CN108051651A - A kind of measuring device and method of small capacitance signal - Google Patents
A kind of measuring device and method of small capacitance signal Download PDFInfo
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- CN108051651A CN108051651A CN201711155004.7A CN201711155004A CN108051651A CN 108051651 A CN108051651 A CN 108051651A CN 201711155004 A CN201711155004 A CN 201711155004A CN 108051651 A CN108051651 A CN 108051651A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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Abstract
The invention discloses a kind of measuring device and method of small capacitance signal, device includes capacitance sensor, twin-core shielding line, capacitance digital conversion circuit and Acquisition Circuit.Method includes：Capacitance digital conversion circuit measures the first capacitance signal of capacitance sensor by the first core of twin-core shielding line；Capacitance digital conversion circuit measures the second capacitance signal by the second core of twin-core shielding line, and second core is hanging；Acquisition Circuit obtains the capacitance of capacitance sensor according to the first capacitance signal and the second capacitance signal measured.The present invention is additionally arranged twin-core shielding line to carry out capacitance measurement, it is connected by the first core with capacitance sensor and mode that the second core is hanging, so that the present invention is when the capacitance sensor to there is a pole to be grounded measures, measurement error caused by connecting cable and PCB parasitic capacitances can be eliminated, ensure that the precision and stability of measurement.It the composite can be widely applied to field of measuring technique.
Description
Technical field
The present invention relates to field of measuring technique, the especially a kind of measuring device and method of small capacitance signal.
Background technology
The development of modern industry has become more and more important the real-time monitoring of duty parameter.Operating mode is used for all kinds of
In the sensing system of parameter monitoring, capacitance sensor measuring system is to use to obtain most common one kind, in its conduct of industry spot
The measuring cell of the physical quantitys such as flow, pressure, displacement, liquid level, speed, acceleration, application are very extensive.
Capacitance sensor measuring system generally comprises capacitance sensor and measured capacitance value unit.Wherein, capacitance sensor
Measurement structure mainly include 2 kinds：One kind is composition capacitor (pattern 1) between two electrode of sensor, as shown in Figure 1；It is another
It is that capacitor (pattern 2) is formed between sensor electrode and the electrode plate of ground connection.In Fig. 1 and Fig. 2,1 is sensor electrode, and 2 are
Target is measured, 3 be grounding electrode, and when measurement target 2 is placed between two electrodes, measurement target 2 is situated between as medium substitution air
Matter causes capacitance to raise, and the variation of capacitance will be influenced by measuring the factors such as materials behavior, thickness, the temperature of target 2, this
Sample can obtain real-time duty parameter by the variation of capacitance.Therefore, by the structure application of Fig. 1 or Fig. 2 in a mold
Real-time procedural information can be then monitored by monitoring capacitance in real time.
The effect of measured capacitance value unit is to measure the capacitance of capacitance sensor.One kind of measured capacitance value unit is specific
Realize that structure is as shown in Figure 3.In Fig. 3, capacitance measurement unit is mainly by capacitance-digital quantizer and Acquisition Circuit this two parts group
Into wherein capacitance-digital quantizer can measure the discharge parameter of testing capacitance sensor and reference capacitor, Jin Erfen respectively
The ratio of testing capacitance sensor and reference capacitor is not drawn.With 8 channel capacitors-number converted measurement of German acam companies
Exemplified by chip PCap01, measurement structure is as shown in figure 4, CREFOn the basis of capacitor vias capacitance, C1~C7For 7 electricity to be measured
Hold the capacitance of sensor passage.
Capacitance sensor to be measured and reference capacitor are measured respectively using capacitance-digital quantizer, and calculated
Export the ratio of its discharge time(wherein τNDischarge parameter, τ for testing capacitance sensorrefOn the basis of capacitor put
Electrical parameter), the ratio of this discharge time and testing capacitance sensor capacitance value CNWith reference capacitor capacitance CrefRatio
Proportional relation, physical relationship are as follows：
Reference capacitor is high-precision and the ceramic condenser of high-temperature stability, so known to reference capacitor capacitance
On the premise of, it can be converted by numerical value and directly calculate the capacitance of testing capacitance sensor.
And the ratio for the discharge time that Acquisition Circuit unit then exports above-mentioned capacitance-digital conversion circuitIt is adopted
Collection, and then calculate the corresponding capacitance of testing capacitance sensor and feed back to control system.
Capacitance variations of the capacitive sensor system in measurement process include three aspects：The change of capacitance sensor in itself
Change, the error that the error that the wire rod of connection capacitance sensor introduces, circuit internal parasitic capacitances introduce.Capacitance sensor is in itself
Variation is that measurement is required, and wire rod and the variation measurement caused by circuit internal parasitic capacitances should avoid.
It, can be in PCap01 since its two-plate and the earth completely cut off for capacitance sensor shown in FIG. 1 (i.e. pattern 1)
Directly the connecting cable of two-plate is compensated to eliminate its caused error inside capacitance-number conversion chip, is compensated
Process is as shown in Fig. 5, Fig. 6, Fig. 7 and Fig. 8, Fig. 5 C into Fig. 8pexFor the parasitic capacitance of wire rod.PCap01 capacitances-number conversion
Chip compensates internal parasitic capacitance and internal comparator delay by ground capacity；By hanging capacitance, external pair is compensated
Ground parasitic capacitance, compensation process are as follows：1) as shown in figure 5, turning off the switch A0 and B1, switch A1 and B0 is opened, is measured at this time
Discharge time τPC0；2) as shown in fig. 6, turning off the switch A1 and B0, A0 and B1 is opened, measures discharge time τ at this timePC1；3)
As shown in fig. 7, turning off the switch A0 and A1, switch B0 and B1 is opened, measures discharge time τ at this timePC01；4) as shown in figure 8, beating
A0, A1, B0 and B1 are switched, measures discharge time τ at this timeCint。
It can finally draw the discharge time τ of testing capacitorNFor：
τN=τPC0+τPC1-τPC01-τCint
It can similarly draw the discharge time τ of reference capacitorref, and CrefFor it is known that then can with reference to discharge time ratio
To calculate CN。
The measurement procedure of capacitance sensor shown in FIG. 1 is as shown in figure 9, C in Fig. 90On the basis of capacitor measure, C1To treat
Survey capacitance sensor measurement.
In this compensation process, for eliminating wire rod, (wire rod includes copper wire on pcb board and inserts step 3) shown in Fig. 7
Head) introduced capacitance C itselfpexInfluence, and step 4) shown in Fig. 8 is then used for eliminating and posting inside capacitance-digital quantizer
It is influenced caused by raw capacitance.
But for such capacitance sensor shown in FIG. 1, since it is needed using two electrode slices, in actual use
It limits more and can not use, such as it can not just be used in the moulding that at least certain one side is smooth is required, because
The two sides of mold, which is respectively mounted sensor pole piece, can make the two sides of moulding leave the trace of pole plate, so can only use figure at this time
Capacitance sensor shown in 2 is grounded another pole piece of capacitance sensor.
It, can only be by being used in PCap01 capacitances-number conversion chip for capacitance sensor shown in Fig. 2
Structure as shown in Figure 10 (C in Figure 100On the basis of capacitor, C1For testing capacitance sensor) it compensates, compensation process
It is as follows：Turn off the switch A1 and open switch B1 (under this pattern, switch B1 must whole process be kept open), measure at this time
Discharge time τPC1；Then open switch A1 and open switch B1, measure discharge time τ at this timeCint, can finally draw to be measured
The discharge time τ of capacitance sensorNFor：
τN=τPC1-τCint
It can similarly draw the discharge time τ of reference capacitorref, and CrefFor it is known that can then calculate CN。
The measurement procedure of capacitance sensor shown in Fig. 2 is as shown in figure 11, C in Figure 110On the basis of capacitor measure, C1-C7
It is measured for testing capacitance sensor.
However, structure shown in Fig. 10 employs the capacitor sensor structure of pole ground connection, in capacitance-number conversion electricity
Road can only compensate the parasitic capacitance inside power down road, but can not eliminate and be surveyed caused by connecting cable and PCB parasitic capacitances
Measure error.
In conclusion the prior art when the capacitance sensor to there is a pole to be grounded measures, can not eliminate connection electricity
Measurement error caused by cable and PCB parasitic capacitances, it is impossible to ensure the precision and stability of measurement, it is difficult to for measuring easily quilt
The small capacitance signal that noise floods.
The content of the invention
In order to solve the above technical problems, it is an object of the invention to：The small electric of a kind of high-precision and high stability is provided
Hold the measuring device of signal.
Another object of the present invention is to：A kind of measurement side of the small capacitance signal of high-precision and high stability is provided
Method.
The technical solution used in the present invention is：
A kind of measuring device of small capacitance signal, including capacitance sensor, twin-core shielding line, capacitance-number conversion electricity
Road and Acquisition Circuit, the twin-core shielding line include the first core and the second core, and the output terminal of the capacitance sensor passes through
First core and then the first input end for being connected to capacitance-digital conversion circuit, one end of second core is hanging, and described
The other end of two cores is connected to the second input terminal of capacitance-digital conversion circuit, the output of the capacitance-digital conversion circuit
End is connected to the input terminal of Acquisition Circuit.
Further, the input terminal of the capacitance-digital conversion circuit includes at least 3 capacity measurement passages.
Further, each capacity measurement passage of the capacitance-digital conversion circuit is connected with anti-static circuit.
Further, the twin-core shielding line further includes First Line core insulation layer and the second core insulating layer, the First Line
Core is wrapped up by First Line core insulation layer, and second core is wrapped up by the second core insulating layer.
Further, it is enclosed with gauze screen outside the First Line core insulation layer and the second core insulating layer.
Further, the anti-static circuit uses PESD5V0F1BL antistatic diodes.
Further, the capacitance-digital conversion circuit uses PCap01 chips.
Another technical solution for being taken of the present invention is：
A kind of measuring method of small capacitance signal, comprises the following steps：
The first capacitance that capacitance-digital conversion circuit measures capacitance sensor by the first core of twin-core shielding line is believed
Number；
Capacitance-digital conversion circuit measures the second capacitance signal by the second core of twin-core shielding line, and described second
Core is hanging；
Acquisition Circuit obtains the capacitance of capacitance sensor according to the first capacitance signal and the second capacitance signal measured.
Further, the Acquisition Circuit obtains capacitance sensing according to the first capacitance signal and the second capacitance signal measured
The step for capacitance of device, specially：
The Acquisition Circuit compares the poor method of work according to the first capacitance signal and the second capacitance signal measured using capacitance
Calculate the capacitance of capacitance sensor.
Further, the step of capacitance of capacitance sensor is uploaded to host computer by Acquisition Circuit is further included.
The advantageous effect of the device of the invention is：Including capacitance sensing, twin-core shielding line, capacitance-digital conversion circuit and
Acquisition Circuit, twin-core shielding line include the first core and the second core, are additionally arranged twin-core shielding line to carry out capacitance measurement, pass through
The mode that first core is connected with capacitance sensor and the second core is hanging so that the present invention is in the capacitance to there is a pole to be grounded
When sensor measures, connecting cable and PCB parasitic capacitances can be eliminated caused by measurement error, ensure that the essence of measurement
Degree and stability, so as to easily measure small capacitance signal.Further, the input terminal of capacitance-digital conversion circuit is extremely
Include 3 capacity measurement passages less so that capacitance-digital conversion circuit has multiple channel test ability, can meet simultaneously more
The measurement request of a capacitance sensor, simplifies circuit, reduces cost.Further, each electricity of capacitance-digital conversion circuit
Hold TCH test channel and be all connected with anti-static circuit, can prevent the electrostatic at capacitance sensor end from being introduced by shielding line connected to it
And capacitance-digital conversion circuit is damaged, extend the service life of measuring device.
The beneficial effects of the method for the present invention is：Pass through the First Line of twin-core shielding line including capacitance-digital conversion circuit
Core measures the first capacitance signal of capacitance sensor, and capacitance-digital conversion circuit is surveyed by the second core of twin-core shielding line
It measures the second capacitance signal and Acquisition Circuit and capacitance biography is obtained according to the first capacitance signal and the second capacitance signal measured
The step of capacitance of sensor, is additionally arranged twin-core shielding line to carry out capacitance measurement, passes through the first core and capacitance sensor phase
Even and the hanging mode of the second core so that the present invention can disappear when the capacitance sensor to there is a pole to be grounded measures
Except measurement error caused by connecting cable and PCB parasitic capacitances, the precision and stability of measurement ensure that, so as to easily
Measure small capacitance signal.
Description of the drawings
Fig. 1 is the capacitor arrangement schematic diagram of background technology pattern 1；
Fig. 2 is the capacitor arrangement schematic diagram of background technology pattern 2；
Fig. 3 is a kind of specific implementation structure diagram of background technology measured capacitance value unit；
Fig. 4 is the measuring principle figure of 8 channel capacitors-number converted measurement chip PCap01；
Fig. 5 is measurement structure signal when PCap01 capacitances-number conversion chip only opens switch A1 and B0 in mode 1
Figure；
Fig. 6 is measurement structure signal when PCap01 capacitances-number conversion chip only opens switch A0 and B1 in mode 1
Figure；
Fig. 7 is measurement structure signal when PCap01 capacitances-number conversion chip only opens switch B0 and B1 in mode 1
Figure；
Fig. 8 is measurement when PCap01 capacitances-number conversion chip opens simultaneously switch A0, B0, A1 and B1 in mode 1
Structure diagram；
Fig. 9 is the measured waveform figure of PCap01 capacitances-number conversion chip in mode 1；
Figure 10 is collocation structure schematic diagram of the PCap01 capacitances-number conversion chip under pattern 2；
Figure 11 is measured waveform figure of the PCap01 capacitances-number conversion chip under pattern 2；
Figure 12 is a kind of functional block diagram of the measuring device of small capacitance signal of the present invention；
Figure 13 is a kind of structure diagram of the measuring device of small capacitance signal of the present invention；
Figure 14 is a kind of step flow chart of the measuring method of small capacitance signal of the present invention.
Specific embodiment
With reference to Figure 12 and Figure 13, a kind of measuring device of small capacitance signal is shielded including capacitance sensor 101, twin-core
Line, capacitance-digital conversion circuit and Acquisition Circuit, the twin-core shielding line include the first core 203 and the second core 205, institute
The output terminal for stating capacitance sensor 101 is connected to the first input of capacitance-digital conversion circuit by the first core 203
End, one end of second core 205 is hanging, and the other end of second core 205 is connected to capacitance-digital conversion circuit
Second input terminal, the output terminal of the capacitance-digital conversion circuit are connected to the input terminal of Acquisition Circuit.
Preferred embodiment is further used as, the input terminal of the capacitance-digital conversion circuit includes at least 3 capacitances
TCH test channel.
Preferred embodiment is further used as, each capacity measurement passage of the capacitance-digital conversion circuit connects
It is connected to anti-static circuit.
With reference to Figure 13, preferred embodiment is further used as, the twin-core shielding line further includes First Line core insulation layer
202 and the second core insulating layer 204, first core 203 wrapped up by First Line core insulation layer 202, second core 205
It is wrapped up by the second core insulating layer 204.
With reference to Figure 13, preferred embodiment, the First Line core insulation layer 202 and the insulation of the second core are further used as
Gauze screen 201 is enclosed with outside layer 204.
Preferred embodiment is further used as, the anti-static circuit uses PESD5V0F1BL antistatic diodes.
Preferred embodiment is further used as, the capacitance-digital conversion circuit uses PCap01 chips.
With reference to Figure 14, a kind of measuring method of small capacitance signal comprises the following steps：
The first capacitance that capacitance-digital conversion circuit measures capacitance sensor by the first core of twin-core shielding line is believed
Number；
Capacitance-digital conversion circuit measures the second capacitance signal by the second core of twin-core shielding line, and described second
Core is hanging；
Acquisition Circuit obtains the capacitance of capacitance sensor according to the first capacitance signal and the second capacitance signal measured.
Preferred embodiment is further used as, the Acquisition Circuit is according to the first capacitance signal measured and the second electricity
Hold the step for signal obtains the capacitance of capacitance sensor, be specially：
The Acquisition Circuit compares the poor method of work according to the first capacitance signal and the second capacitance signal measured using capacitance
Calculate the capacitance of capacitance sensor.
Wherein, capacitance compares the poor method of work, refers to the corresponding capacitance of the first capacitance signal subtracting the second capacitance signal pair
The capacitance answered obtains the actual capacitance value of capacitance sensor.
Be further used as preferred embodiment, further include Acquisition Circuit the capacitance of capacitance sensor is uploaded to it is upper
The step of machine.
The present invention is explained in detail and illustrated with reference to Figure of description and specific embodiment.
Embodiment 1
The prior art can not eliminate connecting cable and PCB when the capacitance sensor to there is a pole to be grounded measures
Measurement error caused by parasitic capacitance, it is impossible to ensure the precision and stability of measurement, it is difficult to easily be flooded by noise for measuring
Small capacitance signal.For this purpose, a kind of measuring device of new small capacitance signal is present embodiments provided, by using twin-core
Shielding line eliminates measurement error caused by connecting cable and PCB parasitic capacitances.As shown in Figure 12 and Figure 13, which fills
Putting mainly includes capacitance sensor 101, twin-core shielding line, capacitance-digital conversion circuit, anti-static circuit and Acquisition Circuit.
As shown in figure 13, the present embodiment has used twin-core shielding line to carry out capacitance measurement, and twin-core shielding line includes first
Core 203, the second core 205, First Line core insulation layer 202, the second core insulating layer 204 and gauze screen 201, the first core
203 are connected with capacitance sensor 101, and the second core 205 is hanging, and two cores are closely packed together.Wherein, the first core 203 corresponds to
205 corresponding second core insulating layer 204 of First Line core insulation layer 202 and the second core, used insulating materials is equal
It is the material (such as tefolon materials) with high dielectric constant stable, therefore is believed that：First core 203 and gauze screen 201
Between, the equivalent capacity formed between the second core 205 and gauze screen 201 is of substantially equal；First core 203 and the second core 205
Suffered temperature or humidity influence unanimously, and the institute of the two at every point of time is impacted identical.Capacitance-digital conversion circuit needs
Increase a capacity measurement passage, for testing second core 205 (line not connect vacantly) equivalent capacitance value.Capacitance-number turns
It changes circuit and PCap01 capacitances-number conversion chip with multiple channel test ability can be selected, multiple capacitances can be met simultaneously
The measurement capability of sensor, simplifies circuit, reduces cost.
Capacitance-the digital conversion circuit of the present embodiment needs to measure testing capacitance sensor using two passages
Capacitance, the two passages be measure simultaneously and measuring condition it is completely the same, one of channel measurement testing capacitance sensing
Device, it is assumed that its test result is C1, then have：
C1=CSensor+C1 equivalent capacity of cable+C1 parasitic capacitance of PCB copper wire+CChip internal parasitic capacitance
Wherein, CSensorFor the actual capacitance value of testing capacitance sensor, C1 equivalent capacity of cableFor the first core 203 and gauze screen
Equivalent capacity between 201, C1 parasitic capacitance of PCB copper wireFor PCB copper wire 1, (PCB copper wire 1 is to connect Pcap01 chips measurement port to PCB
The copper wire of chip carrier socket 1, be PCB on copper sheet) parasitic capacitance, CChip internal parasitic capacitanceUsed by capacitance-digital conversion circuit
The parasitic capacitance of chip.
The equivalent electricity that the second hanging core 205 of another passage independent measurement of capacitance-digital conversion circuit is formed
Hold, it is assumed that its test result is C2, then have：
C2=C2 equivalent capacity of cable+C2 parasitic capacitance of PCB copper wire+CChip internal parasitic capacitance
Wherein, C2 equivalent capacity of cableFor the equivalent capacity between the second core 205 and gauze screen 201, C2 parasitic capacitance of PCB copper wireFor PCB copper wire 2
The parasitism of (PCB copper wire 2 is the copper wire for connecting Pcap01 chips measurement port to chip carrier socket on PCB 2, is the copper sheet on PCB)
Capacitance, CChip internal parasitic capacitanceThe parasitic capacitance of chip used by for capacitance-digital conversion circuit.
Since the first core 203 and 205 length of the second core are of substantially equal, insulating materials is identical and all in same gauze screen
It is interior, it is believed that all sames such as various interference, temperature change, humidity variation suffered by two cores, and then can consider same
The equivalent capacity at both moment (or being spaced in two very short moment) is equal, that is to say, that C1 equivalent capacity of cable≈C2 equivalent capacity of cable；Separately
Outside, in PCB design, should ensure that the periphery of its capacitance sensor connector line without other copper wire or plane layer (such as
Plane or power plane), and should try one's best and ensure length, width and the consistency of thickness of PCB copper wire 1 and PCB copper wire 2, therefore
It is considered that C1 parasitic capacitance of PCB copper wire≈C2 parasitic capacitance of PCB copper wire；And used by capacitance-digital conversion circuit chip internal parasitic capacitance
CChip internal parasitic capacitanceIt can inherently be fallen by the structure compensation of Fig. 8.
Then, Acquisition Circuit reads C respectively by the measurement result inside bus reading capacitance-digital conversion circuit1
With C2Value, then the poor method computing of work is compared by capacitance can draw CSensorResult CSensor≈C1-C2。
In addition, the electrostatic of sensor side is introduced by shielding line connected to it and damages capacitance-number turn in order to prevent
Circuit is changed, the present embodiment both increases anti-static circuit in each TCH test channel of capacitance-digital conversion circuit.Such as：In electricity
Each TCH test channel of appearance-digital conversion circuit increases an antistatic diode PESD5V0F1BL, the capacitance of normal condition
Value only has 0.4pf, and the influence to entire measuring system can ignore substantially, and can also be compensated by subsequent software come
Eliminate the influence.
Capacitance-digital conversion circuit in the measuring device of the present embodiment is integrated with capacitance measurement and the temperature of multichannel
Function is measured, is drifted about using capacitance caused by can eliminating humiture caused by wire rod after double shield line technology, simultaneously also
Eliminating influences caused by the parasitic capacitance of copper wire on pcb board, additionally it is possible to compensation deals are made to the parasitic capacitance of chip internal,
This significantly increases the stability of measurement.Simultaneously as having used double shield line, extraneous various interference act on two simultaneously
On root line, the interference superposition amount of measurement can be eliminated by the data processing in later stage, this undoubtedly greatly enhances entire system
The antijamming capability of system.
Embodiment 2
Based on the measuring device of embodiment 1, as shown in figure 14, a kind of measurement of small capacitance signal is present embodiments provided
Method specifically includes following steps：
S101, capacitance-digital conversion circuit measure the first of capacitance sensor by the first core of twin-core shielding line
Capacitance signal；
S102, capacitance-digital conversion circuit measure the second capacitance signal by the second core of twin-core shielding line, described
Second core is hanging；
S103, Acquisition Circuit obtain the electricity of capacitance sensor according to the first capacitance signal and the second capacitance signal measured
Capacitance；
The capacitance of capacitance sensor is uploaded to host computer by S104, Acquisition Circuit.
To in this present embodiment the step of number, only for the purposes of illustrate explanation and set, to the order between step
Any restriction is not done, the execution sequence of each step in the present embodiment can be fitted according to the understanding of those skilled in the art
Answering property adjusts.
In the step S103, the corresponding capacitance of the first capacitance signal is subtracted the second capacitance signal and corresponded to by Acquisition Circuit
Capacitance, obtain the actual capacitance value of capacitance sensor.
The measuring method of the present embodiment is additionally arranged twin-core shielding line to carry out capacitance measurement, is passed by the first core and capacitance
The mode that sensor is connected and the second core is hanging so that the present invention is measured in the capacitance sensor to there is a pole to be grounded
When, connecting cable and PCB parasitic capacitances can be eliminated caused by measurement error, ensure that the precision and stability of measurement, from
And easily measure small capacitance signal.
Embodiment 3
During polymer shaping, injection moulding process is particularly, uses capacitance sensor On-line sampling system or detection
State of the macromolecule melt in injection mold, the prediction of detection and end product quality for entire injection moulding process have extremely
Close important role.
The present invention a kind of measuring device and method of small capacitance signal, the prison available for injection molding machine mold cavity state
Control, the ungrounded electrode of capacitance sensor can be located at the one side of mold, by twin-core shielding line connection electrode and the present apparatus
Capacitance-digital conversion circuit, the value of capacitance-digital conversion circuit measuring capacitance in real time sensor simultaneously pass through at Acquisition Circuit
It after reason, sends supervisory controller and carries out control decision, realize real-time, on-line monitoring to injection moulding process；The measuring method
Can also prediction model be established as target sample using the injection moulding process of certain number, realized in injection moulding process to product weight
On-line prediction, eliminate the subsequent detection link of product weight；In addition, the feedback based on the measuring method, machine Control system
System can also carry out closed loop adjustment to injection moulding process, reduce the appearance of unqualified substandard products to a certain extent.
In conclusion for the prior art when the capacitance sensor to there is a pole to be grounded measures, it can not the company of elimination
Connect measurement error problem caused by cable and PCB parasitic capacitances, the present invention proposes a kind of high-precision and high stability
The measuring device and method of small capacitance signal eliminate cable, pcb board and the mistake brought of measurement chip internal parasitic capacitance
Difference, measures while can realizing multichannel capacitance, directly exports the capacitance of sensor to be measured.
The above are implementing to be illustrated to the preferable of the present invention, but the present invention is not limited to the embodiment, ripe
A variety of equivalent variations or replacement can also be made on the premise of without prejudice to spirit of the invention by knowing those skilled in the art, this
Equivalent deformation or replacement are all contained in the application claim limited range a bit.
Claims (10)
1. a kind of measuring device of small capacitance signal, it is characterised in that：Including capacitance sensor, twin-core shielding line, capacitance-number
Word conversion circuit and Acquisition Circuit, the twin-core shielding line include the first core and the second core, the capacitance sensor it is defeated
Outlet is connected to the first input end of capacitance-digital conversion circuit by the first core, and one end of second core hangs
Sky, the other end of second core are connected to the second input terminal of capacitance-digital conversion circuit, the capacitance-number conversion
The output terminal of circuit is connected to the input terminal of Acquisition Circuit.
2. a kind of measuring device of small capacitance signal according to claim 1, it is characterised in that：Capacitance-the number
The input terminal of conversion circuit includes at least 3 capacity measurement passages.
3. a kind of measuring device of small capacitance signal according to claim 2, it is characterised in that：Capacitance-the number
Each capacity measurement passage of conversion circuit is connected with anti-static circuit.
4. a kind of measuring device of small capacitance signal according to claim 1, it is characterised in that：The twin-core shielding line
Further including First Line core insulation layer and the second core insulating layer, first core is wrapped up by First Line core insulation layer, and described the
Two cores are wrapped up by the second core insulating layer.
5. a kind of measuring device of small capacitance signal according to claim 4, it is characterised in that：First core is exhausted
Gauze screen is enclosed with outside edge layer and the second core insulating layer.
6. a kind of measuring device of small capacitance signal according to claim 3, it is characterised in that：The anti-static circuit
Using PESD5V0F1BL antistatic diodes.
7. according to a kind of measuring device of small capacitance signal of claim 1-6 any one of them, it is characterised in that：The electricity
Appearance-digital conversion circuit uses PCap01 chips.
8. a kind of measuring method of small capacitance signal, it is characterised in that：Comprise the following steps：
Capacitance-digital conversion circuit measures the first capacitance signal of capacitance sensor by the first core of twin-core shielding line；
Capacitance-digital conversion circuit measures the second capacitance signal, second core by the second core of twin-core shielding line
Vacantly；
Acquisition Circuit obtains the capacitance of capacitance sensor according to the first capacitance signal and the second capacitance signal measured.
9. a kind of measuring method of small capacitance signal according to claim 8, it is characterised in that：The Acquisition Circuit root
The step for capacitance of capacitance sensor being obtained according to the first capacitance signal and the second capacitance signal measured, specially：
The Acquisition Circuit compares the poor method of work using capacitance and calculates according to the first capacitance signal and the second capacitance signal measured
Go out the capacitance of capacitance sensor.
10. a kind of measuring method of small capacitance signal according to claim 8 or claim 9, it is characterised in that：Further include acquisition
The step of capacitance of capacitance sensor is uploaded to host computer by circuit.
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| CN201711155004.7A CN108051651B (en) | 2017-11-20 | 2017-11-20 | Device and method for measuring micro capacitance signal |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109323715A (en) * | 2018-10-31 | 2019-02-12 | 四川泛华航空仪表电器有限公司 | A kind of test fixture for capacitance type sensor |
| CN113884833A (en) * | 2021-10-21 | 2022-01-04 | 迈普通信技术股份有限公司 | System and method for detecting welding quality of capacitor |
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