CN207423284U - A kind of single-sensor gas flow measurement circuit of temperature control type - Google Patents
A kind of single-sensor gas flow measurement circuit of temperature control type Download PDFInfo
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- CN207423284U CN207423284U CN201720135399.3U CN201720135399U CN207423284U CN 207423284 U CN207423284 U CN 207423284U CN 201720135399 U CN201720135399 U CN 201720135399U CN 207423284 U CN207423284 U CN 207423284U
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- resistance
- switching transistor
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Abstract
The utility model discloses a kind of single-sensor gas flow measurement circuit of temperature control type, including switching transistor L1, platinum resistance RH, resistance R1, signal conditioning circuit, analog-to-digital conversion module ADC, micro-control unit MCU and Pulse width modulation module PWM；The switching transistor L1Emitter connect power supply；The switching transistor L1Collector on be sequentially connected in series resistance R1With platinum resistance RH, and platinum resistance RHOne end ground connection；The resistance R1With platinum resistance RHBetween node and switching transistor base stage between be sequentially connected in series the micro-control unit MCU, analog-to-digital conversion module ADC and signal conditioning circuit, and the signal output part of the Pulse width modulation module PWM is connected to switching transistor L1Base stage and micro-control unit MCU between.The influence that can eliminate gas temperature to measurement is measured using the circuit, measurement accuracy is improved, and lowers the cost of measuring system.
Description
Technical field
The utility model belongs to gas flow measurement technical field more particularly to a kind of single-sensor gas stream of temperature control type
Measurement circuit.
Background technology
Gas flow is an important parameter in industrial processes, and accurate measurement gas flow is fully sharp in the energy
With, ensure product quality and improve production efficiency etc. all to play an important role.Nowadays flow sensor is extensive
It is applied to the industrial circles such as auto industry, aerospace, Medical Devices, energy measurement.With micromachining technology day by day
Maturation, the probe production and processing technology of heat type gas flow sensor have also obtained significant progress, have made sensor to building ring
The adaptability in border is further strengthened, but the improvement of these production technologies can not still eliminate the measurement error that temperature change is brought.
Generally speaking, defect present in traditional technology includes：
1st, since the volume of gas is the function of temperature and pressure, by the variation of medium temperature, pressure influenced and gas
Quality be not at any time, temperature and pressure variation and change.In current industrial processes control, business accounting, trade
In clearing and scientific research, it is mostly mass flow, tends not to meet the requirements using existing volume flowmeter.
2nd, with the increase of measurement caliber, the volume and weight of instrument, into geometric growth, bring crushing with bore
Greatly, the problems such as operating cost is excessively high.The measurement of current flux is measured in pipeline a bit using sampling theorem and insertion mounting means
Or the flow velocity of multiple spot simply calculates flow, accuracy is not generally high.
Although the 3, the dynamic property of gas flow measurement thermal flowmeters to be improved have higher response speed,
It is also to need to further improve in application fields such as automobiles.
4th, at present, most of circuit configurations that temperature-compensating is completed using single-sensor, as shown in Figure 4.In circuit
Use two resistance Rx、RyIt connects with sensing element, the resistance in access circuit is controlled using a switching switch so that visit
Head operating temperature is in Tx、TyBetween convert.It should be noted that it must is fulfilled for a primary condition：Circuit is from RxIt is switched to RyWhen
qmIt remains unchanged, if tested gas velocity variation is violent or circuit switch speed is slow, can all break through the restrictive condition.Only when
When tested gas velocity changes very steady, single-sensor temperature compensation algorithm could be used, otherwise will be caused compared with large compensation
Error.
Utility model content
Based on this, in view of the above-mentioned problems, it is necessary to propose a kind of single-sensor gas flow measurement circuit of temperature control type, profit
The influence that can eliminate gas temperature to measurement is measured with the circuit, measurement accuracy is improved, and lowers the cost of measuring system.
The technical solution of the utility model is：The single-sensor gas flow measurement circuit of a kind of temperature control type, including switch
Triode L1, platinum resistance RH, resistance R1, signal conditioning circuit, analog-to-digital conversion module ADC, micro-control unit MCU and pulse width
Modulation module PWM；The switching transistor L1Emitter connect power supply；The switching transistor L1Collector on be sequentially connected in series
Resistance R1With platinum resistance RH, and platinum resistance RHOne end ground connection；The resistance R1With platinum resistance RHBetween node with switch three poles
The micro-control unit MCU, analog-to-digital conversion module ADC and signal conditioning circuit, and the arteries and veins are sequentially connected in series between the base stage of pipe
The signal output part for rushing width modulation module PWM is connected to switching transistor L1Base stage and micro-control unit MCU between.
Heat exchange mode has convection current, heat transfer and the radiation etc. a variety of in test process.Flow sensor is by measuring because of gas
Body flow and caused by probe temperature variation reflect gas flow, sensor rotor working process is mainly in a manner of forced convection
Heat transfer, other heat exchange mode heat output very littles can be ignored.According to heat transfer principle, the electrical power of platinum resistance is supplied to
The heat taken away equal to the gaseous exchange heat exchange of flowing.I.e.:
Qc=hA (tH-tc) (1)
In formula：QcFor heat caused by Forced Convection Heat Transfer, h is surface coefficient of heat transfer, and A is platinum resistance RHSurface area,
tHIt is platinum resistance RHTemperature, tcIt is platinum resistance RHThe gas temperature surveyed.
According to nusselt number and King formula, can obtain：
In formula：M, n is constant, qmFor the mass flow of gas.
When in the unit interval, platinum resistance RHGenerated Joule heat W=U2/ R and heat dissipation amount QcWhen reaching heat balance
Have：
When platinum resistance is in work temperatureH1Under, known according to formula (3)：
Wherein U1It is platinum resistance in temperature TH1When both end voltage.
When platinum resistance is in work temperatureH2Under, known according to formula (4):
Wherein U2It is platinum resistance in temperature TH2Both end voltage.
Assuming that TH1＞ TH2, known by formula (4) and (5)：
Effectively eliminate influence of the gas temperature to flow, control platinum resistance RHIt is operated in temperature TH1And TH2, pass through ADC
Sampling obtains U1And U2, calculate the mass flow q of gasm。
Wherein, platinum resistance uses PT20, and platinum resistance is placed on to the geometric center of pipe under test caliber, is controlled by PWM
Electric current in platinum resistance causes platinum resistance to be operated under thermostatic mode.Signal conditioning circuit mainly includes a systems such as filtering, amplification
Column processing.The voltage at platinum resistance both ends is after signal conditioning circuit, by the voltage after ADC module acquisition conditioning.MCU passes through public affairs
Formula calculates the resistance value of platinum resistance this moment, and with setting work temperatureH2Under resistance compare.Then, according to result of the comparison,
The pulse signal that PWM module generates certain duty cycle is controlled, the electric current in platinum resistance is adjusted by the on-off circuit of triode
Whole, so that platinum resistance resistance value reaches the working temperature constant of setting value, i.e. platinum resistance, ADC module gathers platinum resistance two at this time
Terminal voltage U2.Then control platinum resistance operating temperature reaches TH1, and gather the voltage U of platinum resistance1, gas is calculated according to formula
Flow.
As further improvement of the utility model, which further includes switching transistor L2, switching transistor L2's
Collector and switching transistor L1Base stage between be serially connected with resistance R8, switching transistor L2Base stage on be serially connected with resistance R7.It passes
System measuring circuit uses single triode as contactor, it is necessary to add in difference amplifier in signal conditioning circuit mostly
Circuit to the carry out difference amplifier of platinum resistance both end voltage, is then connected to the ADC of MSP430 microcontrollers into a series of filter excessively
Module；Difference operational amplifying circuit adds the component number of this measuring system, and the voltage data acquisition at platinum resistance both ends is made
Into certain influence.The measuring circuit of whole system in the utility model using two triodes as on-off circuit, passes through list
The rectangular wave of piece machine output controls the voltage at platinum resistance both ends.
As further improvement of the utility model, the switching transistor L1Emitter on be also sequentially connected in series resistance
R2With platinum resistance Rw, and platinum resistance RwOne end ground connection.
As further improvement of the utility model, the signal conditioning circuit includes resistance R3, resistance R4, resistance R5, electricity
Hinder R6, capacitance C1, capacitance C2And amplifier；The resistance R3With resistance R4Series connection, and resistance R3One end and the resistance R1With
Platinum resistance RHBetween node connection, resistance R4One end and the amplifier the first signal input part between connect；The electricity
Hinder R5It is serially connected between the secondary signal input terminal of amplifier and ground wire；The resistance R6With capacitance C1Series connection, and capacitance C1's
One end is connected to resistance R3With resistance R4Between node, resistance R6One end be connected with the secondary signal input terminal of amplifier；Institute
State capacitance C2One end be connected with the first signal input part of amplifier, capacitance C2The other end ground connection.
The beneficial effects of the utility model are：
(1) in the gatherer process of platinum resistance both end voltage, the ground wire of measuring circuit is connected with the ground wire on microcontroller,
The filtered circuit of voltage of platinum resistance is directly connected to the collection terminal of ADC module on microcontroller, effectively simplifies whole system
Circuit, while improve the accuracy of measurement data；
(2) with the control circuit of traditional two resistance of use and switch, in the utility model, a resistance is first with sensitivity
Part platinum resistance is connected, and reduces the electric elements in measuring circuit, so as to reduce the measurement error of system itself；Pass through control
Platinum resistance is operated in the mode of two design temperatures, simplifies the time of switching switch, is conducive to the response of whole system；
(3) influence of the gas temperature to measurement is eliminated, measurement accuracy is improved, and reduces the cost of measuring system.
Description of the drawings
Fig. 1 is the circuit diagram of the single-sensor gas flow measurement circuit of temperature control type described in embodiment；
Fig. 2 is the circuit diagram of the single-sensor gas flow measurement circuit of temperature control type in another embodiment；
Fig. 3 is the circuit diagram of the single-sensor gas flow measurement circuit of temperature control type in another embodiment；
Fig. 4 is the circuit diagram that traditional single-sensor carries out temperature-compensating；
Reference sign：
R1-R8Resistance, C1、C2Capacitance, L1、L2Triode, RH、RwPlatinum resistance, Q amplifiers.
Specific embodiment
The embodiment of the utility model is described in detail below in conjunction with the accompanying drawings.
Embodiment 1
As shown in Figure 1, a kind of single-sensor gas flow measurement circuit of temperature control type, including switching transistor L1, platinum electricity
Hinder RH, resistance R1, signal conditioning circuit, analog-to-digital conversion module ADC, micro-control unit MCU and Pulse width modulation module PWM；Institute
State switching transistor L1Emitter connect power supply；The switching transistor L1Collector on be sequentially connected in series resistance R1And platinum resistance
RH, and platinum resistance RHOne end ground connection；The resistance R1With platinum resistance RHBetween node and switching transistor base stage between according to
It is secondary to concatenate the micro-control unit MCU, analog-to-digital conversion module ADC and signal conditioning circuit, and the Pulse width modulation module
The signal output part of PWM is connected to switching transistor L1Base stage and micro-control unit MCU between.
Heat exchange mode has convection current, heat transfer and the radiation etc. a variety of in test process.Flow sensor is by measuring because of gas
Body flow and caused by probe temperature variation reflect gas flow, sensor rotor working process is mainly in a manner of forced convection
Heat transfer, other heat exchange mode heat output very littles can be ignored.According to heat transfer principle, the electrical power of platinum resistance is supplied to
The heat taken away equal to the gaseous exchange heat exchange of flowing.I.e.:
Qc=hA (tH-tc) (1)
In formula：QcFor heat caused by Forced Convection Heat Transfer, h is surface coefficient of heat transfer, and A is platinum resistance RHSurface area,
tHIt is platinum resistance RHTemperature, tcIt is platinum resistance RHThe gas temperature surveyed.
According to nusselt number and King formula, can obtain：
In formula：M, n is constant, qmFor the mass flow of gas.
When in the unit interval, platinum resistance RHGenerated Joule heat W=U2/ R and heat dissipation amount QcWhen reaching heat balance
Have：
When platinum resistance is in work temperatureH1Under, known according to formula (3)：
Wherein U1It is platinum resistance in temperature TH1When both end voltage.
When platinum resistance is in work temperatureH2Under, known according to formula (4):
Wherein U2It is platinum resistance in temperature TH2Both end voltage.
Assuming that TH1＞ TH2, known by formula (4) and (5)：
Effectively eliminate influence of the gas temperature to flow, control platinum resistance RHIt is operated in temperature TH1And TH2, pass through ADC
Sampling obtains U1And U2, calculate the mass flow q of gasm。
Wherein, platinum resistance uses PT20, and platinum resistance is placed on to the geometric center of pipe under test caliber, is controlled by PWM
Electric current in platinum resistance causes platinum resistance to be operated under thermostatic mode.Signal conditioning circuit mainly includes a systems such as filtering, amplification
Column processing.The voltage at platinum resistance both ends is after signal conditioning circuit, by the voltage after ADC module acquisition conditioning.MCU passes through public affairs
Formula calculates the resistance value of platinum resistance this moment, and with setting work temperatureH2Under resistance compare.Then, according to result of the comparison,
The pulse signal that PWM module generates certain duty cycle is controlled, the electric current in platinum resistance is adjusted by the on-off circuit of triode
Whole, so that platinum resistance resistance value reaches the working temperature constant of setting value, i.e. platinum resistance, ADC module gathers platinum resistance two at this time
Terminal voltage U2.Then control platinum resistance operating temperature reaches TH1, and gather the voltage U of platinum resistance1, gas is calculated according to formula
Flow.
As shown in Fig. 2, in another embodiment, above-mentioned measuring circuit further includes switching transistor L2, switching transistor L2
Collector and switching transistor L1Base stage between be serially connected with resistance R8, switching transistor L2Base stage on be serially connected with resistance R7。
Traditional measurement circuit is transported mostly using single triode as contactor, it is necessary to add in difference in signal conditioning circuit
Electric discharge road to the carry out difference amplifier of platinum resistance both end voltage, is then connected to MSP430 microcontrollers into excessively a series of filtering
ADC module；Difference operational amplifying circuit adds the component number of this measuring system, and the voltage data at platinum resistance both ends is gathered
It affects.The measuring circuit of whole system in the utility model using two triodes as on-off circuit, passes through
The rectangular wave of microcontroller output controls the voltage at platinum resistance both ends.
As shown in figure 3, in another embodiment, the switching transistor L1Emitter on be also sequentially connected in series resistance
R2With platinum resistance Rw, and platinum resistance RwOne end ground connection.
In another embodiment, the signal conditioning circuit includes resistance R3, resistance R4, resistance R5, resistance R6, capacitance
C1, capacitance C2And amplifier；The resistance R3With resistance R4Series connection, and resistance R3One end and the resistance R1With platinum resistance RHIt
Between node connection, resistance R4One end and the amplifier the first signal input part between connect；The resistance R5It is serially connected with
Between the secondary signal input terminal and ground wire of amplifier；The resistance R6With capacitance C1Series connection, and capacitance C1One end be connected to
Resistance R3With resistance R4Between node, resistance R6One end be connected with the secondary signal input terminal of amplifier；The capacitance C2's
One end is connected with the first signal input part of amplifier, capacitance C2The other end ground connection.
Embodiment described above only expresses the specific embodiment of utility model, and description is more specific and detailed, but
Can not the limitation to utility model patent scope therefore be interpreted as.It should be pointed out that the ordinary skill for this field
For personnel, on the premise of utility model design is not departed from, various modifications and improvements can be made, these belong to practicality
New protection domain.
Claims (3)
1. a kind of single-sensor gas flow measurement circuit of temperature control type, it is characterised in that：Including switching transistor L1, platinum resistance
RH, resistance R1, signal conditioning circuit, analog-to-digital conversion module ADC, micro-control unit MCU and Pulse width modulation module PWM；It is described
Switching transistor L1Emitter connect power supply；The switching transistor L1Collector on be sequentially connected in series resistance R1With platinum resistance RH,
And platinum resistance RHOne end ground connection；The resistance R1With platinum resistance RHBetween node and switching transistor base stage between successively
Concatenate the micro-control unit MCU, analog-to-digital conversion module ADC and signal conditioning circuit, and the Pulse width modulation module PWM
Signal output part be connected to switching transistor L1Base stage and micro-control unit MCU between；Further include switching transistor L2, open
Close triode L2Collector and switching transistor L1Base stage between be serially connected with resistance R8, switching transistor L2Base stage on go here and there
It is connected to resistance R7。
2. the single-sensor gas flow measurement circuit of temperature control type according to claim 1, it is characterised in that：The switch
Triode L1Emitter on be also sequentially connected in series resistance R2With platinum resistance Rw, and platinum resistance RwOne end ground connection.
3. the single-sensor gas flow measurement circuit of temperature control type according to claim 2, it is characterised in that：The signal
Modulate circuit includes resistance R3, resistance R4, resistance R5, resistance R6, capacitance C1, capacitance C2And amplifier；The resistance R3With resistance R4
Series connection, and resistance R3One end and the resistance R1With platinum resistance RHBetween node connection, resistance R4One end and the amplification
It is connected between first signal input part of device；The resistance R5It is serially connected with the secondary signal input terminal and ground wire of amplifier
Between；The resistance R6With capacitance C1Series connection, and capacitance C1One end be connected to resistance R3With resistance R4Between node, resistance R6's
One end is connected with the secondary signal input terminal of amplifier；The capacitance C2One end and the first signal input part phase of amplifier
Even, capacitance C2The other end ground connection.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201720135399.3U CN207423284U (en) | 2017-02-15 | 2017-02-15 | A kind of single-sensor gas flow measurement circuit of temperature control type |
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| CN201720135399.3U CN207423284U (en) | 2017-02-15 | 2017-02-15 | A kind of single-sensor gas flow measurement circuit of temperature control type |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110940389A (en) * | 2019-11-21 | 2020-03-31 | 浙江大学 | Thermal gas mass flowmeter based on Fuzzy-PI dual-mode undisturbed switching control |
-
2017
- 2017-02-15 CN CN201720135399.3U patent/CN207423284U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110940389A (en) * | 2019-11-21 | 2020-03-31 | 浙江大学 | Thermal gas mass flowmeter based on Fuzzy-PI dual-mode undisturbed switching control |
| CN110940389B (en) * | 2019-11-21 | 2021-03-23 | 浙江大学 | Thermal gas mass flowmeter based on Fuzzy-PI dual-mode undisturbed switching control |
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