JP3147990B2 - Impedance measuring device and measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance measuring apparatus and a measuring method used for measuring a large-capacity capacitor, a high-inductance inductor, and the like in a production line of electronic parts and the like, and more particularly, to reducing a transient phenomenon in a measuring circuit. The present invention relates to an impedance measuring device and a measuring method for increasing the number of objects to be measured per unit time thereby.

[0002]

2. Description of the Related Art Conventionally, for example, in a production line for an electronic component or the like, the impedance of the component is measured because it is necessary to judge the quality of the produced component. If this measurement is delayed, there will be inconveniences such as the entire line cannot operate smoothly.
High-speed measurement is required for the impedance measuring device.

FIG. 6 is a diagram schematically showing an impedance measuring apparatus, in which an object to be measured (in this case, a capacitor C
_DUT ) has one terminal connected to the high voltage side,
Hc, the other terminals are low voltage side voltage and current measurement terminals Lp, L
connected to c respectively. Then, a measurement signal from a measurement signal source (in this case, a voltage signal source Vs) is applied between Hc, Hp and Lc, Lp via a power supply resistor Rs, and a voltage between Hp, Lp is measured by a voltmeter 1. By measuring the current flowing between Hc and Lc by the ammeter 2 as a voltage value, the impedance (that is, the capacitance) of the _DUT under test can be obtained.

In a part manufacturing line, when an object to be measured is connected to a measuring device, a measurement signal (usually a sine wave) is suddenly applied to the object to be measured. If inductive, the response will have a transient period. Since it is practically difficult to accurately measure the amplitude and phase of the sine wave component during this transition period, conventionally, measurement has been started after the transient phenomenon has been sufficiently reduced. For example, in the case of measuring the impedance of the capacitor _CDUT, the larger the capacitance, the longer the transition period. Therefore, the waiting time until the measurement becomes longer, which is an obstacle to the high-speed measurement.

[0005] The present invention provides an impedance measuring apparatus and a measuring method that can quickly determine the characteristics of electric elements such as capacitors and inductors used in a production line, whose approximate values are known, without deteriorating measurement accuracy. The purpose is to do.

[0006]

For example, in the measurement of the impedance of an electronic component, when a measurement signal is applied to an object to be measured from a certain time, a transient phenomenon depending on the measurement circuit occurs. In impedance measurement, the concept of giving a measurement signal from a specific phase to a measurement target is generally considered because the measurement target includes a measurement target in a measurement circuit and the impedance value of the measurement target cannot usually be predicted. Cannot exist.

The inventor of the present invention has proposed that when the present invention is applied to a test apparatus for judging the quality of electronic parts or the like on a production line, the approximate value of the impedance of the object to be measured is known in advance, and Attention has been paid to the fact that the circuit state of the measurement circuit including the measurement target is almost specified.
It is known that driving a measurement signal source (hereinafter referred to as a “signal source”) with a phase that minimizes the transient component can reduce the transient phenomenon of the measurement circuit and shorten the measurement time. And obtained the present invention.

That is, the impedance measuring apparatus according to the present invention is characterized in that the signal source can output the measurement signal value to zero and the initial phase of the sine wave measurement signal can be set to a specific phase or an arbitrary phase. Further, the impedance measuring method of the present invention,

[0009]

Equation 2 θo = sin ⁻¹ [1 / {1+ (fc / fo) ² }] + 180 · n [degree]

Fo: the frequency of the signal source; fc: when the object to be measured is capacitive, the low-pass voltage measuring circuit of the low-pass type voltage measuring circuit including the object to be measured as a part of the circuit. The cut-off frequency obtained based on the approximate value of the impedance of the object, or a low-pass current measurement circuit configured to include the object to be measured as part of the circuit when the object to be measured is inductive. The measurement signal is output in the vicinity of an initial phase θo represented by a cutoff frequency obtained based on the approximate value of the impedance of the object to be measured, where n is an integer.

[0011]

[Action]

(1) In the present invention, when an object to be measured is connected to the measurement terminal of the device, the signal source outputs a measurement signal starting from a specific phase to a measurement circuit including the object to be measured. The specific phase is determined by a measurement circuit including the object to be measured.

(2) Hereinafter, the theory of the present invention and the method of determining the specific phase will be described in detail with reference to FIGS. 1 (A) and 1 (B). FIG. 1A is a diagram showing a voltage measuring circuit portion taken out from the measuring circuit of FIG. 6, and FIG. 1B is a diagram showing a current measuring circuit portion taken out. FIG. 1 (A)
Is a first-order low-pass filter (LPF) type circuit, and the circuit of FIG. 1B is a first-order high-pass filter (HPF) type circuit. FIG. 1 (A), (B)
When a sine wave signal is suddenly applied from a certain phase from a voltage signal source Vs to a measured object (capacitor C _{DUT in the} same figure), the response is when a sine wave voltage signal is suddenly applied to an LPF or HPF. , And becomes a composite signal of the transient component and the sine wave component.

That is, in FIG. 1A, the output of the voltmeter 1 (the output terminal is indicated by Vch) can be regarded as a signal after passing through the LPF composed of the power supply resistor Rs and the capacitor _CDUT . In FIG. 3B, the output of the ammeter (the output terminal is indicated by Ich) can be regarded as a signal after passing through the HPF composed of Rs and _CDUT . In FIG. 3B, the current signal is converted into a voltage signal by the inverting amplifier A to which the feedback resistor Rr is connected, and is measured by the voltmeter 2 '. When a sine wave signal is suddenly input to the LPF type circuit or the HPF type circuit of FIGS. 1 (A) and 1 (B), Vch and Ich outputs become
Each of them can be obtained as follows using the Laplace transform.

(A) Output of voltmeter (Vch) Assuming that the cut-off angular frequency of the primary LPF type circuit is ωc and the angular frequency of the signal source is ωo, the transfer function T of the LPF type circuit is
(s) and the Laplace transform F (s) of the sine wave signal starting from a certain phase θ are

[0015]

[Number 3] T (s) = ωc / ( s + ωc) F (s) = (ωo · cosθ + s · sinθ) / (s 2 + ωo 2)

## EQU1 ## The product of T (s) and F (s) is Vv (s)
Then

[0017]

Equation 4] Vv (s) = T (s ) · F (s) = (ωc · ωo · cosθ + ωc · s · sinθ) / {(s + ωc) · (s 2 + ωo 2)}

## EQU1 ## This is subjected to the inverse Laplace transform, and the angular frequencies ωc and ωo are converted into the frequencies fc and fo, and the output (Vch output) Vvo of the voltmeter 1 described below can be obtained.

[0019]

Vvo = [(fo · cos θ−fc · sin θ) · exp {− (2πfc) · t｝ +1] · Vac · sin (2πfo · t + φ)

Where Vac is the amplitude component of the sine wave component, φ
Is also a phase component.

(B) Regarding the output of the ammeter (Ich) As in (a), if each cutoff frequency of the primary HPF type circuit is ωc and the angular frequency of the signal source is ωo, the HPF
The transfer function T (s) of the circuit is

[0022]

T (s) = (s · Rr) / {Rs · (s + ωc)}

The angular frequencies ωc and ωo are represented by the frequency f
By rearranging to c and fo, the following ammeter output (Ich output measured by the voltmeter 2 ') Vio can be obtained.

[0024]

Vio = (Rr / Rs) · [(fc / fo) (fo · cos θ−fc · sin θ) · Vac · exp {− (2πfc) · t} +1] · Vac · sin (2πfo · t + φ)

Where Vac is the amplitude component of the sine wave component, φ
Is also a phase component. In the above (Equation 5) and (Equation 7), Vac and φ mean the amplitude and phase of the sine wave component, and these are LPF type circuits or HPFs.
It depends on the frequency characteristics of the circuit. Further, in (Equation 5) and (Equation 7), when [] is expanded, the first term is a transient term that decays exponentially, and the second term is a term (steady term) of a sine wave signal to be actually measured. is there.

Incidentally, for example, in the case of a large-capacity capacitor, fc becomes small. Therefore, the output Vvo of the voltmeter 1
The initial value of the transient term becomes larger, and the output Vio of the voltmeter 2 'is increased.
The initial value of the transient term becomes smaller. That is, the influence of the transient phenomenon in the voltage measurement circuit becomes dominant. Therefore, when measuring the capacitance of a capacitive object to be measured, the coefficient of the transient term of (Equation 5)

[0027]

[Equation 8] (fo · cos θ−fc · sin θ)

If is set to zero, the transient phenomenon is drastically reduced. Although not described in detail, when measuring an inductor having a high inductance, the influence of a transient phenomenon in the current measurement circuit becomes dominant. Current measurement circuit including inductor (LPF
Assuming that the low-pass frequency of the circuit is fc, the voltmeter 2 '
The coefficient of the transient term of the output can be expressed in the same way as (Equation 8).

Assuming that (Equation 8) = 0, solving this for θ gives

[0030]

Equation 9 θ = sin ⁻¹ [1 / {1+ (fc / fo) ² }] + 180 · n [degree]

(Where n is an integer). Therefore, if a sine wave is output near the phase θ (this is assumed to be θo) satisfying the above (Equation 9), the influence of the transient phenomenon can be reduced. In general, if a sine wave is output with a phase within a range of θo ± 30 ° (preferably about ± 10 °),
The effects of the present invention can be achieved.

[0032]

An embodiment of the present invention will be described below with reference to the drawings. FIGS. 2A and 2B are explanatory diagrams showing a specific configuration of a signal source used in the present invention. FIG. 1A shows a circuit configuration in a case where a digital waveform signal for measurement is converted into an analog signal using a D / A converter and output from an arbitrary phase. The phase data calculator 11 has a function of specifying an initial phase address, and calculates an address in the ROM 12 corresponding to the specified initial phase from the specified initial phase. Then, the digital waveform data is sequentially output from the address to the D / A converter 13, and the analog signal from the D / A converter 13 is converted into a voltage including the object to be measured,
The current is output to the current measurement circuit (see FIGS. 1A and 1B).

FIG. 2B shows a circuit configuration when an analog waveform signal from a sine wave oscillator is output from an arbitrary phase. The sine wave output from the sine wave oscillator 14 is input to the phase detector 15, and when the sine wave phase reaches the specified initial phase, the switch 16 is turned on to measure the analog signal. Output to measurement circuit including target.

FIG. 3 shows a case where the object to be measured is a capacitor.
It is a figure showing a voltage measurement circuit (LPF type circuit). FIG.
As described above in (A), the C _DUT under test is
Is capacitive, the transient of the measurement signal is dominated by the transient in the voltage measurement circuit. Therefore, by reducing the transient phenomenon of the circuit in the voltage measurement circuit, the transient phenomenon of the measurement signal is reduced. In FIG. 3, the signal source resistance Rs is 100Ω, and the object to be measured is approximately 10Ω.
0μF capacitor, frequency fo of signal source Vs is 100H
It has been set to z. 100Ω source resistance Rs and 100Ω
When the cutoff frequency is obtained from the LPF type circuit constituted by the μF capacitor C _DUT and θo is calculated from (Equation 9),

[0035]

[Equation 10] θo = 80.957 ° + 180 · n [degrees]
(However, n is an integer)

## EQU1 ## FIGS. 4A and 4B show FIG.
FIG. 9 is a waveform diagram showing outputs (Vch output Vvo) of the voltmeter 1 at initial phases 0 ° and 80.957 ° of the signal source Vs in the circuit shown in FIG. The figures (A) and (B)
, The signal source Vs has zero output from time 0 to 10 ms, and outputs a sine wave after time 10 ms. Further, the phase of the signal source Vs is also shown. As can be seen from these figures, when the initial phase of the signal source Vs is 0 °, a transient phenomenon is remarkably exhibited, whereas when the initial phase of the Vs is 80.957, no transient phenomenon occurs. Close to.

FIG. 5 shows the time (waiting time t) until the transient phenomenon is sufficiently attenuated and the impedance measurement becomes possible in FIGS. 4A and 4B, and the error (%) of the measured value. 6 is a graph illustrating the relationship of. From this figure, compared to the error (indicated by a ₂₎ in the conventional impedance measurement initial phase of the measurement signal from the signal source Vs will be determined freely, the initial phase of the measurement signal is determined by a fixed Error in inductance measurement of the invention (a ₁
) Is sufficiently small, and it can be seen that the measurement time is greatly reduced.

In the above embodiment, the initial phase is determined by (Equation 9). However, the operation of inputting the capacitance value (approximate value) of the measured capacitor may be complicated. The transient phenomenon becomes a problem when the cutoff frequency fc is small. As this fc becomes smaller, the value of (Equation 9) approaches 90 °. On the other hand, when fc increases, the value of (Expression 9) deviates from 90 °. In this case, the initial value of the transient phenomenon becomes small and the time constant of the transient phenomenon becomes small. The effect is also reduced. Therefore, even if the initial phase of the sine wave is always fixed to 90 ° and the impedance is measured, the transient phenomenon can be suppressed to a small value, and the practical use value is high.

Further, in the above embodiment, the case where the capacitor is measured has been described, but the present invention is naturally applicable to the measurement of the inductor. In the case of the measurement of the inductor, the initial phase can be determined by (Equation 9) simply by reversing the relationship between Vch and Ich.
Further, the present invention is applied not only when the object to be measured is a capacitor or an inductor, but also when the object to be measured is a circuit board or a network. In this case, particularly effective measurement is performed when the approximate transfer function of the measured object is known and the Q value of the circuit is not so large.

[0040]

The present invention is configured as described above.
The following effects can be obtained. (1) Conventionally, a large-capacity capacitor or the like requiring a long waiting time can be measured at high speed. Therefore, the measurement time in the production line is reduced. Further, since the measurement unit price per component can be kept low, the price of the product itself can be reduced. (2) The signal source used in the present invention can be easily configured by adding a zero output and phase control function to a conventional signal source. As a signal source, not only a digital signal source but also an analog signal source can be used.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a measurement principle of the present invention;
3A is a diagram illustrating an example of a configuration of a voltage measurement circuit, and FIG. 3B is a diagram illustrating a configuration of a current measurement circuit.

FIGS. 2A and 2B are diagrams specifically showing a signal source of the measuring apparatus of the present invention, wherein FIG. 2A shows a case where a waveform is generated from a specific initial phase based on signal data stored in a ROM, and FIG. FIG. 7 is a diagram illustrating a case where a waveform is generated from a specific initial phase based on a signal generated by an oscillator.

FIG. 3 is a diagram showing an example of a voltage measurement circuit used in implementing the present invention.

4A and 4B are diagrams showing impedance measurement results in an example of the present invention in comparison with conventional measurement, wherein FIG. 4A shows a conventional measurement situation, and FIG. 4B shows a measurement situation of the present invention, respectively. is there.

FIG. 5 is a correlation diagram between a waiting time and a measurement error, showing the effect of the measurement method of the present invention in comparison with the prior art.

FIG. 6 is a diagram showing a circuit configuration of the impedance measuring device.

[Explanation of symbols]

_{Reference Signs List} 1 voltmeter 2 ammeter 2 'voltmeter for current measurement Vs signal source C _DUT target (capacitor) Rs power supply resistance

Claims (5)

(57) [Claims] 1. A sine wave measurement signal is applied between two terminals of an object to be measured whose approximate value of impedance is known, and its response voltage and response current are measured by a voltmeter and an ammeter, respectively. In the impedance measuring apparatus for determining the impedance of the measurement target, the measurement signal source can output the measurement signal value to zero, and can set the initial phase of the sine wave measurement signal to a specific phase or an arbitrary phase. . 2. A sine-wave measurement signal is applied between two terminals of an object to be measured whose impedance approximate value is known, and its response voltage and response current are measured by a voltmeter and an ammeter, respectively. In the impedance measuring method for obtaining the impedance of the following equation, θo = sin ^-1 [1 / {1+ (fc / fo) ² }]
+ 180 · n [degrees] fo: frequency of the signal source, fc: when the object to be measured is capacitive, a low-pass voltage measurement circuit including the object to be measured as a part of the circuit, A cut-off frequency obtained based on the approximate value of the impedance of the measured object, or, if the measured object is inductive, a low-pass type configured to include the measured object in a part of the circuit Of the current measurement circuit,
A method for outputting a measurement signal in the vicinity of an initial phase θo represented by a cutoff frequency obtained based on the approximate value of the impedance of the measured object, where n is an integer. 3. A signal source, a voltmeter, and an ammeter, wherein the signal source supplies a sine wave measurement signal between two terminals of a device under test whose approximate value of impedance is known, and a response voltage of the signal. And a response current measured by the voltmeter and the ammeter, respectively, to obtain the impedance of the measured object, wherein the signal source comprises: fo (frequency of the signal source) and fc (the frequency of the signal source) When the measured object is capacitive, the measured object is obtained based on the approximate value of the impedance of the measured object of the low-pass voltage measurement circuit including the measured object as a part of a circuit. A cutoff frequency, when the object to be measured is inductive, the impedance of the object to be measured in a low-pass current measurement circuit configured to include the object to be measured as part of a circuit; By entering the cut-off frequency) obtained on the basis of the approximate value of the dance, formula, .theta.o = sin ^-1 [1 / √ {1+ (fc / fo) 2} ] + 180
A phase data calculator for calculating an initial phase value θo based on n [degrees] (where n is an integer), further calculating an address value corresponding to the initial phase value, and outputting the address value; Storage means connected to the phase data calculator, for inputting the address value, and sequentially outputting digital waveform data from data specified by the address value, connected to the storage means D / A for sequentially converting digital waveform data output from the storage means into analog values
An impedance measuring device comprising a converter. 4. A signal source, a voltmeter, and an ammeter, wherein the signal source supplies a sine wave measurement signal between two terminals of an object to be measured whose approximate value of impedance is known, and a response voltage of the signal. And a response current measured by the voltmeter and the ammeter, respectively, to obtain the impedance of the measured object, wherein the signal source is a sine wave oscillator, and the sine wave oscillator output is turned on. And a switch for monitoring the output of the sine wave oscillator, and a phase detector operable to turn on the switch when the output of the sine wave oscillator coincides with any input initial phase value. Characteristic impedance measuring device. 5. A low-pass voltage measurement method comprising: fo (frequency of a signal source); and fc (when the object to be measured is capacitive, the object to be measured is included in a part of a circuit. A circuit, a cutoff frequency obtained based on the approximate value of the impedance of the measured object; a low cutoff frequency including the measured object as a part of the circuit when the measured object is inductive; By inputting a cut-off frequency obtained based on the approximate value of the impedance of the object to be measured in the band-pass current measurement circuit, a calculation formula: θo = sin ⁻¹ [1 / √ ｛1+ (fc / fo) ) ² ｝] + 180
The method according to claim 4 , further comprising: an initial phase calculation unit that calculates an initial phase value θo based on n [degrees] (where n is an integer) and outputs the calculated initial phase value θo to a phase detector. Impedance measurement device.