directly absorbed, and to phase-lock amplify the harmonic signal to obtain an electric signal proportional to the gas concentration, thereby inverting the gas concentration. A typical implementation is by applying a low frequency triangular wave to the laser drive current while superimposing a high frequency sinusoidal signal, the resulting second harmonic signal can be detected by a lock-in amplifier as the wavelength of the laser sweeps slowly across the gas absorption peak. To achieve stability of wavelength scanning, a TEC (Thermal Electronic Cooler) refrigerator is generally necessary, however the extra power consumption introduced by the refrigerator, and the high cost in a multi-point configuration, limit the application of this method to multi-point gas detection over a long distance and a large area.
Reference to the literature
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Disclosure of Invention
The invention aims to solve the problems that the concentration calibration of a plurality of gas chambers is complicated and the measurement precision and the detection limit are influenced in the multi-point gas detection technology in the prior art, reduce the cost by utilizing the optical fiber multiplexing technology, and provide a multi-point gas detection method with wavelength scanning, which is suitable for more multi-point gas detection occasions.
In order to achieve the purpose, the invention adopts the following technical scheme:
a multi-point gas detection method of wavelength scanning comprises a semiconductor laser, a pulse generation circuit, a circulator, a wavelength calibration element, a gas absorption chamber, a reflector, a first coupler, a delay optical fiber, a photoelectric detector and a signal acquisition system;
the circulator is a three-port optical fiber circulator, the pulse generating circuit drives a semiconductor laser, and the semiconductor laser is connected with the input end of the circulator; the number of the couplers and the number of the delay optical fibers are multiple; the input end of the first coupler is connected with the first output end of the circulator, one output end of the first coupler is connected with the wavelength calibration element, and the first coupler is connected with the following couplers through delay optical fibers; the gas absorption chambers and the reflectors are provided in plurality and are arranged corresponding to the number of the couplers and the delay optical fibers; each gas absorption chamber is connected with the corresponding coupler, and each reflector is connected with the corresponding gas absorption chamber; the second output end of the circulator is connected with the photoelectric detector; the photoelectric detector is connected with the signal acquisition system;
when the emitted light is pulsed light, the distance L from the ith reflection point back to the photodetector i The following relationships exist:
wherein, t i The time when the photoelectric detector detects the ith reflection point, c is the propagation speed of light in vacuum, and n is the refractive index of the quartz optical fiber, and the positioning measurement of the gas can be realized through the formula;
according to beer-lambert law:
I out(ν) ＝I in(ν) exp(-α v Cγ)
wherein alpha is v The gas absorption coefficient is shown, and gamma represents the effective absorption optical path of the gas; c represents the gas volume percentage; i is in(ν) The intensity of the laser light of wavelength v before it is input into the gas sample, I out(ν) The light intensity of the laser with the wavelength v after the laser is input into the gas sample;
the semiconductor laser emits pulsed light to perform wavelength scanning, spectrum scanning of at least one absorption peak of gas to be detected is realized in the gas absorption chamber, and the shape of a spectrum can also change according to different gas concentrations; converting the voltage-concentration calibration into time domain measurement, carrying out voltage-concentration calibration according to the voltage intensity change at a certain moment in the pulse of the gas absorption peak by combining with the beer-Lambert law, and then inversely calculating the gas concentration according to the voltage intensity at the moment to realize gas detection under wavelength scanning;
during multipoint detection, gas detection under wavelength scanning can be achieved in each gas absorption chamber, signals in each gas absorption chamber cannot generate crosstalk by combining a time division multiplexing method of optical fibers, and the signal-to-noise ratio is improved through multiple-time superposition averaging processing.
The semiconductor laser is a DFB laser or a VCSEL laser, and the central wavelength needs to be close to the absorption peak of the gas molecule to be detected.
The pulse generating circuit emits pulses with a width of at least 10ns, and the pulse current needs to be larger than the threshold current of the semiconductor laser.
The wavelength calibration element is an etalon or a fiber grating calibration device.
The splitting ratio of the coupler and the first coupler is at least 50, preferably 90.
The gas absorption chamber comprises a first collimator, a second collimator and a fixed tube; the first collimator and the second collimator are arranged at two ends of the fixed pipe, through holes are formed in the fixed pipe, and laser is emitted from the first collimator and then enters the second collimator.
The maximum optical path coupling loss in the gas absorption chamber is 1dB.
The mirror has a reflectivity of at least 90%.
The shortest length of the delay fiber is determined by the laser emission pulse width.
The signal acquisition system is connected to a computer for processing by adopting a data acquisition card, and noise reduction processing is carried out by superposing and averaging time domain signals acquired by the photoelectric detector, so that the detection limit of the system to the gas concentration is improved.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the intra-pulse spectral scanning can replace the conventional TDLAS method of stabilizing the center wavelength by using a TEC (Thermal Electronic Cooler) and then performing wavelength scanning after applying a low frequency signal and a high frequency signal to the laser driving current.
2. The invention does not need to use a laser of an integrated refrigerator, can greatly reduce the power consumption caused by the refrigerator in the application occasions with smaller environmental temperature change range, can further reduce the total cost of the system, and has wide prospect in the multipoint gas detection occasions.
3. The light source is pulsed light, multipoint detection can be carried out by directly utilizing a time division multiplexing method of the optical fiber, the problem of loss generated in the cavity of each gas absorption chamber can be solved by using a plurality of couplers, the gas absorption chambers and the reflectors, so that quantitative detection of gas concentration at a plurality of positions is realized, and the wavelength calibration element can be used as a reference of the wavelength of the pulsed light source.
4. According to the invention, a complex phase-locking technology is not needed to detect the second harmonic, the signal-to-noise ratio in each gas chamber can be improved after a synchronous superposition average algorithm is compiled by Labview, and self-calibration can be realized in a wavelength scanning mode in one gas absorption chamber.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
FIG. 2 is a diagram of the test results of the embodiment of the present invention.
Fig. 3 is a diagram illustrating a multipoint detection process according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.
Referring to fig. 1, the present invention provides a multipoint gas detection method of wavelength scanning, and the implementation system includes a semiconductor laser 1, a pulse generation circuit 2, a circulator 3, a wavelength calibration element 7, a first gas absorption chamber 10, a second gas absorption chamber 14, a third gas absorption chamber 18, a first reflector 11, a second reflector 15, a third reflector 19, a first coupler 6, a second coupler 9, a third coupler 13, a fourth coupler 17, a first delay fiber 8, a second delay fiber 12, a third delay fiber 18, a photodetector 4 and a signal acquisition system 5;
the pulse generating circuit 2 drives a semiconductor laser 1, and the semiconductor laser 1 is connected with an input end 301 of a circulator 3; the coupler and the delay optical fiber are provided with a plurality of couplers, the input end 601 of the first coupler 6 is connected with the output end 302 of the circulator 3, the output end 603 of the first coupler 6 is connected with the wavelength calibration element 7, the output end 602 of the first coupler 6 is connected with the first delay optical fiber 8, the first delay optical fiber 8 is connected with the input end 901 of the second coupler 9, the output end 902 of the second coupler 9 is connected with the second delay optical fiber 12, the output end 903 of the second coupler 9 is connected with the first gas absorption chamber 10, the first gas absorption chamber 10 is connected with the first reflector 11, the second delay optical fiber 12 is connected with the input end 1301 of the third coupler 13, the output end 1302 of the third coupler 13 is connected with the third delay optical fiber 16, the output end 1303 is connected with the second gas absorption chamber 14, the second gas absorption chamber 14 is connected with the second reflector 15, the third delay optical fiber 16 is connected with the input end 1701 of the fourth coupler 17, the output end 3 of the fourth coupler 17 is connected with the third gas absorption chamber 17018, and the third gas absorption chamber 19 is connected with the third reflector 19.
The semiconductor Laser 1 is a DFB (Distributed Feedback Laser) Laser, and the central wavelength needs to be around the absorption peak of the gas molecule to be measured, specifically, for methane, the central wavelength is 1650nm, and for acetylene, the central wavelength is 1530nm.
The pulse generating circuit 2 adopts a commercial optical time domain reflectometer circuit, the width of a transmitted pulse is 2.5 mu s, and the peak current of the pulse is more than 100mA.
The circulator 3 is a three-port optical fiber circulator, when incident light enters from a 301 port and exits from a 302 port, and when incident light enters from the 302 port and exits from a 303 port, 1550nm of central wavelength can be selected, the insertion loss is less than 0.8dB, and the isolation is more than 45dB.
The wavelength calibration element 7 serves as a trigger channel, and provides requirements for adopting a synchronous superposition averaging method in a subsequent signal processing process, the fiber grating is adopted in the embodiment, the reflectivity is greater than 90%, and the central wavelength is matched with the emission wavelength of the laser.
The central wavelength of the first, second, third and fourth couplers can be 1550nm, the splitting ratio is 90.
The first delay fiber 8, the second delay fiber 12, and the third delay fiber 16 may be 1km length of ordinary single mode fiber.
The first, second and third gas absorption cells 10, 14, 18 comprise a first collimator 1001, a second collimator 1002, a third collimator 1401, a fourth collimator 1402, a fifth collimator 1801 and a sixth collimator 1802. The first collimator 1001 and the second collimator 1002 are coupled and have insertion loss, the third collimator 1401 and the fourth collimator 1402 are coupled and have insertion loss, and the fifth collimator 1801 and the sixth collimator 1802 are coupled and have insertion loss, and the coupling insertion loss is less than 1dB.
The first, second and third mirrors 11, 15, 19 may be faraday mirrors having a reflectivity of at least 90%.
Specifically, in this embodiment, two collimators of the gas absorption chamber are fixedly connected by using two ends of a fixing tube; the fixed pipe is made of stainless steel, the length of the fixed pipe is 80-120 mm, the inner diameter of the fixed pipe is 3mm +/-0.1 mm, the size of the fixed pipe is not limited to the scheme, and the fixed pipe can be adjusted according to requirements; two through holes are formed in the fixing pipe, the distance between the two through holes and the two ends of the fixing pipe is 10-20 mm, the aperture is 1-2 mm, the number of the through holes is not limited to the scheme, the through holes can be increased according to requirements, and the distance between the through holes can be adjusted.
The signal acquisition system 5 is accessed to a computer for processing by adopting a data acquisition card (hantek 6074D), and the time domain signals acquired by the photoelectric detector are subjected to superposition average noise reduction processing by using a Labview compiling synchronous superposition average algorithm, so that the detection limit of the system to the gas concentration is improved.
Starting a pulse generating circuit 2 to drive a semiconductor laser 1, after pulse light enters an input end 301 of a circulator 3, the pulse light enters a wavelength calibration element 7 from an output end 302 through an output end 603 of a first coupler 6, is reflected back to an input end 601 of the first coupler 6, enters an output end 303 of the circulator 3, is received by a photoelectric detector 4, transmits a signal to a signal acquisition system 5, enters a first delay optical fiber 8 through an output end 602 of the first coupler 6, enters a first gas absorption chamber 10 through an output end 903 of a second coupler 9, is reflected back to an input end 901 of the second coupler 9 through a first reflector 11, passes through the first delay optical fiber 8, the first coupler 6 and an output end 303 of the circulator 3, is received by the photoelectric detector 4, transmits the signal to the signal acquisition system 5, enters a second delay optical fiber 12 through an output end 902 of the second coupler 9, enters the second gas absorption chamber 14 through the output end 1303 of the third coupler 13, is reflected by the second mirror 15 to the input end 1301 of the second coupler 13, passes through the second delay optical fiber 12, the second coupler 9, the first delay optical fiber 8, the first coupler 6 and the output end 303 of the circulator 3, is received by the photodetector 4, transmits the signal to the signal acquisition system 5, enters the third delay optical fiber 16 after passing through the output end 1302 of the third coupler 13, enters the third gas absorption chamber 18 through the output end 1703 of the fourth coupler 17, is reflected by the third mirror 19 to the input end 1701 of the fourth coupler 17, passes through the third delay optical fiber 16, the third coupler 13, the second delay optical fiber 12, the second coupler 9, the first delay optical fiber 8, the first coupler 6 and the output end 303 of the circulator 3, is received by the photodetector 4, and transmits the signal to the signal acquisition system 5. And calculating the gas concentration in the signal acquisition system 5 by a synchronous superposition average algorithm written by Labview.
The detection principle of the present invention is given below:
the invention is based on the principle of optical fiber time division multiplexing, when the emitted light is pulsed light, the distance L from the ith reflection point to the photodetector i The following relationships exist:
wherein, t i The time at which the i-th reflection point is detected by the photodetector, c is the speed at which the light travels in vacuum, which is about 3X 10 8 m/s, n is the refractive index of the quartz fiber and is about 1.4-1.6, so that the positioning measurement is realized.
The principle of gas detection is based on the beer-lambert law, and the interaction between light and gas generates an absorption phenomenon, and the incident light intensity and the transmitted light intensity generally have the following relationship under an unsaturated absorption condition:
I out(ν) ＝I in(ν) exp(-α v Cγ)
wherein alpha is v Is the gas absorption coefficient in cm -1 (ii) a Gamma represents the effective absorption optical path of the gas in cm; c represents the gas volume percentage, and the unit is ppm; i is in(ν) Is excited by a wavelength vLight intensity before light input into the gas sample, I out(ν) The light intensity after the laser with the wavelength v is input into the gas sample.
The effect achieved by this embodiment is as shown in fig. 2, when the semiconductor laser with the center wavelength of 1650nm is driven by pulse, and the emission pulse width is 100ns, the wavelength scanning effect is generated, after methane gas with different concentrations is injected into the gas absorption chamber, one absorption peak 1650.968nm of near-infrared methane is completely scanned, and the shape of the spectrum changes according to the different concentrations of the injected gas. And converting into time domain measurement, and carrying out voltage-concentration calibration according to the voltage intensity change at a certain moment in the pulse of the gas absorption peak by combining with the beer-Lambert law, and then inversely calculating the concentration of the methane gas to be measured through the voltage intensity.
The effect of the embodiment under the multipoint test is shown in fig. 3, in the drawing, three signals respectively correspond to the first absorption gas chamber 10, the second absorption gas chamber 14, and the third absorption gas chamber 18, about 5% of methane gas is injected into each gas chamber, and since the three signals are all realized by spectrum scanning and all scan one absorption peak 1650.968nm of methane, the gas concentration can be calibrated in all the three absorption gas chambers according to the voltage intensity at the absorption peak. The signal shown in fig. 3 (a) is acquired once by using a data acquisition card (hantek 6074D) as the signal acquisition system 5, the signal-to-noise ratio is poor, multiple times of signal superposition averaging are performed by using Labview, and the average effect is obviously improved after 100 times, as shown in fig. 3 (b). Assuming that the noise is white, after averaging n times, the improvement of the SNR will reach
Since a certain time is required for averaging, the number of averaging times can be adjusted according to the actual detection time and detection sensitivity.
The invention does not need to use a laser of an integrated refrigerator, can greatly reduce the power consumption caused by the refrigerator in the application occasions with smaller environmental temperature change range, can further reduce the total cost of the system, and has wide prospect in the multipoint gas detection occasions. The light source is pulsed light, multipoint detection can be carried out by directly utilizing a time division multiplexing method of the optical fiber, the problem of loss generated in the cavity of each gas absorption chamber can be solved by using a plurality of couplers, gas absorption chambers and reflectors, namely introducing branch paths, so that the quantitative detection of the gas concentration at a plurality of positions is realized, and the wavelength calibration element can be used as a reference of the wavelength of the pulsed light source. The present invention can perform the spectral scanning within the pulse instead of the conventional TDLAS method of stabilizing the center wavelength by using a TEC (Thermal Electronic Cooler) and then performing the wavelength scanning after applying a low frequency signal and a high frequency signal to the laser driving current. According to the invention, a complex phase locking technology is not required to detect the second harmonic, the signal-to-noise ratio in each gas chamber can be improved after a synchronous superposition averaging algorithm is compiled by Labview, and self-calibration can be realized in a wavelength scanning mode by one gas absorption chamber.
Claims (10)
1. A wavelength scanning multipoint gas detection method is characterized in that: the device comprises a semiconductor laser, a pulse generating circuit, a circulator, a wavelength calibration element, a gas absorption chamber, a reflector, a first coupler, a delay optical fiber, a photoelectric detector and a signal acquisition system;
the circulator is a three-port optical fiber circulator, the pulse generating circuit drives a semiconductor laser, and the semiconductor laser is connected with the input end of the circulator; the number of the couplers and the number of the delay optical fibers are multiple; the input end of the first coupler is connected with the first output end of the circulator, one output end of the first coupler is connected with the wavelength calibration element, and the first coupler is connected with the subsequent couplers through delay optical fibers; the gas absorption chambers and the reflectors are provided in plurality and are arranged corresponding to the number of the couplers and the delay optical fibers; each gas absorption chamber is connected with the corresponding coupler, and each reflector is connected with the corresponding gas absorption chamber; the second output end of the circulator is connected with the photoelectric detector; the photoelectric detector is connected with the signal acquisition system;
when the emitted light is pulsed light, the distance L from the ith reflection point back to the photodetector i The following relationships exist:
wherein, t i The time when the photoelectric detector detects the ith reflection point, c is the propagation speed of light in vacuum, and n is the refractive index of the quartz optical fiber, and the positioning measurement of the gas can be realized through the above formula;
according to beer-lambert law:
I out(ν) ＝I in(ν) exp(-α v Cγ)
wherein alpha is v The gas absorption coefficient is shown, and gamma represents the effective absorption optical path of the gas; c represents the gas volume percentage; i is in(ν) The intensity of the laser light of wavelength v before it is input into the gas sample, I out(ν) The light intensity of the laser with the wavelength v after the laser is input into the gas sample;
the semiconductor laser emits pulsed light to perform wavelength scanning, spectrum scanning of at least one absorption peak of gas to be detected is realized in the gas absorption chamber, and the shape of a spectrum can also be changed according to different gas concentrations; converting the voltage-concentration calibration into time domain measurement, carrying out voltage-concentration calibration according to the voltage intensity change at a certain moment in the pulse of the gas absorption peak by combining with the beer-Lambert law, and then inversely calculating the gas concentration according to the voltage intensity at the moment to realize gas detection under wavelength scanning;
during multipoint detection, gas detection under wavelength scanning can be achieved in each gas absorption chamber, signals in each gas absorption chamber cannot generate crosstalk by combining a time division multiplexing method of optical fibers, and the signal-to-noise ratio is improved through multiple-time superposition averaging processing.
2. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the semiconductor laser is a DFB laser or a VCSEL laser, and the central wavelength needs to be close to the absorption peak of the gas molecules to be detected.
3. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the pulse generating circuit emits pulse with a width of at least 10ns, and the pulse current needs to be larger than the threshold current of the semiconductor laser.
4. A method of wavelength-scanning multi-point gas detection as claimed in claim 1, wherein: the wavelength calibration element is an etalon or a fiber grating calibration device.
5. A method of wavelength-scanning multi-point gas detection as claimed in claim 1, wherein: the splitting ratio of the coupler and the first coupler is at least 50, preferably 90.
6. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the gas absorption chamber comprises a first collimator, a second collimator and a fixed tube; the first collimator and the second collimator are arranged at two ends of the fixed tube, the fixed tube is provided with a through hole, and laser is emitted from the first collimator and then enters the second collimator.
7. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the maximum optical path coupling loss in the gas absorption chamber is 1dB.
8. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the mirror has a reflectivity of at least 90%.
9. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the shortest length of the delay fiber is determined by the laser emission pulse width.
10. A wavelength-scanning multipoint gas detection method as claimed in claim 1 wherein: the signal acquisition system adopts a data acquisition card to be connected with a computer for processing.
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