TWI729631B - Method for measuring impedance - Google Patents

Abstract

The invention discloses a method for measuring impedance of a device under test, briefly named DUT. In a first mode, a first end of the DUT is powered the cross voltage of the DUT is measured by the first testing module to obtain a first voltage value, and the current flow through the DUT is measured by the second testing module to obtain a first current value. In a second mode, a second end of the DUT is powered, the cross voltage of the DUT is measured by the second testing module to obtain a second voltage value, and the current flow through the DUT is measured by the first testing module to obtain a second current value. A real impedance value of the DUT is calculated according to the first voltage value , the second voltage value, the first current value, and the second current value.

Description

Impedance measurement method

The present invention relates to a measurement method, in particular to an impedance measurement method of a component under test.

In order to cope with the trend that the device under test has multiple pins and more and more complex functions, testing devices have gradually adopted a multi-channel measurement architecture with greater flexibility. For example, in order to support the high parallel test function, the test device can adopt any pin measurement structure. In other words, no matter how the device under test is connected to the pins of the test device, the test device can obtain the voltage, current or other electrical parameters of the electronic component through different internal measurement circuits. In this way, the flexible multi-channel measurement architecture can increase the user's operating convenience and can improve the competitiveness of the product.

However, obtaining the voltage, current or other electrical parameters of electronic components by different measurement circuits will actually encounter some problems. For example, the measurement circuit may cause measurement errors due to internal component deviation, aging, or environmental factors (such as temperature and humidity). In particular, the degree of error in different measurement circuits is likely to be different, resulting in errors that cannot be offset in calculations. Therefore, the industry needs a new measurement method to solve the problem of errors in voltage and current obtained by different measurement circuits.

The present invention provides an impedance measurement method, which can provide electrical energy from different directions for the component under test, and then use different measurement circuits to measure the voltage and current respectively, so that the errors of different measurement circuits can be offset by calculation.

The present invention provides an impedance measurement method, which is applied to measure the component under test. The first end of the component under test is electrically connected to the first test module, and the second end of the component under test is electrically connected to the second test module. The impedance measurement method includes the following steps. In the first mode, power is supplied to the first terminal of the device under test. In the first mode, the first test module measures the voltage across the device under test to obtain the first voltage value, and the second test module measures the current flowing through the device under test to obtain the first current value. In the second mode, power is supplied to the second end of the device under test. In the second mode, the second test module measures the voltage across the device under test to obtain the second voltage value, and the first test module measures the current flowing through the device under test to obtain the second current value. According to the first voltage value, the second voltage value, the first current value, and the second current value, the true impedance value of the component under test is calculated.

In some embodiments, the impedance measurement method may further include the following steps in the step of calculating the true impedance value of the device under test. In the first mode, the first voltage value can be divided by the first current value to obtain the first impedance measurement value. Also, in the second mode, the second voltage value can be divided by the second current value to obtain the second impedance measurement value, wherein the real impedance value is related to the first impedance measurement value and the second impedance measurement value. In addition, the impedance measurement method can further multiply the first impedance measurement value by the second impedance measurement value to obtain the first calculation value, and can take the root of the first calculation value to obtain the true impedance value. In addition, the first voltage value and the second current value may both include a first circuit error factor associated with the first test module, and the second voltage value and the first current value may both include a second circuit error factor associated with the second test module. Circuit error factor.

In some embodiments, in the step of supplying power to the first end of the device under test, the first test module may supply power to the first end of the device under test. Moreover, in the step of supplying power to the second end of the component under test, the second test module can supply power to the second end of the component under test.

In summary, the impedance measurement method provided by the present invention can provide electrical energy from the first end and the second end of the device under test, and then use the respective measurement of the first test module and the second test module. The circuit measures the voltage and current respectively. In addition, the voltage and current obtained by the first test module and the second test module can be interactively calculated, thereby offsetting errors between different test modules through calculation.

The features, objectives and functions of the present invention will be further disclosed below. However, the following are only examples of the present invention, and should not be used to limit the scope of the present invention, that is, all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention will still be the essence of the present invention. Without departing from the spirit and scope of the present invention, it should be regarded as a further implementation aspect of the present invention.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a circuit using an impedance measurement method according to an embodiment of the present invention. As shown in FIG. 1, the impedance measurement method of the present invention can be applied between the first test module 10 and the second test module 12, and the first test module 10 and the second test module 12 can be used to measure Measure the component characteristics such as voltage, current and impedance of the same component under test 20. This embodiment does not particularly limit the hardware components corresponding to the first test module 10 and the second test module 12, for example, the first test module 10 and the second test module 12 may be two independent test cards. , And the first test module 10 and the second test module 12 can be arranged in the same test device (not shown). Alternatively, the first test module 10 and the second test module 12 may each be an independent device, and are electrically connected to the same device under test 20, respectively. In addition, this embodiment does not limit the type of the component under test 20, as long as the component under test 20 needs to use the first test module 10 and the second test module 12 to measure the characteristics of the components such as voltage, current, and impedance. It belongs to the category of the component under test 20 referred to in this embodiment. The internal components of the first test module 10 and the second test module 12 are respectively described below.

The first test module 10 may include a voltage sensing unit 100, a current sensing unit 102, and a measurement circuit 104. The voltage sensing unit 100 and the current sensing unit 102 may be electrically connected to the first terminal 200 of the device under test 20 And the measuring circuit 104 can be electrically connected to the voltage sensing unit 100 and the current sensing unit 102. Here, although the example in FIG. 1 shows that the first test module 10 includes a power supply 106, and the power supply 106 is also electrically connected to the first end 200 of the device under test 20, the power supply 106 is not a necessary component in practice. For example, the power supply 106 may also be provided outside the first test module 10, for example, it may be an external power supply. In other words, as long as the power supply 106 can supply power to the device under test 20 from the first end 200, it is in line with the scope of the power supply 106 in this embodiment.

Similarly, the second test module 12 may include a voltage sensing unit 120, a current sensing unit 122, and a measuring circuit 124. The voltage sensing unit 120 and the current sensing unit 122 may be electrically connected to the first device under test 20. The two terminals 202 and the measuring circuit 124 can be electrically connected to the voltage sensing unit 120 and the current sensing unit 122. Like the power supply 106, the power supply 126 can also be provided outside the second test module 12, for example, it can also be an external power supply. For the convenience of description, this embodiment assumes that the first test module 10 and the second test module 12 include a power supply 106 and a power supply 126. In addition, although FIG. 1 uses two signal input and output terminals as an example, it is not used to limit the number of signal input and output terminals of the device under test 20. In practice, the component under test 20 may also include more signal input and output terminals, and the first terminal 200 and the second terminal 202 may only be two of the signal input and output terminals.

In a practical example, the first test module 10 and the second test module 12 can operate in two modes, which are referred to herein as the first mode and the second mode. In the first mode, the power supply 106 can supply power to the first terminal 200 of the device under test 20, the first test module 10 measures the voltage of the device under test 20, and the second test module 12 measures the device under test. 20 current. In practice, the voltage sensing unit 100 in the first test module 10 can be used to measure the voltage across the device under test 20, and transmit data corresponding to the voltage across the device under test 20 to the measurement circuit 104, and the measurement The circuit 104 obtains the first voltage value through conversion. In addition, the current sensing unit 122 in the second test module 12 is used to measure the current flowing through the device under test 20, and send data corresponding to the current flowing through the device under test 20 to the measuring circuit 124, The measuring circuit 124 obtains the first current value through conversion. In one example, the common ground terminal (not shown) of the first test module 10 and the second test module 12 can be connected together, so that the voltage sensing unit 100 can obtain the standby terminal through the first terminal 200 and the common ground terminal. Measure the voltage across the element 20. In addition, the current sensing unit 122 can measure the current flowing through the device under test 20 in a resistance series connection or current coupling manner. Since there are many methods for measuring current, this embodiment is not particularly limited.

In order to simplify the test conditions, the power supply 106 and the power supply 126 can be set to not work at the same time, that is, the power supply 126 can be turned off in the first mode. At this time, if the first voltage value converted by the measuring circuit 104 is expressed as V1, and the first current value converted by the measuring circuit 124 is expressed as I1, then the first impedance measurement value Z1 of the component under test 20 can be Expressed as the following formula (1): Z1 = V1 / I1 (1)

In an example, the first impedance measurement value Z1 can be calculated by the processor of the test device or an external computer, which is not limited in this embodiment. In addition, since the first voltage value V1 is obtained through the measurement circuit 104 and also includes the error of the measurement circuit 104 itself, the first voltage value V1 is not the actual cross voltage of the device under test 20. Similarly, since the first current value I1 is also obtained through the measuring circuit 124, it also includes the error of the measuring circuit 124 itself, so the first current value I1 is not actually the current flowing through the device under test 20. Suppose that in this embodiment, the error of the measurement circuit 104 itself is expressed as Gm1, and the error of the measurement circuit 124 itself is expressed as Gm2. In practice, there are many reasons for errors in the measurement circuit 104 and the measurement circuit 124, such as temperature differences, humidity differences, aging differences, internal component errors, etc. between different circuits. This embodiment does not specifically limit the reasons for the errors. . Continuing the above, if the errors Gm1 and Gm2 of the measurement circuit 104 and the measurement circuit 124 itself are substituted into equation (1), equation (1) can be sorted into equation (2): Z1 = (Vdut × Gm1) / (Idut × Gm2) (2)

Where Vdut is the actual voltage across the device under test 20, and Idut is the current actually flowing through the device under test 20. In other words, since Vdut and Idut are the actual voltage and current of the device under test 20, respectively, after dividing Vdut by Idut, the actual impedance value of the device under test 20 can be theoretically obtained. The actual impedance value of the measuring element 20 is called the true impedance value, and is expressed as Zdut. If Vdut/Idut is expressed by Zdut, then equation (2) can be sorted into equation (3): Z1 = Zdut × (Gm1/Gm2) (3)

It can be seen that, traditionally, if different test modules are used to measure the same component under test, the measured impedance value of the component under test contains the respective error items of the two test modules, which is likely to be different from that of the component under test. The actual impedance value of the test element is not the same. Accordingly, this embodiment will enter the second mode after the first mode, and measure the impedance value of the device under test 20 again. In the second mode, the power supply 106 can be turned off, and the power supply 126 can supply power to the second end 202 of the device under test 20 instead. Then, the second test module 12 measures the voltage of the device under test 20, and the first test module 10 measures the current of the device under test 20. Similar to the first mode, the voltage sensing unit 120 in the second test module 12 can be used to measure the voltage across the device under test 20, and transmit data corresponding to the voltage across the device under test 20 to the measurement circuit 124. The second voltage value is obtained by conversion by the measuring circuit 124. In addition, the current sensing unit 102 in the first test module 10 is used to measure the current flowing through the component under test 20, and send data corresponding to the current flowing through the component under test 20 to the measuring circuit 104, The measuring circuit 104 obtains the second current value through conversion.

At this time, if the second voltage value converted by the measurement circuit 124 is represented as V2, and the second current value converted by the measurement circuit 104 is represented as I2, the second impedance measurement value Z2 of the component under test 20 can be Expressed as the following formula (4): Z2 = V2 / I2 (4)

Similar to the first mode, the second impedance measurement value Z2 can also be calculated by the processor of the test device or an external computer, and this embodiment is not limited herein. In addition, since the second voltage value V2 in the second mode is obtained through the measuring circuit 124, it also includes the error of the measuring circuit 124 itself, so the second voltage value V2 is not the actual cross voltage of the device under test 20 either. Similarly, since the second current value I2 is also obtained through the measuring circuit 104, it also includes the error of the measuring circuit 104 itself, so the second current value I2 is not actually the current flowing through the device under test 20. If the errors Gm1 and Gm2 of the aforementioned measurement circuit 104 and the measurement circuit 124 itself are substituted into equation (4), equation (4) can be sorted into equation (5): Z2 = (Vdut × Gm2) / (Idut × Gm1) (5)

Next, the actual cross-voltage and current Vdut and Idut of the component under test 20 are divided to obtain the true impedance value Zdut of the component under test 20. If Vdut/Idut is expressed by Zdut, then equation (5) can be sorted into equation (6): Z2 = Zdut × (Gm2/Gm1) (6)

In one example, in order to obtain the true impedance value Zdut of the component under test 20, the processor of the test device or an external computer can multiply the equation (3) and the equation (6) to calculate the equation (7) ): Z1 × Z2 = Zdut ² × [(Gm1×Gm2)/(Gm2×Gm1)] (7)

(8) Since "(Gm1×Gm2)/(Gm2×Gm1)" in equation (7) can be pinned to 1, it can be seen that the real impedance value Zdut will be directly related to the first impedance measurement value Z1 and the second impedance value The product of the measured value Z2. In other words, the true impedance value Zdut can be calculated by the following formula (8): Zdut=

(8)

(9) On the other hand, from equation (1) and equation (4), since the first impedance measurement value Z1 is directly related to the first voltage value V1 and the first current value I1, the second impedance measurement value Z2 is directly related Based on the second voltage value V2 and the second current value I2, the equation (8) can also be expressed as the equation (9): Zdut=

(9)

It can be seen that the true impedance value Zdut of the component under test is calculated based on the first voltage value V1, the second voltage value V2, the first current value I1, and the second current value I2. It is worth mentioning that this embodiment does not limit the sequence of the first mode and the second mode. For example, the second mode may also precede the first mode. In addition, this embodiment does not limit that the true impedance value Zdut must be calculated by formula (8) or formula (9). Those with ordinary knowledge in the technical field should understand that there are many undesirable factors in the actual circuit. This embodiment just does not The ideal factors are summarized into the errors Gm1 and Gm2 of the measurement circuit 104 and the measurement circuit 124 themselves, and are not used to limit the method of calculating the true impedance value Zdut. For example, if the first voltage value V1 has an offset (offset), a correction step may be required. Therefore, this embodiment only illustrates that the true impedance value Zdut of the device under test is related to the first voltage value V1, the second voltage value V2, the first current value I1, and the second current value I2, but it is not limited thereto.

In order to illustrate the impedance measurement method of this embodiment, the following description will be made with the circuit structure of FIG. 1. Please refer to FIG. 1 and FIG. 2 together. FIG. 2 is a flowchart illustrating the steps of an impedance measurement method according to an embodiment of the present invention. As shown in the figure, in step S30, it is demonstrated that in the first mode, the power supply 106 can supply power to the first terminal 200 of the device under test 20. In step S32, it is demonstrated that in the first mode, the voltage sensing unit 100 in the first test module 10 measures the voltage across the device under test 20, and transmits the data corresponding to the voltage across the device under test 20 to The measuring circuit 104 then converts the measuring circuit 104 to obtain the first voltage value V1. In addition, the current sensing unit 122 in the second test module 12 measures the current flowing through the device under test 20, and transmits data corresponding to the current flowing through the device under test 20 to the measuring circuit 124, and then the measurement The measuring circuit 124 obtains the first current value I1 through conversion.

Next, in step S34, it is demonstrated that in the second mode, the power supply 126 can supply power to the second end 202 of the device under test 20. In step S36, it is demonstrated that in the second mode, the voltage sensing unit 120 in the second test module 12 measures the voltage across the device under test 20, and transmits the data corresponding to the voltage across the device under test 20 to The measuring circuit 124 then converts the measuring circuit 124 to obtain the second voltage value V2. In addition, the current sensing unit 102 in the first test module 10 measures the current flowing through the device under test 20, and transmits data corresponding to the current flowing through the device under test 20 to the measurement circuit 104, and then the measurement The measuring circuit 104 obtains the second current value I2 by conversion. Finally, in step S38, the processor of the test device or an external computer can calculate the value of the device under test 20 according to the first voltage value V1, the second voltage value V2, the first current value I1, and the second current value I2. The true impedance value Zdut. The remaining details of the impedance measurement method in this embodiment have been described in the previous embodiment, and this embodiment will not be repeated here.

In summary, the impedance measurement method provided by the present invention can provide electrical energy from the first end and the second end of the device under test, and then use the respective measurement of the first test module and the second test module. The circuit measures the voltage and current respectively. In addition, the voltage and current obtained by the first test module and the second test module can be interactively calculated, thereby offsetting errors between different test modules through calculation.

10: The first test module 100: Voltage sensing unit 102: current sensing unit 104: Measuring circuit 106: Power 12: The first test module 120: Voltage sensing unit 122: current sensing unit 124: measurement circuit 126: Power 20: component under test 200: first end 202: second end S30~S38: Step flow

FIG. 1 is a schematic diagram of a circuit using an impedance measurement method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the steps of an impedance measurement method according to an embodiment of the present invention.

no

S30~S38: Step flow

Claims (6)

An impedance measurement method is applied to measure an element under test, a first end of the element under test is electrically connected to a first test module, and a second end of the element under test is electrically connected to a second test Module, the impedance measurement method includes: In a first mode, power is supplied to the first end of the device under test; In the first mode, the first test module measures the voltage across the device under test to obtain a first voltage value, and the second test module measures the current flowing through the device under test to Obtain a first current value; In a second mode, power is supplied to the second end of the device under test; In the second mode, the second test module measures the voltage across the device under test to obtain a second voltage value, and the first test module measures the current flowing through the device under test to Obtain a second current value; and According to the first voltage value, the second voltage value, the first current value, and the second current value, a true impedance value of the device under test is calculated. The impedance measurement method of claim 1, wherein the step of calculating the true impedance value of the component under test further includes: In the first mode, dividing the first voltage value by the first current value to obtain a first impedance measurement value; and In the second mode, divide the second voltage value by the second current value to obtain a second impedance measurement value; The real impedance value is related to the first impedance measurement value and the second impedance measurement value. The impedance measurement method described in claim 2 further includes: Multiplying the first impedance measurement value and the second impedance measurement value to obtain a first calculation value; and Root the first calculated value to obtain the true impedance value. The impedance measurement method of claim 3, wherein the first voltage value and the second current value both include a first circuit error factor associated with the first test module, and the second voltage value and the second current value Each current value includes a second circuit error factor associated with the second test module. The impedance measurement method according to claim 1, wherein in the step of supplying power to the first end of the device under test, the first test module supplies power to the first end of the device under test. The impedance measurement method of claim 1, wherein in the step of supplying power to the second end of the device under test, the second test module supplies power to the second end of the device under test.

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