CN100346153C

CN100346153C - Filter wheel assembly of negative optical filtering multi-component infrared analyzer

Info

Publication number: CN100346153C
Application number: CNB2003101087983A
Authority: CN
Inventors: 杨灿谦; 刘大平
Original assignee: Shanghai Research Institute of Chemical Industry SRICI
Current assignee: Shanghai Research Institute of Chemical Industry SRICI
Priority date: 2003-11-24
Filing date: 2003-11-24
Publication date: 2007-10-31
Anticipated expiration: 2023-11-24
Also published as: CN1621809A

Abstract

The present invention discloses a filter wheel assembly for negative light-filtering multielement infrared analyzers, which comprises a filter wheel and a synchronous motor, wherein the filter wheel is a round metal disc, an analysis air cell and a reference air cell on the metal disc are arranged in the ranging sequence of S1, S2, R1 and R2 in an anticlockwise direction, and the synchronous motor drives the filter wheel directly through a shaft coupling; the rotary speed of the synchronous motor is set to be 1500 RPM, the rotary angular frequency of the filter wheel is kept to be 1/2 synchronous with the angular frequency of the AC network; consequently, the interference of commercial frequency signals are fundamentally and completely eliminated, and the defects of big gear drive noise, easy damage and short service life are eliminated; simultaneously, a radial narrow groove is arranged on the wheel edge of the filter wheel as a synchronous groove so that the processing of the filter wheel is more convenient, and the problem unsolved for years is solved.

Description

The filter wheel assembly of negative many components infrared spectrum analyser that filters

Technical field

The present invention relates to infrared analytical instrument, relate in particular to a kind of filter wheel assembly of negative many components of optical filtering infrared spectrum analyser, this filter wheel assembly is finished optical modulation in light path.

Background technology

Trace amounts of CO, CO based on negative optical filtering principle ₂Two component infrared spectrum analysers because it is cheap, are easy to make, and two during the last ten years, is used widely in the little nitrogenous fertilizer industry of China, becomes indispensable instrument in the production,

This analyser is based on CO, CO ₂The ultimate principle that the infrared light of specific wavelength is had absorption.CO ₂At wavelength 4.65 μ m places, CO has the strong absorption band at wavelength 4.3 μ m places, and its absorption intensity is relevant with component concentration to be measured.Negative optical filtering infrared spectrum analyser is a kind of of infrared spectrum analyser, negative optical filtering CO, the CO of domestic production at present ₂Two proximate analysis instrument typical structures are seen Fig. 1.It comprises

infrared light supply

8,9; Filter wheel assembly 10, light

source interference filter

11,12,

anti-interference air chamber

13,14;

Work air chamber

15,16; Taper

infrared light gatherer

17,18; Indium antimonide

infrared sensor

19,20;

Photoelectrical coupler

21,22;

Synchronous generator

23,24; Electronic processing circuit 25,26.The first half is the CO path, and the latter half is CO ₂Path.Filter wheel assembly 10 is a critical component, sees also Fig. 2, and filter wheel assembly 10 comprises filter wheel 101, syncmotor 102, reduction gearing 103, filter wheel 101 by syncmotor 102 through gear 103 coupling gearing-down.Filter wheel 101 structures on a rosette, are equipped with four air chambers referring to Fig. 3, are circular cylinder, and axially two ends allow infrared light axially pass through with the sealing of calcium fluoride wafer.S ₁, S ₂For analyzing air chamber 27, R ₁, R ₂Be reference air chamber 28, its geometry is identical.Analyze in the air chamber 27 and charge into N ₂, it does not have absorption to infrared light.Charge into CO, CO that certain proportion mixes in the reference air chamber 28 ₂Gas.

Filter wheel 101 rotates in a clockwise direction, analyzes air chamber and reference air chamber and will enter light path system in turn.By the infrared light that infrared

light supply

8,9 sends, after being subjected to filter wheel assembly 10 and carrying out optical modulation, by narrow passband optical interference filter 11,12.The centre wavelength of

optical filter

11,12 passbands respectively with CO, CO ₂The consistent wavelength of absorption peak makes in the infrared spectrum of

infrared light supply

8,9 emission that near the infrared light the component characteristic peak to be measured could be by the work air chamber, thus the selectivity of raising instrument.Infrared light enters the

anti-interference air chamber

13,14 of two sealings by after the optical filter.The anti-interference air chamber 13 of CO passage fills with CO ₂Gas, and CO ₂The anti-interference air chamber 14 of path fills the gas with CO, to eliminate the interference of other component to tested component.Then, infrared light is by

work air chamber

15,16; In the work air chamber, infrared light is subjected to tested component and absorbs, and absorption intensity is relevant with tested component concentration.Remaining infrared light gathers infrared light on the indium

antimonide infrared sensor

19,20 through the

infrared light gatherer

17,18 of a pyramidal structure.The indium antimonide infrared sensor flows by constant DC, and its output terminal alternating voltage is coupled to

electronic processing circuit

25,26.

Because the infrared light that sends from infrared light supply is subjected to the modulation of filter wheel 101, the waveform that the indium antimonide infrared sensor obtains is shown in Fig. 4 a-d.

Filter wheel whenever turns around, and obtains by S ₁-R ₁-S ₂-R ₂Tactic four peaks.As reference air chamber R ₁And R ₂When advancing people's light path, the light approaching from the infrared spectrum medium wavelength of light source and tested gas absorption wavelength is almost all sponged by the reference air chamber, the tested gas of work in the air chamber absorption that do not recur, form shorter two peaks (representing with R1, R2), its peak heights and area and tested gas concentration are irrelevant.When the analysis air chamber on the filter wheel enters light path, because what the analysis air chamber on the filter wheel filled is nitrogen, infrared light to light path does not have absorption, and the absorbing state of the infrared light in the light path depends on the concentration of tested component in the work air chamber, forms two higher peak S1, S2.The height at this peak and area increase with tested gas concentration and reduce.The output signal of indium antimonide infrared detector is amplified through electronic processing circuit, and separated in synchronization, series of steps such as integration, computing, linear process obtain DC voltage (or electric current) output that changes with tested component concentration ratio.

The synchronous groove of cutting on the

CD

29,30 of two arcs of filter wheel 101 is used for producing synchronizing signal, is used for separated in synchronization is realized at indium antimonide infrared detector output peak.Article two,

synchronous groove

29,30 is corresponding to two 90 geometric angle zones of two analysis air chambers, and when the light path of

synchronous groove

29,30

photoelectrical couplers

21,22, photoelectrical coupler produces output, makes

synchronous generator

23,24 output high level.

The AC signal of indium antimonide infrared sensor output is very little, has only about 1mV, and variable quantity is a trace level, is subjected to power frequency and disturbs very big.In traditional design, disturb for fear of power frequency, the filter wheel rotating speed is designed to and 25 revolutions per seconds of certain values that stagger, i.e. some deviation of signal frequency and power frequency.Adopted gear drive between the driven in synchronism motor of filter wheel and the filter wheel for this reason.The syncmotor rotating speed is chosen to be 3000rpm, is respectively 66 and 29 gear reduction of speed through two numbers of teeth, and the rotating speed that makes filter wheel is 1318rpm.The signal waveform repetition frequency is 43.9Hz, and the cycle is that 23.15ms and power frequency 50Hz stagger.

The filter wheel assembly of traditional design has following three defectives:

1. the design of staggering of signal frequency and power frequency can not reduce the influence that power frequency is disturbed, and is that the beat frequency of 50-43.9=6.1Hz disturbs because it has introduced frequency.Because its frequency is very low, can not eliminate with wave filter.

2. gear transmission noises is big, fragile, the life-span short, greasy dirt is arranged.

3. the synchronous groove processing difficulties of circular arc.

The problems referred to above can not get solving always for many years.

Summary of the invention

The objective of the invention is defective, propose a kind of filter wheel assembly of negative many components of optical filtering infrared spectrum analyser, fundamentally solving anti-power frequency interference problem and synchronous groove processing difficulties problem at above-mentioned filter wheel assembly existence.

In order to finish above-mentioned purpose, the present invention adopts following technical scheme

Should comprise filter wheel, syncmotor by the negative filter wheel assembly that filters many components infrared spectrum analyser, filter wheel is a rosette, rosette is provided with the cylindrical chamber of four symmetrical distributions, wherein two are analysis air chamber S1, S2, two is reference air chamber R1, R2, four air chamber S1, S2, the axial two ends of R1, R2 seal with the calcium fluoride wafer, and described analysis air chamber and reference air chamber are provided with arranging with counterclockwise side by putting in order of S1, S2, R1, R2.

Described syncmotor directly drives filter wheel by shaft coupling.

Described syncmotor rotating speed is set to 1500 rev/mins.

Described filter wheel rotates in a clockwise direction, and its angle of rotation frequency keeps 1/2 synchronous with the angular frequency of AC network.

A radially narrow groove is offered as synchronous groove in described filter wheel wheel edge.

The initial edge of the radially narrow groove on the described filter wheel and the angle of horizontal direction are 45 °.

In technique scheme, different with traditional filter wheel assembly, the present invention is provided with analysis air chamber on the rosette and reference air chamber with counterclockwise side by putting in order of S1, S2, R1, R2 with arranging, and syncmotor directly drives filter wheel by shaft coupling; The syncmotor rotating speed is set to 1500 rev/mins, filter wheel angle of rotation frequency keeps 1/2 synchronous with the angular frequency of AC network, thereby can fundamentally eliminate the interference of power frequency rate signal fully, also eliminated the shortcoming that gear transmission noises is big, fragile, the life-span is short.Simultaneously, a radially narrow groove is offered as synchronous groove in filter wheel wheel edge, makes that the processing of filter wheel is convenient easily, has solved the problem that had not always solved for many years.

Description of drawings

Fig. 1 is conventional negative many components infrared spectrum analyser principle schematic that filters.

Fig. 2 is conventional negative many components infrared spectrum analyser filter wheel modular construction synoptic diagram that filters.

Fig. 3 is a filter wheel air chamber distribution schematic diagram shown in Figure 2.

Fig. 4 is conventional negative many components infrared spectrum analyser indium antimonide sensor CO path signal waveform synoptic diagram that filters, and wherein, Fig. 4 a is an indium antimonide detector output signal waveform;

Fig. 4 b is a synchronization waveform;

Fig. 4 c is a separated in synchronization post analysis passage waveform;

Fig. 4 d is a reference channel waveform after the separated in synchronization.

Fig. 5 is the filter wheel modular construction synoptic diagram of many components of the negative optical filtering of the present invention infrared spectrum analyser.

Fig. 6 is a filter wheel air chamber distribution schematic diagram shown in Figure 5.

Fig. 7 is many components of the negative optical filtering of the present invention infrared spectrum analyser CO path signal waveform synoptic diagram, wherein

Fig. 7 a is an indium antimonide infrared detector signal output waveform;

Fig. 7 b is a synchronization waveform;

Fig. 7 c is a separated in synchronization post analysis passage waveform;

Fig. 7 d is a reference channel waveform after the separated in synchronization.

Fig. 8 is being subjected to each signal waveform of power frequency interference back for many components of the negative optical filtering of the present invention infrared spectrum analyser antimony smoke sensor CO path, wherein,

Indium antimonide detector output signal waveform when Fig. 8 a disturbs for no power frequency;

Fig. 8 b is a synchronization waveform;

Fig. 8 c is the undesired signal waveform;

Fig. 8 d disturbs back indium antimonide detector output signal waveform for being subjected to power frequency;

Fig. 8 e is a separated in synchronization post analysis channel signal waveform;

Fig. 8 f is a reference channel signal waveform after the separated in synchronization.

Fig. 9 scheme of installation that is photoelectrical coupler at the bottom of the infrared spectrum analyser seat.

Figure 10 is after using filter wheel assembly of the present invention, synchronizing signal occurring principle synoptic diagram.

Figure 11 is the synchronization waveform synoptic diagram that Figure 10 produced.

Embodiment

Please in conjunction with Fig. 5, shown in Figure 6, should negative filter the filter wheel assembly 10 of many components infrared spectrum analyser ' comprise filter wheel 101 ', syncmotor 102 ', filter wheel 101 ' be a rosette, rosette is provided with the S1 of cylindrical chamber, S2, R1, the R2 of four symmetrical distributions, wherein two are analysis air chamber S1, S2, two is reference air chamber R1, R2, four air chamber S1, S2, the axial two ends of R1, R2 seal with the calcium fluoride wafer, and described analysis air chamber and reference air chamber are provided with arranging with counterclockwise side by putting in order of S1, S2, R1, R2.

Described syncmotor 102 ' directly by shaft coupling 104 drive filter wheels 101 ', syncmotor 102 ' rotating speed is set to 1500 rev/mins.

The rotation of described filter wheel 101 ' in a clockwise direction, its angle of rotation frequency keep 1/2 synchronous with the angular frequency of AC network.

A radially narrow groove 105 is offered as synchronous groove in described filter wheel 101 ' wheel edge, and the initial edge of radially narrow groove 105 and the angle of horizontal direction are 45 °.

Indium antimonide infrared detector signal output waveform figure in the analyser (the following describes is example with the CO path all) sees that Fig. 7 a, signal peak press the S1-S2-R1-R2 order and occur.This signal exchanges through electronic processing circuit and amplifies, automatic gain control, and DC level is carried out separated in synchronization after recovering then.Synchronizing signal is seen Fig. 7 b, the analysis channel waveform that after separated in synchronization, obtains such as Fig. 7 c, reference channel waveform after separated in synchronization is Fig. 7 d, and waveform 7c and waveform 7d are carried out Integral Processing respectively, calculates analysis channel and the reference channel waveform area mean value V to the time respectively _SAnd V _R, again V _SAnd V _RCarry out the output that computing promptly obtains two analyzed components.Suppose to exist power frequency to disturb, signal waveform at this moment such as Fig. 8, Fig. 8 a are indium antimonide detector output signal waveform, Fig. 8 b is a synchronizing signal, Fig. 8 c is a undesired signal, and Fig. 8 d is the signal waveform after being disturbed, and analysis channel after the separated in synchronization and reference channel waveform are Fig. 8 e, Fig. 8 f.Be easy to find out because signal waveform and power frequency are disturbed fully synchronously from Fig. 8, and in a power frequency period, the integration that exchanges undesired signal is always zero, so the integration of Fig. 8 e and Fig. 8 f and be not subjected to the industrial frequency noise effect of signals, the component output signal is constant.

Referring to Fig. 9, symmetry has been installed two photoelectrical couplers 21 on infrared spectrum analyser base 31 vertical center axis, 22, it and work

air chamber

15,16 geometric relationship is also referring to Fig. 9, filter wheel 101 ' edge embeds photoelectrical coupler 21, in 22 the light path (referring to Figure 10), filter wheel 101 ' is gone up synchronous groove 105 forward positions and transverse axis angle (see figure 6) at 45, when synchronous groove 105 enters photoelectrical coupler 21 respectively, during 22 light path, photoelectrical coupler 21, the light that 22 light emitting diode sides are sent passes synchronous groove 105, shine on the photistor, produce the photocurrent pulse.The output terminal of two

photoelectrical couplers

21,22 links to each other with R, the S input end of a rest-set flip-flop 34 respectively, makes this trigger 34 upset in turn, produces a square wave output.

Referring to Figure 11, Figure 11 a is the signal output waveform of indium antimonide detecting device.At the S1 peak on the first appearance, photoelectrical coupler 21 positive pulses of output (referring to Figure 11 b) above just in time the groove forward position enters synchronously make the rest-set flip-flop set.After filter wheel 101 ' rotates half-turn, just in time be the incipient moment of R1 peak, groove enters below photoelectrical coupler 22 synchronously, and it produces a photocurrent pulse (referring to Figure 11 c), the rest-set flip-flop that resets, and it is output as level "0".Figure 11 d is a synchronous oscillogram, and its cycle is 40ms.

On technology was made, filter wheel 101 ' of the present invention was processed by aluminum alloy materials, and the main part external diameter is 90mm, and edge part external diameter is 108mm, and the external diameter of four cylindrical chamber is 25mm.Wall thickness is 2.5mm, so the light transmission part diameter is 20mm.It is processed by copper product, and inwall is polished to 0.8 (surfaceness) and gold-plated processing, and the air chamber two ends are with the sealing of calcium fluoride wafer, and to allow infrared light see through, wherein two analysis air chamber S1, S2 fill to seal behind the high pure nitrogen, and two reference air chambers fill with CO+CO ₂, sealing then.Four air chambers (begin with synchronous groove reference point, counterclockwise) install with S1, S2, R1, R2 order.Flexible coupling of the beam warp of filter wheel (this shaft joint is in another part patented claim) links to each other with the driven in synchronism motor.Its rotating speed is 1500 rev/mins.Synchronous groove width 2mm on the filter wheel, long 5mm.

Filter wheel assembly of the present invention has solved the problem that negative filter wheel power frequency is disturbed on the principle at all, and filter wheel can directly be driven by syncmotor, has exempted that traditional gear transmission noises is big, fragile, the life-span short, shortcoming such as greasy dirt is arranged; And groove is simple in structure synchronously, and handling ease has solved the problem that had not always solved for many years.

Claims

1, a kind of filter wheel assembly of negative many components of optical filtering infrared spectrum analyser, this filter wheel assembly comprises filter wheel, syncmotor, and filter wheel is a rosette, and rosette is provided with the cylindrical chamber of four symmetrical distributions, and wherein two are analysis air chamber S ₁, S ₂, two is reference air chamber R ₁, R ₂, four air chamber S ₁, S ₂, R ₁, R ₂Axially two ends are with the sealing of calcium fluoride wafer, and it is characterized in that: described analysis air chamber and reference air chamber are pressed S ₁, S ₂, R ₁, R ₂Put in order and be provided with counterclockwise to arrange.

2, the filter wheel assembly of negative many components of optical filtering infrared spectrum analyser as claimed in claim 1 is characterized in that: described syncmotor directly drives filter wheel by shaft coupling.

3, the filter wheel assembly of negative many components of optical filtering infrared spectrum analyser as claimed in claim 2 is characterized in that: described syncmotor rotating speed is set to 1500 rev/mins.

4, the filter wheel assembly of negative many components of optical filtering infrared spectrum analyser as claimed in claim 3, it is characterized in that: described filter wheel rotates in a clockwise direction, and its angle of rotation frequency keeps 1/2 synchronous with the angular frequency of AC network.

5, as the filter wheel assembly of claim 1 or 2 or 4 described negative many components of optical filtering infrared spectrum analysers, it is characterized in that: a radially narrow groove is offered as synchronous groove in described filter wheel wheel edge, and this narrow well width is 2mm.

6, the filter wheel assembly of negative many components of optical filtering infrared spectrum analyser as claimed in claim 5 is characterized in that: the initial edge of the synchronous groove on the described filter wheel and the angle of horizontal direction are 45 °.