Intelligence constant current individual air dust sampler and constant current control method
Technical field
The present invention relates to labour protection, health and epidemic prevention monitoring instrument, especially for a kind of intelligent constant current individual air dust sampler of various harmful gases and dust concentration monitoring.
Background technology
Dust sampler is widely used in labour protection, health and epidemic prevention department, is used for the monitoring of various harmful gases and dust concentration.In environmental protection, metallurgy, building materials, chemical industry, prevention and cure of occupational disease ... in industry, the environment that the labor operation place of dust is normally arranged with dust sampler evaluation, weigh a labor operation class dust to health effects, provide theoretical foundation the transformation of the research of prevention and cure of occupational disease, production environment, equipment.The method that dust sampler is measured dust mass concentration in the air is the heavy method of meter, its principle is to extract the dust laden air of certain volume with this dust sampler, dust is trapped on the known filter membrane of quality, weigh the dust-laden filter membrane quality then in the laboratory, calculate the mass concentration of dust according to following formula:
------mass concentration of----dust, mg/m in the formula: ρ
3
m
1-----------filter membrane is gathered the quality before the dust, mg;
m
2-----------filter membrane is gathered the quality behind the dust, mg;
Q-----------sampling flow, L/min;
T-----------sampling time, min;
By following formula as can be known, accurately measure the dust mass concentration, be to control well sampling flow and sampling time, the sampling time control ratio is easier to accomplish, does not have big problem, key is to control sampling flow, the fluctuation of sampling flow must cause the totally error of volume of gas production, causes the error of dust mass concentration thus, for accurate measurement accumulative total gas production volume, the problem of constant current sampling has been proposed.Original dust sampler adopts spinner-type flowmeter to measure instantaneous gas production flow mostly, there are two problems in it, one is when sampling, after the sampling thief spinner-type flowmeter is set up instantaneous delivery, sampling thief is with the increase in sampling time, and the grit that the filter paper in the sampling head (drip catcher) captures increases, and the gas circuit resistance strengthens thereupon, the instantaneous delivery of former setting will descend, and has brought the error of gas production volume thus.Another is to adopt spinner survey, and spinner-type flowmeter can not provide electric signal output, can't realize FEEDBACK CONTROL, compensation correction automatically, can not constitute closed-loop control system.If select conventional orifice flowmeter for use, in the low discharge scope of this instrument, exist precision, resolution not high, also there is the big shortcoming of gas circuit resistance in the big deficiency that waits of gas circuit resistance with mass flow sensor, and the cost height.Existing personal sampler because the aspiration pump pulsation is bled, produces the air-flow spike, when doing the flow contrast with other flowmeter, because the fluctuation of air-flow is difficult for the reading contrast.
Summary of the invention
The purpose of this invention is to provide and a kind ofly can control the gas production flow automatically, accumulative total gas production volume metering is accurate, can accurately measure the intelligent constant current individual air dust sampler and the constant current control method of dust mass concentration.
Described intelligent constant current individual air dust sampler comprises sampling head, tool housing, in tool housing, be provided with inlet air filtration mouth, aspiration pump, air chamber, single-chip microcomputer, battery, with in the sampling head that the air intake opening of inlet air filtration mouth is connected the filter membrane that is used to capture dust is housed, it is characterized in that: described sampling thief also is provided with buffering air-capacitor, air-capacitor, flow closed control circuit; Air chamber is provided with orifice plate and connects mouth, orifice plate, orifice plate seat, air chamber diaphragm, pressure tap and little differential pressure sensor; The test lead of little differential pressure sensor is by the pressure tap UNICOM on flexible pipe and the air chamber, its signal output part is connected with an input port of single-chip microcomputer by amplifier, A/D converter, and the output control terminal of single-chip microcomputer links to each other with the electric signal control end of aspiration pump drive motor through the air pump control module.
The gas outlet UNICOM of the air intake opening of described buffering air-capacitor and inlet air filtration mouth, the air intake opening UNICOM of its gas outlet and aspiration pump, the gas outlet UNICOM of the air intake opening of air-capacitor and aspiration pump, the air intake opening UNICOM of its gas outlet and air chamber; Aforementioned orifice plate connects mouth and is located at the air chamber wall outside, it is inboard and connect by air chamber wall through hole and orifice plate that mouth is bonding to be connected that the orifice plate seat is located at air chamber wall, orifice plate connects the pressure tap of mouth outer end by orifice plate center damping hole and orifice plate seat central through hole and air chamber inner chamber UNICOM, and the air chamber diaphragm is connected with cross section sealing in the air chamber.
Described buffering air-capacitor, air-capacitor are formed by latch, cushion gas cavity volume, air-capacitor pressing plate, two air-capacitor diaphragms, springs; Two middle clamp springs of air-capacitor diaphragms also are arranged in the cavity that is made up by latch, air-capacitor pressing plate and screw, constitute the air-capacitor chamber between two air-capacitor diaphragms, which is provided with air intake opening, gas outlet.
Described flow closed control circuit comprises single-chip microcomputer, little differential pressure sensor, keyboard, LCD display unit, sound alarm unit, air pump control module and power supply; Detect the back pressure of the tested gas in air chamber gas outlet by little differential pressure sensor, and this back pressure electric signal is input to the input end of single-chip microcomputer; The output terminal of single-chip microcomputer is connected with the input end of air pump control module, LCD display unit and sound alarm unit respectively.
Be provided with a plurality of apertures that are communicated with air chamber in the outlet nozzle of described air chamber, the other end of a plurality of apertures all with atmosphere UNICOM
The constant current control method feature that is used for intelligent constant current individual air dust sampler is:
A. set up the flux modification curve, the working gas of different flow is provided, measure the air chamber back pressure under the different flow, set up the relation curve of back pressure and flow, this curve is stored in the data-carrier store of single-chip microcomputer; Set in advance the flow value and the sampling time of gas to be measured simultaneously by keyboard;
B. detect the back pressure of air chamber gas outlet working gas with little differential pressure sensor, this back pressure electric signal is amplified, converts the data-in port that digital signal is input to single-chip microcomputer to through A/D converter;
C. the digital signal with the current back pressure of survey compares with the back pressure, the discharge relation curve values that are stored in the single-chip data storer, in flow value and sampling time scope that step a sets, export in real time in order to control the control signal of aspiration pump flow by the control port of single-chip microcomputer, implement constant current output;
D. in step c, single-chip microcomputer sends the traffic sampling instruction earlier, little differential pressure sensor detects the back pressure of air chamber gas outlet working gas, and the setting value among this back pressure numerical value and step a, the c compared, if then reduce the dutycycle of aspiration pump, if then increase its dutycycle less than preset value greater than preset value; Detect the sampling time simultaneously, as then continuing traffic sampling less than preset value and regulating its dutycycle, arrive preset value as the sampling time and then close aspiration pump automatically, sampling finishes.
Measuring the flow principle is: at the air chamber of gas circuit outlet setting as Fig. 3, the outlet nozzle of air chamber has a plurality of apertures as the lotus root core, and certain length is arranged, its effect is that the gas that does not allow gas circuit enter air chamber discharges too soon, allowing air chamber and atmosphere set up certain pressure differential is back pressure, connecing mouth, certain-length is arranged is to keep air-flow certain straight length of giving vent to anger, air chamber is steadily given vent to anger, the air chamber of being made up of diaphragm is equivalent to an air-capacitor that volume is plastic, good filter action is arranged, allow back pressure be in plateau, according to certain relation of back pressure and flow foundation, back pressure records surely, and sampling flow just records accurately.Outlet nozzle lotus root core aperture sectional area big or small most important, it has determined the resolution and the precision of flow.Determine valve lotus root core aperture sectional area size with instrument flow full scale, the aperture sectional area is big, and the back pressure of foundation is just little, and resolution is not high; The aperture sectional area is little, and the back pressure of foundation is just big, but back pressure crosses conference and make the gas circuit resistance big, and the instrument load capacity is descended, and does not reach the required maximum flow of instrument, so must take into account the relation between the two, determines suitable outlet nozzle lotus root core aperture sectional area.
The invention has the beneficial effects as follows:
1. with gas circuit back pressure method measurement of discharge, resistance is little, the instrument load capacity is strong, under the acting in conjunction of the software and hardware of instrument, and flow measurement precision height, this method flow electric signal output, traffic figure shows, realized that the flow closed loop controls the automatic constant current sampling automatically, the accumulative total gas production volume of metering is accurate, thereby has improved the precision of dust mass concentration;
2. intelligent equipment design; programming is provided with Temporal Sampling; wear in the work course of work the operator; sometimes owing to bending over or other reason causes gas circuit folding dead; the sampling flow precision that causes following the tracks of setting is overproof, and the instrument auto stop of can reporting to the police makes the time of instrument misoperation be not counted in sampling thief T.T.; improve accumulative total gas production volume accuracy, thereby improved the precision of dust mass concentration.The instrument electric weight shows, undervoltage warning, prompting charging.
3. instrument and upper machine communication calibration, convenient for production.
4. instrument has carried out Industrial Moulding Design, and good looking appearance is worn conveniently.
The present invention can realize the flow closed-loop control, and the automatic constant current sampling has improved the accuracy of measuring the dust mass concentration, uses reliably, can produce in batches, is widely used.
Description of drawings.
Fig. 1 is a systematic schematic diagram of the present invention,
Fig. 2 is buffering air-capacitor and air-capacitor structural representation,
Fig. 3 is the side view of Fig. 2,
Fig. 4 is the air chamber structure synoptic diagram,
Fig. 5 is the side view of Fig. 4,
Fig. 6 is flow loop control theory figure,
Fig. 7 is flow closed control circuit figure,
Fig. 8 is a flow closed-loop control program flow diagram.
Among the figure: the 1-filter tip, 2-cushions air-capacitor, 3-aspiration pump, 4-filtering air-capacitor, the 5-air chamber, the 5-1-orifice plate connects mouth, the 5-2-orifice plate, 5-3-orifice plate seat, 5-4-air chamber diaphragm, the 5-5-screw, 5-6-air intake opening, 5-7-pressure tap, the 5-8-gas outlet, 6-little differential pressure sensor, 7-single-chip microcomputer, the 8-button, 9-display, 10-latch, 11-cushion gas cavity volume, 12-air-capacitor pressing plate, 13-screw, 14-air-capacitor diaphragm, 15-spring, 16-flow closed control circuit, the 17-LCD display unit, 18-sound alarm unit, 19-air pump control module, 20-power supply.
Embodiment
The invention will be further described below in conjunction with accompanying drawing.Among Fig. 1,4, described intelligent constant current individual air dust sampler comprises sampling head, tool housing, in tool housing, be provided with inlet air filtration mouth 1, aspiration pump 3, air chamber 5, single-chip microcomputer 7, battery, with in the sampling head that the air intake opening of inlet air filtration mouth 1 is connected the filter membrane that is used to capture dust is housed, it is characterized in that: described sampling thief also is provided with buffering air-capacitor 2, air-capacitor 4, flow closed control circuit 16; Air chamber 5 is provided with orifice plate and meets mouth 5-1, orifice plate 5-2, orifice plate seat 5-3, air chamber diaphragm 5-4, pressure tap 5-7 and little differential pressure sensor 6; The test lead of little differential pressure sensor 6 is by the pressure tap 5-7 UNICOM on flexible pipe and the air chamber 5, its signal output part is connected with an input port of single-chip microcomputer 7 by amplifier, A/D converter, and the output control terminal of single-chip microcomputer 7 links to each other through the electric signal control end of air pump control module 19 with aspiration pump 3 drive motor.
The gas outlet UNICOM of the air intake opening of described buffering air-capacitor 2 and inlet air filtration mouth 1, the air intake opening UNICOM of its gas outlet and aspiration pump 3, the gas outlet UNICOM of the air intake opening of air-capacitor 4 and aspiration pump 3, the air intake opening 5-6 UNICOM of its gas outlet and air chamber 5; Aforementioned orifice plate meets mouth 5-1 and is located at the air chamber 5 walls outside, it is inboard and connect by air chamber wall through hole and orifice plate that mouth 5-1 is bonding to be connected that orifice plate seat 5-3 is located at air chamber 5 walls, orifice plate meets the pressure tap 5-7 of mouth 5-1 outer end by orifice plate 5-2 center damping hole and orifice plate seat 5-3 central through hole and air chamber 5 inner chamber UNICOMs, and air chamber diaphragm 5-4 is connected with cross section sealing in the air chamber 5.
Show that as Fig. 2,3 described buffering air-capacitor 2, air-capacitor 4 are formed by latch 10, cushion gas cavity volume 11, air-capacitor pressing plate 12, two air-capacitor diaphragms 14, springs 15; Two air-capacitor diaphragms 14 middle clamp springs 15 also are arranged in the cavity that is made up by latch 10, air-capacitor pressing plate 12 and screw 13, constitute air-capacitor chamber 11 between two air-capacitor diaphragms 14, which is provided with air intake opening, gas outlet.
At Fig. 6 flow loop control theory figure, Fig. 7 is among the flow closed control circuit figure, and described flow closed control circuit 16 comprises single-chip microcomputer 7, little differential pressure sensor 6, keyboard 8, LCD display unit 17, sound alarm unit 18, air pump control module 19 and power supply 20; Detect the back pressure of the tested gas in air chamber 5 gas outlets by little differential pressure sensor 6, and this back pressure electric signal is input to the input end of single-chip microcomputer 7; The output terminal of single-chip microcomputer is connected with the input end of air pump control module 19, LCD display unit 17 and sound alarm unit 18 respectively.
Fig. 5 has represented to be provided with a plurality of apertures that are communicated with air chamber in the outlet nozzle 5-8 of air chamber 5, the other end of a plurality of apertures all with atmosphere UNICOM.
The constant current control method that is used for intelligent constant current individual air dust sampler can be referring to Fig. 8,6.
Concrete grammar is:
A. set up the flux modification curve, the working gas of different flow is provided, measure the air chamber back pressure under the different flow, set up the relation curve of back pressure and flow, this curve is stored in the data-carrier store of single-chip microcomputer 7; Set in advance the flow value and the sampling time of gas to be measured simultaneously by keyboard 8;
B. detect the back pressure of air chamber 5 gas outlet working gass with little differential pressure sensor 6, this back pressure electric signal is amplified, converts the data-in port that digital signal is input to single-chip microcomputer 7 to through A/D converter;
C. the digital signal with the current back pressure of survey compares with the back pressure, the discharge relation curve values that are stored in single-chip microcomputer 7 data-carrier stores, in flow value and sampling time scope that step a sets, export in real time in order to control the control signal of aspiration pump 3 flows by the control port of single-chip microcomputer 7, implement constant current output;
D. in step c, single-chip microcomputer sends the traffic sampling instruction earlier, little differential pressure sensor 6 detects the back pressure of air chamber 5 gas outlet working gass, and the setting value among this back pressure numerical value and step a, the c compared, if then reduce the dutycycle of aspiration pump 3, if then increase its dutycycle less than preset value greater than preset value; Detect the sampling time simultaneously, as then continuing traffic sampling less than preset value and regulating its dutycycle, arrive preset value as the sampling time and then close aspiration pump 3 automatically, sampling finishes.
Principle of work of the present invention: the sampling thief gas circuit is made up of inlet air filtration mouth, buffering air-capacitor, aspiration pump, filtering air-capacitor, air chamber, outlet nozzle: see Fig. 1.
(instrument outside) is connected to sampling head before the inlet air filtration mouth of sampling thief, and interior dress captures the filter membrane of dust, is used for capturing the collection dust; The inlet air filtration mouth is used to prevent that dust from entering aspiration pump inside; The buffering air-capacitor is used for steady pumping airflow, and high-end at the sampling thief flow range makes sampling thief air inlet (instantaneous delivery) become very steady, can make good comparison calibration with other flowmeter, is the vitals of sampling thief; Aspiration pump is the power source of instrument gas production; The filtering air-capacitor is an aspiration pump outlet side wave filter, plays auxiliary smooth air effect; Air chamber is the key component of instrument, sets up in the gas circuit outlet, surveys its gas circuit outlet air chamber back pressure (pressure differential between air chamber and the atmosphere) by little differential pressure sensor.The electric signal that little differential pressure sensor records send central microprocessor to handle through integrated operational amplifier amplification, A/D conversion, shows sampling flow; When setting traffic sampling, computing machine compares sampling flow automatically and sets flow, carrying out closed loop controls automatically, within the specific limits, no matter airflow fluctuation, or the variation of gas circuit load resistance is all set flow from motion tracking, carry out the automatic constant current sampling, guarantee to measure the precision of dust mass concentration.
Vitals buffering filtering air-capacitor, it constitutes buffering filtering air-capacitor by gentle cavity volume of spring of two air-capacitor diaphragm therebetween, and structure is seen Fig. 2.
When design buffering filtering air-capacitor, the size of air-capacitor, diaphragm pliability, the size of spring force is crucial, consider the effective filtering in this instrument flow range, determine the correlation parameter of air-capacitor chamber, diaphragm, spring etc. by a large amount of experiments, only under suitable buffering air-capacitor effect, the spike of the pulsation pumping airflow of aspiration pump just can be cushioned air-capacitor and effectively absorb, play filter action, guarantee the stationarity of charge air flow.
The key component air chamber connects mouth by air chamber, air chamber diaphragm, orifice plate, admission piece, outlet nozzle, orifice plate and forms and see Fig. 3 air chamber component figure.
The course of work of the present invention:
1. substitute the bad for the good instrument stand-by;
2. the filter membrane oven dry is weighed stand-by;
3. sampling head installs filter membrane, and the instrument start sets sampling start-stop sequential, connects sampling head and instrument;
4. wear sampling head and instrument, entered the operation place;
5. start sampling thief, begin sampling;
6. instrument countdown sampling is then reported to the police and is shut down;
7. take off sampling head and instrument, take out from sampling head and caught the dirt filter membrane;
8. filter membrane oven dry is weighed stand-byly, draws the filter membrane weightening finish;
9. calculate the mass concentration of dust.
Casing, inlet air filtration mouth, buffering air-capacitor, aspiration pump, air-capacitor, air chamber, outlet nozzle material are: ABS; The abutting edge all uses methenyl choloride bonding;
Pressure testing: good after bond is bonding by component-assembled, block the pressure that the gas outlet adds 5kPa and try the water, gas leak phenomenon must not be arranged.
Calibration: after the instrument complete machine assembles, connect host computer, download instrument software, connect instrument calibration gas circuit and soap-foam flowmeter, start the instrument sampling pump, 20 different flows evenly are provided in full range, calibrate by host computer with connection.