CN101799496B - Capacitor measurement device and method thereof - Google Patents
Capacitor measurement device and method thereof Download PDFInfo
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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 to the method and apparatus of large electric capacity Quick Measurement.The method and apparatus of measurement electric capacity of the present invention can also effectively be avoided the capacitive absorption effects.
Background technology
Capacitance measurement has become a for example important feature of digital multimeter of surveying instrument.Present capacitance measurement technology is unsatisfactory, and being not only owing to wait for the charging of unknown capacitance device needs long Measuring Time, and the absorption effect of capacitor affects accuracy of measurement.Novel 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 object of the invention is to propose, not only so that measure the scope of large electric capacity and greatly enlarge, measuring speed improves greatly, and higher accuracy is provided in whole measurement range, has also realized simultaneously the elimination on the impact of capacitor absorption effect.
Purpose of the present invention can also be to the measurement of measured capacitance device, adopt controlled, can select the steady currents of different sizes, different directions that the measured capacitance device is carried out charging and discharging.Change the size of steady current and the enlargement factor of variable gain amplifier, the Measuring Time of the capacitor of different electric capacitys 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 Fast simulation/digital quantizer, 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 by the magnitude of voltage of described Fast simulation/digital quantizer measurement on the measured capacitance device of the amplifier amplification of variable gain, this voltage value is connected to described four thresholding digital comparators.
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 namely measured the change in voltage scope that capacitance is got, the bias voltage when also changing capacitance measurement simultaneously.
Fast simulation/digital quantizer 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 the default threshold value of described four thresholding digital comparators and four and carry out numeral relatively, comparative result is delivered to microprocessor process.The output of the described Fast simulation/digital quantizer respectively digital value different from four compares, and four different digital values are set respectively charging numeric door limit value V1, 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 discharge and recharge the time as the measurement measured capacitance interval.Described Fast simulation/digital quantizer 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 process, 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 steady current of the different sizes of described microprocessor-based control output, 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 arranges threshold value V1 and the V2 of charge and discharge to described four thresholding digital comparators, voltage threshold and the bias voltage value of charging and discharging when changing capacitance measurement; Described Fast simulation/digital quantizer 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 the back discharge to measured capacitance, described microprocessor according to positive charge and back discharge through predetermined two the 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 value combinations of described four thresholding digital comparators, the charge and discharge thresholding when changing capacitance measurement, and the charge and discharge change in voltage that the actual measurement capacitance is got is interval.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 Fast simulation/digital quantizer amplifies the amplifier through described variable gain converts digital quantity fast to, deliver to the default thresholding of four thresholding digital comparators and four and carry out numeral relatively, comparative result is delivered to microprocessor process.The amplifier of described variable gain is measured the voltage amplification on the electric capacity to Fast simulation/digital quantizer scope.
The present invention is in the situation of using less charging and discharging currents, the amplification that cooperates Low Noise Variable Gain Amplifier, can make the less charge and discharge voltage amplification that presents when measuring large electric capacity, with the working range of suitable Fast simulation/digital quantizer and the working range of four thresholding digital comparators; In the situation of less charging and discharging currents, can greatly shorten the time of large capacitance measurement, for example make the time shorten of the large electric capacity of measuring 1 farad to only needing with 0.5 second, also can shorten to 1 second to the Measuring Time of measuring 10 farads electric capacity even.This is speed not seen before.Utilize Fast simulation/digital quantizer and four thresholding digital comparators can respectively obtain in the charging and discharging period result of an electric capacity measuring, further improved measuring speed.
The four thresholding digital comparators that the present invention arranges, the output that can make Fast simulation/digital quantizer respectively digital value different from four compare, and these four different digital values can be set according to the needs of measuring.Set respectively charging numeric door limit value V1, the digital threshold value V2 that discharges is as discharging and recharging thresholding; Two digital threshold values of V3 and V4 are set as the interval of measuring measured capacitance and discharge and recharge the time between V1 and V2, make the selection of V3 and two digital threshold values of V4 avoid the scope of capacitive absorption effects.
Fast simulation among the present invention/digital quantizer is measured through the voltage value on the measured capacitance device after the variable gain amplifier amplification, offer four thresholding digital comparators, comparative result send microprocessor to process, microprocessor determines the change moment of charge and discharge, 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, with Fast simulation/digital quantizer Quick Measurement, obtain the voltage change on the electric capacity in the very short time interval, 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 more accurately the exact value of charging and discharging currents, 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, determine and the size and Orientation of control positive and negative constant flow source;
3) enlargement factor of decision and control amplifier;
4) adjust as required the threshold value of four thresholdings;
5) to capacitor 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) electric capacity numberical value of quantity and the unit 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 of large electric capacity Quick Measurement, and eliminates the impact of absorption effect in measuring process.For the selection of range, the present invention also provides more efficiently automatic range selecting circuit method.
Description of drawings
Fig. 1 is 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 on the actual change in voltage synoptic diagram that the capacitor charging/discharging of absorption effect impact is arranged.
Fig. 4 is the situation map that the present invention arranges four thresholding digital comparators.
Fig. 5 is that the present invention arranges the synoptic diagram of measuring the charge and discharge time between threshold value V3, V4 after four digital comparison threshold values.
Fig. 6 is among the present invention, and V1=50mV is set, V2=550mV, V3=100mV, the waveform synoptic diagram of four thresholdings of V4=500mV.
Fig. 7 is among the present invention, and V3=100mV is set, and during V4=500mV, microprocessor need to be to being in 100mV, the time interval T+ between the 500mV, the canonical schema that T-measures.
Fig. 8 is that the present invention carries out the exemplary waveforms figure that automatic range detects, changes range at the capacitance measurement initial period;
Fig. 9 is the situation that the present invention changes the threshold value of four thresholding digital comparators.
Embodiment
Being example below in conjunction with accompanying drawing 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; Fast simulation/digital quantizer 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 (without 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 the electric capacity C of measured capacitance, 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.
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 occur, if still calculate capacitance according to the mode of the ideal capacitor of Fig. 2, obviously deviation can occur.Common capacitance measurement method is not considered the impact of the absorption effect of capacitor, and in fact often the absorption effect impact is larger 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 impact that absorption effect affects is avoided in the interval that arranges 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 arranges, not only solve in the common capacitance measurement method use analog comparator determine charge and discharge threshold value poor stability, not malleable, have the shortcoming such as hysteresis effect, and because the introducing of two new threshold value V3, V4, so that measure the zone that can avoid the absorption effect impact, 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 the 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; Measured capacitance device C after the access of forward constant current source
xOn voltage begin to rise (referring to Fig. 8), deliver to Fast simulation/digital quantizer AD1 measurement after this voltage amplifies through variable gain amplifier and convert digital quantity to; Measure, calculate after the charging beginning voltage change (for example value of obtaining VX1) through (for example 1mS) behind the 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
xThen charging can measure and obtain through the magnitude of voltage (for example VX2) on measured capacitance device when (for example 1mS) behind the interval sometime, according to measured capacitance device C in this time interval again
xThe variation of upper magnitude of voltage size (VX2-VX1) 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 upper 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 discharging electric 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 in time linear the rising, from no-voltage, charging voltage on the measured capacitance device rises through threshold value V1 after amplifying through variable gain amplifier, then arrive threshold value V3 (referring to Fig. 4, Fig. 5), at this moment the output of Fast simulation/digital quantizer AD1 and four thresholding digital comparators result relatively makes the time counter of microprocessor internal begin timing; When charging voltage arrived threshold value V4, the output of Fast simulation/digital quantizer AD1 and four thresholding digital comparators result relatively made the time counter of microprocessor internal stop timing, 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 Fast simulation/digital quantizer AD1 and four thresholding digital comparators result relatively, make microprocessor control variable constant current source export negative sense constant-current discharge electric current identical with former forward constant-current charge size of current, opposite direction, 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, the linear decline of slope that then 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 Fast simulation/digital quantizer AD2 and four thresholding digital comparators result relatively makes the time counter of microprocessor internal begin timing; When sparking voltage arrived threshold value V3, the output of Fast simulation/digital quantizer AD1 and four thresholding digital comparators result relatively made the time counter of microprocessor internal stop timing, 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 to 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 upper decline, when after the sparking voltage on the measured capacitance device amplifies through variable gain amplifier, reaching threshold value V1, the output of Fast simulation/digital quantizer 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 of opposite direction, the measured capacitance device begins positive charge, same because the impact of absorption effect, the relevant zone of one section absorption effect appears in the voltage on the capacitor, then just put linear rising of slope of charging current and the decision of measured capacitance values size according to the forward constant current, begin second and measure circulation.
If necessary, 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 front 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 large electric capacity that surpasses 1mF, the time that reach charge and discharge voltage 500mV variation can become more and more longer.Introduced specially Low Noise Variable Gain Amplifier among the present invention, 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 large electric capacity more than the 1mF, measure delivering to Fast simulation/digital quantizer 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 large 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 the large 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 large electric capacity up to 1F, the speed of its measurement is greatly about about 500mS; Even for the large electric capacity up to 10F, the speed of its measurement is approximately also only about 5S.This has surmounted measurement range and the measuring speed of present other method greatly.
If also will pursue faster speed, for the large electric capacity more than the 1F, can also adopt again the method that changes four thresholding digital comparator threshold values further to improve measuring speed, for example see Fig. 9, four threshold values are adjusted to V1=10mV; V2=110mV; V3=20mV; V4=100mV.Then the Measuring Time of the large 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 slewing rate up to the ∑ of 1 μ S or 10 μ S-Δ converter, 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 large electric capacity of little electric capacity can both accomplish fast, accurate.
In Fig. 1 of the present invention, R0 is sample resistance, and AD2 is analog/digital converter, if necessary, can set up and by this part metering circuit, obtain the more accurately actual numerical value of charging and discharging currents, 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 between the measurement input end of the device that measured capacitance device access consists of by method of the present invention and the signal ground, owing to originally be in open-circuit condition 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; Then back discharge is got back to 50mV through 500mV, 100mV; 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 it is very short to discharge and recharge the time, 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 at display electric capacity is 0.
When the electric capacity 150 through overdischarge, when the measured capacitance device of 000 μ F accesses, at this moment measure voltage between input end and the signal ground close to 0V, enlargement factor is that the output of 1 low noise amplifier is also close to 0V, the AD1 analog/digital converter measures the result close to 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, along with passage of time, the AD1 analog/digital converter is constantly measured, and subtracting each other through the measurement result behind the 1mS and the measurement result before the 1mS, obtain the change in voltage numberical value of quantity on the measured capacitance device.
According to table 1, the measured capacitance device than high capacitance is measured, consider that usually the rate of change of AD1 analog/digital converter output voltage reading is between every millisecond of 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 rusults, change the forward constant current source is charged to measured capacitance with 0.05 larger μ A, and subtracting each other through the measurement result before the measurement result behind the 1mS and the 1mS, can find that voltage variety is still less than 500 μ V; Microprocessor control forward constant current source charges to measured capacitance with 0.5 larger μ A, and subtracting each other through the measurement result behind the 1mS and the measurement result before the 1mS ... until microprocessor control forward constant current source charges to measured capacitance with the 1mA of maximum, and subtracting each other through the measurement result behind the 1mS and the measurement result before the 1mS, find that voltage variety is still much smaller than 500 μ V; At this moment microprocessor is when the 1mA that keeps the forward constant current source with maximum charges to measured capacitance, the enlargement factor of control low noise amplifier A1 is brought up to 10 times by 1 times, and subtracting each other through the measurement result behind the 1mS and the measurement result before the 1mS, find that voltage variety is still much smaller than 500 μ V; Microprocessor is when the 1mA that keeps the forward constant current source with maximum charges to measured capacitance, the enlargement factor of control low noise amplifier A1 is brought up to 100 times by 10 times, subtract each other through the 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 selecting circuit, enters normal measuring state.Tested 150, the repeatedly charge and discharge 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 with existing measurement mechanism, not only large capacitance measurement is had very fast advance, and by absorption effect is eliminated, have higher accuracy.
Claims (9)
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 Fast simulation/digital quantizer, 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 Fast simulation/digital quantizer measurement on the measured capacitance of the amplifier amplification of described variable gain; The measurement result of described Fast simulation/digital quantizer outputs to described four thresholding digital comparators; The output of the described Fast simulation/digital quantizer respectively digital value different from four compares, and described four different digital values are set respectively charging numeric door limit value V1, 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 the interval of measuring measured capacitance and discharge and recharge the time, the impact that capacitance measurement is brought to eliminate the capacitor absorption effect between V1 and V2.
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 Fast simulation/digital quantizer amplifies the amplifier through described variable gain converts digital quantity fast to, deliver to the default thresholding of described four thresholding digital comparators and four and carry out numeral relatively, comparative result is delivered to microprocessor process.
4. capacitance measuring device according to claim 3, it is characterized in that described Fast simulation/digital quantizer is the voltage value on the measured capacitance 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 process; 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 measured capacitance; 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 measured capacitance discharge; 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.
5. capacitance measuring device according to claim 1 is characterized in that described positive and negative constant flow source is subjected to described microprocessor-based control to export the steady current of different size and Orientations.
6. capacitance measuring device 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 electric capacity, 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.
7. capacitance measuring device according to claim 6, it is characterized in that described microprocessor can change four threshold value settings of four thresholding digital comparators, threshold value V1, the V2 of charging and discharging 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 eradicating efficacy.
8. capacitance measuring device according to claim 6, by constant current positive charge and the back discharge to measured capacitance, described microprocessor according to positive charge and back discharge through the time between described four thresholding digital comparators predetermined two threshold value V3, the V4, 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.
9. capacitance measuring device according to claim 6 is characterized in that the amplifier of described variable gain is the scope of the voltage amplification on the electric capacity to suitable Fast simulation/digital quantizer measurement.
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| 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 |
| JP5867652B2 (en) * | 2012-05-30 | 2016-02-24 | 株式会社村田製作所 | Module and capacity detection method |
| CN103439379A (en) * | 2013-08-29 | 2013-12-11 | 复旦大学 | Reading circuit and reading method based on electrochemical sensor |
| US9360511B2 (en) * | 2013-10-21 | 2016-06-07 | Qualcomm Mems Technologies, Inc. | Closed loop dynamic capacitance measurement |
| CN104155529A (en) * | 2014-08-20 | 2014-11-19 | 中北大学 | Transient small capacitance measuring instrument |
| 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 |
| JP7311380B2 (en) * | 2019-10-01 | 2023-07-19 | 株式会社日立産機システム | Power supply capacitor capacitance measurement device and power supply capacitor capacitance measurement 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 |
| CN113391192B (en) * | 2021-06-16 | 2022-08-02 | 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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| US6215319B1 (en) * | 1997-08-01 | 2001-04-10 | Kevin G. Hafer | High accuracy measuring system |
| US6683462B2 (en) * | 2000-11-30 | 2004-01-27 | Agilent Technologies, Inc. | Apparatus for and method of measuring capacitance with high accuracy |
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