Zero calibration and span calibration method for dust concentration detection instrument

Abstract

The invention discloses a zero calibration and span calibration method for a dust concentration detection instrument. The method comprises the following steps: S1, starting the dust concentration detection instrument; s2, a zero calibration step; s3, a span correction step, which comprises the following sub-steps: S31, collecting span correction data when leaving a factory; and S32, re-calibrating in use. The method specifically comprises the following steps: S321, cleaning the interior of the detection chamber; the zero calibration and span calibration method comprises the following steps of S311, S312, S313, S314, S316, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317, S317

Description

Technical Field

[0001] The invention relates to the technical field of dust concentration detection instruments, and in particular to a zero calibration and span calibration method for dust concentration detection instruments. Background Art

[0002] The dust concentration detection instrument is a commonly used instrument for detecting particle concentration based on the principle of photoelectric conversion, wherein the dust concentration detection instrument has a detection chamber, a laser transmitter is arranged on the left side of the detection chamber, and a light trap opposite to the laser transmitter is arranged on the right side, an air inlet channel and an air outlet channel are arranged at the upper and lower ends of the detection chamber, respectively, and a light intensity receiver and a concave reflector are arranged at the front and rear sides of the detection chamber, respectively. During detection, the dust-laden gas enters the detection chamber from the air inlet channel, and the laser transmitter generates a laser, which is blocked and reflected by the particles in the gas, and a part of the reflected light is directly reflected onto the light intensity receiver, and the other part is reflected by the concave reflector and focused on the light intensity receiver for reception. However, the current dust concentration detection instrument is generally calibrated at the factory, and when errors occur in the data after use, on-site calibration is difficult, and it is also difficult to determine whether the problem is with the laser transmitter or the light intensity receiver based on the specific error situation. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a zero calibration and span calibration method for a dust concentration detection instrument, which can accurately calibrate the zero and span of the dust concentration detection instrument to meet the needs of on-site calibration.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a method for zero calibration and span calibration of a dust concentration detection instrument, comprising the following steps:

[0005] S1. Connect the dust concentration detection instrument to the circuit and the gas path. The dust concentration detection instrument has a detection chamber. A laser transmitter is arranged on the left side of the detection chamber, and a light trap opposite to the laser transmitter is arranged on the right side. The upper and lower ends of the detection chamber are respectively provided with an air inlet channel and an air outlet channel. The front and rear sides of the detection chamber are respectively provided with a light intensity receiver and a concave reflector; the light trap is also connected to a calibration collection optical fiber, and a light head connected to the calibration emission optical fiber is also arranged in the detection chamber. The calibration collection optical fiber and the calibration emission optical fiber are connected through an optical fiber signal on-off switch, and the optical fiber signal on-off switch includes a switch seat , the switch seat is provided with an optical fiber channel and a central installation chamber, the optical fiber channel runs through the switch seat, and the switch seat is respectively provided with an incident optical fiber connector and an output optical fiber connector at both ends of the optical fiber channel, the incident optical fiber connector and the output optical fiber connector are respectively connected to the calibration collection optical fiber and the calibration emission optical fiber, a rotating body is rotatably installed in the central installation chamber, a blocking block for blocking the optical fiber channel is provided on the rotating body, and a rotating power device for driving the rotating body to rotate is provided on the switch seat, and the rotating power device drives the rotating body to rotate so that the blocking block deflects between the blocking closing position and the opening position;

[0006] S2, zero calibration step, including the following steps:

[0007] S21, clean air is introduced from the air inlet channel for a set time, the laser transmitter is started, and the optical fiber signal channel switch is in the closed state;

[0008] S22, after the light enters the light trap and passes through the calibration collection optical fiber, the signal is disconnected, and the light intensity receiver reads the light intensity reading at this time. If the reading at this time is not zero, the rotating body continues to drive the shielding block to deflect toward the shielding closing position until the reading of the light intensity receiver is zero; at this time, the rotating body records and saves the current position as the shielding closing position; if the light intensity receiver still reads not zero after the rotating body deflects to the limit, the reading of the light intensity receiver is cleared and the light intensity state of the current state is recorded as zero;

[0009] S3, the calibration step, includes the following sub-steps:

[0010] S31, collection of calibration data before leaving the factory;

[0011] S311, after the zero calibration is completed, the optical fiber signal on-off switch drives the shielding block to deflect to the open position, at which time the calibration collection optical fiber and the calibration emission optical fiber are connected, and the light intensity receiver receives the light emitted by the light emitting head. At this time, the laser transmitter is adjusted to emit the laser at the first fixed frequency F1 and the first fixed power p1. The light is attenuated after passing through the calibration collection optical fiber and the calibration emission optical fiber, and the light intensity receiver receives the light emitted by the light emitting head and obtains the first detection frequency f1 and the first detection light intensity I1;

[0012] S312, repeat step S311 for a total of n times, the laser emitter is sequentially set at the second fixed frequency F2 and the second fixed power p2, the third fixed frequency F3 and the third fixed power p3, ..., the Nth fixed frequency F n and the Nth fixed power p n The laser is emitted, and the light intensity receiver receives and obtains the second detection frequency f2 and the second detection light intensity I2, the third detection frequency f3 and the third detection light intensity I3, ..., the nth detection frequency f n and the nth detection light intensity I n ;

[0013] S313, all fixed frequencies, detection frequencies, fixed powers, and detection light intensities are collected into a one-to-one corresponding parameter table and stored;

[0014] S32. The dust concentration detection instrument is normally sampled and tested under the detection environment. When in use, the optical fiber signal on-off switch is in the off state. Recalibration is performed after the set time. Specifically, the following steps are included:

[0015] S321, clean air is introduced from the air inlet passage to purge the particles in the detection chamber to make the detection chamber clean; the optical fiber signal on-off switch is turned on;

[0016] S322, repeat steps S311 to S313, the laser transmitter emits lasers in sequence according to the fixed frequency and fixed power in the parameter corresponding table, the light intensity receiver receives the signals in sequence and obtains the current first detection frequency f'1 and the first detection light intensity I'1, the second detection frequency f'2 and the second detection light intensity I'2, ..., the nth detection frequency f' n and the nth detection light intensity I' n ;

[0017] S323, compare f'1 with f1, f'2 with f2, ..., f' n and f n ; Compare I'1 and I1, I'2 and I2, ..., I' n and I n , calculate the percentage error λ of each set of comparison data 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强n , when λ 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强nWhen more than one third of the percentage errors exceed the set error, n frequency error compensation coefficient groups u are introduced. 频1 to u 频n and n light intensity compensation coefficients u 强1 to u 强n , and adjust the corresponding frequency error compensation coefficient group u 频1 to u 频n And the light intensity compensation coefficient u 强1 to u 强n , so that all data errors are lower than the set error.

[0018] Preferably, the zero calibration and span calibration method further includes a method for determining the state of the laser transmitter, and the specific determination method is as follows:

[0019] In step 312 and step 312, the n groups of fixed powers include a maximum power and a midpoint fixed power; when more than one-third of the percentage errors exceed the set error, the numerical values ​​of all percentage errors that exceed the set error are compared. If the numerical values ​​of all percentage errors are equal or basically close, the laser transmitter fails. This judgment method can comprehensively judge the power attenuation of the laser transmitter in the full power state, rather than the reception fluctuation of the light intensity receiver, so that the problem can be easily and accurately found and the laser transmitter can be replaced.

[0020] Preferably, the fiber optic signal on-off switch uses the inner rotor of the driving motor as the rotating body, the blocking block is fixed on the inner rotor, a wiring harness is wound around the inner rotor, a stator magnet is embedded in the outer periphery of a central mounting chamber in the switch seat, the inner rotor and the stator magnet together constitute the driving motor, and a socket is provided on the switch seat, and pins connected to the wiring harness are provided in the socket.

[0021] After adopting the above technical scheme, the effects of the present invention are: 1. In the zero calibration and span calibration method, an optical fiber signal on-off switch is used to lead out the optical signal in the optical trap and pass it into the detection chamber again, so that the light emitted by the current laser transmitter can be used for zero calibration and span calibration, and the overall accuracy is higher; 2. The zero calibration and span calibration can realize on-site calibration after use; 3. The zero calibration and span calibration compares and calibrates the two key parameters of frequency and light intensity, and the instrument detection results after calibration are more accurate; 4. This method uses an optical fiber signal on-off switch, and also corrects its blocked and closed position, so that the effect of blocking and closing the optical fiber is more reliable, thereby eliminating the error of blocking and closing the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0023] Figure 1is a connection diagram of a dust concentration detection instrument and an optical fiber signal on-off switch according to an embodiment of the present invention;

[0024] Figure 2 This is the main view of the fiber optic signal on-off switch;

[0025] Figure 3 yes Figure 2 The cross-sectional view at AA;

[0026] Figure 4 It is a three-dimensional view after hiding the first end plate;

[0027] In the attached drawings: 1. Dust concentration detection instrument; 11. Detection chamber; 12. Laser transmitter; 13. Light intensity receiver; 14. Air inlet channel; 15. Air outlet channel; 16. Light trap; 2. Fiber optic signal on-off switch; 21. Switch seat body; 22. First end plate; 23. Second end plate; 24. Incident fiber optic connector; 25. Emitting fiber optic connector; 26. Rotating body; 27. Blocking block; 28. Limiting trough; 3. Calibration collection fiber optic; 4. Calibration emission fiber optic; 5. Light-emitting head. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below through specific examples.

[0029] like Figure 1 As shown, a method for zeroing and spanning a dust concentration detection instrument 1 comprises the following steps:

[0030] S1. Connect the dust concentration detection instrument 1 to the circuit and the gas path. The dust concentration detection instrument 1 has a detection chamber 11. A laser emitter 12 is arranged on the left side of the detection chamber 11, and a light trap 16 opposite to the laser emitter 12 is arranged on the right side. An air inlet channel 14 and an air outlet channel 15 are arranged at the upper and lower ends of the detection chamber 11, respectively. A light intensity receiver 13 and a concave reflector are arranged at the front and rear sides of the detection chamber 11, respectively. The light trap 16 is also connected to a calibration collection optical fiber 3. A light emitting head 5 connected to a calibration emission optical fiber 4 is also arranged in the detection chamber 11. The calibration collection optical fiber 3 and the calibration emission optical fiber 4 are connected via an optical fiber signal on-off switch 2. The optical fiber signal on-off switch 2 comprises a switch seat, on which an optical fiber channel and a central installation chamber are arranged, the optical fiber channel runs through the switch seat, and an incident optical fiber connector 24 and an outgoing optical fiber connector 25 are respectively installed at both ends of the optical fiber channel on the switch seat, the incident optical fiber connector 24 and the outgoing optical fiber connector 25 are respectively connected to the calibration collection optical fiber 3 and the calibration emission optical fiber 4, a rotating body 26 is rotatably installed in the central installation chamber, and a shielding block 27 for shielding the optical fiber channel is arranged on the rotating body 26, and a rotating power device for driving the rotating body 26 to rotate is arranged on the switch seat, and the rotating power device drives the rotating body 26 to rotate so that the shielding block 27 deflects between the shielding closing position and the opening position;

[0031] S2, zero calibration step, including the following steps:

[0032] S21, clean air is introduced from the air inlet channel 14 for a set time, the laser transmitter 12 is started, and the optical fiber signal channel switch is in a closed state;

[0033] S22, after the light enters the light trap 16 and passes through the calibration collection optical fiber 3, the signal is disconnected, and the light intensity receiver 13 reads the light intensity reading at this time. If the reading at this time is not zero, the rotating body 26 continues to drive the shielding block 27 to deflect toward the shielding closing position until the reading of the light intensity receiver 13 is zero; at this time, the rotating body 26 records and saves the current position as the shielding closing position, so that the position of the optical fiber signal on-off switch 2 is also calibrated; if the light intensity receiver 13 still reads not zero after the rotating body 26 deflects to the limit, the reading of the light intensity receiver 13 is cleared and the light intensity state of the current state is recorded as zero;

[0034] S3, the calibration step, includes the following sub-steps:

[0035] S31, collection of calibration data before leaving the factory;

[0036] S311, after the zero calibration is completed, the optical fiber signal on-off switch 2 drives the shielding block 27 to deflect to the open position, at which time the calibration collection optical fiber 3 and the calibration emission optical fiber 4 are connected, and the light intensity receiver 13 receives the light emitted by the light head 5. At this time, the laser transmitter 12 is adjusted to emit the laser at the first fixed frequency F1 and the first fixed power p1. The light attenuates after passing through the calibration collection optical fiber 3 and the calibration emission optical fiber 4, and the light intensity receiver 13 receives the light emitted by the light head 5 and obtains the first detection frequency f1 and the first detection light intensity I1;

[0037] S312, repeat step S311 for a total of n times, the laser emitter 12 sequentially follows the second fixed frequency F2 and the second fixed power p2, the third fixed frequency F3 and the third fixed power p3, ..., the Nth fixed frequency F n and the Nth fixed power p n The laser is emitted, and the light intensity receiver 13 receives and obtains the second detection frequency f2 and the second detection light intensity I2, the third detection frequency f3 and the third detection light intensity I3, ..., the nth detection frequency f n and the nth detection light intensity I n ;

[0038] S313, all fixed frequencies, detection frequencies, fixed powers, and detection light intensities are collected into a one-to-one corresponding parameter table and stored. The parameter table can be used for comparison in subsequent calibration.

[0039] S32, the dust concentration detection instrument is normally sampled and tested under the detection environment, and the optical fiber signal on-off switch 2 is in the closed state during use, and is recalibrated after the set time, specifically including the following steps:

[0040] S321, clean air is introduced from the air inlet passage 14 to purge the particles in the detection chamber 11, so that the detection chamber 11 is clean; the optical fiber signal on-off switch 2 is in a closed state during the purge, and the laser transmitter 12 continues to emit laser, and then the reading of the light intensity receiver 13 gradually returns to zero, so that the zeroing operation can be performed; then the optical fiber signal on-off switch 2 is turned on;

[0041] S322, repeat steps S311 to S313, the laser transmitter 12 emits lasers in sequence according to the fixed frequency and fixed power in the parameter corresponding table, and the light intensity receiver 13 receives the signals in sequence and obtains the current first detection frequency f'1 and the first detection light intensity I'1, the second detection frequency f'2 and the second detection light intensity I'2, ..., the nth detection frequency f' n and the nth detection light intensity I' n ;

[0042] S323, compare f'1 with f1, f'2 with f2, ..., f'n and f n ; Compare I'1 and I1, I'2 and I2, ..., I' n and I n , calculate the percentage error λ of each set of comparison data 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强n , that is to say, there are 2n percentage errors in total;

[0043] When 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强n When more than one third of the percentage errors in the data exceed the set error, n frequency error compensation coefficient groups u are introduced 频1 to u 频n and n light intensity compensation coefficients u 强1 to u 强n , and adjust the corresponding frequency error compensation coefficient group u 频1 to u 频n And the light intensity compensation coefficient u 强1 to u 强n , so that all data errors are lower than the set error.

[0044] In this embodiment, preferably, the zero calibration and span calibration method further includes a method for determining the state of the laser transmitter 12, and the specific determination method is as follows:

[0045] In step 312 and step 312, the n groups of fixed powers include a maximum power and a midpoint fixed power; when more than one-third of the percentage errors exceed the set error, the numerical values ​​of all percentage errors that exceed the set error are compared. If the numerical values ​​of all percentage errors are equal or basically close, the laser transmitter 12 fails. This judgment method can comprehensively judge the power attenuation of the laser transmitter 12 in the full power state, rather than the reception fluctuation of the light intensity receiver 13, so that the problem can be easily and accurately found and the laser transmitter 12 can be replaced.

[0046] Preferably, the optical fiber signal on-off switch 2 uses the inner rotor of the driving motor as the rotating body 26, the blocking block 27 is fixed on the inner rotor, a wiring harness is wound around the inner rotor, a stator magnet is embedded in the outer periphery of the central mounting chamber in the switch seat, the inner rotor and the stator magnet together constitute the driving motor, since the inner rotor and the stator are the basic structure of the motor, the wiring harness is omitted in the drawings in this embodiment, a connector is provided on the switch seat, and pins connected to the wiring harness are provided in the connector.

[0047] like Figures 2 to 4 As shown in the accompanying drawings, a fiber optic signal on-off switch 2 is illustrated, including a switch seat, on which a fiber optic channel and a central installation chamber are arranged, the fiber optic channel runs through the switch seat, and an incident fiber optic connector 24 and an output fiber optic connector 25 are respectively installed at both ends of the fiber optic channel on the switch seat, a rotating body 26 is rotatably installed in the central installation chamber, a blocking block 27 for blocking the fiber optic channel is arranged on the rotating body 26, and a rotating power device for driving the rotating body 26 to rotate is arranged on the switch seat, and the rotating power device drives the rotating body 26 to rotate so that the blocking block 27 deflects between the blocking closing position and the opening position.

[0048] Among them, Figure 3 As shown, the rotating body 26 is an inner rotor, the blocking block 27 is fixed on the inner rotor, a wiring harness is wound around the inner rotor, a stator magnet is embedded in the outer periphery of the central mounting chamber in the switch seat, the inner rotor and the stator magnet together constitute a drive motor, and a socket is provided on the switch seat, and pins connected to the wiring harness are provided in the socket.

[0049] like Figure 3 As shown, the switch seat includes a switch seat body 21 and a first end plate 22 and a second end plate 23 detachably fixed at both ends of the switch seat body 21. Figure 4 The first end plate 22 is omitted, and the switch seat body 21 is provided with the central mounting chamber. The first end plate 22 and the second end plate 23 are respectively provided with a first optical fiber mounting hole and a second optical fiber mounting hole, and the first optical fiber mounting hole and the second optical fiber mounting hole are provided with a first threaded hole section and a second threaded hole section. The switch seat body 21 is also provided with an intermediate optical fiber mounting hole. The first optical fiber mounting hole, the intermediate optical fiber mounting hole and the second optical fiber mounting hole are coaxially arranged and cooperate to form the optical fiber channel. The incident optical fiber connector 24 and the output optical fiber connector 25 are respectively threadedly connected to the first threaded hole section and the second threaded hole section, and the blocking block 27 is located between the first threaded hole section and the intermediate optical fiber mounting hole or the second threaded hole section and the intermediate optical fiber mounting hole.

[0050] The switch seat body 21 is provided with a limit groove 28, the blocking block 27 is in the limit groove 28, one end of the limit groove 28 is a limit end, and the blocking block 27 blocks the optical fiber channel when cooperating with the limit end.

[0051] Therefore, when the power is turned on, the inner rotor rotates forward and reverse, thereby driving the shielding block 27 to deflect forward and reverse between the shielding closing position and the opening position. Among them, the rotary power device in this embodiment can be selected from common motors or rotary electromagnets to control the rotation of the rotating body 26.

[0052] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for zero and span calibration of a dust concentration detection instrument, characterized in that: The following steps are involved: S1. Connect the dust concentration detection instrument to the circuit and the gas path. The dust concentration detection instrument has a detection chamber. A laser transmitter is arranged on the left side of the detection chamber, and a light trap opposite to the laser transmitter is arranged on the right side. The upper and lower ends of the detection chamber are respectively provided with an air inlet channel and an air outlet channel. The front and rear sides of the detection chamber are respectively provided with a light intensity receiver and a concave reflector; the light trap is also connected to a calibration collection optical fiber, and a light head connected to the calibration emission optical fiber is also arranged in the detection chamber. The calibration collection optical fiber and the calibration emission optical fiber are connected through an optical fiber signal on-off switch, and the optical fiber signal on-off switch includes a switch seat , the switch seat is provided with an optical fiber channel and a central installation chamber, the optical fiber channel runs through the switch seat, and the switch seat is respectively provided with an incident optical fiber connector and an output optical fiber connector at both ends of the optical fiber channel, the incident optical fiber connector and the output optical fiber connector are respectively connected to the calibration collection optical fiber and the calibration emission optical fiber, a rotating body is rotatably installed in the central installation chamber, a blocking block for blocking the optical fiber channel is provided on the rotating body, and a rotating power device for driving the rotating body to rotate is provided on the switch seat, and the rotating power device drives the rotating body to rotate so that the blocking block deflects between the blocking closing position and the opening position; S2, zero calibration step, including the following steps: S21, clean air is introduced from the air inlet channel for a set time, the laser transmitter is started, and the optical fiber signal channel switch is in the closed state; S22, after the light enters the light trap and passes through the calibration collection optical fiber, the signal is disconnected, and the light intensity receiver reads the light intensity reading at this time. If the reading at this time is not zero, the rotating body continues to drive the shielding block to deflect toward the shielding closing position until the reading of the light intensity receiver is zero; at this time, the rotating body records and saves the current position as the shielding closing position; if the light intensity receiver still reads not zero after the rotating body deflects to the limit, the reading of the light intensity receiver is cleared and the light intensity state of the current state is recorded as zero; S3, the calibration step, includes the following sub-steps: S31, collection of calibration data before leaving the factory; S311, after the zero calibration is completed, the optical fiber signal on-off switch drives the shielding block to deflect to the open position, at which time the calibration collection optical fiber and the calibration emission optical fiber are connected, and the light intensity receiver receives the light emitted by the light emitting head. At this time, the laser transmitter is adjusted to emit the laser at the first fixed frequency F1 and the first fixed power p1. The light is attenuated after passing through the calibration collection optical fiber and the calibration emission optical fiber, and the light intensity receiver receives the light emitted by the light emitting head and obtains the first detection frequency f1 and the first detection light intensity I1; S312, repeat step S311 for a total of n times, the laser emitter is sequentially set at the second fixed frequency F2 and the second fixed power p2, the third fixed frequency F3 and the third fixed power p3, ..., the Nth fixed frequency F n and the Nth fixed power p n The laser is emitted, and the light intensity receiver receives and obtains the second detection frequency f2 and the second detection light intensity I2, the third detection frequency f3 and the third detection light intensity I3, ..., the nth detection frequency f n and the nth detection light intensity I n ; S313, all fixed frequencies, detection frequencies, fixed powers, and detection light intensities are collected into a one-to-one corresponding parameter table and stored; S32. The dust concentration detection instrument is normally sampled and tested under the detection environment. When in use, the optical fiber signal on-off switch is in the off state. Recalibration is performed after the set time. Specifically, the following steps are included: S321, clean air is introduced from the air inlet passage to purge the particles in the detection chamber to make the detection chamber clean; the optical fiber signal on-off switch is turned on; S322, repeat steps S311 to S313, the laser transmitter emits lasers in sequence according to the fixed frequency and fixed power in the parameter corresponding table, the light intensity receiver receives the signals in sequence and obtains the current first detection frequency f'1 and the first detection light intensity I'1, the second detection frequency f'2 and the second detection light intensity I'2, ..., the nth detection frequency f' n and the nth detection light intensity I' n ; S323, compare f'1 with f1, f'2 with f2, ..., f' n and f n ; Compare I'1 and I1, I'2 and I2, ..., I' n and I n , calculate the percentage error λ of each set of comparison data 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强n , when λ 频1 , 频2 , ..., λ 频n and λ 强1 , 强2 , ..., λ 强n When more than one third of the percentage errors exceed the set error, n frequency error compensation coefficient groups u are introduced. 频1 to u 频n and n light intensity compensation coefficients u 强1 to u 强n , and adjust the corresponding frequency error compensation coefficient group u 频1 to u 频n And the light intensity compensation coefficient u 强1 to u 强n , so that all data errors are lower than the set error.

2. A method for zero and span calibration of a dust concentration detection instrument as claimed in claim 1, characterized in that: The zero calibration and span calibration method also includes a method for determining the state of the laser transmitter, and the specific determination method is as follows: In step 312 and step 312, the n groups of fixed powers include a maximum power and a midpoint fixed power; when more than one-third of the percentage errors exceed the set error, the numerical values ​​of all percentage errors that exceed the set error are compared. If the numerical values ​​of all percentage errors are equal or basically close, the laser transmitter fails.

3. A method for zero and span calibration of a dust concentration detection instrument as claimed in claim 2, characterized in that: The optical fiber signal on-off switch uses the inner rotor of the driving motor as the rotating body, the blocking block is fixed on the inner rotor, a wiring harness is wound around the inner rotor, a stator magnet is embedded in the outer periphery of the central mounting chamber in the switch seat, the inner rotor and the stator magnet together constitute the driving motor, a connector is provided on the switch seat, and pins connected to the wiring harness are provided in the connector.

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