CN201285296Y - Flow detection unit - Google Patents
Flow detection unit Download PDFInfo
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- CN201285296Y CN201285296Y CNU2008200376842U CN200820037684U CN201285296Y CN 201285296 Y CN201285296 Y CN 201285296Y CN U2008200376842 U CNU2008200376842 U CN U2008200376842U CN 200820037684 U CN200820037684 U CN 200820037684U CN 201285296 Y CN201285296 Y CN 201285296Y
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Abstract
A flow rate detecting unit comprises an outer housing and a sensing element. The outer housing is a liquid collecting part made of material having good thermal conductance. The sensing element is arranged in the outer housing and comprises a resistance temperature detector (RTD) comprising resistors Rf and Rt which are paired and are connected in series. Both ends of the Rf and the Rt which are connected in series are respectively provided with a signal acquisition point, a signal acquisition point is arranged between the Rf and the Rt which are connected in series, and a heat generation resistor RH is arranged beside the Rf. The utility model has the outstanding advantages of small volume, simple structure, no rotatable parts or abrasion, little loss of pressure, low requirements for field installation circumstances, and the like. The flow rate detecting unit is suitable for a flow rate transducer.
Description
Technical field
The present invention instrument field that designs an apparatus specifically is a kind of flow detection unit that adopts thermodynamic (al) thermal diffusion principle design.
Background technology
Since entering the industrialization epoch, the automatic measurement process variable becomes requisite part, and these process variable comprise such as flow, pressure, temperature, potential of hydrogen, humidity, turbidity or the like.Flow measurement is very important ingredient in industry spot, and the degree of accuracy of flow measurement, real-time have a strong impact on the quality of industrial products, many aspects such as industrial safety.The most frequently used principle that flowmeter adopted roughly comprises differential pressure type, electromagnetic type, vortex street, ultrasonic type, float-ball type or the like in the just present industry spot.But above-mentioned listed flowmeter is selection in the ordinary course of things, if but customer requirement is higher, such as will reach convection cell influence little (relating generally to the excessive crushing that do not have), installation and maintenance convenient (easy accessibility) time, with regard to having that crushing is big, complex structure is huge inconvenience or the like shortcoming is installed according to the flowmeter of above-mentioned flow measurement principle design.
Summary of the invention
The utility model can be realized above-mentioned requirements according to the flow detection unit of thermodynamic (al) thermal diffusion principle design, and theoretical foundation is, utilizes the thermal diffusion principle, and theoretical formula is:
V ∝ sqrt (T) formula (1)
T ∝ R
fFormula (2)
Get by formula (1) and formula (2): V ∝ sqrt (R
f)
V-rate of flow of fluid wherein
The flow sensor variation of temperature that T-fluctuations in discharge causes
R
T--the change in resistance that-flow sensor is caused by temperature variation
As can be known, flow velocity and flow sensor change in resistance square proportional utilizes this principle, two thermistors (temperature sensor) is set, with the constant voltage source power supply, by benchmark sensor (R
T) and flow sensor (R
f) variation of tie point voltage, handle through amplification filtering, detect flow signal.
Utilizing the flowmeter of thermal diffusion principle design most important is exactly the precision of temperature-sensing element, and will reach thermally equilibrated condition.The utility model is just mainly started with from this two aspect, obtains high measuring accuracy and fast response time by utilizing high-precision platinum resistance (selecting matching resistor by advanced means) and changing the thermal diffusion channel architecture.
Concrete technical scheme is as follows:
A kind of flow detection unit comprises shell and sensing device, and described shell is that the material composition with thermal conductive resin meets liquid portion, is provided with sensing device in the enclosure, and sensing device comprises resistance temperature detector RTD, and this RTD comprises the resistance R _ f and the Rt of pairing; Rf and Rt are connected in series; Rf and Rt two ends in series connection are provided with signal acquisition point, are provided with signal acquisition point between Rf that connects and Rt; At the other heating resistor RH that is provided with of Rf.The material of shell is a stainless steel
Be provided with heat insulation structural between described Rf and the Rt between described Rf and the Rt, this structure is the cylinder that a heat-barrier material is made, there is the space centre, and the outer wall of this main body is provided with groove and is used to place Rt, and Rf is located at the bottom surface of cylinder.Described cylinder is a right cylinder.
Described matching resistor Rf is identical with the Rt resistance, and resistance varies with temperature unanimity.
Because the sensing part must be very responsive to temperature when utilizing thermal conduction principle to measure flow, and stability is also very good.Therefore in order to make two thermistor couplings reach optimum efficiency, selecting thermistor becomes a very crucial step.Ubiquity principle according to things, select 9 more stable resistance (error is ± 0.5) earlier with accurate ohmmeter, per 3 are together in parallel and are composed in series reference resistance again, indivedual deviation ratios of elimination relatively more commonly used method preferably in the mathematics Probability Statistics Theory that Here it is., and then and measured resistance be connected on+5V and GND between, get intermediate point Vmid voltage, satisfy voltage between 2.5 ± 0.0025.Can make each resistance error like this between ± 2, just not give up if do not satisfy.
The utlity model has that volume is little, simple in structure, no-rotary part, nothing wearing and tearing, crushing are little, to remarkable advantages such as on-the-spot installation environment requirement are low, be applicable to flow sensor.
Description of drawings
Fig. 1, flow rate test unit are synoptic diagram
Flow and voltage curve after Fig. 2, the improvement
Flow and voltage curve before Fig. 3, the improvement
Structural representation between Fig. 4, Rf and the Rt
Fig. 5, choose thermistor method schematic diagram
Among Fig. 2,3, transverse axis is represented voltage, and the longitudinal axis is represented electric current
A is that Rt position, B are that Rf position, C are that reference resistance, D are measured resistance
Embodiment
The utility model is described in further detail below in conjunction with accompanying drawing and embodiment.
A kind of flow detection unit comprises shell and sensing device, and described shell is that the material composition with thermal conductive resin meets liquid portion, is provided with sensing device in the enclosure, and sensing device comprises resistance temperature detector RTD, and this RTD comprises the resistance R _ f and the Rt of pairing; Rf and Rt are connected in series; Rf and Rt two ends in series connection are provided with signal acquisition point, are provided with signal acquisition point between Rf that connects and Rt; At the other heating resistor RH that is provided with of Rf.
Be provided with heat insulation structural between described Rf and the Rt, this structure is the cylinder that a heat-barrier material is made, there is the space centre, and the outer wall of this main body is provided with groove and is used to place Rt, and Rf is located at the bottom surface of cylinder.Described matching resistor Rf is identical with the Rt resistance, and resistance varies with temperature unanimity.
The material of described shell is a stainless steel.Cylinder is a right cylinder.
As shown in Figure 1: this flow detection unit has the stainless steel of thermal conductive resin and forms the liquid portion that connects, when fluid flows through, two RTD (Rf and Rt) that are positioned at its inside are sensing external agency temperature rapidly, and one of them RTD (Rf) is heated by a thermal source also on the basis of sensing external agency temperature in addition.When not having flow or low discharge because thermal source continues heating to Rf, cause Rf and Rt temperature to differ bigger, but be subjected to the heating power restriction and the state I that tends to balance, continuous increase along with flow, the part heat of Rf is pulled away, thereby set up numerous new equilibrium point, and these equilibrium points has continuity.State I I tends to balance when arriving maximum flow.Again external circuit is incorporated on the RTD that reaches balance, just produces numerous electrobalance state, thereby realized the conversion from the fluctuations in discharge to the electric signal by numerous different thermal equilibrium state.And in manufacturing process, choose matching resistor Rf and Rt by sophistication, and the heat pathway of a special construction of design makes electric signal more stable between Rf and Rt, and reach the also shortening far away of time of equilibrium point.Increase stability, improved real-time.Electric signal-discharge relation the curve ratio of itself and general thermal equilibrium flow rate test unit is seen Fig. 2 and Fig. 3.
Claims (5)
1, a kind of flow detection unit, comprise shell and sensing device, it is characterized in that described shell is that the material composition with thermal conductive resin meets liquid portion, is provided with sensing device in the enclosure, sensing device comprises resistance temperature detector RTD, and this RTD comprises the resistance R _ f and the Rt of pairing; Rf and Rt are connected in series; Rf and Rt two ends in series connection are provided with signal acquisition point, are provided with signal acquisition point between Rf that connects and Rt; At the other heating resistor RH that is provided with of Rf.
2, flow detection according to claim 1 unit, it is characterized in that being provided with heat insulation structural between described Rf and the Rt, this structure is the cylinder that a heat-barrier material is made, there is the space centre, and the outer wall of this main body is provided with groove and is used to place Rt, and Rf is located at the bottom surface of cylinder.
3, flow detection according to claim 1 and 2 unit is characterized in that described matching resistor Rf is identical with the Rt resistance, and resistance varies with temperature unanimity.
4, flow detection according to claim 1 and 2 unit, the material that it is characterized in that described shell is a stainless steel.
5, flow detection according to claim 2 unit is characterized in that described cylinder is a right cylinder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2008200376842U CN201285296Y (en) | 2008-06-18 | 2008-06-18 | Flow detection unit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2008200376842U CN201285296Y (en) | 2008-06-18 | 2008-06-18 | Flow detection unit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201285296Y true CN201285296Y (en) | 2009-08-05 |
Family
ID=40950282
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNU2008200376842U Expired - Fee Related CN201285296Y (en) | 2008-06-18 | 2008-06-18 | Flow detection unit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201285296Y (en) |
-
2008
- 2008-06-18 CN CNU2008200376842U patent/CN201285296Y/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20090805 Termination date: 20170618 |