CN2836004Y

CN2836004Y - Thermostatic combustible gas concentration detector

Info

Publication number: CN2836004Y
Application number: CN 200520073556
Authority: CN
Inventors: 赵飞
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-12
Filing date: 2005-07-12
Publication date: 2006-11-08
Anticipated expiration: 2015-07-12

Abstract

The utility model relates to a kind of constant temperature combustable gas concentration detector.Its technical scheme is: it contains electric bridge and the compensating element, of being made up of sensitive element, resistance, wherein said electric bridge connects and composes the thermostatic control loop by comparer and power governor, described compensating element, is with an expansion compensating resistance formation in parallel compensating circuit or only constitute compensating circuit with compensating element,, connect with compensating circuit and insert in the constant-current power supply circuit in the thermostatic control loop, thermostatic control loop output detection signal V1, compensating circuit output compensating signal V0.Advantage is: 1) make sensitive element always work in temperature constant state, long term operation stability is good, long service life; 2) adopt detection signal and compensating signal to export respectively, be convenient to the Intelligent treatment of follow-up circuit, make pick-up unit have good zero stability and diadic is judged, finally draw testing result more accurately, simultaneously to the combustable gas concentration reacting condition rapidly, can effectively expand the combustable gas concentration sensing range.

Description

A kind of constant temperature combustable gas concentration detector

Technical field

The utility model relates to a kind of safety equipment that combustable gas concentration is measured, and more particularly, relates to a kind of constant temperature combustable gas concentration detector.

Background technology

Be to utilize the catalytic combustion type gas sensor to detect to the detection of combustable gas concentration method commonly used at present.The catalytic combustion type gas sensor is not right with insensitive and close with sensitive element temperature characterisitic compensating element, (hereinafter to be referred as the compensating element) composed component to inflammable gas of catalyzer by the sensitive element to the inflammable gas sensitivity that has catalyzer (hereinafter to be referred as sensitive element) and one usually, with sensitive element, compensating element, and resistance insert electric bridge, utilizing sensitive element self temperature in test environment to change with combustable gas concentration makes the signal of the unbalance output of electric bridge detect combustable gas concentration, utilize the drift of the electric bridge output signal that the close temperature characteristic compensation sensitive element of compensating element, and sensitive element causes owing to environmental parameter changes again, to improve the degree of accuracy that detects.But also there is following defective in the existing pick-up unit that utilizes the catalytic combustion type gas sensor to detect inflammable gas:

1, zero point drift is big.Has only when the temperature characterisitic of compensating element, and sensitive element is identical the electric bridge output signal drift phenomenon that could full remuneration causes theoretically by gas sensor.But be subjected to the restriction of production technology and technological level at present, make the identical element of temperature characterisitic to being impossible, even if close also difficult its difficulty, make pairing work time-consuming bothersome, cause actual element that temperature characterisitic is differed greatly, this just makes compensating element, the full remuneration environmental parameter not change the electric bridge output signal drift that causes, directly influences the accuracy of testing result.

2, sensing range is little.Existing method is that when combustable gas concentration reached certain value, the working temperature of sensitive element was too high, will cause the permanent damage of himself by the working temperature indirect detection combustable gas concentration of detection sensitive element., all will protect sensitive element in the practical application, method is when detected combustable gas concentration reaches certain value for this reason, stops to power to sensitive element.This just limits sensitive element and can only work in the low-concentration combustible gas environment, and the scope that detects combustable gas concentration is narrower.

3, stability is poor.Because sensitive element is the working temperature wide fluctuations when detecting combustable gas concentration, make on the sensitive element that because the carbon distribution structure that rough burning produces is very unstable this will directly cause the drift that detects bridge zero and the change of accuracy of detection.

4, component wear rate height.When combustable gas concentration maintains higher level in the testing environment, existing detection method will make sensitive element be operated in the higher temperature state always, and this can cause the evaporation of catalyzer and sex change to wear out, and sensitive element is scrapped too early.In addition; though in using sensitive element is protected; but because the monitoring of the combustable gas concentration of hazardous environment can not stop, pick-up unit will recover the power supply to sensitive element by phased manner, so that can continue detection in combustable gas concentration falls back to the scope of sensitive element safety the time.If still more than the sensitive element upper limit of detection, then exploratory each time power supply all is that sensitive element is once damaged to combustable gas concentration, greatly reduces the serviceable life of element at this moment.

5, can't discern the diadic effect.After combustable gas concentration in the testing environment surpasses certain value, because it has tied up the share of oxygen in the air, make that inflammable gas is superfluous and can not fully burn, at this moment the working temperature of sensitive element reduces with the rising of combustable gas concentration, see also Fig. 1, though the concentration difference of inflammable gas like this, the temperature value that sensitive element induces may be identical, diadic effect that Here it is.Existing pick-up unit can't be discerned this diadic effect, can be a lower concentration value with a higher combustable gas concentration value erroneous judgement, and this erroneous judgement is extremely dangerous in actual applications.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art, proposes a kind of constant temperature combustable gas concentration detector, and it is realized by following technical scheme:

It contains electric bridge and the compensating element, of being made up of sensitive element, resistance, wherein said electric bridge connects and composes the thermostatic control loop by comparer and power governor, described compensating element, is with an expansion compensating resistance formation in parallel compensating circuit or only constitute compensating circuit with compensating element,, connect with compensating circuit and insert in the constant-current power supply circuit in the thermostatic control loop, thermostatic control loop output detection signal V1, compensating circuit output compensating signal V0.

Power governor in the described thermostatic control loop is power adjustments triode serial connection sample resistance or power adjustments triode, described power governor is in parallel with the power input of electric bridge, the input end of described comparer is connected with the detection output terminal of electric bridge, and its output terminal connects the control end of power governor.

Described thermostatic control loop output detection signal V1 is taken to the voltage signal at described sample resistance two ends or is taken to voltage between the interdependent node that changes with thermostatic control loop both end voltage, and it is voltage signals that described compensating circuit output compensating signal V0 is taken to the compensating element, two ends.

The beneficial effects of the utility model are: 1) adopt the power adjustments to sensitive element, make sensitive element always work in temperature constant state, its long term operation stability is good, long service life thereby make; 2) adopt detection signal and compensating signal to export respectively, this provides great imagination space for the Intelligent treatment of follow-up circuit, utilize soft bridge technology, make pick-up unit have good zero stability and diadic is judged, finally draw testing result more accurately, simultaneously to the combustable gas concentration reacting condition rapidly, can effectively expand the combustable gas concentration sensing range.

Description of drawings

Fig. 1 is the sensitive element family curve that self temperature changes with combustable gas concentration in test environment

Fig. 2 is a circuit block diagram of the present utility model

Fig. 3 is the circuit theory diagrams of the utility model one embodiment

Fig. 4 is the circuit theory diagrams of another embodiment of the utility model

Embodiment

Below in conjunction with the drawings and specific embodiments the utility model is described further.

Contrast Fig. 2, the utility model is made up of electric bridge, comparer, power governor and compensating circuit.Comparer connects electric bridge and power governor constitutes the thermostatic control loop, and connecting with equalizing network and insert in the constant-current power supply circuit in the thermostatic control loop, exports a detection signal V0 by the thermostatic control loop, and compensating circuit is exported a compensating signal V1.

In conjunction with Fig. 3, electric bridge is made of sensitive element Rm and resistance R 1, R2, R3, Rw, and Rm is an element that has catalyzer to the inflammable gas sensitivity, and the resistance of R1, R2, R3 is respectively 10 Ω, 10K Ω, 10K Ω, and Rw is the potentiometer of resistance 5K Ω.Detection output terminal e, the f of electric bridge connects the input end of comparer U, the output terminal of comparer U is connected with the control utmost point of power adjustments triode G, it is in parallel with power input c, the d of electric bridge again that the collector of power adjustments triode G connects sampling R5, constitutes closed loop thermostatic control loop.Power adjustments triode G adopts the triode of BD137 model in the above-mentioned loop, and comparer adopts the 1/2LM358 operational amplifier.Wherein power adjustments triode G and sample resistance R5 (resistance 10 Ω) have constituted power governor.A compensating element, Rb and an expansion compensating resistance R4 constitute compensating circuit, and thermostatic control loop and compensating circuit are in series and insert in the 120mA continuous current circuit.Adjust the electric bridge parameter and make that stream has the initialization electric current in the power adjustments triode in pure air, electric bridge is in equilibrium state; When changing or detect combustable gas concentration, environmental parameter make the temperature of sensitive element that rising be arranged or during the trend that reduces, be that Rm has the trend that increases or reduce, electric bridge is unbalance, comparer U amplifies this unbalance signal and export to the control utmost point of power adjustments triode G, make the electric current of the power adjustments triode of flowing through increase or reduce, owing to be to adopt the constant current power supply, the total current of current channel is a definite value, the electric current of this branch road of sensitive element Rm will reduce or increase accordingly so flow through, and make sensitive element keep temperature constant state, the resistance value that is Rm remains unchanged, the electric bridge state that restores balance.In whole operating ambient temperature range, (be generally 0 ℃～40 ℃) purpose of good constant temperature effect is all arranged for reaching sensitive element, must the initialization electric current be arranged stream in the power adjustments triode, if directly compensating element, Rb is connected with the thermostatic control loop, the imbalance of sensitive element and compensating element, initialization electric current will be caused, inserted resistance is the expansion compensating resistance R4 of 300 Ω for this reason, if this uneven difference is very little, R4 can not connect yet.The voltage V1 at apparent sample resistance R5 two ends of connecting with the power adjustments triode has reflected the variation of environmental parameter or combustable gas concentration, and itself and equalizing network both end voltage V0 are drawn, and can obtain the detection output signal.

Empty frame among Fig. 3 partly is the follow-up circuit that the utility model connects, and the detection signal V1 and the compensating signal V0 of its energy the utility model output carry out Intelligent treatment.Voltage signal V1 and V0 access A/D converter are carried out digital conversion, and the digital signal after the conversion is sent into signal processing means processes.Signal processing apparatus is one and has running software function digit processor that it can set up compensation policy according to sensitive element and the operating in the early stage temperature changing regularity of compensating element,, and correlation parameter is carried out the corresponding modify compensation.And voltage signal V1 that will be after digitizing and V0 constitute two arms of electric bridge, and two arms in addition with the software simulation electric bridge promptly constitute soft electric bridge.Thereby can dynamically adjust the brachium pontis parameter of soft electric bridge,, obtain compensation effect preferably to adapt to sensitive element and the not quite identical current conditions of compensating element, temperature characterisitic.According to the ratio characteristic of V1 and V0, correctly discern the diadic effect that occurs in the inflammable gas testing process simultaneously, thereby improve the safety in utilization of detecting instrument.The display circuit of being made up of the LED charactron through the detection signal of signal processing means processes shows, and send output circuit to be used for externally online or warning on the spot.

The utility model also can be designed to circuit arrangement shown in Figure 4.Its circuit is formed consistent with the circuit composition shown in Fig. 4, and the exit of different is V1 is different, is taken to the emitter (being the c node) of power adjustments triode G and the voltage signal of sample resistance one end (being the d node).According to above-mentioned circuit theory, this voltage signal V1 changes with temperature control loop both end voltage, and it has reflected the changing value of environmental parameter or combustable gas concentration.

Claims

1, a kind of constant temperature combustable gas concentration detector, contain electric bridge and the compensating element, formed by sensitive element, resistance, it is characterized in that described electric bridge connects and composes the thermostatic control loop by comparer and power governor, described compensating element, is with an expansion compensating resistance formation in parallel compensating circuit or only constitute compensating circuit with compensating element,, connect with compensating circuit and insert in the constant-current power supply circuit in the thermostatic control loop, thermostatic control loop output detection signal V1, compensating circuit output compensating signal V0.

2, a kind of constant temperature combustable gas concentration detector according to claim 1, it is characterized in that the power governor in the described thermostatic control loop is power adjustments triode serial connection sample resistance or power adjustments triode, power governor is in parallel with the power input of electric bridge, the input end of described comparer is connected with the detection output terminal of electric bridge, and its output terminal connects the control end of power governor.

3, a kind of constant temperature combustable gas concentration detector according to claim 1, it is characterized in that described thermostatic control loop output detection signal V1 takes from the voltage signal at described sample resistance two ends or takes from voltage signal between the interdependent node that changes with thermostatic control loop both end voltage, described compensating circuit output compensating signal V0 is a voltage signal of taking from the compensating element, two ends.