CN103645218A - Capacitive fuel composition sensor with slow oscillator and high-speed switch - Google Patents
Capacitive fuel composition sensor with slow oscillator and high-speed switch Download PDFInfo
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- CN103645218A CN103645218A CN201310612081.6A CN201310612081A CN103645218A CN 103645218 A CN103645218 A CN 103645218A CN 201310612081 A CN201310612081 A CN 201310612081A CN 103645218 A CN103645218 A CN 103645218A
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Abstract
The invention relates to a capacitive fuel composition sensor with a slow oscillator and a high-speed switch, and provides a voltage divider, wherein the voltage divider comprises a sensor and a reference capacitor voltage; in order to achieve a lower power consumption, the reference capacitor voltage is oscillated at a lower frequency (such as 6KHz) between two voltages, but because a capacitor switches quickly, a variable periodic fast voltage is generated at the two ends of the voltage divider and is used for generating a voltage peak at the node of the capacitor to indicate the capacitance ratio, so that the fuel composition can be explained.
Description
Technical field:
The present invention, relevant for oil-engine driven automobile, is adapted to the automobile with fuel blend work to those especially, and for example the gasoline of known variables concentration and alcohol mix.The engine best effort of this automobile, changes along with one or more engine operating parameter response fuel composition signals, and the sensor of this signal in engine fuel supply produces, and the parameter sensitivity of this sensor to fuel mixture shows propellant composition.
Background technology:
Several fuel composition sensors for vehicle motor are known by people in the prior art.They comprise optical sensor, microwave remote sensor and capacitive transducer.In the field of capacitive character fuel composition sensor, the electric conductivity that problem is alcohol that must overcome, when alcohol concentration surpasses 30%, because capacitor plate is by fuel mixture short circuit, it can reduce the precision of sensor very largely.
Capacitive character fuel composition sensor, it can be in alcohol concentration until accurately work for 100% time.This sensor provides an electric capacity in motor fuel pipeline, an electric reference impedance and this capacitor's series, an oscillator, the combination of oscillating voltage to electric capacity/impedance is provided, have a voltage assembly, its frequency is at least 1 megahertz, but is less than the required frequency of microwave circuit device.Sensor further comprises a circuit, and this circuit is responsive to the electrical quantity of the capacitor being determined by electric capacity, determines its electric capacity, therefore determines the specific inductive capacity of fuel mixture.The high frequency of this voltage assembly, for capacitance sensing, provides a condenser impedance, this impedance is widely lower than the equivalent resistance impedance in parallel of fuel, and this is the electric conductivity due to fuel, like this, condensance is preponderated, so sensor provides the accurate indication of an electric capacity.
Summary of the invention:
Sensor of the present invention offers a voltage divider, this voltage divider comprises sensor, quotes a voltage, for lower power consumption to electric capacity, this voltage vibrates between two voltage with relatively low frequency, the frequency of 6KHz for example, still, this capacitance switch is rapid, be created in the periodicity quick voltage that voltage divider two ends change, be used for producing voltage peak on the node of capacitor, show this capacity ratio, therefore propellant composition can be described.
Technical solution of the present invention
By accompanying drawing and the description of preferred version subsequently, the further details of the present invention and advantage will be apparent.
Contrast patent documentation: CN2828763Y electrostatic capacity sensor for vehicle 200520113988.9
Accompanying drawing explanation:
Fig. 1 has shown an automobile, has motor fuel and controls, and adds according to fuel composition sensor of the present invention.
Fig. 2-4th, different views, has shown and has used at the capacitive transducer according in fuel composition sensor of the present invention.
Fig. 5 has shown according to fuel composition sensor part circuit diagram of the present invention.
Fig. 6 has shown the figure line of specific inductive capacity with the ratio of the burning needed air/fuel of various fuel (A/F).
Fig. 7 shows series of voltage waveform, helpful to understanding in Fig. 5 the work of circuit.
Fig. 8-10 have shown respectively the LF oscillator in fuel composition sensor in Fig. 5 circuit, the circuit diagram of high-speed switch and high speed peak follower.
Embodiment:
Fig. 1 provides an automobile, and it comprises the engine 11 in engine room 12, the fuel that engine 11 receives from fuel tank 13 by fuel channel 15, and too much fuel is returned to fuel tank by conduit 14, fuel tank 13 is at the other end of car.Fuel in fuel tank 13 is the potpourri of two kinds of fuel, and one of them is gasoline, and another is alcohol, such as methyl alcohol or ethanol.Fuel channel 15 comprises fuel composition sensor 16, and this sensor is positioned at engine room 12 near on the point of engine 11.Fuel composition sensor 16 produces a signal, the relative scale of alcohol and gasoline in the fuel of the clear process of this signal list.The fuel vapo(u)r holding tank 17 of a standard is connected to fuel tank 13 by jet chimney 18, is used for collecting steam over there, is connected to the gas handling system of engine 11 by jet chimney 19.
The work of engine 11, is controlled by an electronic controller 20, and as shown in the figure, this controller can be positioned at the rear of engine room or other are local easily.Controller 20 can be the digital machine of a sequencing, is similar to the controller that those use at present on automobile.This device is well-known, it comprises a microprocessor, RAM, ROM and suitable input/output circuitry, be accompanied by the program suitable in ROM that is kept at, be used for coordinating the input message from different sensors receive, carry out computing, table look-up and output command to each actuator in engine associated components.20 couples of fuel composition signal V of controller
oUTresponsive, this signal is from fuel composition sensor 16 and fuel temperature signal, along with air/fuel ratio, the duration of ignition, filter cleaning speed, and other optimize the necessary factor of engine operation according to the natural fuel potpourri that offers engine, revise this engine operating parameter.
The physical construction of sensor 16 as in Figure 2-4.This structure is supplied with holding altogether between sensor outer housing and external capacitive electrode, and like this, these parts are with regard to unnecessary mutual isolation.Because this design feature, due to the cost that outer electrode ground connection is reduced, is greater than the cost of the required electronic equipment of any this sensor.
The outer tube 26 of low carbon stainless steel, install wherein one end, makes laser welded seam reach the expansion openend of a coupling unit 21, and the other end is installed wherein, and laser welded seam reaches the expansion openend of another coupling unit 22. Coupling unit 21 and 22 all consists of stainless steel, has an outside hexagon, and defines passage 23,24 and pass through respectively, and each passage 23,24 all has respectively internal whorl part 27,28, and these are the annexes for burning line 15.Outer tube 26 forms a part for the outer electrode of sensor outer housing and capacitive transducer.
Stainless steel inner tube 40 is axially configured in outer tube 26, to form the internal electrode of capacitive transducer and define an annular chamber 25 between pipe 26 and 40.Inner tube 40 closed at both ends are at a tapering part 41, and the column part 42 of small diameter and an expansion longitudinal joints 43 all consist of stainless steel.In Fig. 3, axially can see, in outer tube 26, inner tube 40 is unsettled by supporting 30 two ends.Each support comprises an interior section 31, and it has a circular hole 32, and this circular hole receives the column part 42 of inner tube 40, also has three radially outstanding pins 33 of 120 angles each other, ends at outer tube 26, the opening 34 that pin 33 defines between them.Supporting 30 can consist of alcohol impedance, and electrical isolation polymer resin is such as nylon (R).Therefore a fuel path is defined as, and by the passage 24 of coupling unit 22, by the opening between pin 33, by managing the annular chamber 25 between 26 and 40, by another, supports the opening 34 of 30 pins 33, by the passage 23 of coupling unit 21.The dielectric of managing the fuel formation capacitive transducer in 26 and 40 inlet plenums 25, capacitive transducer is by these electrode definitions.
Between screw 37 and adjacent support 30, a glass insulator 38 is retained in the opening of coupling unit 21, and parts 21 are adjacent with circuit board 36.Stainless pin 39 designs are through circuit board 36 and insulator 38, and it does not just contact with coupling unit 21 or pipe 26 like this.Pin 39 because be welded on physically with electricity on, keep in touch with adjacent joint 43, and on circuit board 36, be welded on suitable circuit tracing, as the internal electrode of capacitive transducer.The tie point of pin 39 is 9.7mm to total distance of circuit board and joint 43.Therefore, the inside and outside electrode of capacitive transducer is all electrically connected to circuit board, by the wire of a minimum length.
The other end of circuit board 36 is connected respectively to the clamp member up and down 46,47 of fixture 45 by a pair of screw 44.Screw 44 stationary fixture parts 46,47 together, are fixed to circuit board 36 fixture 45 equally. Clamp member 46 and 47 comprises the semicircle opening of coupling, defines an inner circular aperture 48 together with these openings, is used for receiving outer tube 26.Fixture 45 is arranged on around outer tube 26 tightly, in a kind of stable mode, fix the other end of circuit board 36, with respect to pipe 26, there is no excessive vibration, but allow to relatively rotate so that torsional torque, this torque is applied between coupling unit 21 and 22, is not applied on circuit board 36.In fact; for the element of holding circuit plate 36 and other parts of sensor are away from this environment; a supplementary shell (not showing); can pass through machine screws (not showing); contrary screw 37 is affixed on the fixture 45 of sensor 16; for example,, by fully expanding all parts that bolt 44 surrounds sensor except joint 21 and 22 hexagonal ends.
Although opening and breach all in sensor have enough sizes, prevent the significant fuel limitation stream of their meetings, the cumulative volume of the fuel that 25 the insides, chamber comprise is minimum, owing to eliminating or reducing flow, the extreme flow that prevents the fuel in chamber 25 reduces or accumulates, this may cause in sensor the difference of specific inductive capacity between fuel mixture, and those fuel mixtures just will enter the firing chamber of engine 11.
The electronic equipment that has shown sensor in Fig. 5.These assemblies are arranged on circuit board 36.In an integrated circuit (IC) version of this circuit, parts as much as possible will be included in integrated circuit, and that will be one of circuit board component.Voltage V after an adjusting
+offer these parts, the voltage of 6.5V for example, by an input isolated amplifier, the voltage V after a less adjusting
rEFsize is 5.0V, and they all relate to the ground voltage end of circuit board 36, thus a sensor ground voltage GND of the conduit of capacitive transducer 26 definition.Standard voltage regulator circuit for generation of voltage V+ does not show.
About Fig. 5, LF oscillator 100 produces an output voltage, and this voltage converts as 6KHz with relatively low frequency between V+ and earth potential.This output voltage is adapted to control the conduction state of high-speed switch 120, and this high-speed switch is alternately V
rEFbe connected to one end of reference capacitance (680pF) with earth potential, this electric capacity is connected to ground by sensor 16.Reference capacitance 101 and sensor 16 define a node 102 between them, to form a voltage divider, its output terminal is on node 102.Sensor 16 comprises a capacitive transducer 103, and it has coaxial electrode, comprises the conduit 26 and 40 of Fig. 2-4, and the fuel mixture dielectric in chamber 25, as previously mentioned, further comprises a leak resistance in parallel 104.The electric capacity of capacitive transducer 103, converts along with the specific inductive capacity of the fuel mixture between its electrode (for example,, for gasoline and methyl alcohol, scope is 39-755pF); Leak resistance 104 changes along with the conductivity of equal fuel potpourri.Therefore, they are all along with propellant composition changes.Bias resistance 105(10K) also provide between node 102 and ground, the bias voltage of a stable state is provided on node 102.High speed peak detector 125, the input of its signal is by a direct-current blocking-up electric capacity 106(0.22 μ F) be connected to the output that 102, one latchs of node are inputted reception oscillators 100.In addition, node 102 is to also having the stray capacitance of 6-10pF between ground.
Fig. 9 has shown the example of a high-speed switch 120.High-speed switch field effect transistor 115, such as (R) 2N7000 of Motorola or its equivalent, is selected to obtain the switching speed of 30 nanoseconds.In fact, the switching speed of equipment, when there is no extra gate resistance, is 10-15 nanosecond; The resistance 118 of one 510 ohm connect with this, forms a little RC and postpones, so switching speed can be slowed down to 30 nanoseconds with inner gate capacitance.Field effect transistor 115 has a ground connection source electrode, and drain electrode is by resistance 116(10K) be connected to V
rEF, this voltage offers shunt capacitance 117(0.22 μ F), make switching noise away from power supply with being connected to.The drain electrode 115 of field effect transistor is the output of high-speed switch 120, and this output is connected to reference capacitance 101.
During running, under the frequency of 6KHz, oscillator 100 causes field effect transistor 115 conductings and disconnection.The drain voltage of field effect transistor 115 is as shown in the waveform 182 in Fig. 7 (B), and the square wave of a 6KHz of processing.But that is not a perfect square wave, because voltage transitions is not instantaneous.In Fig. 7 (B), the slope of voltage transitions is exaggerated for observability.Before 115 conductings of being on the scene effect pipe, the voltage in its drain electrode is at V
rEF.Along with node 102 ground connection, reference capacitance 101 is charged to V
rEF.Due to field effect transistor 115 conductings, its drain voltage becomes earth potential within 30 nanoseconds.If node 102 is not to there is no resistive current path between ground, its voltage will be reduced to a voltage at one time, and as mentioned above, this voltage depends on intrinsic standoff ratio and the propellant composition of capacitive voltage divider.The resistance 105 of 10K does not allow sufficient Leakage Current, affects widely the voltage drop fast on node 102; But it allows capacitor electric discharge after transient voltage declines, and the voltage on node 102 is got back to earth potential like this.
But, when high methanol concentration, (for example surpass 30% methyl alcohol), leak resistance 104 will be much smaller than the resistance 105 of 10K, and will allow to reveal before the complete conducting of a big chunk being on the scene effect pipe 115 of capacitor charging, unless the switching speed of high-speed switch is very fast.Will to cause voltage on node 102 can not decline before again rising the same far away in the charging of loss like this; Small-sized voltage peak will cause a mistake in the propellant composition showing.High-speed switch 120 switches are faster, near certain a bit, will lose fewer charging so, and voltage peak downward on node 102 will be more accurate when showing propellant composition.Independent bipolar transistor, has switching time of typical 70-100 nanosecond, still fast not.Can construct the bipolar transistor network with faster switching time, cost is the complicacy of extra-pay and circuit.As previously mentioned, field effect transistor 115, has switching time of 10-15 nanosecond; But that is too fast, because the lead-in wire (combination of pin 48 and coupling unit 21 and screw 37) of capacitive transducer 103 has inductance, capacitive transducer 103 is between electrod assembly 26,40 and circuit board.In very fast switching speed, this inductance can cause error.For example, this inductance can produce a vibration, and this vibration causes voltage peak downward on node 102 to postpone, and energy is by the interim induction field that is stored in pipeline.In this duration of oscillation, more variation may leakage capacitor.Equally, the inductance of lead-in wire produces one along the voltage drop of lead-in wire, the lead-in wire of about every 1/4 inch-have 50 millivolts on one end of each electric capacity.All of these factors taken together has caused the error of sensor, and this error usually increases along with switching speed.Can provide best signal the switching time that it has been determined that for 30 nanoseconds, and this signal has minimum error in high methanol concentration.Allowing lower switching time more charging to reveal, is due to more small-sized output voltage peak value.But switching speed can increase error faster, this is the natural capacity due to capacitive transducer lead-in wire.
To consider to be in addition described to the significance of the circuit design here.Resistance 116 resistances are 10K.Choose this value as the compromise between competition factor.It is desirable to, when field effect transistor 115 conductings or conduction, drain voltage is in fact ground connection.In fact, its drain voltage will be by the voltage divider impact decision in the inner drain/source impedance of resistance 116 being on the scene effect pipes, and internal driving only has several ohm.Resistance 116 impedances are larger, and being on the scene effect pipe conduction period, drain voltage is current potential more closely.But during each oscillation period before 115 conductings of being on the scene effect pipe, reference capacitance 101 is charged to V completely again
rEFnecessary equally.Because resistance 116 is on the charge path of reference capacitance 101, the increase of its resistance means the longer duration of charging; For the component value of other uses, the resistance of 20K produces considerable time.What oscillation frequency was same is the compromise between competition factor.Lower frequency will increase the size of integrating condenser 150, and integrating condenser is not described; This will slow down the global response time.But higher frequency will allow, within each oscillation period, reference capacitance 101 even has recharge time still less, as described above, extra downward pressure is placed in the impedance of resistance 116.
Voltage waveform on node 102 can be found out by the waveform 184 from Fig. 7 (C).Each downward peak 185 is a new electric capacity measuring (therefore can measure propellant composition).The less peak making progress 186 is due to upper identical impact in the other direction, along with field effect transistor 115 disconnects, during alternate oscillation device is progressively carried out.In these peak making progress circuit below, ignore.Voltage on node 102 moves up, and peak value is detected by high speed peak detector 125 below, at ground and V
rEFbetween an analog output signal is provided.
Figure 10 has shown a scheme of high speed peak detector 125.The input end 126 of capacitor 106 is connected to pull-up circuit 132, and this circuit comprises operational amplifier 133(LM158), normal phase input end is connected to V
rEF, anti-phase input is connected to V+ by resistance 134, output is by resistance 135(10K) and be connected to terminal 126 and its anti-phase input.This circuit is moved upwards up to V the voltage on node 102
rEF, making it is above Ground for circuit below, the different voltage levvls of capacitance 106 separated these some parts of circuit in Fig. 5.
Terminal 126 is also connected to quick comparer 130(LT1016) positive input, its output is provided to an input end of Sheffer stroke gate latch 140, and this latch comprises Sheffer stroke gate 141 and 142, and another input 139 is connected to the output of LF oscillator 100.The output of latch 140 is by diode 143 and resistance 144(100K) offer operational amplifier 145(LM158) anti-phase input, its positive input has the fixed reference potential from voltage divider, this voltage divider comprises resistance 146 and 147 series connection, both end voltage V+.The output of operational amplifier 145 is by electric capacity 150(0.33 μ F) feed back to anti-phase input, be further used as the output of sensor and the reference of the anti-phase input of comparer 130 fast.The anti-phase input of operational amplifier 145 is by resistance 151(750K) be connected to ground.Comparer 130 needs one than the normal slow larger DC bias current of comparer fast, and this electric current is provided by circuit 132.During downward peak 185 in Fig. 7 (C), circuit 132 has high impedance to reduce sensor error, is exactly due to this high DC bias current.
In Figure 10, the work of the remainder of circuit will be about Fig. 7 (D)-7(F) describe.Sensor voltage V
sIGdepend on an integrating circuit, it comprises operational amplifier 145 and its feedback capacity 150, as shown in the waveform 188 in Fig. 7 (F).In every half cycle oscillator, oscillator output is very low, and the latch output of Sheffer stroke gate 142 keeps low level, and electric capacity 150 is allowed through resistance 151 electric discharges.The resistance that resistance 151 is relatively high, for the V of rising
sIGguaranteed electric discharge slowly.In the contrary half period of oscillator 100, oscillator output high level, the output of latch is still low level, unless the output step-down of high-speed comparator, the downward peak of the voltage on node 102, is moved up by circuit 132, lower than sensor voltage V
sIGtime, that will occur.The output of comparer 130 is as shown in the waveform 190 in Fig. 7 (D) fast; Shown so downward peak 191.The response of latch 140 is for changing its output, as 7(E) in waveform 192 as shown in, high level is for the remainder of oscillator half period, as shown in Figure 193.Electric capacity 150 will be by diode 143 and resistance 144 chargings, and with a kind of many speed faster than electric discharge, this is because resistance 144 has less resistance; Sensor voltage V
sIGtherefore will relatively promptly reduce; As shown in the part 195 in waveform 188.V
sIGcommon constant rising, as shown in the part 196 and 197 in waveform 188, by more brief, the institute that declines faster interrupts, as shown in part 195, V
sIGfollow the downward peak of voltage on node 102 and maintain a level, this water-glass understands the electric capacity of capacitive transducer 103, therefore shows propellant composition.
Voltage V
rEF-GND is applied in resistance 116 two ends, and makes in Fig. 5 sensor circuit, field effect transistor 115 switches of Fig. 9.V
rEFbe also supplied to the pull-up circuit 140 of describing according to Figure 10.Fig. 5, the equivalent equation formula of 8,9 and 10 sensor circuit is: V
sIG-GND=(V
rEF-GND) * (1-CAP
rATIO).
CAP
rATIOcapacity ratio C
101/ (C
101+ C
103+ C
stray), C wherein
101and C
103the electric capacity of reference capacitance 101 and capacitive transducer 103, C
strayit is the stray capacitance of sensor.
Claims (8)
1. a capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch, it is characterized in that: a kind of fuel composition sensor, for the fuel mixture in internal combustion engine fuel feeding line, fuel mixture comprises two kinds of fuel with differing dielectric constant, relative concentration is unknown, at least one fuel conducts electricity, sensor comprises: the capacitive transducer in burning line, adjustment is to adapt to the fuel flow rate through that burning line, like this, the fuel mixture that offers engine just comprises a dielectric, this dielectric has determined electric capacity wherein, but also comprise the capacitor that a short circuit electricity is led, a reference capacitance with fixed capacity amount, connects with capacitive transducer, forms a voltage divider, and this voltage divider has an output node, circuit arrangement, it comprises the field effect transistor of a square-wave oscillator and a speed-sensitive switch output, this field effect transistor is connected with both ends of power resistance, this reference and the series connection of coupling condenser being on the scene effect pipe two ends, electrode of coupling condenser is connected to the node of resistance and field effect transistor, this circuit arrangement is in the effectively duplication of production of relatively low frequency, the predetermined quick voltage conversion at the tandem compound two ends of reference capacitance and capacitive transducer, for producing a corresponding voltage transformation at output node, this predetermined quick voltage conversion comprises an initial voltage conversion, this conversion is proportional with the capacity ratio of sensor and reference capacitance in fact, a contrary voltage transformation subsequently, this conversion is due to the Leakage Current that flows through fuel mixture, rely on initial voltage map table to understand propellant composition.
2. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 1, it is characterized in that: field effect transistor has the conduction initial time that was less than for 30 nanoseconds, an and conduction control gate, be used under low frequency alternately conducting and disconnect field effect transistor, alternately produces the first voltage transformation and contrary voltage transformation, the door of field effect transistor, make the internal capacitance of a resistance in series and field effect transistor form a RC delay, slow down conduction initial time to 30 nanoseconds.
3. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 1, it is characterized in that: fuel mixture comprises two kinds of fuel with differing dielectric constant, relative concentration is unknown, at least one fuel conducts electricity, this sensor comprises: the capacitive transducer in a burning line, adjustment is to adapt to the fuel flow rate that flows through this pipeline, like this, the fuel mixture that offers engine just comprises a dielectric, this dielectric has determined electric capacity wherein, but also comprises the capacitor that a short circuit electricity is led, a reference capacitance with fixed capacity amount, connects with capacitive transducer, forms a voltage divider, and this voltage divider has an output node, circuit arrangement, for duplication of production under low frequency, the predetermined quick voltage conversion at the tandem compound two ends of reference capacitance and capacitive transducer, for producing a corresponding voltage transformation at output node, this predetermined quick voltage conversion comprises an initial voltage conversion, this conversion is proportional with the capacity ratio of sensor and reference capacitance in fact, define a maximum sensor voltage, this voltage table understands propellant composition, a contrary voltage transformation subsequently, this conversion is due to the Leakage Current that flows through fuel mixture, rely on initial voltage map table to understand propellant composition, peak-detector circuit is connected to this output node, and the continuous signal of a propellant composition is provided, and propellant composition is from continuous maximum sensor voltage.
4. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 3, is characterized in that: the duration of quick voltage conversion was substantially for 30 nanoseconds.
5. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 3, is characterized in that: described low frequency is not more than in fact 6KHz.
6. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 3, it is characterized in that: peak-detector circuit comprises: signal difference device, the first input is connected to output node, and the second input and output provide their difference; A latch, it has the first state and the second state, this circuit arrangement of responsive and signal difference device, be used for keeping the first state in very first time section, within second time period alternate with very first time section, keep the second state, and work when peak value sensor voltage surpasses the voltage on the second input end of signal difference device; An integrating condenser, provides second input end of a voltage to signal difference device; Capacitor charging device, it responds latch, and latch, when the first state, charges to integrating condenser with first rate at first direction, and latch, when the second state, charges to integrating condenser with the second speed faster in second direction.
7. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 6, it is characterized in that: further comprise a DC-isolation electric capacity, between the first input of output node and signal difference device, also have a voltage level shifting circuit, it is connected to the first input of signal difference device.
8. a kind of capacitive character fuel composition sensor with slow oscillator and speed-sensitive switch according to claim 3, it is characterized in that: described circuit arrangement comprises a square-wave oscillator, an output speed-sensitive switch field effect transistor is connected with the resistance of both ends of power, reference and the series connection of coupling condenser being on the scene effect pipe two ends, coupling condenser has an electrode, and this electrode is connected to the node of resistance and field effect transistor.
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| CN105958943A (en) * | 2016-04-21 | 2016-09-21 | 新茂国际科技股份有限公司 | Relaxation oscillator |
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| CN104460763A (en) * | 2014-12-14 | 2015-03-25 | 衢州市煜鑫农产品加工技术开发有限公司 | Constant-temperature control switching circuit |
| CN104460763B (en) * | 2014-12-14 | 2017-01-11 | 衢州昀睿工业设计有限公司 | Constant-temperature control switching circuit |
| CN105958943A (en) * | 2016-04-21 | 2016-09-21 | 新茂国际科技股份有限公司 | Relaxation oscillator |
| CN105958943B (en) * | 2016-04-21 | 2018-12-04 | 新茂国际科技股份有限公司 | relaxation oscillator |
| US10432176B2 (en) | 2016-04-21 | 2019-10-01 | Syncmos Technologies International, Inc. | Relaxation oscillators with reduced errors or no errors in output frequencies caused by changes in temperatures and/or fabrication processes |
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Application publication date: 20140319 |