JPH08220157A - Method and apparatus for measuring impedance - Google Patents

Abstract

PURPOSE: To measure the impedance accurately up to high impedance regardless of the leak current of switching element by providing a plurality of semiconductor switch elements for grounding. CONSTITUTION: Semiconductor switch elements S11 -Sn1 , S11 -Sn2 for selection are turned ON/OFF selectively to conduct the inverting input terminal and the output terminal of an operational amplifier A1 and the opposite ends of any one of resistors Rx1 -Rxn to be measured. The remainders are disconnected from the amplifier A1 and the resistance of any one of the resistors Rx1 -Rxn is measured selectively. In this regard, the semiconductor switch elements S13 -Sn3 for selection are turned ON/OFF selectively to disconnect the opposite ends of any one of the resistors Rx1 -Rxn from the ground. At the same time, the opposite ends of the remaining resistors Rx1 -Rxn are conducted with the ground. With such arrangement, leak current of a switching element being turned OFF has no effect on the measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the impedance of impedance elements such as resistors, capacitors and coils. For example, a plurality of impedance elements are set at the same time, and the impedance elements are selected one by one using a switch. More particularly, the present invention relates to an impedance measuring method and an impedance measuring apparatus suitable for measuring the impedance of an object.

For example, in a multi-element type electronic component in which a plurality of impedance elements are integrated on one chip, the impedance of each impedance element is measured, and for example, the measured value of the impedance of each impedance element is compared with a nominal value. The degree of error is detected, and an error whose measured value exceeds the standard with respect to the nominal value is discarded as a defective product, and only non-defective electronic components are sorted and shipped.

[0003]

2. Description of the Related Art At present, most (more than half) of the production of resistors, capacitors and coils in Japan are of the chip type without lead wires, and the ratio of chips is expected to increase more and more. In many cases, a plurality of resistors, capacitors, and coils are built in one chip.

For example, in the case of an electronic component in which a plurality of resistors are integrated on one chip, an electronic component to be measured is set in an impedance measuring device, and a plurality of resistors are selected one by one by switching a switch. Thus, the respective resistance values of the plurality of resistors are measured one by one.
Conventionally, for example, when the resistance of each of the measured resistors is sequentially measured by sequentially switching the measured resistors with a switch, for example, a mechanical switch such as a reed relay having extremely small contact resistance and extremely large insulation resistance is used. The switching is performed by using a switch having an insulation resistance value of 10 ¹⁴ Ω (= 100000 GΩ) or more when turned off. If this is used, it should be measured. Even if the resistance value of the measured resistor is 1 GΩ,
The measurement error is 0.001%, and even if the number of resistors that are simultaneously set in the impedance measuring device is 11, and 10 resistors are opened by the switch, the measurement error is 0.01%. Not only that, it is possible to measure with high accuracy up to a high resistance value.

As described above, the resistance,
When the impedance of an impedance element such as a capacitor or a coil is measured by switching with a switch, a contact switch such as a reed relay having a relatively high inspection speed and a relatively long life is generally used. However, recently, in order to increase the inspection speed and extend the life of the switch for switching the impedance element,
In many cases, a semiconductor switch element (for example, a CMOS analog switch, a photo MOS relay, a V-MOSFET, a field-effect transistor, or the like) that can interrupt an analog current is used instead of a reed relay.

FIG. 6 is a circuit diagram of a conventional impedance measuring apparatus using a semiconductor switch element such as an analog switch capable of interrupting an analog current for selecting a resistor to be measured, which is an impedance element to be measured. In this impedance measuring device, as shown in FIG. 6, one end of a reference resistance (input resistance) R ₁ is connected to the inverting input terminal of an operational amplifier (for example, LF155A; made by National Semiconductor) A ₁ whose non-inverting input terminal is grounded. Then, a reference voltage source (DC voltage source) E ₁ that generates a constant DC voltage E _d is connected to the other end of the reference resistor R ₁ , and the device under test is connected between the inverting input terminal and the output terminal of the operational amplifier A _1. the selection circuit SE ₁ provided, and outputs a voltage E _n of the output terminal of the operational amplifier a ₁ as an impedance corresponding voltage. Reference voltage source E
₁ is composed of a resistor R ₄ and the Zener diode ZD generates a DC voltage E _d to. E _m is the voltage at the inverting input terminal of the operational amplifier A _1, the E _x is the voltage between the inverting input terminal and the output terminal of the operational amplifier A _1.

The element-under-test selection circuit SE ₁ is, for example, a semiconductor switch element (analog switch, for example, ADG) capable of interrupting an analog current to the inverting input terminal of the operational amplifier A _1.
201; manufactured by Analog Devices, Inc .: the same applies to other semiconductor switch elements.) _One end of S ₁ is connected to operational amplifier A
Be connected to one end of the intermittent possible semiconductor switching element S ₂ analog current to _the output terminal, one end of the measuring resistor R _x1 is connected to the other end of the semiconductor switching element S _1, the semiconductor switching element S ₂ Is connected to the other end of the resistor to be measured R _x1 . The element to be measured selection circuit SE _1, similar to the above semiconductor switching element S _3, S ₄ and the measurement resistor circuit consisting of R _x2, comprising a semiconductor switching element S _5, S ₆ and the measurement resistor R _x3 circuit, ‥‥‥, semiconductor switching elements S _2n-1, S _2n and the measurement resistor consisting R _xn circuit is provided.

The voltage at the output terminal of the operational amplifier A ₁ is amplified by an amplifier circuit composed of an operational amplifier (for example, LF155A; manufactured by National Semiconductor) A ₂ and resistors R ₂ and R ₃ and, for example, a voltage having a resistance scale. The resistance value is supplied to the display means DP constituted by a meter or the like, and the resistance value is displayed on the display means DP. The impedance measuring device shown in FIG. 6 turns on the semiconductor switch elements S ₁ and S ₂ and turns off the semiconductor switch elements S _{3 to} S _2n in a state where the resistors to be measured R _{x1 to} R _xn are set. resistor R _x2 to R _xn is released from the operational amplifier a _1, will be current flows through the inverting input terminal from the output terminal of the operational amplifier a ₁ only through the measurement resistor R _x1, the output terminal of the operational amplifier a ₁ at this time will be the voltage E _n in is proportional to the resistance value of the measurement resistor R _x1, display the voltage E _n of the output terminal of the operational amplifier a ₁ is amplified by an operational amplifier a ₂ and the like means D
By supplying the resistance to P, the resistance value of the measured resistor R _x1 can be measured, that is, displayed on the display means DP.

Similarly, the semiconductor switch elements S ₃ , S
₄ to turn on the semiconductor switch elements S ₁ , S ₂ , S ₅ .
By turning off S _2n , the resistance value of the measured resistor R _x2 can be displayed on the display means DP. The same applies to the other measured resistors R _{x3 to} R _xn .

[0010]

When the impedance element is selected by using the semiconductor switch element as described above, the inspection speed can be increased as described above.
While there are advantages such as longer switch life, measurement errors due to the effect of leakage current when the semiconductor switch element is off become a bottleneck, and measurement accuracy decreases when the impedance element to be measured has a relatively high impedance. It was impossible to use.

Here, the reason why the measurement accuracy is low is explained.
This will be described with reference to the equivalent circuit of FIG. Figure 7 shows the opea
Amp A₁And element under test selection circuit SE₁Equivalent circuit
Then, the semiconductor switch element S₁, S₂Turn on and other
Semiconductor switch element S₃~ S _2nTurn off the
Armor R_x13 shows a state in which the resistance value is measured. In FIG.
In the equivalent circuit, the semiconductor switch element S₁, S₂On
Ignoring resistance, semiconductor switch element S₃~ S_2nOFF resistance
R₃~ R_2nIt is represented by. i₁~ I_nIs the measured resistor
R_x1~ R_xn(Each with the same nominal value)
And i_xIs operational amplifier A₁Inverted input from output terminal of
This is the current flowing to the terminal.

For example, as the semiconductor switch elements S _{1 to} S _2n , an analog switch (ADG201:
Taking the Analog Devices Corp.) as an example, the analog switch is turned off when the leakage current (i ₂ through i _n) is 100nA per circuit (max) also occurs, it is a 10 circuit component (n = 11 in the case) becomes 1 .mu.A, the resistance values of the measured resistor R _x1 to R _xn and 1 M.OMEGA, difference between the voltage E _n of the voltage E _n and the inverting input terminal of the output terminal of the operational amplifier a ₁ at this time If the voltage E _x of 10 is set to 10 V, the current i ₁ flowing through the measured resistor R _x1 is ₁ μA.
A 100% error occurs due to the leak current. To reduce the error to 0.1%, it is practical only for measuring a resistor having a resistance value of 1 kΩ.

Furthermore, in order to reduce the error when measuring the resistance value of the resistor to be measured having a low resistance value, when a photo-mos relay, which is a semiconductor switch having a small ON resistance, is used, the CMOS analog switch About ten times as much leakage current is generated, and only lower resistance can be measured. The problem of the measurement error due to the leak current as described above can be solved by developing a semiconductor switch element with an ultra-low leak current comparable to a reed relay, which can measure even higher impedance, but at present, At present, such a thing is not available yet.

FIG. 8 shows an analog switch such as an analog switch.
A semiconductor switch element capable of interrupting current is connected to a coil or capacitor.
Conventionally used to select impedance elements to be measured such as sensors
The circuit diagram of another impedance measuring device of FIG. This a
As shown in FIG.
An operational amplifier whose input terminal is grounded (for example, LF155A;
National Semiconductor Corporation) A₁To the inverting input terminal
Reference resistance (input resistance) R₁Connect one end of the
₁AC voltage e with constant frequency and constant amplitude _iOccurs
Reference voltage source (AC voltage source) e₁Connect and Opean
A₁Select the device under test between the inverting input terminal and the output terminal of
Selector SE₂And the operational amplifier A₁Output terminal voltage
e_nOutput as an impedance-corresponding voltage.
ing. e_mIs operational amplifier A₁Voltage at the inverting input terminal of
e_xIs operational amplifier A₁Output terminal and inverted input terminal
Is the voltage of.

The element to be measured select circuit SE _2, in the device under test select circuit SE ₁ of FIG. 6, the measurement resistor R _x1 to R
Instead of _xn , impedance elements to be measured Z _{x1 to} Z _xn are set, and the other configuration is the same as that of FIG. Voltage at the output terminal of the operational amplifier A ₁ is an operational amplifier (e.g., LF155A; manufactured by National Semiconductor Corporation) are then amplified by the amplifier circuit consisting of A ₂ and resistor R _2, R ₃ into a voltage e _o outputted, further detection circuit ( Alternating current·
After being converted into a DC voltage E _o at DC converter circuit) RE,
For example, the resistance value is supplied to the display means DP including a voltmeter having a resistance value scale and the resistance value is displayed on the display means DP.

The impedance measuring device shown in FIG. 8 has the same problem as the impedance measuring device shown in FIG. SUMMARY OF THE INVENTION An object of the present invention is to provide an impedance measuring method and an impedance measuring apparatus capable of accurately measuring impedance up to a high impedance element to be measured without being affected by leakage current of a semiconductor switch element. .

[0017]

According to a first aspect of the present invention, there is provided an impedance measuring method wherein an analog current is intermittently inserted between an inverting input terminal and an output terminal of an operational amplifier and both ends of a plurality of impedance elements to be measured. By selectively turning on and off a group of semiconductor switch elements for selecting an element, one of the inverting input terminal and the output terminal of the operational amplifier and one of the plurality of impedance elements to be measured is provided.
Both ends of the measured impedance elements are electrically connected to each other, and both ends of the remaining measured impedance elements of the plurality of measured impedance elements are opened from the inverting input terminal and the output terminal of the operational amplifier. The impedance of any one of the measured impedance elements is selectively measured.

At this time, by selectively turning on and off the grounding semiconductor switch element group which is connected between the impedance-measured element side terminal of the element selection semiconductor switch element group and the ground and is capable of interrupting the analog current. In addition, both ends of one of the plurality of impedance elements to be measured are opened from the ground, and the other ends of the plurality of impedance elements to be measured are connected to the ground.

According to a second aspect of the present invention, there is provided an impedance measuring apparatus, wherein one end of a reference resistor is connected to an inverting input terminal of an operational amplifier having a non-inverting input terminal grounded, and a reference voltage source is connected to the other end of the reference resistor. A device-under-test selection circuit is provided between the input terminal and the output terminal to output the voltage of the output terminal of the operational amplifier as a voltage corresponding to the impedance.

The device to be measured selection circuit connects one end of a first semiconductor switching device capable of interrupting an analog current to the inverting input terminal of the operational amplifier, and connects the other end of the first semiconductor switching device to the impedance device to be measured. One end is connected,
One end of a second semiconductor switch element capable of interrupting analog current is connected to the other end of the first semiconductor switch element;
The other end of the semiconductor switch element is grounded, the output terminal of the operational amplifier is connected to one end of a third semiconductor switch element capable of interrupting analog current, and the other end of the third semiconductor switch element is connected to the other end of the impedance element to be measured. The ends are connected and the third
The other end of the fourth semiconductor switch element is connected to one end of a fourth semiconductor switch element capable of interrupting analog current, and the other end of the fourth semiconductor switch element is grounded. And the first
Or, a plurality of sets of fourth semiconductor switching elements are provided.

According to a third aspect of the present invention, there is provided an impedance measuring apparatus, wherein one end of a reference resistor is connected to an inverting input terminal of an operational amplifier having a non-inverting input terminal grounded, and a reference voltage source is connected to the other end of the reference resistor. A device-under-test selection circuit is provided between the input terminal and the output terminal to output the voltage of the output terminal of the operational amplifier as a voltage corresponding to the impedance.

In the device under test selection circuit, one end of the first semiconductor switching device capable of interrupting the analog current is connected to the inverting input terminal of the operational amplifier, and the analog current can be interrupted at the other end of the first semiconductor switching device. A third semiconductor switch element is connected to one end, the other end of the second semiconductor switch element is connected to one end of the impedance element to be measured, and the other end of the first semiconductor switch element is capable of interrupting an analog current. Connected to one end of the third semiconductor switching device, the other end of the third semiconductor switching device is grounded, and one end of a fourth semiconductor switching device capable of interrupting an analog current is connected to the output terminal of the operational amplifier. One end of a fifth semiconductor switch element capable of connecting and disconnecting an analog current is connected to the other end of the switch element, and the measured impedance element is connected to the other end of the fifth semiconductor switch element. The other end is connected, one end of the fourth semiconductor switch sixth semiconductor switch device capable of connecting and disconnecting an analog current to the other end of the device connected, is grounded and the other end of the semiconductor switching device of the sixth. And the first to sixth
Are provided in plural sets.

An impedance measuring apparatus according to a fourth aspect is the impedance measuring apparatus according to the second or third aspect, wherein the reference voltage source is a DC voltage source for generating a constant DC voltage. According to a fifth aspect of the impedance measuring device of the second or third aspect, the reference voltage source is an AC voltage source that generates an AC voltage having a constant amplitude and a constant frequency.

[0024]

According to the configuration of the first aspect of the present invention, when measuring the impedance of any one of the plurality of impedance elements to be measured,
Both ends of the remaining ones of the plurality of impedance elements to be measured are grounded, and the leakage current of the semiconductor switch element which is off on both sides of the remaining ones of the plurality of impedance elements to be measured. Does not flow from the output terminal of the operational amplifier to the non-inverting input terminal through the rest of the plurality of impedance elements to be measured. Among the semiconductor switch elements in the off state on the respective opposite sides of the plurality of impedance elements to be measured, the semiconductor switch element on the output terminal side of the operational amplifier is inserted between the output terminal of the operational amplifier and ground. Since the output impedance of the operational amplifier is extremely small, the influence of the leakage current of the semiconductor switch element on the output terminal side of the operational amplifier can be ignored. Further, among the semiconductor switch elements in the off state on both sides of the remaining impedance elements to be measured, the semiconductor switch element on the inverting input terminal side of the operational amplifier is the inverting input terminal of the operational amplifier, the ground, and , And the voltage gain of the open loop of the operational amplifier is sufficiently large and the voltage of the inverting input terminal is extremely small, so that it can be ignored. Therefore, any one of the plurality of impedance elements to be measured is hardly affected by the leakage current of the semiconductor switch element in the off state on each of the remaining sides of the plurality of impedance elements to be measured. It is possible to measure the impedance of one measured impedance element, and therefore it is possible to accurately measure the impedance of even the measured impedance element having a high impedance.

According to the configuration of the second aspect of the present invention, the first and third semiconductor switch elements of any one set of the device-under-test selection circuit are turned on and the second and fourth semiconductor switch elements are turned on. By turning off the switch element and turning off the first and third semiconductor switch elements of the remaining set in the element-under-test selection circuit and turning on the second and fourth semiconductor switch elements, The inverting input terminal and the output terminal and both ends of any one set of the measured impedance element of the measured element selection circuit are electrically connected to each other, and the remaining set of the measured impedance element of the measured element selection circuit are connected. Open from both the inverting input terminal and the output terminal of the operational amplifier, and connect both ends of the impedance element to be measured in any one set of the element to be measured circuit. Along with releasing from the ground, the two ends of the measured impedance element of the remaining set of the measured element selection circuit and the ground are conducted, and the measured impedance element of any one set of the measured element selection circuit Selectively measure impedance.

In this case, both ends of the remaining set of impedance elements to be measured in the element selection circuit to be measured are grounded, and the remaining sets of impedance to be measured of the element selection circuit to be measured are grounded. The leakage current of the first and third semiconductor switching elements that are off at both ends flows from the output terminal of the operational amplifier to the non-inverting input terminal through the remaining set of the measured impedance elements of the measured element selection circuit. Absent. Of the first and third semiconductor switch elements in the off state on both sides of the remaining set of the measured impedance elements of the measured element selection circuit, the third semiconductor switch element on the output terminal side of the operational amplifier is The state is inserted between the output terminal of the operational amplifier and the ground, and the output impedance of the operational amplifier is extremely small. Therefore, the influence of the leakage current of the semiconductor switch element on the output terminal side of the operational amplifier can be ignored.
Also, of the first and third semiconductor switch elements in the off state on both sides of the remaining set of the measured impedance elements of the measured element selection circuit, the first semiconductor on the inverting input terminal side of the operational amplifier The switch element is inserted between the inverting input terminal of the operational amplifier and the ground, and can be ignored because the open-loop voltage gain of the operational amplifier is sufficiently large and the voltage of the inverting input terminal is extremely small. Accordingly, the device under test is hardly affected by the leakage current of the first and third semiconductor switching devices that are off on both sides of the remaining set of the device under test of the device under test selection circuit. It is possible to measure the impedance of any one set of the measured impedance elements of the selection circuit, and therefore it is possible to accurately measure the impedance up to the high impedance measured elements.

According to the third aspect of the present invention, any one of the first, second and third elements of the device-under-test selection circuit is selected.
Turning on the fourth and fifth semiconductor switch elements and turning off the third and sixth semiconductor switch elements,
By turning off the first, second, fourth and fifth semiconductor switch elements of the remaining set in the element-under-test selection circuit and turning on the third and sixth semiconductor switch elements, the operational amplifier While conducting both the inverting input terminal and the output terminal and both ends of the impedance element under test of any one of the element under test selection circuits,
Both ends of the measured impedance element of the remaining set of the measured element selection circuit are opened from the inverting input terminal and output terminal of the operational amplifier, and the measured impedance element of any one set of the measured element selection circuit is Both ends are released from ground, and both ends of the measured impedance element of the remaining set of the measured element selection circuit are conducted to the ground, and the measured impedance of any one set of the measured element selection circuit is measured. Selectively measure the impedance of the device.

In this case, both ends of the remaining set of impedance elements to be measured of the element to be measured are grounded, and the remaining sets of impedance to be measured of the element to be measured are selected. The leakage current of the first, second, fourth, and fifth semiconductor switch elements that are off at both ends is non-inverted from the output terminal of the operational amplifier through the remaining set of measured impedance elements of the measured element selection circuit. It does not flow to the input terminal. Of the first and fourth semiconductor switch elements in the off state on both sides of the remaining set of impedance elements to be measured in the element to be measured selection circuit, the fourth semiconductor switch element on the output terminal side of the operational amplifier is The state is inserted between the output terminal of the operational amplifier and the ground, and the output impedance of the operational amplifier is extremely small. Therefore, the influence of the leakage current of the semiconductor switch element on the output terminal side of the operational amplifier can be ignored. Also, of the first and fourth semiconductor switch elements in the off state on both sides of the remaining set of impedance elements to be measured in the element to be measured selection circuit, the first semiconductor on the inverting input terminal side of the operational amplifier The switch element is inserted between the inverting input terminal of the operational amplifier and the ground, and can be ignored because the open-loop voltage gain of the operational amplifier is sufficiently large and the voltage of the inverting input terminal is extremely small. Therefore, it is hardly affected by the leakage current of the first and fourth semiconductor switch elements that are in the off state on both sides of the remaining set of the measured impedance elements in the measured element selection circuit.
It is possible to measure the impedance of any one set of the measured impedance elements of the measured element selection circuit, and thus to accurately measure the impedance of the measured impedance elements having a high impedance.

According to the configuration of the fourth aspect of the invention, the resistance value of the resistor as the impedance element can be measured. According to the configuration of the invention described in claim 5, the impedance of the coil and the capacitor as the impedance element can be measured.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an impedance measuring apparatus according to a first embodiment of the present invention in which a semiconductor switch element capable of interrupting an analog current such as an analog switch is used for selecting a resistor to be measured as an impedance element to be measured. Show. The impedance measuring apparatus, as shown in FIG. 1, instead of the device under test select circuit SE ₁ in FIG. 6,
But using element selection circuit SE ₅ to be measured, other configurations are the same as the impedance measurement device of FIG.

Device under test selection circuit SE₃Is an operation
Amplifier A₁Analog current can be intermittently applied to the inverting input terminal of
First semiconductor switch element (analog switch, for example,
ADG201; manufactured by Analog Devices, Inc .: other semiconductor
The same applies to the switch element) S ₁₁Connect one end of the first
Semiconductor switch element S₁₁Analog current can be intermittently applied to the other end
Functioning second semiconductor switch element S₁₂Connect one end of the
1 semiconductor switching element S₁₁The analog current to the other end of
Connectable third semiconductor switch element S₁₃Connect one end of
And the third semiconductor switch element S₁₃Ground the other end of the
Pair A₁An analog current can be intermittently output to the output terminal of
Fourth semiconductor switch element S_{twenty one}Connect one end of the 4th half
Conductor switch element S_{twenty one}Analog current can be interrupted at the other end of
Fifth semiconductor switch element S_{twenty two}Connect one end of the
Semiconductor switch element S_{twenty one}Analog current at the other end
Possible sixth semiconductor switch element S_{twenty three}Connect one end of
Sixth semiconductor switch element S_{twenty three}Ground the other end of the
Semiconductor switch element S₁₂To the other end of the measured resistor R_x1One
Ends are connected to each other, and the fifth semiconductor switch element S_{twenty two}At the other end of
Measured resistor R_x1The other end of is connected.

[0032] the measured element selection circuit SE ₃ is similar to the above semiconductor switching element _{S 31, S 32, S 33} , S 41,
A circuit composed of S ₄₂ , S ₄₃ and a resistor R _x2 to be measured, a circuit composed of semiconductor switch elements S ₅₁ , S ₅₂ , S ₅₃ , S ₆₁ , S ₆₂ , S ₆₃ and a resistor R _x3 to be measured; , Semiconductor switching elements S _{(2n-1) 1} , S _{(2n-1) 2} , S _{(2n-1) 3} , S
_{A circuit including (2n) 1} , S _{(2n) 2} , S _{(2n) 3} and a resistor to be measured R _xn is provided.

Here, the impedance measuring device of FIG.
The used impedance measurement method will be described. this
In the impedance measurement method, the operational amplifier A₁Inversion of
Force terminal and output terminal and multiple resistors R under test_x1~ R
_xnBetween the two ends of the
Semiconductor switch element S for continuous selection₁₁~ S_n1, S ₁₂
~ S_n2By selectively turning on and off
A₁Inverting input and output terminals and multiple DUTs
Resistor R_x1~ R_xnEach one of the two ends
And the plurality of resistors to be measured R_x1~ R
_xnOp amp A at both ends₁Inverting input terminal
And multiple resistors R to be measured_x1
~ R_xnSelect one of the resistance values (DC resistance)
Measurement.

At this time, the semiconductor switch elements S _{11 to} S _n1 ,
By S ₁₂ are respectively connected between the measured resistor terminal and ground to S _n2 selectively turning on and off the semiconductor switching element S ₁₃ to S _n3 for intermittent ground plane an analog current, a plurality as well as free from any one of the ground both ends of the measurement resistor R _x1 to R _xn of, thereby turning on the remaining ends and the ground of the plurality of the measurement resistor R _x1 to R _xn .

Hereinafter, the impedance measuring apparatus shown in FIG.
The measurement of the resistance value will be described specifically. Of FIG.
The impedance measuring device is a resistor R to be measured._x1~ R_xnTo
In the set state, the semiconductor switch element S₁₁, S
₁₂, S_{twenty one}, S_{twenty two}To turn on the semiconductor switch element S₁₃,
S_{twenty three}To turn off the semiconductor switch element S₃₁, S₃₂,
S ₄₁, S₄₂, ‥‥‥, S_{(2n-1) 1}, S_{(2n-1) 2}, S
_{(2n) 1}, S_{(2n) 2}Turn off the semiconductor switch element
S₃₃, S₄₃, ‥‥‥, S_{(2n-1) 3}, S_{(2n) 3}Turn on
Then, the measured resistor R_x2~ R_xnIs operational amplifier A₁Open from
Released, resistor R to be measured_x1Operational amplifier A only through₁
Current will flow from the output terminal of
The operational amplifier A at this time₁Output terminal voltage E_nBut
Measured resistor R_x1Is proportional to the resistance value of
Amplifier A₁Output terminal voltage E_nIs the operational amplifier A ₂Etc.
By amplifying and supplying it to the display means DP, the measured resistor
R_x1Resistance value is measured, that is, displayed on the display means DP.
be able to.

Similarly, the semiconductor switch element S₃₁, S
₃₂, S₄₁, S₄₂To turn on the semiconductor switch element S₃₃,
S₄₃To turn off the semiconductor switch element S₁₁, S₁₂,
S_{twenty one}, S _{twenty two}, S₅₁, S₅₂, S₆₁, S₆₂, ‥‥‥, S
_{(2n-1) 1}, S_{(2n-1) 2}, S_{(2n) 1}, S _{(2n) 2}Turn off
And the semiconductor switch element S₁₃, S_{twenty three}, S₅₃, S₆₃‥‥‥
‥, S_{(2 n-1) 3}, S_{(2n) 3}By turning on the
Resistor R_x2Can be displayed on the display means DP.
it can. Other resistor R to be measured_x3~ R_xnThe same applies to
is there.

According to the impedance measuring apparatus of this embodiment, as described above, each semiconductor switch element S ₁₁ ,
By switching on and off of S ₁₂ , S ₁₃ , ‥‥‥, S _{(2n) 1} , S _{(2n) 2} , S _{(2n) 3} , the inverting input terminal and output terminal of the operational amplifier A ₁ and the element to be measured selection circuit with each to conduct, for example in the two ends of the measuring resistor R _x1 SE _3, an inverting input terminal ends of the operational amplifier a ₁ of the remaining measured resistor R _x2 to R _xn of the element to be measured select circuit SE ₃ and then released from an output terminal, with the opening the both ends of the measuring resistor R _x1 of the element to be measured select circuit SE ₃ from ground, to conduct both ends and ground of the measured resistor R _x2 to R _xn, The resistance value of the measured resistor R _x1 can be selectively measured. In this case, both ends of the remaining resistors to be measured R _{x2 to} R _xn are grounded, and the first, second, and second ends of the remaining resistors to be measured R _{x2 to} R _xn are turned off. fourth and fifth semiconductor switching elements _{S 11, S 12, S 21} , to flow the leakage current of S ₂₂ is through the remainder of the measured resistor R _x2 to R _xn from the output terminal of the operational amplifier a ₁ to the non-inverting input terminal There is no. Among the first and fourth semiconductor switch elements S ₁₁ and S ₂₁ in the off state on both sides of the remaining resistors R _{x2 to} R _{xn to} be measured, the fourth semiconductor switch on the output terminal side of the operational amplifier A ₁ element S ₂₁ becomes the inserted state between the output terminal and ground of the operational amplifier a _1, the output impedance of the operational amplifier a ₁ is very small, the operational amplifier a
Effect of the leakage current of the _first output terminal of the semiconductor switching element S ₂₃ is negligible. Further, the remaining resistors to be measured R _x2 to
One of the first and fourth semiconductor switching elements S _11, S ₂₁ which is the opposite sides of the off state of the R _xn, first semiconductor switch element S ₁₁ of the inverting input terminal of the operational amplifier A ₁ is an operational amplifier A ₁ because of it the inserted state between the inverting input terminal and ground, the voltage of the voltage gain of the open loop of the operational amplifier a ₁ is sufficiently large inverting input terminal is very small, negligible. Therefore, hardly affected the leakage current of the remaining measured resistor R _x2 first and fourth that is the opposite sides of the off state of the to R _xn semiconductor switching element S _11, S _21, the measured resistance The impedance of the device R _x1 can be measured, and therefore, the impedance can be measured with high accuracy even to a high impedance element to be measured.

Here, the reason why the measurement accuracy is increased will be described with reference to the equivalent circuit of FIG. Figure 2 is an equivalent circuit of the portion of the operational amplifier A ₁ and the device under test selection circuit SE _3, the semiconductor switching element _{S 11, S 12, S 21} , S 22 is turned on, the semiconductor switching element S _13, S ₂₃ clear , Semiconductor switch elements S ₃₁ , S ₃₂ , S ₄₁ , S ₄₂ ,..., S _{(2
n-1) 1} , S _{(2n-1) 2} , S _{(2n) 1} , S _{(2n) 2} are turned off,
Semiconductor switch elements S ₃₃ , S ₄₃ , ‥‥‥, S _{(2n-1) 3} ,
It shows a state in which S _{(2n) 3} is turned on and the resistance value of the measured resistor R _x1 is measured. In the equivalent circuit of FIG. 2, semiconductor switch elements S ₁₁ , S ₁₂ , S ₂₁ , S ₂₂ , S ₃₃ , S ₄₃ , ....
The ON resistances of ‥, S _{(2n-1) 3} and S _{(2n) 3} are ignored, and the semiconductor switch elements S ₁₃ , S ₂₃ , S ₃₁ , S ₃₂ , S ₄₁ , S ₄₂ , ‥
オ フ, S _{(2 n-1) 1} , S _{(2n-1) 2} , S _{(2n) 1} , S _{(2n) 2} are set to off resistances r ₁₃ , r ₂₃ , r ₃₁ , r ₃₂ , r ₄₁ , r ₄₂ , ‥‥
‥, r _{(2n-1) 1} , r _{(2n-1) 2} , r _{(2n) 1} , r _{(2n) 2} . i ₁ through i _n is the current through the measured resistor R _x1 to R _xn (nominal value same) respectively, i _x is the current flowing from the output terminal of the operational amplifier A ₁ to the inverting input terminal.

Here, in the above-described equivalent circuit, taking the above-described analog switch (ADG201: manufactured by Analog Devices) as an example of the semiconductor switch elements S _{1 to} S _2n , numerically indicate that the error is reduced. explain. As shown in the equivalent circuit of FIG. 2, the off resistance r ₂₃ of the semiconductor switches S ₂₃ , S ₄₁ ,..., S _{(2n) 1 in} the off state,
_{r 41, ‥‥‥, r (2n} ) 1 are all in parallel, they enter a state between the output terminal and the ground of the operational amplifier A ₁ (the equivalent circuit and r _o the combined resistance shown in FIG. 3) and , Its effects can be ignored.

That is, taking the case of using, for example, LF155A manufactured by National Semiconductor as the operational amplifier A ₁ , the closed loop gain Gc = 10 at DC.
Then, the output impedance of the operational amplifier A ₁ is 0.
2 Ω or less, r _o = E _n / total leak current of the semiconductor switch (for example, 1 μA) ≈10 V / 1 μA =
Since it is 10MΩ, the effect is 0.2Ω / 10000000Ω
= 2/10 because it is ^8, E _n ≒ Ex, i.e., E _m ≒
It can be considered 0.

Further, the semiconductor switch S in the off state₁₃, S
₃₁, ‥‥‥, S_{(2n-1) 1}Off resistance r₁₃, R₃₁‥‥‥
‥, r_{(2n-1) 1}Are all in parallel, operational amplifier A₁Anti
The state that it is between the input terminal and the ground (combined resistance
FIG. 3 shows an equivalent circuit where ri is
i₂, I₃, ..., i_nIs the operational amplifier A₁Output terminal
Voltage E_nTherefore, the operational amplifier A₁To the inverting input terminal of
And the combined resistance r_iThe impact of the opean
A₁Open-loop voltage gain G₀Is big enough
Can be ignored. National Semiconductor
In the case of LF155A manufactured by the company, G₀= 106dB ≒ 200000
Because there is, E_x= 10V, R_x= 1 MΩ, i₁
= E_x/ R_x= 10 V / 1 MΩ = 10 μA,
The above r_oAs in r_i= 10MΩ
If i_ri= E_m/ (G₀× r_i) = 10V / 200000 ÷ 1
0MΩ = 0.5 × 10^-FiveμA, i_ri/ I₁=
0.5 x 10 ^Five/10=0.5×10⁶Is it the effect of
I, i₁= I_xCan be considered.

FIG. 4 is a circuit diagram of an impedance measuring apparatus according to a second embodiment of the present invention in which a semiconductor switching element such as an analog switch capable of interrupting an analog current is used for selecting an impedance element to be measured such as a coil or a capacitor. Is shown. The impedance measuring apparatus, as shown in FIG. 4, in place of the element to be measured select circuit SE ₂ in FIG. 8, but with the device under test selection circuit SE _4, other configurations are impedance measuring apparatus of FIG. 8 Is the same as

The element to be measured select circuit SE _4, in the device under test selection circuit SE ₃ in FIG. 1, the measurement resistor R _x1 to R
Instead of _xn , impedance elements to be measured Z _{x1 to} Z _xn are set, and the other configuration is the same as that of FIG. According to the impedance measuring apparatus of this embodiment, the impedances of the measured impedance elements Z _{x1 to} Z _xn such as coils and capacitors can be measured in the same manner as in the first embodiment. Similarly, the same effect can be expected by selecting the conditions of the components (semiconductor switch, operational amplifier, etc.) used for the required measurement accuracy.

[0044] Note that the semiconductor switching element S _12, S ₂₂ in FIG _{1, ‥‥‥, S (n-} 1) 2, S n2 , the semiconductor switching elements _{S 13, S 23, ‥‥‥,} S (n _{−1) 3} , S _{n3 has} an ON resistance that is not completely zero, for example, suppresses a leak current flowing through the resistors R _{x2 to} R _xn when measuring the resistor R _x1 ,
Although provided to further reduce the measurement error, the semiconductor switching elements S ₁₃ , S ₂₃ , ‥‥‥, S _{(n−1) 3} , S _n3
As shown in FIG.
As shown in the figure, the semiconductor switch elements S ₁₂ , S ₂₂ ,.
素 子, S _{(n-1) 2} , element to be measured SE ₅ omitting S _n2
It is also possible to use.

[0045]

According to the impedance measuring method of the present invention, when measuring the impedance of any one of the plurality of impedance elements to be measured, a plurality of impedance elements to be measured are measured. The other end of each of the elements can be grounded,
Any one of the plurality of impedance elements to be measured, which is hardly affected by the leakage current of the semiconductor switching element in the off state on the respective opposite sides of the plurality of impedance elements to be measured. It is possible to measure the impedance of the impedance element to be measured, and thus it is possible to accurately measure the impedance of the impedance element to be measured having a high impedance.

According to the impedance measuring device of the second aspect, the second semiconductor switch element having one end connected to the other end of the first semiconductor switch element and the other end grounded, and the third semiconductor switch element Since a fourth semiconductor switch element having one end connected to the other end and the other end grounded is provided, when measuring the impedance of any one of the measured impedance elements of the measured element selection circuit, Both ends of the measured impedance element of the remaining set of the measuring element selection circuit can be grounded, and both sides of the measured impedance element of the remaining set of the measured element selection circuit are in the off state. The impedance of the impedance element to be measured of any one of the element selection circuits to be measured is hardly affected by the leakage current of the first and third semiconductor switching elements. Impedance becomes possible to measure, thus it is possible to accurately measure the impedance to be measured impedance element with high impedance.

According to the impedance measuring apparatus of the third aspect, the second semiconductor switch element having one end connected to the other end of the first semiconductor switch element and one end of the impedance element to be measured connected to the other end, A third semiconductor switch element having one end connected to the other end of the first semiconductor switch element and the other end grounded; and a fourth semiconductor switch element having one end connected to the other end and the other end connected to the impedance element to be measured. The fifth semiconductor switch element to which the end is connected and the sixth semiconductor switch element having one end connected to the other end of the fourth semiconductor switch element and the other end grounded are provided. When measuring the impedance of any one set of the measured impedance elements, both ends of the remaining set of the measured impedance elements in the measured element selection circuit can be grounded. Being substantially affected by the leakage current of the first, second, fourth and fifth semiconductor switch elements in the off state on both sides of the remaining set of the measured impedance elements of the measured element selection circuit. In addition, it is possible to measure the impedance of any one set of the measured impedance elements in the measured element selection circuit, and therefore it is possible to accurately measure the impedance of the measured impedance elements having a high impedance.

According to the impedance measuring apparatus of the fourth aspect, the semiconductor switch element for selecting any one of the plurality of resistors as the impedance element to be measured is hardly affected by the leak current of the semiconductor switch element. It is possible to accurately measure the resistance value of a resistor having a high resistance. According to the impedance measuring apparatus of the fifth aspect, a high impedance is hardly affected by a leakage current of a semiconductor switch element for selecting one of a plurality of coils or capacitors as impedance elements to be measured. The impedance can be measured with high accuracy even for a coil or a capacitor having the following.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an impedance measuring device according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a main part of the impedance measuring device of FIG.

FIG. 3 is an equivalent circuit diagram of the circuit of FIG.

FIG. 4 is a circuit diagram showing a configuration of an impedance measuring device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a modified example of the impedance measuring device.

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

7 is an equivalent circuit diagram of a main part of the impedance measuring device of FIG.

FIG. 8 is a circuit diagram showing a configuration of a second conventional impedance measuring device.

[Explanation of symbols]

A ₁ operational amplifier SE ₃ device to be measured selection circuit E ₁ reference voltage source R ₁ reference resistance S _{11 to} S _n3 semiconductor switching device

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[Procedure amendment]

[Submission date] February 24, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (5)

[Claims] _1. An inverting input terminal and an output terminal of an operational amplifier (A ₁ ) and a plurality of impedance elements to be measured (R _x1
To R _xn ), each of which is inserted between both ends of the element selection semiconductor switch element group (S ₁₁
To S _{(2n) 1} ) are selectively turned on and off, so that the inverting input terminal and output terminal of the operational amplifier (A ₁ ) and the plurality of impedance elements to be measured (R _{x1 to} R _xn ).
Are electrically connected to both ends of one of the impedance elements to be measured, and both ends of the remaining impedance elements to be measured among the plurality of impedance elements to be measured (R _{x1 to} R _xn ) are connected to the operational amplifier. (A ₁ )
The impedance measuring method, wherein the impedance measuring device is opened from the inverting input terminal and the output terminal and selectively measures the impedance of any one of the plurality of impedance elements to be measured (R _{x1 to} R _xn ). the element selection semiconductor switching element group (S ₁₁ ~
S _{(2n) 1)} of selectively turning on and off the connected respectively to the analog interruptor ground plane for semiconductor switching element group between the measured impedance element-side terminal and the ground _{(S 13 ~S (2n) 3} ) By doing so, any one of the plurality of impedance elements to be measured (R _{x1 to} R _xn )
Impedance measurement, characterized in that both ends of each of the impedance elements to be measured are opened from the ground, and the other ends of the plurality of impedance elements to be measured (R _{x1 to} R _xn ) are electrically connected to the ground. Method. 2. An operational amplifier having a non-inverting input terminal grounded.
(A₁) And this operational amplifier (A₁) Inverting input terminal
Reference resistance (R₁) And this reference resistance (R₁) Is connected to a reference voltage source (E
₁) And the operational amplifier (A₁) Inverting input terminal and output terminal
The element to be measured selection circuit (SE₃), And the device-under-test selection circuit (SE)₃) Is the operational amplifier
(A₁Connect one end to the inverting input terminal of
Impedance element (R_x1~ R_xn) One end is connected
The first semiconductor switch element (S₁₁
~ S_{(2n-1) 1}) And the first semiconductor switch element (S
₁₁~ S_{(2n-1) 1}) Is connected to one end and the other end is grounded
Second semiconductor switch element capable of interrupting analog current
(S₁₃~ S _{(2n-1) 3}) And the operational amplifier (A₁Out)
Connect one end to the force terminal and the impedance element to be measured to the other end
(R_x1~ R_xn) Is connected to the other end and analog current can be interrupted
Functional third semiconductor switch element (S_{twenty one}~ S_{(2n) 1})When,
The third semiconductor switch element (S_{twenty one}~ S_{(2n) 1}) Other
Analog current with one end connected and the other grounded can be intermittent
Functional fourth semiconductor switch element (S_{twenty three}~ S_{(2n) 3}) And
The operational amplifier (A₁) Output terminal voltage
It is characterized in that it is output as a voltage corresponding to
Impedance measuring device. 3. An operational amplifier having a non-inverting input terminal grounded.
(A₁) And this operational amplifier (A₁) Inverting input terminal
Reference resistance (R₁) And this reference resistance (R₁) Is connected to a reference voltage source (E
₁) And the operational amplifier (A₁) Inverting input terminal and output terminal
The element to be measured selection circuit (SE₃), And the device-under-test selection circuit (SE)₃) Is the operational amplifier
(A₁Analog current with one end connected to the inverting input terminal
Semiconductor switch element (S₁₁~ S
_{(2n-1) 1}) And the first semiconductor switch element (S₁₁~
S_{(2n-1) 1}) To the other end and connect the other end to the measured impedance
-Dance element (R_x1~ R_xnAnalog to which one end is connected
Semiconductor switch element (S₁₂~
S_{(2n-1) 2}) And the first semiconductor switch element (S₁₁
~ S_{(2n-1) 1}) With one end connected to the other end and the other end grounded
A third semiconductor switch element (S
₁₃~ S _{(2n-1) 3}) And the operational amplifier (A₁) Output end
The fourth half which can interrupt the analog current with one end connected to the
Conductor switch element (S_{twenty one}~ S_{(2n) 1}) And this fourth half
Conductor switch element (S_{twenty one}~ S_{(2n) 1}Connect one end to the other end of
The other end of the impedance element to be measured (R_x1~
R_xn) The other end of which is connected
5 semiconductor switch elements (S_{twenty two}~ S_{(2n) 2}) And the above
4 semiconductor switch element (S_{twenty one}~ S_{(2n) 1}) To the other end
The other end is connected and the other end is grounded.
6 semiconductor switch element (S_{twenty three}~ S_{(2n) 3}) And multiple pairs
The operational amplifier (A₁) Output terminal voltage
It is characterized in that it is output as a voltage corresponding to
Impedance measuring device. 4. The impedance measuring device according to claim 2, wherein the reference voltage source is a DC voltage source for generating a constant DC voltage. 5. The impedance measuring apparatus according to claim 2, wherein the reference voltage source is an AC voltage source that generates an AC voltage having a constant amplitude and a constant frequency.