CN101799496A - Capacitor measurement device and method thereof - Google Patents
Capacitor measurement device and method thereof Download PDFInfo
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- CN101799496A CN101799496A CN 201010121059 CN201010121059A CN101799496A CN 101799496 A CN101799496 A CN 101799496A CN 201010121059 CN201010121059 CN 201010121059 CN 201010121059 A CN201010121059 A CN 201010121059A CN 101799496 A CN101799496 A CN 101799496A
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Abstract
The invention relates to capacitor measurement device and method thereof. The device comprises a four-threshold digital comparator, a variable gain amplifier, a size variable positive and negative constant flow source, a rapid analog/digital converter, a microprocessor and a display, wherein the microprocessor receives output signals of the four-threshold digital comparator and the analog/digital converter and outputs measurement results to the display; the microprocessor selects the positive and negative constant flow source and the amplification factor of the amplifier according to the capacity of a measured capacitor; and voltage on the measured capacitor amplified by the variable gain amplifier is measured by the rapid analog/digital converter, and the measurement results are output to the four-threshold digital comparator. In the capacitor measurement method, by the constant flow forward charge and back discharge of the measured capacitor, the microprocessor figures out the measurement result of a primary capacitance value according to time interval of the forward charge and back discharge between two threshold values preset by the four-threshold digital comparator, the numerical value of the constant flow source and the amplification factor of the variable gain amplifier. The invention greatly reduces the measurement time of the capacitor under the condition of using smaller charge/discharge current and eliminates the influence of the absorption effect of the capacitor on the measurement accuracy by the installation of the four-threshold digital comparator.
Description
Technical field
The present invention relates to a kind of apparatus and method of measuring electric capacity, particularly provide to be applicable to a kind of electric capacity of quick and precisely measuring, especially the method and apparatus that big electric capacity is measured fast.The method and apparatus of measurement electric capacity of the present invention can also effectively be avoided the influence of electric capacity absorption effect.
Background technology
Capacitance measurement has become a for example important feature of digital multimeter of surveying instrument.Present capacitance measurement technology makes us dissatisfied, and being not only owing to wait for the charging of unknown capacitance device needs long Measuring Time, and the absorption effect of capacitor influences accuracy of measurement.New measuring method is provided, and the more wide-measuring range of expanded capacitor also can be realized quick and precisely measuring, and is desirable.
As everyone knows, the flow through current i of capacitor C
cWith voltage U on the capacitor
CRate over time
Between the pass be:
Perhaps can be expressed as:
Or
That is, if a constant current i
cBeing added to above the measured capacitance C, is Δ U through the change in voltage on the capacitor behind the time interval Δ t
C, then according to i
c, Δ t, Δ U
CValue, can know the value of measured capacitance device C.
Ultimate principle according to such has proposed a lot of capacitance measurement methods, and the file 1-5 that for example sees reference is respectively:
1.US?5,461,321?Apparatus?and?method?for?measuring?capacitancefrom?the?duration?of?a?charge-discharge?charge?cycle
2.US?6,191,723?Fast?capacitance?measurement
3.US?6,275,047?Capacitance?measurement
4.US?6,624,640?Capacitance?measurement
5.US?6,683,462?Apparatus?for?and?method?of?measuringcapacitance?with?high?accuracy
Summary of the invention
A kind of new capacitance measurement method and device have been the objective of the invention is to propose, make that not only the scope of measuring big electric capacity greatly enlarges, measuring speed improves greatly, and higher accuracy is provided in whole measurement range, has also realized the elimination to the influence of capacitor absorption effect simultaneously.
Purpose of the present invention can also be to the measurement of measured capacitance device, adopts steady currents controlled, that can select different sizes, different directions that the measured capacitance device is charged and discharges.Change the size of steady current and the enlargement factor of variable gain amplifier, the Measuring Time of capacitors of different capacitance is in the predetermined scope of design.
The objective of the invention is to realize by following technical solution: the amplifier, microprocessor and the display that the inventive system comprises variable gain.Described microprocessor is accepted the signal of the output of four thresholding digital comparators and quick analog/digital converter, and output is measured and result arrives described display; Described microprocessor is selected the enlargement factor of the amplifier of the size of positive and negative constant flow source and variable gain according to the electric capacity of measured capacitance, and, this voltage value is connected to described four thresholding digital comparators by the magnitude of voltage of described quick analog/digital converter measurement on the measured capacitance device of the amplifier amplification of variable gain.
Four thresholding digital comparators of the present invention can be set different four threshold values combinations, and the charge and discharge thresholding when changing capacitance measurement is promptly measured the change in voltage scope that capacitance is got, the bias voltage when also changing capacitance measurement simultaneously.
Quick analog/digital converter of the present invention converts digital quantity to after the amplifier of the described variable gain of the process of the voltage on the measured capacitance is amplified fast, deliver to described four thresholding digital comparators and four default threshold values and carry out numeral relatively, comparative result is delivered to microprocessor handle.The output of described quick analog/digital converter compares with four different digital values respectively, and four different digital values are set charging numeric door limit value V1 respectively, and the digital threshold value V2 that discharges is as discharging and recharging thresholding; Between V1 and V2, set V3 and two digital threshold values of V4 as measuring the interval that measured capacitance discharges and recharges the time.Described quick analog/digital converter is measured through the voltage on the measured capacitance device after the variable gain amplifier amplification, the output measurement result is given described four thresholding digital comparators, described four thresholding digital comparators send comparative result described microprocessor to handle, and are implemented between the charge and discharge and change thereby described microprocessor changes the direction of constant current source when discharge reaches V1 and charging and reaches two digital threshold values of V2; Described microprocessor was measured the time interval that charge or discharge are between V3 and two digital threshold values of V4, calculated the amount of capacity of measured capacitance, and showed.
Positive and negative constant flow source of the present invention is subjected to the different sizes of control output of described microprocessor, the steady current of direction.
Capacitance measurement method of the present invention measuring the incipient stage, can be selected the capacitance measurement range automatically fast, selects the enlargement factor of the amplifier of the size of described positive and negative constant flow source and described variable gain according to the electric capacity of measured capacitance; The amplifier of described variable gain and the combination of positive and negative constant flow source change and determine to measure the range of electric capacity; Described microprocessor is provided with the threshold value V1 and the V2 of charge and discharge to described four thresholding digital comparators, the voltage threshold and the bias voltage value of charging and discharge when changing capacitance measurement; Described quick analog/digital converter provides the data of measurement voltage on the electric capacity of the amplifier amplification of variable gain to described four thresholding digital comparators and described microprocessor; By constant current positive charge and back discharge to measured capacitance, described microprocessor according to positive charge and back discharge through predetermined two threshold value V3 of four thresholding digital comparators and the time between V4, and the numerical values recited of constant current source, calculate the measurement result that also respectively obtains a capacitance.
Microprocessor of the present invention is set four threshold values combination of described four thresholding digital comparators, the charge and discharge thresholding when changing capacitance measurement, and the actual measurement capacitance charge and discharge change in voltage interval of being got.In the time of charge and discharge thresholding when changing capacitance measurement, the bias voltage when also having changed capacitance measurement.Voltage on the measured capacitance after described quick analog/digital converter amplifies the amplifier through described variable gain converts digital quantity fast to, deliver to four thresholding digital comparators and four default thresholdings and carry out numeral relatively, comparative result is delivered to microprocessor handle.The amplifier of described variable gain is measured the voltage amplification on the electric capacity to quick analog/digital converter scope.
The present invention is under the situation of using less charging and discharging currents, the amplification that cooperates the low noise variable gain amplifier, can make the less charge and discharge voltage amplification that presents when measuring big electric capacity, with the working range that is fit to quick analog/digital converter and the working range of four thresholding digital comparators; Under the situation of less charging and discharging currents, can shorten the time of big capacitance measurement greatly, for example make the time of the big electric capacity of measuring 1 farad only shorten to and need also can shorten to 1 second to the Measuring Time of measuring 10 farads electric capacity even with 0.5 second.This is a speed not seen before.Utilize quick analog/digital converter and four thresholding digital comparators respectively to obtain the result that electric capacity is measured the period, further improved measuring speed in charging and discharge.
The four thresholding digital comparators that the present invention is provided with can make the output of quick analog/digital converter compare with four different digital values respectively, and these four different digital values can be set according to the needs of measuring.Set charging numeric door limit value V1 respectively, the digital threshold value V2 that discharges is as discharging and recharging thresholding; Two digital threshold values of V3 and V4 are set as measuring the interval that measured capacitance discharges and recharges the time between V1 and V2, make the selection of V3 and two digital threshold values of V4 avoid the scope that the electric capacity absorption effect influences.
Voltage value on the measured capacitance device after the analog/digital converter measurement is amplified through variable gain amplifier fast among the present invention, offer four thresholding digital comparators, comparative result send microprocessor to handle, the change of microprocessor decision charge and discharge constantly, and the time interval that charge or discharge are between V3 and two digital threshold values of V4 measured, according to the electric current of used charge and discharge and the size in these time intervals, can calculate the amount of capacity of measured capacitance, and show.
The present invention is at the initial period of capacitance measurement, measure fast with quick analog/digital converter, obtain the voltage change on the at interval interior electric capacity of very short time, the enlargement factor of selecting the amplifier of suitable charge and discharge electric current and variable gain for microprocessor provides foundation, thereby realizes fast automatic measurement range selection.
Use sample resistance and analog/digital converter that charging and discharging currents is measured, can obtain the exact value of charging and discharging currents more accurately, it is more accurate to make capacitance measurement calculate the result.
Acting as of microprocessor:
1) accepts the output data of AD converter, differentiate and select suitable capacitance measurement range;
2) accept the output data of AD converter, also can accept four threshold compatarors result relatively, after analyzing these data and result, the size and Orientation of decision and control positive and negative constant flow source;
3) enlargement factor of decision and control amplifier;
4) adjust the threshold value of four thresholdings as required;
5) to the electric capacity charging voltage through the time T between V3 and two thresholdings of V4+and to capacitor discharge voltage through the time T between V4 and two thresholdings of V3-measure;
The size of employed constant current source and the electric capacity that T+, T-value calculate the measured capacitance device during 6) according to measurement;
7) numerical value and the unit of the electric capacity of output measured capacitance device show to display.
The present invention compared with prior art provides, more accurately method quicker to capacitance measurement, has also greatly expanded the scope that big electric capacity is measured fast, and eliminates the influence of absorption effect in measuring process.For the selection of range, the present invention also provides automatic range system of selection more efficiently.
Description of drawings
Fig. 1 is a basic structure block scheme of the present invention.
Fig. 2 is the present invention's variation diagram of voltage on the capacitor when using constant electric current that ideal capacitor is discharged and recharged.
Fig. 3 is that the present invention uses constant electric current to the actual change in voltage synoptic diagram that the capacitor charging/discharging of absorption effect influence is arranged.
Fig. 4 is the situation map that the present invention is provided with four thresholding digital comparators.
Fig. 5 is the synoptic diagram that the present invention is provided with the charge and discharge time between threshold value V3, V4 of measuring after four digital comparison threshold values.
Fig. 6 is provided with V1=50mV, V2=550mV, V3=100mV, the waveform synoptic diagram of four thresholdings of V4=500mV among the present invention.
Fig. 7 is provided with V3=100mV among the present invention, and during V4=500mV, microprocessor need be to being in 100mV, the time interval T+ between the 500mV, the canonical schema that T-measures.
Fig. 8 carries out the exemplary waveforms figure that automatic range detects, changes range for the present invention at the capacitance measurement initial period;
Fig. 9 changes the situation of the threshold value of four thresholding digital comparators for the present invention.
Embodiment
Below in conjunction with accompanying drawing is that example makes a detailed description to invention.Referring to Fig. 1, mainly comprised the constant current value size and Orientation among the figure and can select the positive and negative constant current source I+, the I-that change; Gain can be selected the low noise amplifier A1 that changes; Quick analog/digital converter AD1; Four thresholding digital comparators; Microprocessor μ P and display.And sample resistance R0 and analog/digital converter AD2.
Referring to Fig. 2, the typical waveform figure of desirable (no absorption effect) capacitor when using positive and negative equal constant current source charge and discharge, V1 is the charging threshold value for discharge threshold value, V2.Suppose that capacitor does not have absorption effect.Can see that voltage on the capacitor changes fully linearly between charge and discharge thresholding V1 and V2, as the time that is charged to V2 from V1 be T,
Its slope
With the charge and discharge current i
cBe directly proportional, be inversely proportional to, so the electric capacity of measured capacitance device can calculate by Constant Electric Current flow valuve and the slope of measuring the charge and discharge voltage waveform with the electric capacity C of measured capacitance.
Referring to Fig. 3, true capacitor is the typical waveform figure that often occurs when using positive and negative equal constant current source charge and discharge of large capacitor especially, because the absorption effect of capacitor makes the charge and discharge waveform that variation take place, if still calculate capacitance, obviously deviation can take place according to the mode of the ideal capacitor of Fig. 2.Common capacitance measurement method is not considered the influence of the absorption effect of capacitor, and in fact often the absorption effect influence is bigger in the capacitance measurement.
Referring to Fig. 4, V1 has increased by two threshold values of V3, V4 in the present invention for discharge threshold value, V2 are the charging threshold value, and the influence that absorption effect influences is avoided in the interval that is provided with between two threshold values of V3, V4;
Referring to Fig. 5, charge and discharge time interval T+, T-between two threshold values of V3, V4 that need to measure.The four thresholding digital comparators that the present invention is provided with, not only solve in the common capacitance measurement method use analog comparator decision charge and discharge threshold value poor stability, not malleable, have shortcoming such as hysteresis effect, and because the introducing of two new threshold value V3, V4, feasible measurement can be avoided the zone of absorption effect influence, and the slope of only measuring the linearity range of charge and discharge voltage becomes possibility.
The beginning of a capacitance measurement is through the measured capacitance device C of overdischarge
xBe linked into metering circuit, owing to measured capacitance device C through overdischarge
xOn voltage level off to 0, microprocessor will control the forward constant current source with a less measuring current to measured capacitance device C
xCharge, this is because at measured capacitance device C
xHere be in open-circuit condition before the access, perhaps can regard as and connect a very little electric capacity; The forward constant current source inserts back measured capacitance device C
xOn voltage begin to rise (referring to Fig. 8), deliver to quick analog/digital converter AD1 measurement after this voltage amplifies through variable gain amplifier and convert digital quantity to; Measure, calculate after the charging beginning through the voltage change (for example value of obtaining VX1) of back (for example 1mS) at interval sometime, according to used charging constant-current supply value and voltage change, microprocessor can calculate measured capacitance C
xApproximate volume, and select to use instead size more suitably the forward continuous current to measured capacitance device C
xCharging can measure and obtain then through the magnitude of voltage (for example VX2) on measured capacitance device during back (for example 1mS) at interval sometime, according to measured capacitance device C in this time interval again
xThe variation size (VX2-VX1) of last magnitude of voltage can know whether the numerical value of constant current source of selection is appropriate, whether needs to adjust again; When the numerical value of the constant current source of selecting has been that maximal value is also felt measured capacitance device C
xThe rate of change of last magnitude of voltage in 1mS is too little, then increases the enlargement factor to 10 times, 100 times or 1000 times of variable gain amplifier; The enlargement factor of proper arrangement charging and discharge current and amplifier will make most of measured capacitance device Measuring Time be in the predetermined scope of design (100mS～1S) for example.
The charging voltage on the measured capacitance device that will make forward constant-current charge electric current continues linear in time the rising, from no-voltage, charging voltage on the measured capacitance device is amplified the back through variable gain amplifier and is risen through threshold value V1, arrive threshold value V3 (referring to Fig. 4, Fig. 5) then, at this moment the output of quick analog/digital converter AD1 and four thresholding digital comparators result relatively picks up counting the time counter of microprocessor internal; When charging voltage arrived threshold value V4, the output of analog/digital converter AD1 and four thresholding digital comparators result relatively made the time counter of microprocessor internal stop timing fast, obtains time value T
+
The positive charge electric current will make the charging voltage on the measured capacitance device continue to rise, when after the charging voltage on the measured capacitance device is amplified through variable gain amplifier, reaching threshold value V2, the output of quick analog/digital converter AD1 and four thresholding digital comparators result relatively, make the negative sense constant-current discharge electric current that the source output of microprocessor control variable constant current is identical with former forward constant-current charge size of current, direction is opposite, the measured capacitance device begins back discharge.
Because absorption effect, one section zone relevant with absorption effect appears in the voltage during back discharge on the capacitor, then linear decline of slope that just determines according to negative sense constant-current discharge size of current and measured capacitance values size.
After amplifying through variable gain amplifier, the sparking voltage on the measured capacitance device descends through threshold value V4, at this moment the output of quick analog/digital converter AD2 and four thresholding digital comparators result relatively picks up counting the time counter of microprocessor internal; When sparking voltage arrived threshold value V3, the output of analog/digital converter AD1 and four thresholding digital comparators result relatively made the time counter of microprocessor internal stop timing fast, obtains time value T-.
According to the enlargement factor of variable gain amplifier, the numerical value I of forward constant-current charge electric current
+With the numerical value I-of reverse constant current charge-discharge electric current, and a value T
+And T-, can calculate twice measurement result of the capacitance of measured capacitance:
Or
If the enlargement factor of variable gain amplifier is not 1, then The above results need be multiplied by the enlargement factor of variable gain amplifier.
The back discharge electric current will make the voltage on the measured capacitance device continue to go up decline, when after the sparking voltage on the measured capacitance device amplifies through variable gain amplifier, reaching threshold value V1, the output of quick analog/digital converter AD1 and four thresholding digital comparators result relatively, make the source output of microprocessor control variable constant current identical with negative sense constant-current discharge size of current, the forward constant-current charge electric current that direction is opposite, the measured capacitance device begins positive charge, same because the influence of absorption effect, the relevant zone of one section absorption effect appears in the voltage on the capacitor, just put linear rising of slope of charging current size and the decision of measured capacitance values size then, begin second and measure circulation according to the forward constant current.
If desired, when positive charge electric current and negative sense discharge current switched mutually, microprocessor can change the size of electric current according to the result of preceding one-shot measurement, so that the time of measuring is in the predetermined scope of design, this also can be regarded as the range adjustment.
As specifying, the threshold value of for example choosing four thresholding digital comparators is V1=50mV; V2=550mV; V3=100mV; V4=500mV; Referring to Fig. 6.The time interval T that at this moment will measure
+, T-is referring to Fig. 7.
For the electric capacity of different capabilities size, typical charge and discharge electric current and obtain the one-shot measurement result and see the following form the desired time:
The charge and discharge on the electric capacity of different electric capacitys of the different electric currents of table 1 present 500mV and change required time (mS) on the AD converter input end
According to table 1, the Measuring Time of most of electric capacity of design is arranged in 100mS～1S scope, because the charge and discharge continuous current is limited to below the 1000 μ A (1mA), for the big electric capacity that surpasses 1mF, the time that reach charge and discharge voltage 500mV variation can become more and more longer.Introduced the low noise variable gain amplifier among the present invention specially, its enlargement factor can be passed through the microprocessor control break, can choose the enlargement factor of 1 times, 10 times, 100 times or 1000 times.For low capacitance measurement, the enlargement factor of amplifier is 1 times; For the big electric capacity more than the 1mF, measure delivering to quick analog/digital converter AD1 after the different enlargement factor amplification of the process of the charge and discharge voltage on the electric capacity, measurement result is delivered to four thresholding digital comparators relatively again.
For example, for the big electric capacity of 100mF, when the charge and discharge electric current is 1000 μ A (1mA), the charge and discharge voltage on it through 100 times of amplifications after, the change in voltage 500mV required time that is presented on analog/digital converter AD1 input end is 500mS; For big electric capacity up to 1F, when the charge and discharge electric current is 1000 μ A (1mA), the charge and discharge voltage on it through 1000 times of amplifications after, the change in voltage 500mV required time that is presented on analog/digital converter AD1 input end also only is 500mS.
That is to say that for the big electric capacity up to 1F, the speed of its measurement is greatly about about 500mS; Even for the big electric capacity up to 10F, the speed of its measurement is approximately also only about 5S.This has surmounted the measurement range and the measuring speed of present other method greatly.
If also will pursue faster speed, for the big electric capacity more than the 1F, can also adopt the method that changes four thresholding digital comparator threshold values further to improve measuring speed again, for example see Fig. 9, four threshold values are adjusted to V1=10mV; V2=110mV; V3=20mV; V4=100mV.Then the Measuring Time to the big electric capacity of 10F is expected further to reduce to 1 second.
Undoubtedly, the method of this invention is also only on the basis of Modern High-Speed Analog-to-Digital Conversion Technology development, for example utilize the ∑-Δ converter of slewing rate up to 1 μ S or 10 μ S, just might propose and obtain to implement, former capacitance measurement method be can't propose such method and obtain implementing.
Owing to adopted the mode of constant current charge and discharge, and in conjunction with the effect of four thresholding digital comparators, the present invention from the measurement that measures very big electric capacity of little electric capacity can both accomplish fast, accurate.
In Fig. 1 of the present invention, R0 is a sample resistance, and AD2 is an analog/digital converter, if necessary, can set up and by this part metering circuit, obtain the actual numerical value of charging and discharging currents more accurately, that reduces that the continuous current source may occur changes the measuring error that causes with temperature and time.For different current measurements, the numerical value of sample resistance also can and be selected by microprocessor control.If the output of controlled variable constant current source has sufficiently high accuracy, R0 sample resistance and AD2 analog/digital converter can.
As object lesson, describe a certain capacity measuring process of the capacitor of 150,000 μ F (0.15F) for example.
Before the measured capacitance device inserts between the measurement input end of the device that constitutes by method of the present invention and the signal ground, owing to be in open-circuit condition originally between input end and the signal ground, be equivalent to only connect a very little electric capacity, according to table 1, constant current source will be exported minimum charging and discharging currents 0.01 μ A, it is 1 state that amplifier A1 is in enlargement factor, and charging and discharging currents causes that at input end voltage rises fast, reaches 550mV through 50mV, 100mV, 500mV; Back discharge is got back to 50mV through 500mV, 100mV then; Swing back and forth discharging and recharging between thresholding 50mV and 550mV, form a triangular wave.The charging 100mV to the interval between the 500mV, and the interval of discharge from 500mV to 100mV, microprocessor is counted, because the time that discharges and recharges is very short, the numerical value that microprocessor count obtains is very little, when less than certain numerical value, microprocessor can be treated to 0 to it, and shows that on display electric capacity is 0.
When electric capacity 150 through overdischarge, when the measured capacitance device of 000 μ F inserts, at this moment the voltage of measuring between input end and the signal ground approaches 0V, enlargement factor is that the output of 1 low noise amplifier also approaches 0V, the AD1 analog/digital converter measures the result who approaches 0V, when microprocessor receives result that the AD1 analog/digital converter measures less than 50mV, the forward constant current source is charged to measured capacitance with 0.01 μ A of minimum, as time passes, the AD1 analog/digital converter is constantly measured, and, obtain the numerical value of the voltage variety on the measured capacitance device subtracting each other through measurement result behind the 1mS and the measurement result before the 1mS.
According to table 1, the measured capacitance device than high capacitance to be measured, the rate of change of considering AD1 analog/digital converter output voltage reading usually is between every millisecond 500 μ V～5mV.
For said 150, the measurement of 000 μ F capacitor, charge to measured capacitance with 0.01 μ A, voltage variety behind 1mS is far smaller than 500 μ V, microprocessor is according to AD1 analog/digital converter output result, change the forward constant current source is charged to measured capacitance with 0.05 bigger μ A, and, can find that voltage variety is still less than 500 μ V subtracting each other through the measurement result before the measurement result behind the 1mS and the 1mS; Microprocessor control forward constant current source charges to measured capacitance with 0.5 bigger μ A, and subtracting each other through measurement result behind the 1mS and the measurement result before the 1mS ... 1mA with maximum charges to measured capacitance until microprocessor control forward constant current source, and, find that voltage variety is still much smaller than 500 μ V subtracting each other through measurement result behind the 1mS and the measurement result before the 1mS; At this moment microprocessor keep the forward constant current source with the 1mA of maximum in the measured capacitance charging, the enlargement factor of control low noise amplifier A1 is brought up to 10 times by 1 times, and, find that voltage variety is still much smaller than 500 μ V subtracting each other through measurement result behind the 1mS and the measurement result before the 1mS; Microprocessor keep the forward constant current source with the 1mA of maximum in the measured capacitance charging, the enlargement factor of control low noise amplifier A1 is brought up to 100 times by 10 times, subtract each other through measurement result behind the 1mS and the measurement result before the 1mS, find that voltage variety has 660 μ V, above 500 μ V and less than 5mV, microprocessor fixedly charging and discharging currents is 100 times in the enlargement factor of 1mA, A1, finishes automatic range and selects, and enters normal measurement state.Tested 150, the charge and discharge repeatedly under the constant current source effect of positive and negative 1mA of the capacitor of 000 μ F size, voltage above it changes between 0.5mV and 5.5mV, and the output of variable gain amplifier A1 changes between 50mV and 550mV, and every 0.75S finishes one-shot measurement.In fact, according to table 1, according to the present invention, the capacitor (2F) of measuring 2,000,000 μ F size also only needs 2S, and in documents, 50,000 μ F capacitance measurements approximately need 2.5 seconds, and can not eliminate absorption effect.Therefore by the measurement mechanism of the present invention's structure and the performance of method, compare with method, not only big capacitance measurement is had advance very fast, and, have higher accuracy by absorption effect is eliminated with existing measurement mechanism.
Claims (10)
1. capacitance measuring device, the amplifier, microprocessor and the display that comprise variable gain, it is characterized in that described microprocessor receives the output signal of four thresholding digital comparators and quick analog/digital converter, and export treated measurement result to described display; Described microprocessor is according to the enlargement factor of the amplifier of the Capacity Selection positive and negative constant flow source of measured capacitance size and described variable gain, and by the voltage of described quick analog/digital converter measurement on the measured capacitance device of the amplifier amplification of described variable gain; The measurement result of described quick analog/digital converter outputs to described four thresholding digital comparators.
2. capacitance measuring device according to claim 1, it is characterized in that described microprocessor sets described four thresholding digital comparators and set four threshold values combinations, charge and discharge thresholding when changing capacitance measurement, to change the change in voltage scope that capacitance is got of measuring, the bias voltage when also changing capacitance measurement simultaneously.
3. capacitance measuring device according to claim 1 and 2, it is characterized in that the voltage on the measured capacitance after described quick analog/digital converter amplifies the amplifier through described variable gain converts digital quantity fast to, deliver to described four thresholding digital comparators and four default thresholdings and carry out numeral relatively, comparative result is delivered to microprocessor handle.
4. capacitance measuring device according to claim 3, the output that it is characterized in that described quick analog/digital converter compares with four different digital values respectively, described four different digital values are set charging numeric door limit value V1 respectively, and the digital threshold value V2 that discharges is as discharging and recharging thresholding; Two digital threshold values of V3 and V4 are set as measuring the interval that measured capacitance discharges and recharges the time, to eliminate the influence that measurement brings to capacitor of capacitor absorption effect between V1 and V2.
5. capacitance measuring device according to claim 4, it is characterized in that described quick analog/digital converter is the voltage value on the measured capacitance device after amplifying through described variable gain amplifier, offer described four thresholding digital comparators and four threshold values and compare, comparative result send described microprocessor to handle; When sparking voltage during less than V1 numeric door limit value, described microprocessor control constant current source becomes the forward constant current source and charges to the measured capacitance device; When charging voltage during greater than V2 numeric door limit value, described microprocessor control constant current source becomes the negative sense constant current source makes the discharge of measured capacitance device; Described microprocessor was measured the time interval that charge or discharge are between V3 and two digital threshold values of V4, calculated the amount of capacity of measured capacitance, and showed.
6. capacitance measuring device according to claim 1 is characterized in that described positive and negative constant flow source is subjected to the control of described microprocessor to export the steady current of different size and Orientations.
7. capacitance measurement method according to claim 1, it is characterized in that measuring the incipient stage, utilization is to the quick measurement of the change in voltage situation on the capacitor, fast automatic selection capacitance measurement range, the enlargement factor of the size by changing described positive and negative constant flow source and the amplifier of described variable gain changes the capacitance measurement range.
8. capacitance measurement method according to claim 7, it is characterized in that described microprocessor can change four threshold value settings of four thresholding digital comparators, charging and voltage threshold V1, the V2 of discharge and threshold value V3, the V4 of actual measurement electric capacity when changing capacitance measurement are to obtain suitable measurement bias voltage, to discharge and recharge scope and better absorption effect elimination effect.
9. according to claim 1 or 8 described capacitance measurement methods, by constant current positive charge and back discharge to measured capacitance, described microprocessor according to positive charge and back discharge through the time between two predetermined threshold values of described four thresholding digital comparators, and the numerical values recited of described positive and negative constant flow source, calculate and respectively obtain the measurement result of a capacitance, accelerated measuring speed.
10. capacitance measurement method according to claim 7, the amplifier that it is characterized in that described variable gain is the scope of the voltage amplification on the electric capacity to suitable quick analog/digital converter measurement.
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101976306A (en) * | 2010-10-28 | 2011-02-16 | 惠州Tcl移动通信有限公司 | Method for calculating discharge time of capacitor, and mobile terminal |
| CN102270075A (en) * | 2011-03-25 | 2011-12-07 | 苏州瀚瑞微电子有限公司 | Capacity measurement method for capacitive touch screen scanning line and circuit module |
| CN103439379A (en) * | 2013-08-29 | 2013-12-11 | 复旦大学 | Reading circuit and reading method based on electrochemical sensor |
| CN104155529A (en) * | 2014-08-20 | 2014-11-19 | 中北大学 | Transient small capacitance measuring instrument |
| CN104272119A (en) * | 2012-05-30 | 2015-01-07 | 株式会社村田制作所 | Module and capacitance detecting method |
| CN104459338A (en) * | 2014-12-26 | 2015-03-25 | 青岛歌尔声学科技有限公司 | Capacitor capacitance value measuring device and measuring method |
| CN105637577A (en) * | 2013-10-21 | 2016-06-01 | 高通Mems科技公司 | Closed loop dynamic capacitance measurement |
| CN111090010A (en) * | 2019-12-26 | 2020-05-01 | 苏州市运泰利自动化设备有限公司 | Multi-channel capacitance testing system and method |
| CN113391192A (en) * | 2021-06-16 | 2021-09-14 | 苏州市运泰利自动化设备有限公司 | Low-voltage capacitance test system and method |
| CN114144685A (en) * | 2019-10-01 | 2022-03-04 | 株式会社日立产机系统 | Power supply capacitor electrostatic capacitance measuring device and power supply capacitor electrostatic capacitance measuring method |
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| US6215319B1 (en) * | 1997-08-01 | 2001-04-10 | Kevin G. Hafer | High accuracy measuring system |
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Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101976306B (en) * | 2010-10-28 | 2014-06-25 | 惠州Tcl移动通信有限公司 | Method for calculating discharge time of capacitor, and mobile terminal |
| CN101976306A (en) * | 2010-10-28 | 2011-02-16 | 惠州Tcl移动通信有限公司 | Method for calculating discharge time of capacitor, and mobile terminal |
| CN102270075A (en) * | 2011-03-25 | 2011-12-07 | 苏州瀚瑞微电子有限公司 | Capacity measurement method for capacitive touch screen scanning line and circuit module |
| CN104272119A (en) * | 2012-05-30 | 2015-01-07 | 株式会社村田制作所 | Module and capacitance detecting method |
| CN104272119B (en) * | 2012-05-30 | 2017-03-15 | 株式会社村田制作所 | Module and capacitance determining method |
| CN103439379A (en) * | 2013-08-29 | 2013-12-11 | 复旦大学 | Reading circuit and reading method based on electrochemical sensor |
| CN105637577B (en) * | 2013-10-21 | 2018-02-16 | 追踪有限公司 | Closed-loop path dynamic capacity measurement |
| CN105637577A (en) * | 2013-10-21 | 2016-06-01 | 高通Mems科技公司 | Closed loop dynamic capacitance measurement |
| CN104155529A (en) * | 2014-08-20 | 2014-11-19 | 中北大学 | Transient small capacitance measuring instrument |
| CN104459338A (en) * | 2014-12-26 | 2015-03-25 | 青岛歌尔声学科技有限公司 | Capacitor capacitance value measuring device and measuring method |
| CN104459338B (en) * | 2014-12-26 | 2017-05-10 | 青岛歌尔声学科技有限公司 | Capacitor capacitance value measuring device and measuring method |
| CN114144685A (en) * | 2019-10-01 | 2022-03-04 | 株式会社日立产机系统 | Power supply capacitor electrostatic capacitance measuring device and power supply capacitor electrostatic capacitance measuring method |
| CN111090010A (en) * | 2019-12-26 | 2020-05-01 | 苏州市运泰利自动化设备有限公司 | Multi-channel capacitance testing system and method |
| CN113391192A (en) * | 2021-06-16 | 2021-09-14 | 苏州市运泰利自动化设备有限公司 | Low-voltage capacitance test system and method |
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