JP2015197309A - Electrostatic capacitance measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the configuration of a voltage measurement system and speed up a measurement time in measuring the electrostatic capacitance of a capacitor from a constant-current value I applied to the capacitor, a charge time T, and a differential voltage between an initial voltage and a final voltage at termination of charging.SOLUTION: An electrostatic capacitance measurement device includes a charge detection comparator 15 for comparing the voltage V of a capacitor Cx with a preset charging termination voltage Vd and outputting a charge termination signal when V=Vd, and a timer 11c for counting a charge time. Charge is begun with a constant current I after the capacitor Cx is discharged, and the charge is completed at a time when a charge termination signal is outputted from the charge detection comparator 15. A charge time T during this period is acquired by the timer 11c, and the electrostatic capacitance of the capacitor Cx is calculated by I×T/Vd. The above procedure being basic, determination is made in the middle of charge as to whether the charge current is appropriate or not, a measurement range is changed as necessary on the basis of the determination result, and capacitance measurement is performed again.

Description

  The present invention relates to a capacitance measuring device that measures the capacitance of a capacitor, which is an element to be measured, and more specifically, a capacitor is charged with a constant current for a predetermined time, its constant current value, charging time, The present invention relates to a capacitance measuring device that measures the capacitance of a capacitor from the difference voltage between the initial voltage of the capacitor and the final voltage at the end of charging.

When a capacitor (capacitor) is charged with a constant current, the voltage rises linearly over time. Therefore, if the charging current (constant current) is I, the charging time is T, the initial voltage at the start of charging is Vinit, and the final voltage at the end of charging is Vfinal, the capacitance C of the capacitor is
C = I × T / (Vfinal−Vinit)
(See Patent Document 1). Usually, since charging is performed after discharging the capacitor, the initial voltage Vinit is 0V.

  As one of capacitance measuring apparatuses using this measurement principle, Patent Document 2 discloses a charge circuit including a constant current source that can be connected to a capacitor in order to generate a linearly increasing voltage ramp waveform, A measuring means for measuring a potential difference ΔV and a time difference Δt between two points of the first point and the second point along the voltage ramp waveform, and a controller for discharging the capacitor, and charging current (constant current) to the capacitor A capacitance measurement system is described in which the capacitance C of a capacitor is obtained from C, I = Δt / ΔV from I, potential difference ΔV and time difference Δt.

JP 2002-277495 A US Pat. No. 6,275,047 (Claim 6)

  According to the invention described in Patent Document 2, it is not always necessary to set the initial voltage of the capacitor to 0 V at the time of completion of discharge when measuring the capacitance, and the voltage ramp waveform of the capacitor that increases linearly by constant current charging is not necessarily required. What is necessary is just to look at a stable potential difference ΔV between two predetermined points and a time difference Δt.

  However, as long as the above measurement principle is used, a voltage measuring means for measuring the potential difference ΔV is required. In the inventions described in Patent Documents 1 and 2, a combination of an A / D converter such as a multi-integration type and a microprocessor is used as the voltage measuring means, which is considerably expensive.

  Further, since it is not determined whether or not the charging current is appropriate for the capacitance of the capacitor to be measured (range switching during charging, determination of starting discharge, etc.), the measurement time is increased as a result.

  Accordingly, an object of the present invention is to charge a capacitor with a constant current for a predetermined time, and calculate the electrostatic capacity of the capacitor from the constant current value, the charging time, and the difference voltage between the initial voltage of the capacitor and the final voltage at the end of charging. Capacitance that simplifies the configuration of the voltage measurement system for capacitor voltage and reduces costs while measuring the capacity, and at the same time switching the range and determining the start of discharge as needed during charging to increase the speed. It is to provide a measuring device.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a charging means comprising a constant current source for charging a capacitor as a device under test with a constant current, a discharging means for discharging the capacitor, and a terminal of the capacitor A voltage measuring means for measuring the instantaneous voltage V, a control means for controlling charging / discharging of the capacitor, and a timer means for measuring a charging time and a discharging time, and a display unit. Is charged with a constant current I, the capacitance waveform C of the capacitor is obtained on the display unit based on the fact that the ramp waveform of the instantaneous voltage V between the terminals of the capacitor changes linearly over time. In the capacitance measuring device to display,
The control means or the voltage measuring means discharges the capacitor to a predetermined voltage range, and then sets a predetermined unit time Δt as one section, and a plurality of n sections (n is a positive integer representing an order including 0). The capacitor is continuously charged by the constant current source, and the instants between the terminals of a predetermined number of the capacitors additionally sampled at predetermined time intervals in each of the plurality of n intervals. The voltage V is obtained, and the difference voltage of the section average voltage VAn and / or the capacitance C of the capacitor is obtained by setting the first section average voltage (n = 0 section) as VA0 and the section average voltage in the n section as VAn. And at least selected from each value of the instantaneous voltage V between the terminals of the capacitor, the section average voltage VAn, the difference voltage of the section average voltage VAn, and the capacitance C of the capacitor. When one of the values is outside a predetermined range, the capacitor is discharged to substantially 0 V, and then the constant current value I of the constant current source is changed to continuously charge the capacitor. The capacitance C of the capacitor is obtained.

According to a second aspect of the present invention, in the first aspect, the control unit or the voltage measuring unit is responsive to a value I of the constant current generated by the constant current source and a measured capacitance range of the capacitor. When a plurality of measurement ranges are set in advance and a predetermined charge termination voltage Vd set for each of the plurality of measurement ranges is compared with the instantaneous voltage V between the terminals of the capacitor, and V = Vd is exceeded It has a charge detection comparator that outputs a charge termination signal,
The control means or the voltage measuring means waits for a predetermined stabilization time for the discharge state to stabilize after discharging between the terminals of the capacitor to a predetermined voltage range, Charging is started at the time when the charging is started at the constant current value I of the set measurement range, and then the charging detection comparator outputs the charging termination signal, and the charging time from the charging start to the charging termination. T is obtained by the timer means, and the capacitance C of the capacitor is expressed by the following equation (1),
C = I × T / Vd (1)
Calculated on the display unit.

  The invention according to claim 3 is characterized in that, in claim 2, the control means or the voltage measuring means has a range switching function for increasing or decreasing the range of the measurement.

  According to a fourth aspect of the present invention, in the third aspect, the control unit or the voltage measuring unit may reduce the charging current when the calculated capacitance C is less than a range lower limit capacity. Processing is performed, and charging of the capacitor is started again.

  According to a fifth aspect of the present invention, in the third aspect, the control means or the voltage measuring means may increase the charging current when the calculated capacitance C exceeds a range upper limit capacity. Processing is performed, and charging of the capacitor is started again.

  According to a sixth aspect of the present invention, in the third aspect, the control unit or the voltage measuring unit is configured such that the charge detection comparator does not output the charge termination signal even if a predetermined timeout time Tout has elapsed. In this case, the charging by the charging unit is stopped, the capacitor is discharged to substantially 0 V by the discharging unit, the range-up process for increasing the charging current is performed, and charging of the capacitor is started again. It is characterized by that.

A seventh aspect of the present invention is the control device according to the sixth aspect, wherein the control unit or the voltage measuring unit is configured such that the timeout time Tout, the maximum range capacity Cmax, the constant current I, the charge end voltage Vd, and a predetermined margin. Where M is the following equation (2),
Tout = M × Vd × Cmax / I (2)
Or the time-out time Tout obtained by the equation (2) is preset in the control means or the voltage measuring means.

  According to an eighth aspect of the present invention, in any one of the third to seventh aspects, a predetermined determination reference value X for the instantaneous voltage V between the terminals of the capacitor is set in the control unit or the voltage measuring unit. The control means or the voltage measuring means compares the instantaneous voltage V between the terminals of the capacitor and the determination reference value X during the charging period of the capacitor, and the instantaneous voltage V between the terminals of the capacitor is When the determination reference value X is exceeded, the charging by the charging means is stopped at that time, the capacitor is discharged to a predetermined voltage range by the discharging means, a range up process or a range down process is performed, and again, It is characterized by starting charging the capacitor.

  According to a ninth aspect of the present invention, in the eighth aspect, a measurement range upper limit voltage VU is set in the control unit or the voltage measurement unit, and the control unit or the voltage measurement unit is connected to a terminal of the capacitor. When the instantaneous voltage V exceeds the measurement range upper limit voltage VU, that is, when the charging voltage increases, if V> VU, charging by the charging means is stopped at that time, and the capacitor is connected by the discharging means. It discharges to a predetermined voltage range, performs the range down process, and starts charging the capacitor again.

  According to a tenth aspect of the present invention, in the eighth aspect, a measurement range upper limit voltage VU is set in the control means or the voltage measurement means, and the control means or the voltage measurement means is set for each of the sections. Further, a section average voltage VAn is obtained from the instantaneous voltage V between terminals of the predetermined number of capacitors sampled by the voltage measuring means, and when the section average voltage VAn exceeds the measurement range upper limit voltage VU, that is, the charging voltage is When VAn> VU, the charging by the charging unit is stopped at that time, the capacitor is discharged to a predetermined voltage range by the discharging unit, the range down process is performed, and the capacitor is again It is characterized by starting charging.

  According to an eleventh aspect of the present invention, in the tenth aspect, the control unit or the voltage measuring unit uses a range down specified voltage Vdown determined by a minimum capacity of each of the measurement ranges and a predetermined constant, and the nth section When the voltage difference between the adjacent two sections average voltage VAn is VD and the voltage difference VD exceeds the range-down specified voltage Vdown, that is, when the charging voltage rises, and VD> Vdown, at that time Charging by the charging unit is stopped, the capacitor is discharged to a predetermined voltage range by the discharging unit, the range down process is performed, and charging of the capacitor is started again.

  According to a twelfth aspect of the present invention, in the eleventh aspect, the control unit or the voltage measuring unit calculates a voltage difference between a section average voltage between the section average voltage VAn and the first section average voltage VA0 as VD (n). And when the voltage difference VD (n) exceeds the value Vdown (n) n times the range-down specified voltage Vdown, the value n times the range-down specified voltage Vdown is Vdown (n). Then, charging by the charging means is stopped, the capacitor is discharged to a predetermined voltage range by the discharging means, the range down processing is performed, and charging of the capacitor is started again.

A thirteenth aspect of the present invention is the control device according to the eleventh or twelfth aspect, wherein the control means or the voltage measuring means is configured to use the range down specified voltage Vdown, the minimum capacity of the measurement range as Cmin, the constant current as I, and the unit of the interval. The following equation (3), where time is Δt and the predetermined margin is J,
Vdown = J × I × Δt / Cmin (3)
Or the range-down prescribed voltage Vdown obtained by the equation (3) is preset in the control means or the voltage measuring means.

  A fourteenth aspect of the present invention is the method according to the tenth aspect, wherein the control unit or the voltage measurement unit uses a range-up specified voltage Vup obtained by a maximum capacity of each of the measurement ranges and a predetermined constant, and When the voltage difference between the adjacent average voltage VAn of two adjacent sections is VD and the range-up specified voltage Vup exceeds the voltage difference VD, that is, when the charging voltage rises, when VD <Vup, Charging by the charging means is stopped, the capacitor is discharged to a predetermined voltage range by the discharging means, the range-up process is performed, and charging of the capacitor is started again.

  According to a fifteenth aspect of the present invention, in the fourteenth aspect, the control unit or the voltage measuring unit calculates a voltage difference between a section average voltage between the section average voltage VAn and the first section average voltage VA0 as VD (n). When the value Vup (n) n times the range-up specified voltage Vup exceeds the voltage difference VD (n), that is, when the charging voltage rises, when VD (n) <Vup (n) The charging by the charging means is stopped at that time, the capacitor is discharged to a predetermined voltage range by the discharging means, the range up process is performed, and charging of the capacitor is started again. Yes.

A sixteenth aspect of the present invention is the control device according to the fourteenth or fifteenth aspect, wherein the control means or the voltage measuring means is configured to use the range-up specified voltage Vup, the maximum capacity of the measurement range Cmax, the constant current I, and the unit of the section. The following equation (4), where Δt is the time and L is the predetermined margin,
Vup = L × I × Δt / Cmax (4)
Or the above-mentioned range-up specified voltage Vup obtained by the equation (4) is preset in the control means or the voltage measuring means.

  According to a seventeenth aspect of the present invention, in any one of the first to sixteenth aspects, the control unit or the voltage measuring unit corrects the constant current value I by a current correction formula I = d × I. The sampled average voltage VAn or the inter-terminal instantaneous voltage V is corrected by the voltage correction formula V = e × V + f, and the capacitance C of the capacitor is corrected by the capacitance correction formula C = g × C + h. Parameters d, e, f, g, and h are set, and when determining whether the measurement range is within a predetermined range, or when calculating the capacitance of the capacitor, the current correction formula or The correction calculation by the voltage correction formula or the capacitance correction formula is performed once or more.

  According to an eighteenth aspect of the present invention, in the seventeenth aspect, the control unit or the voltage measuring unit includes the presence / absence of the correction calculation by the current correction formula, the voltage correction formula, or the capacitance correction formula, and the number of times of the calculation. The correction parameters d, e, f, g, and h can be input / output to / from predetermined keys and a display unit or an external device.

According to a nineteenth aspect of the present invention, there is provided a charging means comprising a constant current source for charging a capacitor as a device under test with a constant current, a discharging means for discharging the capacitor, and a voltage for measuring an instantaneous voltage V between terminals of the capacitor. When charging the capacitor with a constant current I by the charging means, including a measuring means, a control means for controlling charging / discharging of the capacitor and a timer means for measuring the charging time and discharging time, and a display unit In addition, in the capacitance measuring device for obtaining the capacitance C of the capacitor and displaying it on the display unit based on the fact that the ramp waveform of the instantaneous voltage V between the terminals of the capacitor changes linearly with time. ,
If the control means or the voltage measurement means does not obtain the capacitance C of the capacitor, the control means or the voltage measurement means discharges until the instantaneous voltage V between the terminals of the capacitor can be regarded as 0 V, and obtains the capacitance C of the capacitor. In this case, after discharging to a predetermined voltage range determined alternately every discharge, the capacitor is charged in the positive direction or the negative direction by the constant current source charged with the constant current. The capacitor is continuously charged by the constant current source over a plurality of n intervals (n is a positive integer representing an order including 0), with a constant unit time Δt as one interval. For each section of the plurality of n sections, the section average voltage VAn is acquired from the instantaneous voltage V between the terminals of a predetermined number of the capacitors additionally sampled at a predetermined time interval within the section, The initial (n = 0 interval) interval average voltage is VA0, the interval average voltage of the n interval is VAn, the capacitance C of the capacitor or the difference voltage of the interval average voltage VAn is obtained, and the inter-terminal instantaneous of the capacitor is obtained. When at least one value selected from the values of the voltage V, the difference voltage of the section average voltage VAn, and the capacitance C of the capacitor is a value outside a predetermined range, the capacitor is discharged to substantially 0V. After that, the constant current value I of the constant current source is changed, and the capacitor is continuously charged to obtain the capacitance C of the capacitor.

  According to a twentieth aspect of the present invention, in the nineteenth aspect, the control unit or the voltage measuring unit is responsive to a value I of the constant current generated by the constant current source and a measured capacitance range of the capacitor. A plurality of measurement ranges are set in advance, and when the control means or the voltage measurement means performs the range down of the measurement range or the range up of the measurement range, When the range down or the range up of the measurement range is repeated alternately, the capacitance C of the capacitor is obtained based on the fact that the instantaneous voltage V between the terminals of the capacitor changes linearly with time. On the other hand, the range of the measurement range and the range of the measurement range are not repeated alternately every time the charging is performed. The case is characterized by carrying out the range up range down or the measurement range of the measurement range.

  According to the present invention, when the capacitor is charged with the constant current I, the instantaneous voltage V between the terminals of the capacitor is monitored by the charge detection comparator, and the instantaneous voltage V between the terminals of the capacitor is set in the charge detection comparator. The charging is terminated when the charge termination voltage Vd is exceeded, and the charging time T from the start of charging to the end of charging may be measured by a timer, whereby the capacitance C of the capacitor is calculated as I × T / Vd Therefore, it is not necessary to use an expensive voltage measuring means constituted by an A / D converter, a microprocessor or the like, and a low-cost capacitance measuring device can be provided.

  Also, the determination reference value (measurement range upper limit voltage VU, range down specified voltage Vdown, range up specified voltage Vup) is set, and the capacitor instantaneous voltage V and the determination reference value X are compared during the charging period of the capacitor. Then, it is determined whether or not to continue charging the capacitor, and at the time of determination, charging by the charging means is stopped, and the capacitor is discharged to a preset discharge regulation voltage Vz by the discharging means. By performing the range-up process or the range-down process and starting charging the capacitor again, the optimum current can be obtained without waiting until the charging time T when the capacitor voltage V reaches the charge termination voltage Vd. As a result, the measurement time can be shortened.

The schematic diagram which shows the structure of the electrostatic capacitance measuring apparatus which concerns on 1st Embodiment of this invention. The graph which shows an example of the capacitor voltage waveform charged / discharged in the said 1st Embodiment. The flowchart which shows an example of operation | movement of the said 1st Embodiment. The schematic diagram which shows the structure of the electrostatic capacitance measuring apparatus which concerns on 2nd Embodiment of this invention. The graph which shows an example of the capacitor voltage waveform divided into the sections by the said 2nd Embodiment. The flowchart which shows an example of operation | movement of the said 2nd Embodiment. (A) (b) A flowchart showing an interrupt routine executed in the second embodiment.

  Next, the first and second embodiments of the present invention will be described with reference to FIGS. 1 to 7, but the present invention is not limited thereto.

  First, as shown in FIG. 1, a capacitance measuring apparatus 10A according to the first embodiment includes, as a basic configuration, a control unit 11, a constant current source 12 that is a charging unit, a discharging unit 13, A discharge detection comparator 14 and a charge detection comparator 15 are provided.

  The constant current source 12 and the discharge means 13 are connected in parallel to the Hi side terminal of the capacitor Cx as the element to be measured via the switch SW. The Lo side terminal of the capacitor Cx is grounded. Unlike this, the Hi side terminal may be grounded to the ground of the measurement circuit, and the Lo side terminal may be connected to the measurement circuit, or the Hi side terminal and the Lo side terminal may be connected to the measurement circuit. .

  The constant current source 12 includes a plurality of constant current source circuits or variable output type constant current source circuits having different output currents, and supplies a constant current I having a predetermined current value to the capacitor Cx during charging. The discharging means 13 includes a constant current sink circuit that discharges the charge accumulated in the capacitor Cx at a constant current, preferably at a constant current. The constant current source 12 and the discharging means 13 may include means for stopping charging and discharging when a predetermined voltage set in advance is reached.

  The discharge detection comparator 14 is connected to the Hi-side terminal of the capacitor Cx, monitors the instantaneous voltage V between the terminals of the capacitor Cx when discharging, and the instantaneous voltage V between the terminals of the capacitor is set in advance. When the predetermined discharge regulation voltage Vz is reached, a discharge end signal is output to the control means 11 and the discharge means 13. In this embodiment, the discharge regulation voltage Vz is set to 0V.

  The charge detection comparator 15 is connected to the Hi side terminal of the capacitor Cx, and monitors the instantaneous voltage V between the terminals of the capacitor when the capacitor Cx is charged. The charge detection comparator 15 is set with a predetermined charge termination voltage Vd. The charge detection comparator 15 is configured such that when the instantaneous voltage V between the terminals of the capacitor exceeds the charge termination voltage Vd during charging, A charge termination signal is output to the control means 11.

  The charge detection comparator 15 may be either an analog comparator or a digital comparator. In the case of a digital comparator, the charge termination voltage Vd is set as a voltage value.

  The control means 11 is set with a plurality of measurement ranges according to the amount of constant current that can be output from the constant current source 12 that is the charging means and the measurement capacity range of the capacitor Cx. A CPU (central processing unit), a microcomputer, or the like is used as the control means 11, and a memory 11a, a display unit 11b, a timer 11c, and the like are connected to the control means 11.

  The memory 11a includes a ROM in which an operation program of the control means 11 is written and a work RAM. The display unit 11b displays a voltage waveform of the capacitor Cx, measurement conditions, and the like using a liquid crystal display panel or the like. The timer 11c measures the charging time from the start of charging of the capacitor Cx to the end of charging, but may also be used for other time counting.

  Next, the operation of the control means 11 for measuring the capacitance C of the capacitor Cx in the first embodiment will be described with reference to the graph of FIG. 2 and the flowchart of FIG.

  First, in step ST101, as an initial setting, the range of the constant current source 12 is set to the minimum range (the range in which the current value applied to the capacitor Cx is the smallest). In addition, the discharge regulation voltage Vz is set to 0 V in the discharge detection comparator 14, and a predetermined charge termination voltage Vd for terminating the charge is set in the charge detection comparator 15.

  Then, the constant current source 12 is turned off, the discharging means 13 is turned on, the switch SW is turned on to start discharging, and the capacitor Cx is discharged with a constant current (preferably an allowable maximum current) by the discharging means 13, and the process goes to step ST102. The process waits until the capacitor voltage V reaches 0 V, which is the specified discharge voltage Vz.

  In addition, when the discharge is started from the state where the instantaneous voltage V between the terminals of the capacitor is equal to or higher than the end-of-charge voltage Vd, the instantaneous voltage V between the terminals of the capacitor Cx decreases with the discharge, and the instantaneous voltage V between the terminals of the capacitor Cx is substantially reduced. When the discharge specified voltage Vz is reached, the charge detection comparator 15 outputs the charge end signal as ON, but the control means 11 ignores the charge end signal during discharge.

  When the discharge is terminated and V = Vz (= 0 V), the output of the discharge detection detector 14 is turned on, and a discharge termination signal is output to the control means 11 and the discharge means 14, but in step ST103, It waits for s0 time (stabilization time) as the time until the voltage waveform of the capacitor Cx, the discharge current, and the discharge end signal are stabilized. The s0 time may be about 1 ms to 200 ms.

  As shown in FIG. 2, a predetermined margin voltage α (for example, about 15 mV) is added to the discharge regulation voltage Vz to obtain Vz + α, and the capacitor voltage V drops to Vz + α (in this example, Vz = 0V). The discharge end signal may be output from the discharge detection detector 14 at a time when the discharge end detector 14 substantially decreases to α.

  After the stabilization time of s0 has elapsed, the control means 11 turns off the discharge means 13, turns on the constant current source 12, starts the timer 11c, and starts charging in step ST104, and charges the capacitor Cx with the constant current I. . Thereby, as shown in FIG. 2, the instantaneous voltage V between terminals of the capacitor rises linearly as a linear voltage ramp waveform.

  Simultaneously with the start of charging, the discharge detection detector 14 becomes inactive, and the discharge end signal changes from ON to OFF. Simultaneously with the start of charging, the control unit 11 obtains the count value at the start of charging from the timer 11c and stores it in the memory 11a as the charging start time ts.

  After starting charging, the control means 11 determines whether or not the instantaneous voltage V between terminals of the capacitor has reached the charging end voltage Vd in step ST105. When the instantaneous voltage V between the terminals of the capacitor becomes the substantial charge termination voltage Vd, the output of the charge detection comparator 15 is turned on, and a charge termination signal is output to the control means 11.

  Thereby, in step ST106, the control means 11 obtains the count value at the end of charging from the timer 11c, stores it in the memory 11a as the charging end time te, and turns off the constant current source 12 to end the charging.

In the following step ST107, the control means 11 turns on the discharge means 13 to start discharging, calculates the charging time T from the charging start time ts and the charging end time te stored in the memory 11c, and determines the electrostatic capacity of the capacitor Cx. The capacity C is expressed by the following formula (1),
C = I × T / Vd (1)
Calculated by

  Then, in step ST108, the control means 11 determines whether or not the capacitance C is equal to or greater than the range lower limit capacity. If the capacitance C is equal to or greater than the range lower limit capacity, the process proceeds to step ST109. It is determined whether the electrostatic capacity C is equal to or lower than the range upper limit capacity.

  If the determination result in step ST109 is YES and the capacitance C is less than or equal to the range upper limit capacity, the control means 11 calculates the capacitance calculated by the expression (1) in step ST110 on the display unit 11b in step ST107. C is displayed, and in step ST111, it is determined whether or not the measurement is completed.

  If the measurement is completed, in step ST112, the completion process is performed after the discharge started in step ST107 is completed. If the measurement is not completed, the process returns to step ST102, and the capacitance is measured again for the same capacitor Cx.

  In the determination at step ST108, if the capacitance C is less than the range lower limit capacity and the determination is NO outside the range, the process proceeds to step ST108a, and the display unit 11b displays that it is out of the measurement range. After performing the range-down process so that the charging current (constant current) decreases, the process returns to step ST102, and the capacitance is measured again for the same capacitor Cx.

  When performing this range down process, if the capacitance C is 1/10 or less of the lower limit of the range capacity, the two ranges may be lowered simultaneously.

  Further, in the determination in step ST109, when the capacitance C exceeds the range upper limit capacity and the determination is NO outside the range, the process proceeds to step ST109a and the display unit 11b displays that the measurement is out of the measurement range. Then, after performing the range-up process so that the charging current (constant current) increases, the process returns to step ST102, and the capacitance measurement is performed again for the same capacitor Cx.

  In step ST105, when the instantaneous voltage V between the terminals of the capacitor Cx substantially reaches the charge termination voltage Vd (V = Vd, determination result YES), the output of the charge detection comparator 15 is turned on and the control is performed. An end-of-charge signal is output to the means 11, and it is preferable that the end-of-charge signal is output after a predetermined β time delay from the time when V = Vd.

  By setting such an output delay β time, for example, when the capacitor Cx has a small capacity and the time from the start of charging to the end of charging is extremely short, the control means 11 can be given a time margin for processing. . When such a delay β time is set, β time may be subtracted from the charging time T obtained from the charging start time ts and the charging end time te.

  Although not shown in the flowchart of FIG. 3, when a predetermined timeout time Tout is set as an initial setting and the charge detection comparator 15 does not output a charge termination signal even after the timeout time Tout has elapsed, After stopping the charging by the charging unit 12 and discharging the capacitor Cx to substantially the discharge specified voltage Vz by the discharging unit 13, a range-up process for increasing the charging current (constant current I) can be performed.

In this case, the timeout time Tout is expressed by the following formula (2), where Cmax is the maximum capacity of the range, I is the constant current, Vd is the charge termination voltage, and M is a predetermined margin (about 1.2).
Tout = M × Vd × Cmax / I (2)
It can ask for.

  According to the first embodiment, an inexpensive comparator is used in the voltage measurement (detection) system of the capacitor voltage in place of the expensive voltage measurement means configured by an A / D converter, a microprocessor, or the like. Thus, a low-cost electrostatic capacity measuring device can be provided.

  Next, with reference to FIG. 4 thru | or FIG. 7, the electrostatic capacitance measuring apparatus 10B which concerns on 2nd Embodiment of this invention is demonstrated. In this capacitance measuring apparatus 10B, the range up or the range down process is appropriately performed even during the charging period of the capacitor Cx without waiting for the charging time T when the instantaneous voltage V between the terminals of the capacitor reaches the charging termination voltage Vz. Is possible.

  In order to execute range up or range down processing during the charging period, this capacitance measuring device 10B includes the configuration provided in the capacitance measuring device 10A according to the first embodiment of FIG. Voltage measuring means 16 for measuring the instantaneous voltage V between terminals of the capacitor Cx is further provided.

  In the second embodiment, the voltage measuring means 16 includes an amplifier 16a, an A / D converter 16b, and a DSP (digital signal processor) 16c. The voltage measuring means 16 amplifies the inter-terminal instantaneous voltage V of the capacitor Cx to a predetermined value by the amplifier 16a (in this example, an amplification factor of 1), converts it to a digital value by the A / D converter 16b, and then inputs it to the DSP 16c. .

  In the second embodiment, the DSP 16c samples the instantaneous voltage V between terminals of the capacitor Cx at a sampling interval of 1 ms, and when 100 ms has elapsed with 100 ms as one section, the instantaneous voltage between terminals of 100 capacitors Cx. A section average voltage VAn (= ΣV / 100) is calculated from V, and the section average voltage VAn and, if necessary, the inter-terminal instantaneous voltage V of each capacitor Cx as the calculation basis are output to the control means 11. To do.

  The sampling interval and the unit time of one section may be arbitrarily set. For example, the unit time of one section is set to 100 ms as described above, while the sampling interval of the instantaneous voltage V between terminals of the capacitor Cx is set to 100 μs. The instantaneous voltage V between the terminals of 1000 capacitors Cx may be sampled within one section.

  In this embodiment, the sampling ADC is used for the A / D converter 16b. However, as another embodiment, for example, a double integration type AD converter in which the A / D converter itself outputs an average value is used. You can also. Further, the section average voltage VAn may be calculated on the control means 11 side. In such a case, the DSP 16c can be omitted.

  Next, the operation of the control means 11 in the second embodiment will be specifically described with reference to the instantaneous voltage waveform between terminals of the capacitor Cx with the horizontal axis in FIG. 5 as time and the vertical axis as voltage, and the flowcharts in FIGS. explain.

  First, in step ST201, as in step ST101 in the first embodiment, the control unit 11 sets the range of the constant current source 12 to the minimum range (the range where the current value applied to the capacitor Cx is the smallest) as an initial setting. ). In addition, the discharge regulation voltage Vz is set to 0 V in the discharge detection comparator 14, and a predetermined charge termination voltage Vd for the charge detection comparator 15 to detect the termination of charging is set.

  Then, the constant current source 12 is turned off, the discharge means 13 is turned on, the switch SW is turned on to start the discharge, and the capacitor Cx is discharged by the discharge means 13 at a constant current (preferably the maximum allowable current). In ST202, the process waits until the instantaneous voltage V between terminals of the capacitor Cx becomes substantially 0V of the discharge regulation voltage Vz.

  When the discharge is completed and the instantaneous voltage V between the terminals of the capacitor Cx substantially reaches the specified discharge voltage Vz, the output of the discharge detection detector 14 is turned on, and a discharge end signal is sent to the control means 11 and the discharge means 13. As in step ST103 in the first embodiment, the time until the instantaneous voltage waveform between the terminals of the capacitor Cx, the discharge current, and the discharge termination signal is stabilized in step ST203 is s0 time (stabilization time). )wait. The s0 time may be about 1 ms to 200 ms.

  When the voltage measuring means 16 is in a free-running state and outputs the section average voltage VAn at a constant time interval (100 ms in this example), the control means 11 indicates that the voltage measuring means 16 is within the s0 time. The section average voltage VAn to be output is discarded. Similarly, when the voltage measuring means 16 is not free-running, the section average voltage VAn output from the voltage measuring means 16 within s0 time is discarded.

  In step ST204, immediately after elapse of s0 time, the control means 11 sets a variable n representing a time-series order of a fixed unit time (charging period) Δt to 0 (n = 0), and clears the timer acquisition flag. At the same time, the timer 11c is started, and charging of the capacitor Cx from the constant current source 12 is started.

  At this time, the control means 11 executes the charge interruption routine shown in FIG. 7A, obtains the count value at the start of charge from the timer 11c, and stores it in the memory 11a as the charge start time (time) ts. .

  Simultaneously with the start of charging in step ST204, in step ST205, the time until the instantaneous voltage waveform between terminals of the capacitor Cx, the charging current and the waveform of the voltage measuring means 16 are stabilized is s1 time (second stabilization time). wait.

  The s1 time (waiting time) as the second stabilization time is a transmission delay time margin (about 0.0 ms to 10 ms) of the command signal transmitted from the control unit 11 and the measurement value signal output from the voltage measuring unit 16. In consideration of the elapsed time from the reception of the previous measurement value output signal, etc., it is set to about 0.1 ms to 100 ms.

  When the voltage measuring unit 16 is in a free-running state and outputs the section average voltage VAn at a constant time interval (100 ms in this example), the control unit 11 determines that the voltage measuring unit 16 is within the s1 time. The section average voltage VAn to be output is discarded. Similarly, when the voltage measuring means 16 is not free-running, the section average voltage VAn output from the voltage measuring means 16 within s1 time is discarded.

  In step ST206, immediately after the s1 time has elapsed, the control means 11 starts obtaining the section average voltage VAn of the instantaneous voltage V between terminals of the capacitor Cx from the DSP 16c at the end of the section for every fixed unit section Δt.

  As described above, in this embodiment, the constant unit interval Δt is 100 ms, and during that time, the instantaneous voltage V between the terminals of the capacitor Cx rises linearly.

  Assuming that the sampling interval of the instantaneous voltage V between the terminals of the capacitor Cx is 1 ms, the voltage measuring and measuring means 16 sums up the total instantaneous voltage (100 pieces of the inter-terminal instantaneous voltage V of the capacitor Cx sampled during 100 ms of the constant unit interval Δt. A value obtained by dividing the sum (ΣV) by the number of samplings (100), preferably a value obtained by multiplying the voltage value by a unit conversion coefficient is output to the control means 11 as the section average voltage VAn. At this time, if necessary, the sampled instantaneous voltage V between terminals of each capacitor Cx is output to the control means 11.

  Assuming that the sampling data number of the inter-terminal instantaneous voltage V of the capacitor Cx starts from 0, the “0 to 99” th in the first section, the “100 to 199” th in the next section, and the next In the section, the voltage measuring means 16 has 100 pieces in each section so that the first data or the last data in the section does not overlap with the adjacent section in the “200 to 299” th, and so on. Sampling data exists.

  Also in the second embodiment, the control unit 11 is preset with the predetermined timeout time Tout described in the first embodiment, and the control unit 11 performs the timeout in step ST207 following the step ST206. It is determined whether or not it is within time Tout.

  In the determination at step ST207, when the time-out time Tout elapses before the instantaneous voltage V between the terminals of the capacitor CX reaches the charge termination voltage Vd and the determination is NO, the process proceeds to step ST207a and charging by the charging means 12 is performed. Is stopped, the capacitor Cx is discharged by the discharging means 13, and the range-up process for increasing the charging current is performed, and it is displayed on the display unit 11b that it is out of the measurement range, and the process returns to step ST202.

  On the other hand, in the determination in step ST207, in the case of YES determination that the timeout time Tout has not elapsed, the control means 11 confirms whether or not there is a new section average voltage VAn in the next step ST208. To do. In the case of NO determination in which there is no new section average voltage VAn, it is determined in step ST216 whether or not the instantaneous voltage V between terminals of the capacitor Cx has reached the charge end voltage Vd and the charge end time has been acquired. In the case of NO determination that the charge end time has not been acquired, the process returns to step ST207, and if the charge end time has been acquired (YES), the process proceeds to step ST217.

  In the determination in step ST208, if the new section average voltage VAn is YES, the process proceeds to step ST209, and the control means 11 acquires the section average voltage VAn from the DSP 16c. At this time, if necessary, the inter-terminal instantaneous voltage V of each capacitor Cx sampled within a certain unit interval Δt is also acquired.

  Since n = 0 this time, the section average voltage VAn acquired by the control unit 11 from the DSP 16c is the section average voltage VA0 in the first section Δt0. The control means 11 stores the section average voltage VA0 of the first section Δt0 in the memory 11a.

  In the following step ST210, the control means 11 determines that the section average voltage VAn (in this case VA0) or the instantaneous voltage V between terminals of the capacitor Cx is equal to or lower than the preset measurement range upper limit voltage VU (for example, 1 V) (the charge voltage increases). In this case, it is determined whether or not VAn ≦ VU or V ≦ VU.

  In the determination of step ST210, the section average voltage VAn (VA0) or the instantaneous voltage V between terminals of the capacitor Cx exceeds the measurement range upper limit voltage VU (when the charging voltage increases, VAn> VU or V> VU) NO If so, the control means 11 moves to step ST210a, stops the charging by the charging means 12, discharges the capacitor Cx by the discharging means 13, performs the range down process so that the charging current is reduced, and displays The fact that it is outside the measurement range is displayed on the part 11b, and the process returns to step ST202.

  On the other hand, in the determination of step ST210, the section average voltage VAn (VA0) or the instantaneous voltage V between terminals of the capacitor Cx is less than or equal to the measurement range upper limit voltage VU (when the charging voltage increases, VAn ≦ VU or V ≦ If VU) YES, the control means 11 performs the next step ST211 and determines whether n> 0. In this case, since n = 0 is set in the previous step ST204 and n ≦ 0, the process proceeds to step ST215.

  In step ST215, the control means 11 sets n = n + 1, increments the variable n by 1, returns to step ST207, and when the time-out time Tout has not elapsed and is YES, proceeds to step ST209, where n = The section average voltage VA1 in one section Δt1 is acquired and stored in the memory 11a. At this time, if necessary, the inter-terminal instantaneous voltage V of the capacitor Cx is also acquired and stored in the memory 11a.

  In step ST210, for each section time after section Δt1 of n = 1, it is determined whether the section average voltage VAn or the inter-terminal instantaneous voltage V of the capacitor Cx is equal to or lower than the measurement range upper limit voltage VU. If V ≦ VU, it is determined in the next step ST211 whether n> 0, but since n = 1 and n> 0, the process proceeds to the next step ST212.

  In step ST212, the control means 11 determines that the voltage difference VD (n) between the section average voltage VAn of the n (n ≧ 1) section and the section average voltage VA0 of the first section is the first range allowable voltage difference. Whether or not the value is equal to or smaller than a value Vdown (n) of n times the range-down specified voltage Vdown (n is the same value as the variable n in the n-th section), or two adjacent sections in the n-th section Whether or not the voltage difference VD of the average voltage VAn (= VAn−VAn−1: VA1−VA0 in this case) is equal to or lower than the range-down specified voltage Vdown is selected and executed. This selection is performed according to the up / down sensitivity of the measurement range, the noise voltage, etc. in each measurement range.

In this embodiment, the range down specified voltage Vdown is expressed by the following equation (3), where Cmin is the minimum capacity of the measurement range, I is a constant current, Δt is a constant unit time, and J (about 1.1) is a predetermined margin. ,
Vdown = J × I × Δt / Cmin (3)
It is obtained by. Note that Vdown (n), which is a value that is an integral multiple of the range-down specified voltage, is obtained by Vdown × n, where n is a variable in the nth section.

  In step ST212, the voltage difference VD (n) between the section average voltage VAn in the n (n ≧ 1) section and the section average voltage VA0 in the first first section exceeds Vdown (n) (charging voltage) VD (n)> Vdown (n)), or the voltage difference VD of the section average voltage VAn in the two adjacent sections of the n section exceeds Vdown (in the case where the charging voltage increases, If VD> Vdown) and NO, the control means 11 moves to step ST210a, stops charging by the charging means 12, discharges the capacitor Cx by the discharging means 13, and the charging current decreases. While performing a range down process, it displays on the display part 11b that it is outside a measurement range, and returns to step ST202.

  When the process goes from step ST212 to step ST210a to execute the measurement range down process, the control means 11 determines that the value of the voltage difference VD (n) between the n-th section and the first section is the comparison value. If it exceeds 10 times Vdown (n), the measurement range may be reduced by two ranges, and if it exceeds 100, the measurement range may be reduced by three ranges.

  Similarly, the control means 11 may lower the measurement range by two ranges when the value of the voltage difference VD of the section average voltage of two adjacent sections exceeds 10 times the comparison value Vdown. If the number exceeds 100, the measurement range may be lowered by 3 ranges.

  On the other hand, in the determination in step ST212, the voltage difference VD (n) between the section average voltage VAn in the n section and the section average voltage VA0 in the first section is equal to or less than Vdown (n) (the charge voltage increases). In this case, VD (n) ≦ Vdown (n)), or the voltage difference VD of the section average voltage VAn in the two adjacent sections of the n section is equal to or less than Vdown (when the charging voltage increases, VD ≦ Vdown) If YES, the process proceeds to step ST213.

  In step ST213, the control means 11 sets in advance the voltage difference VD (n) between the section average voltage VAn of the n section and the section average voltage VA0 of the first section as the second range allowable voltage difference. Whether the value is equal to or greater than the value Vup (n) of n times the range-up specified voltage Vup (n is the same value as the variable n in the nth section), or the voltage of the section average voltage VAn in two adjacent sections in the nth section Whether or not the difference VD (= VAn−VAn−1) is equal to or higher than the range-up specified voltage Vup is selected and executed.

  The selection related to Vup performed by the control unit 11 is performed according to the minimum resolution of the voltage measuring unit 16 in each measurement range and the measurement range for measuring the maximum capacity, the state of the noise voltage, and the like. Further, when the measurement range is already the maximum measurement range, the control unit 11 suspends the measurement range range-up process in the first few sections of the plurality of n sections depending on the minimum resolution of the voltage measurement unit 16 and the noise voltage. Alternatively, the Vup setting itself may be a smaller value than Vup in other measurement ranges. Even if it is not the maximum measurement range, depending on the minimum resolution of the voltage measurement means 16 and the noise voltage, the first few sections of the plurality of n sections may be put off the range-up process of the measurement range.

In this embodiment, the range-up specified voltage Vup is expressed by the following equation (4) where Cmax is the maximum capacity of the measurement range, I is the constant current, Δt is the unit time of the section, and L is a predetermined margin (about 1.0). ,
Vup = L × I × Δt / Cmax (4)
It is obtained by. Note that Vup (n), which is a value that is an integral multiple of the range-up specified voltage, is also obtained by Vup × n, where n is a variable in the n-th section.

  In the determination in step ST213, the voltage difference VD (n) between the section average voltage VAn and the section average voltage VA0 in the first section is less than the value Vup (n) that is n times the range-up specified voltage Vup (the charge voltage is In the case of increasing, if VD (n) <Vup (n)), or the voltage difference VD of the section average voltage VAn in two adjacent sections of the n section is less than the range-up specified voltage Vup (the charging voltage is In the case of increasing, in the case of NO determination where VD <Vup), the process proceeds to step ST213a.

  In step ST213a, the control unit 11 stops charging by the charging unit 12, discharges the capacitor Cx by the discharging unit 13, performs a range-up process for increasing the charging current, and causes the display unit 11b to be out of the measurement range. Is displayed and the process returns to step ST202.

  Note that when the measurement range is increased, the value Vup (n) that is n times the range-up specified voltage is the voltage difference VD (n) between the n-th interval and the first interval as the comparison value. If it exceeds ten times, the measurement range may be increased by two ranges, and if it exceeds 100, the measurement range may be increased by three ranges.

  Similarly, when the value Vup of the range up specified voltage exceeds 10 times the voltage difference VD of the adjacent average voltage of two adjacent intervals as a comparison value, the measurement range may be increased by two ranges, Moreover, when exceeding 100 times, you may raise a measurement range by 3 ranges.

  In the determination of step ST213, if the maximum range has already been reached, the range is not increased, and “9999” or the like is displayed on the display unit 11b as a display outside the measurement range. The number of display digits may be arbitrarily determined. Also, the display content may be other forms other than numerals, such as “XXXX”.

  On the other hand, in the determination in step ST213, the voltage difference VD (n) between the section average voltage VAn and the section average voltage VA0 in the first section is equal to or greater than Vup (n) (when the charge voltage increases, VD (N) ≧ Vup (n)), or the voltage difference VD of the section average voltage VAn in the two adjacent sections of the n section is equal to or higher than Vup (when the charging voltage increases, VD ≧ Vup). If there is, the process moves to step ST214, and it is determined whether n has reached the specified number of times.

  In the determination in step ST214, if n has reached the specified number of times, the process proceeds to step ST213a, the charging by the charging unit 12 is stopped, the capacitor Cx is discharged by the discharging unit 13, and the charging current is calculated. While performing the range-up process to increase, it displays on the display part 11b that it is outside a measurement range, and returns to step ST202.

  On the other hand, if the determination in step ST214 is YES and n is less than the specified number of times that has not reached the specified number of times, the process proceeds to step ST215, n = n + 1, and the variable n is incremented by 1, Return to ST207.

  If the determination in step ST207 is YES and the determination in step ST208 is YES, steps ST209 to ST215 are repeated, and in the meantime, a NO determination is made in each determination step of steps ST210, ST212, and ST213. In this case, as described above, the charging of the capacitor Cx is stopped, the discharging of the capacitor Cx is started, the range up or the range down is performed, the process returns to step ST202, and the capacitor Cx is charged again (capacity). Start measurement).

  On the other hand, if the determination in step ST208 is NO and there is no new section average voltage VAn, the inter-terminal instantaneous voltage V of the capacitor Cx reaches the charge end voltage Vd in step ST216, and the charge end time is reached. It is determined whether or not it can be acquired. When the instantaneous voltage V between terminals of the capacitor Cx exceeds the charge termination voltage Vd, the signal output of the charge detection comparator 15 is turned ON.

  Thereby, the control means executes the interrupt routine of FIG. 7B, acquires the charge end time, and sets the timer acquisition flag. If the timer acquisition flag is not set in step ST216, the process returns to step ST207. If the timer acquisition flag is set in step ST216, the control unit 11 proceeds to step ST217. Then, the count value at the end of charging is obtained from the timer 11c acquired in the interrupt routine of FIG. 7B, and stored in the memory 11a as the charging end time te, and the constant current source 12 is turned off to complete the charging. To do. Also, the timer acquisition flag is cleared.

  After step ST217, the control means 11 follows the same steps as steps ST107 to ST112 (including ST108a and ST109a) in the first embodiment.

That is, in step ST217, the discharging means 13 is turned on to start discharging, and the charging time T is obtained from the charging start time ts and the charging end time te stored in the memory 11c, and the capacitance C of the capacitor Cx is set to the following. Equation (1)
C = I × T / Vd (1)
Calculated by

  In step ST218, it is determined whether or not the capacitance C is greater than or equal to the range lower limit capacity. If YES in step ST218, the process proceeds to step ST219. Is less than the range upper limit capacity.

  If it is determined in step ST219 that the capacitance C is YES below the range upper limit capacity, the process proceeds to step ST220, and the capacitance C calculated by equation (1) in step ST217 is displayed on the display unit 11b. In step ST221, it is determined whether or not the measurement is completed.

  If the determination in step ST221 is the end of measurement, in step ST222, the termination process is executed after the discharge started in step ST217 is completed. If the measurement is not completed, the process returns to step ST202, and the capacitance measurement is performed again for the same capacitor Cx.

  If the determination result in step ST218 is NO and the capacitance C of the capacitor Cx is less than the range lower limit capacity and out of the range, the process proceeds to step ST218a and the display unit 11b is out of the measurement range. Is displayed, and the range down process is executed so that the charging current (constant current) decreases. Then, the process returns to step ST202, and the capacitance of the same capacitor Cx is measured again.

  When performing the range down process, if the electrostatic capacitance C of the capacitor Cx is 1/10 or less of the lower limit of the range capacity, the ranges may be lowered simultaneously.

  If the determination result in step ST219 is NO and the capacitance C of the capacitor Cx exceeds the range upper limit capacity and is outside the range range, the process proceeds to step ST219a and the display unit 11b is out of the measurement range. Is displayed, and the range up process is executed so that the charging current (constant current) increases. Then, the process returns to step ST202, and the capacitance measurement is performed again for the same capacitor Cx.

  According to the second embodiment, when the initially set initial current range is not appropriate, the range is appropriately increased or ranged without waiting until the charging time T when the inter-terminal instantaneous voltage V of the capacitor Cx reaches the charge termination voltage Vd. The optimal current range can be set by performing the down process, and the range correction steps of the steps ST218a and ST219a prepared after the calculation of the capacitance C of the capacitor Cx are rarely performed, resulting in measurement. Time can be shortened.

  Further, according to the second embodiment, the capacitance C of the capacitor Cx can also be obtained from the section average voltage VAn acquired in step ST209.

That is, as shown in FIG. 5, the capacitor Cx is discharged to a predetermined voltage, and preferably after the first and second stabilization times s0 and s1 have elapsed, a constant unit time Δt with respect to the capacitor Cx. Is a section, and the capacitor Cx is continuously charged with a constant current I over a plurality of n sections (n is a positive integer representing an order including 0), and each section has a predetermined time interval within the section. The section average voltage VAn is obtained from the instantaneous voltage V between the terminals of the predetermined number of capacitors sampled in step 1. The section average voltage of the first section (n = 0 section) is VA0, and the section average voltage of the n section is VAn. , The capacitance C of the capacitor Cx is expressed by the following equation (5),
C = (I × n × Δt) / (VAn−VA0) (5)
For example, the capacitance C according to the equation (5) can be displayed as a reference value together with the capacitance C according to the equation (1) on the display unit 11b.

  The control means 11 corrects the constant current value I by the current correction formula I = d × I, and the sampled average voltage VAn or the inter-terminal instantaneous voltage V of the capacitor Cx is the voltage correction formula V = e × V + f. Correction parameters d, e, f, g, h for correcting the capacitance C of the capacitor Cx using the capacitance correction formula C = g × C + h and determining the consistency of the measurement range or When obtaining the capacitance C of the capacitor Cx, it is preferable to perform correction calculation by the correction current equation, the voltage correction equation, and the capacitance correction equation at least once. These correction calculations may be performed by the voltage measuring means 16.

  The control means 11 sets a plurality of correction parameters d, e, f, g, and h for the correction current equation, the voltage correction equation, and the capacitance correction equation, respectively, and a constant current value I sampled capacitor Cx. Appropriate correction parameters may be used according to the instantaneous voltage V between the terminals and the capacitance C of the capacitor Cx. Further, the corrected capacitance C of the capacitor Cx may be corrected again. These correction parameters can be set via a communication interface by an operation key (not shown) or an external device.

As another method for calculating the capacitance C of the capacitor Cx, the first first interval Δt0 to the nth interval Δtn are taken into consideration when the minimum resolution of the voltage measuring means 16 is large or when there is noise. Is divided into the first half and the second half, and the average of the first half interval average voltage VAn or the instantaneous voltage V of the capacitor Cx sampled in the first half is Va, the average of the first half sampling time is ta, and the second half interval average voltage VAn or The average of the instantaneous voltage V of the capacitor Cx sampled in the latter half is Vb, the average of the sampling time in the latter half is tb, and the capacitance C of the capacitor Cx is replaced by the above equation (1), and the following equation (6):
C = I × (tb−ta) / (Vb−Va) (6)
You may ask for.

As an example, in the case of 5 sections of n = 0 to 4, ta−tb = 2.5Δt and the capacitance C of the capacitor Cx is
C = I × 2.5Δt / {(VA4 + VA3 + VA2) / 3− (VA1 + VA0) / 2}
Or C = I × 2.5Δt / {(VA4 + VA3 + VA2 + VA1) / 4− (VA0)}
Is required.

As another method for calculating the capacitance C of the capacitor Cx, the first first section Δt0 to the nth section Δtn are divided into the first half and the second half, and the number of voltage data in the first half is a, The sum of instantaneous voltage V of capacitor Cx sampled in the first half section average voltage VAn or the first half section is ΣVAa, the number of voltage data in the second half section is b, the second half section average voltage VAn or the second half section is sampled The sum of the instantaneous voltage V of the capacitor Cx is ΣVAb, the sampling interval for acquiring the section average voltage VAn or the instantaneous voltage V is Δt, and the capacitance C of the capacitor Cx is replaced by the following equation (1): 7),
C = I × 0.5 × (a + b) × Δt / ((ΣVAb) / b− (ΣVAa) / a)
= I × 0.5 × a × b × (a + b) × Δt / (a × (ΣVAb) −b × (ΣVAa))
... (7)
Can also be obtained.

  In adopting the calculation method of the capacitance C of these other capacitors Cx, in consideration of the calculation performance of the control means 11 and the minimum number of sections being two sections, the above formulas (6) and ( 7) is selected, but when the first half and the second half are divided into two, when the minimum resolution of the section average voltage VAn and the inter-terminal instantaneous voltage V is large, the first half section is relatively shortened. When the latter half is lengthened to increase the number of digits of the capacitance C of the capacitor Cx, and when there is a lot of noise, it is preferable to set the first half and the latter half to substantially the same time interval.

  As described above, according to the second embodiment, the capacitance C of the capacitor Cx obtained by the various calculation formulas (5), (6), and (7) is changed to the capacitor Cx obtained by the formula (1). Can be displayed together with the display unit 11b together with the electrostatic capacitance C, and the measurement accuracy can be further improved.

  As described above, according to the present invention, the configuration of the voltage measurement system of the capacitor can be simplified to realize cost reduction, and the range switching and the discharge start determination are additionally performed during charging. Thus, a high-speed capacitance measuring device can be provided.

DESCRIPTION OF SYMBOLS 11 Control means 11a Memory 11b Display part 11c Timer 12 Constant current source 13 Discharge means 14 Discharge detection comparator 15 Charge detection comparator 16 Voltage measurement means 16a Amplifier 16b A / D converter 16c DSP
Cx Capacitor to be measured

Claims (20)

Charging means comprising a constant current source for charging a capacitor to be measured with a constant current, discharging means for discharging the capacitor, voltage measuring means for measuring an instantaneous voltage V between terminals of the capacitor, charging to the capacitor Control means having a timer means for controlling the discharge and measuring the charging time and the discharging time, and a display unit,
When the capacitor is charged with a constant current I by the charging means, the capacitance C of the capacitor is calculated based on the fact that the ramp waveform of the instantaneous voltage V between the terminals of the capacitor changes linearly with time. In the capacitance measuring device to obtain and display on the display unit,
The control means or the voltage measuring means discharges the capacitor to a predetermined voltage range, and then sets a predetermined unit time Δt as one section, and a plurality of n sections (n is a positive integer representing an order including 0). The capacitor is continuously charged by the constant current source, and the instants between the terminals of a predetermined number of the capacitors additionally sampled at predetermined time intervals in each of the plurality of n intervals. The voltage V is obtained, and the difference voltage of the section average voltage VAn and / or the capacitance C of the capacitor is obtained by setting the first section average voltage (n = 0 section) as VA0 and the section average voltage in the n section as VAn. And at least selected from each value of the instantaneous voltage V between the terminals of the capacitor, the section average voltage VAn, the difference voltage of the section average voltage VAn, and the capacitance C of the capacitor. When one of the values is outside a predetermined range, the capacitor is discharged to substantially 0 V, and then the constant current value I of the constant current source is changed to continuously charge the capacitor. The capacitance measuring device is characterized in that the capacitance C of the capacitor is obtained. In the control means or the voltage measuring means, a plurality of measurement ranges corresponding to the constant current value I generated by the constant current source and the measurement capacity range of the capacitor are set in advance, Comparing a predetermined charge termination voltage Vd set for each measurement range with the instantaneous voltage V between terminals of the capacitor, and a charge detection comparator that outputs a charge termination signal when V = Vd is exceeded,
The control means or the voltage measuring means waits for a predetermined stabilization time for the discharge state to stabilize after discharging between the terminals of the capacitor to a predetermined voltage range, Charging is started at the time when the charging is started at the constant current value I of the set measurement range, and then the charging detection comparator outputs the charging termination signal, and the charging time from the charging start to the charging termination. T is obtained by the timer means, and the capacitance C of the capacitor is expressed by the following equation (1),
C = I × T / Vd (1)
The capacitance measuring device according to claim 1, wherein the capacitance is calculated and displayed on the display unit.   The capacitance measuring apparatus according to claim 2, wherein the control unit or the voltage measuring unit has a range switching function for increasing or decreasing the range of the measurement.   When the calculated capacitance C is less than the range lower limit capacity, the control means or the voltage measuring means performs a range down process for reducing the charging current, and starts charging the capacitor again. The capacitance measuring apparatus according to claim 3.   When the calculated capacitance C exceeds the range upper limit capacity, the control means or the voltage measurement means performs a range-up process for increasing the charging current, and starts charging the capacitor again. The capacitance measuring apparatus according to claim 3.   The control means or the voltage measuring means stops charging by the charging means when the charge detection comparator does not output the charge termination signal even after a predetermined timeout time Tout has elapsed, and the discharging 4. The capacitance according to claim 3, wherein the capacitor is discharged to substantially 0 V by means, a range-up process for increasing the charging current is performed, and charging of the capacitor is started again. measuring device. The control means or the voltage measuring means has the time-out time Tout, the maximum capacity of the range as Cmax, the constant current as I, the charge termination voltage as Vd, and the predetermined margin as M, the following equation (2):
Tout = M × Vd × Cmax / I (2)
7. The capacitance measurement according to claim 6, wherein the timeout time Tout obtained by the equation (2) is preset in the control means or the voltage measurement means. apparatus.   In the control means or the voltage measuring means, a predetermined determination reference value X for the instantaneous voltage V between terminals of the capacitor is set, and the control means or the voltage measuring means is in charge of the capacitor, The instantaneous voltage V between the terminals of the capacitor and the determination reference value X are compared. When the instantaneous voltage V between the terminals of the capacitor exceeds the determination reference value X, the charging by the charging unit is stopped at that time, 8. The capacitor according to claim 3, wherein the discharging means discharges the capacitor to a predetermined voltage range, performs range up processing or range down processing, and starts charging the capacitor again. The capacitance measuring device according to item.   The control means or the voltage measuring means is set with a measurement range upper limit voltage VU, and the control means or the voltage measuring means has the instantaneous voltage V across the capacitors exceeding the measurement range upper limit voltage VU. In other words, when the charging voltage rises, if V> VU, the charging by the charging unit is stopped at that time, the capacitor is discharged to a predetermined voltage range by the discharging unit, and the range down process is performed. The capacitance measuring apparatus according to claim 8, wherein charging is performed on the capacitor again.   A measuring range upper limit voltage VU is set in the control means or the voltage measuring means, and the control means or the voltage measuring means has a predetermined number of the capacitors sampled by the voltage measuring means for each section. The section average voltage VAn is obtained from the inter-terminal instantaneous voltage V, and when the section average voltage VAn exceeds the measurement range upper limit voltage VU, that is, when the charging voltage rises, and VAn> VU, at that time 9. The charging by the charging unit is stopped, the capacitor is discharged to a predetermined voltage range by the discharging unit, the range down process is performed, and charging of the capacitor is started again. The electrostatic capacity measuring apparatus according to 1.   The control means or the voltage measuring means uses a range-down specified voltage Vdown determined by a minimum capacity of each measurement range and a predetermined constant, and calculates a voltage difference between the interval average voltages VAn of the two adjacent intervals of the n interval as VD When the voltage difference VD exceeds the range-down specified voltage Vdown, that is, when the charging voltage rises, and VD> Vdown, the charging by the charging unit is stopped at that time, and the discharging unit The capacitance measuring apparatus according to claim 10, wherein the capacitor is discharged to a predetermined voltage range, the range down processing is performed, and charging of the capacitor is started again.   The control means or the voltage measuring means sets a voltage difference between the section average voltage VAn and the first section average voltage VA0 to VD (n), and sets a value that is n times the range-down specified voltage Vdown. Vdown (n), and when the voltage difference VD (n) exceeds a value Vdown (n) which is n times the range-down specified voltage Vdown, charging by the charging means is stopped at that time, and the discharging means 12. The capacitance measuring apparatus according to claim 11, wherein the capacitor is discharged to a predetermined voltage range, the range-down process is performed, and charging of the capacitor is started again. The control means or the voltage measuring means has the range down specified voltage Vdown, the minimum capacity of the measurement range as Cmin, the constant current as I, the interval unit time as Δt, and the predetermined margin as J, the following equation (3) ,
Vdown = J × I × Δt / Cmin (3)
The range-down prescribed voltage Vdown obtained by the equation (3) is set in advance in the control means or the voltage measurement means, according to claim 11 or 12. Capacitance measuring device.   The control means or the voltage measuring means uses a range-up specified voltage Vup determined by the maximum capacity of each measurement range and a predetermined constant, and calculates a voltage difference between the interval average voltages VAn of the two adjacent intervals of the n interval as VD As described above, when the range-up regulation voltage Vup exceeds the voltage difference VD, that is, when the charging voltage increases, if VD <Vup, the charging by the charging unit is stopped at that time, and the discharging unit The capacitance measuring apparatus according to claim 10, wherein the capacitor is discharged to a predetermined voltage range, the range-up process is performed, and charging of the capacitor is started again.   The control means or the voltage measuring means sets a voltage difference of the section average voltage between the section average voltage VAn and the first section average voltage VA0 to VD (n), and a value Vup that is n times the range-up specified voltage Vup. When (n) exceeds the voltage difference VD (n), that is, when the charging voltage rises, when VD (n) <Vup (n), charging by the charging means is stopped at that time, 15. The capacitance measuring apparatus according to claim 14, wherein the capacitor is discharged to a predetermined voltage range by a discharging means, the range-up process is performed, and charging of the capacitor is started again. The control means or the voltage measuring means uses the following formula (4), where the range up specified voltage Vup is Cmax, the maximum capacity of the measurement range is Cmax, the constant current is I, the unit time of the section is Δt, and the predetermined margin is L. ,
Vup = L × I × Δt / Cmax (4)
16. The range-up specified voltage Vup obtained by the equation (4) is preset in the control means or the voltage measuring means, according to claim 14 or 15. Capacitance measuring device.   In the control means or the voltage measuring means, the constant current value I is corrected by a current correction formula I = d × I, and the sampled section average voltage VAn or the inter-terminal instantaneous voltage V is converted into a voltage correction formula V = Correction parameters d, e, f, g, h for correcting the capacitance C of the capacitor by a capacitance correction equation C = g × C + h are set, and the measurement range is predetermined. When determining whether or not the capacitance is within the range, or calculating the capacitance of the capacitor, the correction calculation by the current correction formula or the voltage correction formula or the capacitance correction formula is performed once or more. The capacitance measuring device according to claim 1, wherein the capacitance measuring device is characterized in that:   The control means or the voltage measuring means determines whether or not correction calculation is performed by the current correction formula, the voltage correction formula, or the capacitance correction formula, the number of calculations, and the correction parameters d, e, f, g, and h. 18. The capacitance measuring device according to claim 17, wherein input / output is possible with respect to a predetermined key and a display unit or an external device. Charging means comprising a constant current source for charging a capacitor to be measured with a constant current, discharging means for discharging the capacitor, voltage measuring means for measuring an instantaneous voltage V between terminals of the capacitor, and charging / discharging of the capacitor Control means having timer means for measuring the charging time and discharging time, and a display unit,
When the capacitor is charged with a constant current I by the charging means, the capacitance C of the capacitor is calculated based on the fact that the ramp waveform of the instantaneous voltage V between the terminals of the capacitor changes linearly with time. In the capacitance measuring device to obtain and display on the display unit,
If the control means or the voltage measurement means does not obtain the capacitance C of the capacitor, the control means or the voltage measurement means discharges until the instantaneous voltage V between the terminals of the capacitor can be regarded as 0 V, and obtains the capacitance C of the capacitor. In this case, after discharging to a predetermined voltage range determined alternately every discharge, the capacitor is charged in the positive direction or the negative direction by the constant current source charged with the constant current. The capacitor is continuously charged by the constant current source over a plurality of n intervals (n is a positive integer representing an order including 0), with a constant unit time Δt as one interval. For each section of the plurality of n sections, the section average voltage VAn is acquired from the instantaneous voltage V between the terminals of a predetermined number of the capacitors additionally sampled at a predetermined time interval within the section, The initial (n = 0 interval) interval average voltage is VA0, the interval average voltage of the n interval is VAn, the capacitance C of the capacitor or the difference voltage of the interval average voltage VAn is obtained, and the inter-terminal instantaneous of the capacitor is obtained. When at least one value selected from the values of the voltage V, the difference voltage of the section average voltage VAn, and the capacitance C of the capacitor is a value outside a predetermined range, the capacitor is discharged to substantially 0V. Thereafter, the constant current value I of the constant current source is changed, and the capacitor is continuously charged to obtain the capacitance C of the capacitor.   The control means or the voltage measurement means is preset with a plurality of measurement ranges corresponding to the constant current value I generated by the constant current source and the measurement capacity range of the capacitor, and the control means Alternatively, when the voltage measuring unit performs the range down of the measurement range or the range up of the measurement range, the voltage measurement unit alternately repeats the range down of the measurement range or the range up of the measurement range for each charge. The capacitance C of the capacitor is obtained based on the fact that the instantaneous voltage V between the terminals of the capacitor changes linearly with time, and the capacitance C of the capacitor is determined for each charge. If the measurement range range down and the measurement range range up are not repeated alternately, the measurement range range down or Capacitance measurement apparatus according to claim 19, which comprises carrying out the range up the serial measurement range.

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