JPH04301775A - Control method of lcr measuring device - Google Patents

Abstract

PURPOSE:To decide the optimum value of the LCR measurement detecting resistance in a short time by converting the detecting current and the detecting voltage into digital signals by gaining at specific values, dividing the current and the voltage count numbers by their gains, calculating the ratios with the current and the voltage count numbers before the gainings, and deciding whether they are in a specific scope or not. CONSTITUTION:A current gain amplifier 26 amplifies the detected 4 current value signal in a specific multiple, while a voltage gain amplifier 28 amplifies the detected 8 voltage value signal in a specific multiple. By the ratio of a current count number corresponding to the current flowing to a body 1 to be measured, and a voltage count number corresponding to the voltage between terminals, a specific scope is set. Then, the current flowing to the body to measure and the voltage between terminals are detected, applying specific gains respectively to convert into digital signals, and the resultant current count number and the voltage count number are divided by their gains, the ratios with the current and the voltage count numbers prior to the gainings are calculated, and when they are in the specific scopes, the present current detecting resistance is decided as an optimum value making them as the optimum ranges.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention relates to the L component and C component of an object to be measured.
The present invention relates to a method of controlling an LCR measuring device that measures a component and an R component, and more specifically, to a method of controlling an LCR measuring device that allows the measurement to be performed accurately in a short period of time.

0002

[Conventional example] Conventionally, this type of LCR measuring device has a configuration shown in FIGS. 4 and 5, for example, and includes a signal source 2 that applies a measurement signal of a predetermined level to an object to be measured 1, and A frequency setting section 3 that sets a frequency and its object to be measured 1
A current detection unit 4 that detects the current flowing in the current detection unit 4 and converts it into a voltage, a plurality of feedback resistors (current detection resistance) 5 of this current detection unit 4, and a switch 6 that switches between the resistors 5.
a range setting section 7, a voltage detection section 8 that detects the voltage between the terminals of the object to be measured 1, an AC/DC conversion section 9 that converts the voltage value signal of the detected current into DC, and a AC/DC converter 10 that converts a voltage value signal to direct current
, automatic gain control units 11 and 12 that convert the voltage value signal of the detected current and the voltage value signal of the detected voltage into sine waves with the same amplitude regardless of frequency and input level, and detect a phase difference using these sine waves. A subtraction unit 13, a phase comparison unit 14 that detects the phase polarity thereof, and an AC/DC conversion unit 1 that converts the detected phase difference signal obtained by the subtraction unit 13 into direct current.
5, convert the voltage value (Vi) of the detected current converted into DC and the voltage value (Vv) of the detected voltage into digital signals, and convert the detected phase value (θ) converted into DC into a digital signal according to the phase polarity. A/D converter section 16 to convert
The L component, C component, and R component of the object to be measured 1 are converted by the A/D converter section 16 into digital signals.
A microcomputer 17 that calculates the components and controls the range setting section 7 by manual or automatic operation, the calculated L component, C component, R component, the set frequency of the frequency setting section 3, and the object to be measured 1 The display section 18 displays the voltage and current between the terminals of the terminal.

The microcomputer 17 also includes an impedance calculation means 19, a digit adjustment means 20, a digit movement data holding means 21, a measurement range detection means 22, a range switching means 23, an auto/manual switching means 24, and an LCR.
It has calculation means 25.

A method of controlling the LCR measuring device will be explained with reference to the flowchart of FIG. 6. When the LCR measuring device is powered on, the microcomputer 17
The current setting range of the current detection resistor 5 of the range setting section 7 is checked (step ST1), the current detection resistor 5 is set according to the manual setting (step ST2), and the signal to be measured A measurement signal from source 2 is applied. As a result, the current flowing through the object to be measured 1 and the voltage between the terminals of the object to be measured 1 are detected, and these detected currents and voltages are converted into digital signals and sent to the microcomputer 1.
7 is input.

[0005] Subsequently, the impedance of the object to be measured 1 is calculated by the impedance calculating means 19 (step ST3), and the digits of the calculated impedance and the current detection resistor 5 are matched by the digit adjusting means 20. The impedance is converted into the form of display counts (step ST
4) The moving digit data for the digit alignment is stored in the digit moving data holding means 21. The measurement range detection means 22 determines whether the range of the current current detection resistor 5 exceeds the upper limit value of the impedance or is below the lower limit value, that is, whether it is within the impedance display range. is determined (step ST5).

If it is not within the display range, the current detection resistor 5 of the range setting section 7 is switched (step S).
T6), the process returns to the main routine and the above steps are repeated again. If it is within the display range, the current detection resistor 5 is left as is and the process returns to the main routine, where the measurement of the object 1 is performed using the optimum current detected by the current detection resistor 5. be exposed.

In this way, when measuring the L component, C component, and R component of the object to be measured 1, determining the optimum value of the feedback resistance (current detection resistance) of the current detection section 4, that is, setting the range, Since the determination is made using the impedance value of the body 1, it is possible to improve the measurement accuracy without considering the frequency of the measurement signal applied to the body 1. For details, see Japanese Patent Application Laid-Open No. 63-3 by the applicant.
See No. 04173.

[0008]

[Problem to be solved by the invention] However, the above L
In the control method of the CR measuring device, the current detection resistor 5 of the range setting section 7 is switched, and the impedance calculation means 1 is switched.
In step 9, the impedance of the object to be measured 1 is calculated, and the optimum range is determined by determining whether the calculated impedance is within the display range. There was a problem in that it took time to measure the body 1.

Furthermore, even though the range setting section 7 is switched to the optimally determined current detection resistor, if the calculated impedance value contains an error and the error is large, the current detection may result in an incorrect optimal value. This may result in an inaccurate measurement of the object 1 being measured.

That is, the impedance calculation means 19 calculates the impedance of the object to be measured 1 as Z=R×(Vv/Vi
), for example, if the current flowing through the object to be measured 1 is small, that is, the current count number (Vi) corresponding to the voltage value of the detected current is small, the count value will fluctuate and the impedance calculation means 19 This is because an error may occur in the impedance value obtained in , and an erroneous decision may be made to switch to a non-optimal current detection resistor.

The present invention has been made in view of the above-mentioned problems, and its purpose is to determine in a short time the optimum value of a current detection resistor for detecting the current flowing through the object to be measured when measuring the object to be measured. It is an object of the present invention to provide a control method for an LCR measuring device that enables accurate determination of optimum values.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention applies a measurement signal of a predetermined level to an object to be measured, and calculates the current flowing through the object to be measured, and the current flowing between the terminals of the object to be measured. Detecting the voltage and the phase difference between the detected current signal and the detected voltage signal, converting the frequency of each analog signal of the detected current, voltage and phase difference, and counting the frequency-converted signal to make it a digital signal, A range setting section that processes these digital signals in a predetermined manner and measures the L, C, and R components of the object to be measured, and during the measurement, detects the current flowing through the object to be measured and converts it into a voltage value. In a control method for an LCR measurement device that switches a feedback resistor (current detection resistor) to an optimal value, the number of current counts corresponding to the current flowing through the object to be measured and the number of voltage counts corresponding to the voltage between the terminals of the object to be measured. A predetermined range is set to determine the optimum value of the current detection resistor based on the ratio of , the analog signals of the voltage values of the detected current and detected voltage are each converted to a digital signal with a predetermined gain, the current count number and voltage count number of these digital signals are divided by the gain, and the gain is calculated. Obtain the current count number and voltage count number corresponding to the previous detected current and detected voltage, calculate the ratio of these count numbers, judge whether this calculated ratio is within the above-mentioned predetermined range, and The gist of this invention is to switch the current detection resistor when the current detection resistor is not within the predetermined range, and to determine the current current detection resistor to the optimum value when it is within the predetermined range, thereby setting the optimum measurement range for the object to be measured.

[0013]

[Operation] Since the above method is adopted, a plurality of the above feedback resistors (current detection resistors) are provided, and when the current detection resistors are switched to the optimum value and the optimum range is determined, the current detection resistors are sequentially switched and The current flowing through the object to be measured is detected by the switched current detection resistor, and the voltage between the terminals of the object to be measured is detected. The analog signals of these detected currents and detected voltages are gained to a predetermined value, amplified to a value that maximizes the resolution of the A/D conversion, and converted into digital signals. The current count number and voltage count number of these digital signals are divided by their gain, and the current count number (Vicg) and voltage count number (Vvcg) corresponding to the detected current and detected voltage before the gain are obtained. The ratio of numbers is calculated. That is, since A/D conversion is performed with maximum resolution, current count numbers and voltage count numbers corresponding to detected currents and detected voltages can be obtained with high precision, and errors in the count numbers can be suppressed.

[0014] It is determined whether or not the calculation ratio (Vvcg/Vicg) is within a predetermined range (shown in Table 1). For example, when the current detection resistor is switched to the maximum 100 kΩ range, When the calculation ratio is "1" or more, the current current detection resistor is determined to be the optimum value, and the original measurement of the object to be measured is performed. However, when the calculation ratio has not reached "1", the current detection resistor is switched from 100 kΩ to 20 kΩ, and the same process as above is performed.

[0015] In this way, when determining the optimum value of the current detection resistor, there is no need to calculate the impedance of the object to be measured, and a ratio calculation is sufficient, so the time required to determine the optimum range can be shortened, and the Since the measurement time for the object to be measured is shortened and the A/D conversion for obtaining the above count number is performed with maximum resolution, an accurate optimum current detection resistor can be determined.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be explained based on FIGS. 1 to 3. Note that in the figure, the same parts as in FIGS. 4 and 5 are denoted by the same reference numerals, and redundant explanation will be omitted.

In FIGS. 1 and 2, this LCR measurement device converts the voltage value signal of the current detected by the current detection section 4 into one
/2.5 times, 1 time, 2 times, 5 times, 10 times, and 20 times the current gain amplification section 26 that amplifies the current, respectively, a current gain setting section 27 that switches these current amplified signals, and a voltage detection section. The voltage value signal of the detected voltage by 8 is set to 1
/2.5 times, 1 time, 2 times, 5 times, 10 times, and 20 times voltage amplification section 28, voltage gain setting section 29 for switching the voltage amplified signals, and A/D converter. The L component, C component, and R component of the object to be measured 1 are calculated using the converted digital signal by the section 16, and the range setting section 7, current gain setting section 27, and voltage gain setting section 29 are manually or automatically operated. It is equipped with a microcomputer 30 that controls the following. The automatic gain control units 11 and 12 convert the current-gained detected current signal (Vi; current value) and the voltage-gained detected voltage signal (Vv; voltage value) into sine waves of the same amplitude regardless of frequency and input level. Let it be a wave.

The current gain amplification unit 26 includes a 1x amplification unit and a 2x amplification unit.
A double amplification section, a 2.5 times amplification section, a double amplification section, and a double amplification section are connected in series, and the current gain setting section 27
is a switching section 31 that switches the signal of the detected current value amplified by the amplifying section using a signal from the microcomputer 30, and a switching section 31 for switching the signal amplified by the 1x amplifying section and amplifying it to 1/2.5 times. switching section 32 and 1/2
．． It is composed of a five-fold amplifying section 33.

Similarly, the voltage gain amplification section 28 has a 1x amplification section, a 2x amplification section, a 2.5x amplification section, a 2x amplification section, and a 2x amplification section connected in series, and has a voltage gain The setting section 29 includes a switching section 34 that switches the detected voltage value signal amplified by these amplifying sections using a signal from the microcomputer 30, and a switching section 34 that switches the signal amplified by the 1x amplifying section to 1/2.5 times. It is composed of a switching section 35 for amplification and a 1/2.5 times amplifying section 36.

[0020] Also, as in the conventional case, the A/D converter section 16
, the input signal is frequency-converted by a V/F converter,
Next, a digital signal is obtained by counting for a certain period of time with a counter, but the maximum frequency of the V/F converter is 2
04.8kHz, and the count time is the gate on time. The number of counts when the gate is turned off is the A/D converted value, and is set to 204.8kHz for an analog input of 1V, and the maximum number of counts at that time is 1kHz. In the above case, 204.8kHz x 40ms = 8192 counts,
If it is less than 1kHz, 204.8kHz x 80ms = 16
The count becomes 384.

The microcomputer 30 is centered around a CPU that performs calculations, displays, reads switches, and exchanges data with an external interface, and the CPU is a single chip equipped with a memory. The microcomputer 30 also compares the digital signal (count number) from the A/D converter section 16, that is, the count number V of the voltage value signal (Vv) of the detected voltage and the count number I of the voltage value signal of the detected current. V/I ratio calculation means 38 and measurement range detection means 39 for detecting the measurement range based on the comparison result.
, a range switching means 40 that switches the range setting section 7 to a range within the measurement range, an auto/manual switching section 41 that allows the range setting section 7 to switch the range either automatically or manually, and the detection measurement. A current gain switching means 42 that switches the current gain setting section 27 according to the range, a voltage gain switching section 43 that switches the voltage gain setting section 29, and the L component, C component, R component, and Z component of the measured object 1 in the measurement range. It has LCRZ calculating means 44 which calculates the component and calculates the voltage and current between the terminals of the object to be measured 1, and stores data such as a predetermined range shown in Table 1 below in advance.

[0022]

[Table 1] Next, the operation of the LCR measuring device having the above configuration will be explained with reference to the flowchart in FIG. is switched to the current detection resistor (100 kΩ) 5 (step ST10), and the voltage gain amplification section 28 is set to a predetermined amplification degree (step ST10).
T11), the current gain amplification section 26 is set to a current gain of 1 (step ST12). In this case, AC/D
In order to maximize the resolution of the C conversion unit 10, the amplification degree of the voltage gain amplification unit 28 is set to a gain that is as close to 1V as possible within the range where the input voltage of the AC/DC conversion unit 10 does not exceed 1V. is set to When the measurement signal applied to the object to be measured 1 is 2.50Vrms, the switching unit 3
5 is switched to the 1/2.5 times amplifying section 36 side, and this 1
The signal with the voltage value multiplied by /2.5 is sent to the AC/DC converter 10.
is input.

Subsequently, the current count number based on the digital signal (count number) from the A/D converter section 16 is V.
Assuming that it is an IC and the voltage count number is VVC,
The VIC corresponds to the voltage value of the detected current amplified by the current gain amplification section 26, and the VVC corresponds to the voltage value of the detected current amplified by the current gain amplification section 26.
This corresponds to the voltage value of the detection voltage amplified in step 8.

Furthermore, in order to obtain the voltage values of the detected current and detected voltage before passing through the current gain amplification section 26 and the voltage gain amplification section 28, the current count number (VIC) is divided by the gain of the current gain amplification section 26. In addition, the voltage count number (VVC) is divided by the gain of the voltage gain amplification section 28 to calculate the current count number (Vicg) for the current flowing through the object under test 1, and the voltage between the terminals of the object under test 1 is calculated. The voltage count number (Vvcg) for the voltage is calculated (steps ST13, ST14).

Therefore, when the current flowing through the object to be measured 1 is small, in the conventional case, the current count number (Vi)
However, in the case of this invention, the analog signals of the voltage values of the detected current and detected voltage are amplified, and these signals are A/ D-convert it to a digital signal, divide the current count number (Vi) and voltage count number (Vv) of this digital signal by the above gain, and calculate the detected current before the gain, the current count number (Vicg) corresponding to the detected voltage, Since the voltage count number (Vvcg) is obtained, fluctuations in the count number (Vi) can be kept small, that is, accurate count numbers can be obtained.

[0026] Next, the voltage count number (Vvcg)
/current count number (Vicg) is calculated, and when this calculation ratio is calculated (step ST15), the measurement range detection means 39 compares the calculation ratio with a predetermined range shown in Table 1. That is, the calculation ratio Vvcg/Vicg is “
1", 100 kΩ of the current detection resistor 5 which is currently being switched is determined to be the optimum value (step S
T16), proceed to the measurement routine of the LCR measurement device,
Measurement of the object to be measured 1 is performed in the same manner as in the conventional method.

However, when the calculation ratio Vvcg/Vicg does not reach "1" (underflow, that is, when the impedance of the measured object 1 is small and the current flowing through the measured object 1 is large) ), there is no need to measure at the maximum range; if you measure at a lower range,
Since the measurement of the object to be measured 1 is more accurate, the range setting section 7 is set by the range switching means 40 from 100 kΩ to 20 kΩ.
It is switched to the Ω range (step ST17).

[0028] Subsequently, steps ST11 to ST16 are repeated in the 20kΩ range, and the second
It is determined whether the current detection resistor 5 of 0 kΩ is the optimum value based on Table 1, but the calculation ratio Vvcg/Vicg
is greater than or equal to "1" and less than or equal to "6", 20 kΩ of the current current detection resistor 5 is determined as the optimum value, but if it is in a range other than that, the range is switched again. Further, when calculating the Vvcg/Vicg ratio, the current gain setting section 27 is switched by the current gain switching means 42, and the amplification factor of the current gain amplification section 26 is set so that the input of the AC/DC conversion section 9 approaches 1V. determined. Further, the voltage gain setting section 29 is switched by the voltage gain switching means 43, and the amplification factor of the voltage gain amplification section 28 is determined so that the input of the AC/DC conversion section 10 approaches 1V.

When the calculation ratio Vvcg/Vicg does not reach "1" (underflow), or when Vvcg/Vicg exceeds "6" (overflow), that is, The ratio is 1
When ≦Vvcg/Vicg≦6 is not satisfied, the current detection resistor 5 of the range setting section 7 is switched. When there is an underflow, the current detection resistor 5 is switched to 2 kΩ as described above, and conversely, when it is overflow, the current detection resistor 5 is switched to 100 kΩ.

The above process is repeated until the calculation ratio Vvcg/Vicg satisfies the predetermined range conditions shown in Table 1, and when the optimum value of the current detection resistor 5 is determined, that is, the optimum measurement range is determined. Then, a measurement routine for the object to be measured 1 is performed, and the measurement processing and measurement results are displayed.

In this way, when the range setting section 7 is switched to the optimum value of the current detection resistor 5 when measuring the measured object 1, the current flowing through the measured object 1 and the voltage between the terminals of the measured object 1 are changed. is detected, and judgment is made based on whether the ratio of the current count number of the detected current and the voltage count number of the detected voltage satisfies a predetermined range obtained by empirical rules. This has the advantage that the processing time is shorter than when calculating the impedance of 1 and determining whether or not the calculated impedance is within the display range.

Furthermore, in the present invention, since the analog signals of the voltage values of the detected current and the detected voltage of the object under test 1 are amplified by the current gain amplification section 26 and the voltage gain amplification section 28, respectively, The current flowing is at least
Since the voltage value signals of the detected current and detected voltage are A/D converted into digital signals (number of counts) with maximum resolution, it is possible to accurately calculate the number of current counts and voltage counts corresponding to the detected current and voltage. This eliminates the fluctuation of the count as in the conventional example, and allows the optimum value of the current detection resistor 5 to be determined accurately, thereby making it possible to accurately measure the object to be measured 1.

[0033]

[Effects of the Invention] As explained above, according to the present invention, when measuring an object to be measured, the optimum value of the current detection resistor for detecting the current flowing through the object to be measured is determined, and the optimum measurement range is set. In the control method of the switching LCR measuring device, the feedback resistor (current detection resistor) of the range setting section
At the same time, the current flowing through the object to be measured is detected, the voltage between the terminals of the object to be measured is detected, the voltage values of the detected current and the detected voltage are gain-amplified, and these gain-amplified voltage values are Convert it to a digital signal to obtain a current count number and a voltage count number, divide these counts by the gain amplification factor, calculate the ratio of these counts, and check whether this calculation ratio is within a predetermined range. When the current detection resistor is not within this predetermined range, the current detection resistor is determined, and when it is within the predetermined range, the current detection resistor is determined to be the optimum value. To determine the value, it is only necessary to calculate the ratio of the number of voltage counts and the number of current counts, and there is no need to calculate the impedance of the object to be measured, so processing time can be shortened and the measurement of the object to be measured can be reduced. This has the effect of shortening the time.

[0034] When converting the analog signals of the voltage values of the detected current and detected voltage into digital signals (number of counts),
Since the A/D conversion has maximum resolution, even if the current flowing through the object under test is small, it is possible to accurately obtain the current count number and voltage count number corresponding to the detected current and detected voltage. Since the count number does not fluctuate, there is no possibility that the current detection resistor is incorrectly determined to be the optimum value, and the measurement accuracy of the object to be measured is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic partial block diagram of an LCR measurement device showing an embodiment of the present invention and to which a method for controlling an LCR measurement device is applied;

FIG. 2 is a schematic partial block diagram of an LCR measurement device showing an embodiment of the present invention and to which a method for controlling an LCR measurement device is applied;

FIG. 3 is a flowchart diagram illustrating a method of controlling the LCR measuring device shown in FIGS. 1 and 2.

[Fig. 4] Schematic partial block diagram of a conventional LCR measuring device

[Fig. 5] Schematic partial block diagram of a conventional LCR measuring device

FIG. 6 is a flowchart diagram illustrating a method of controlling the LCR measuring device shown in FIGS. 4 and 5.

[Explanation of symbols]

26 Current gain amplification section 27 Current gain setting section 28 Voltage gain amplification section 29 Voltage gain setting section 30 Microcomputer 38 V/I ratio calculation means 39 Measurement range detection means 42 Current gain switching means 43 Voltage gain switching means

Claims (1)

[Claims] Claim 1: A measurement signal of a predetermined level is applied to an object to be measured, and the current flowing through the object to be measured, the voltage between the terminals of the object to be measured, and the phase difference between the detected current signal and the detected voltage signal are determined. The detected analog signals of current, voltage, and phase difference are A/D converted into digital signals, and these digital signals are processed in a prescribed manner to measure the L, C, and R components of the object to be measured. , and during the measurement, a feedback resistor (current detection resistor) of a current detection means that detects the current flowing through the object to be measured and converts it into a voltage value.
In a control method for an LCR measuring device, the current detection resistor is controlled by a ratio of a current count number corresponding to a current flowing through the object to be measured and a voltage count number corresponding to a voltage between terminals of the object to be measured. Set a predetermined range for determining the optimal value of , and when measuring the object to be measured,
Switching the current detection resistor, detecting the current flowing through the object to be measured and the voltage between its terminals, and converting analog signals of the voltage values of the detected current and detected voltage into digital signals by respectively gaining a predetermined gain, The current count number and voltage count number of these digital signals are divided by their gain to obtain the current count number and voltage count number corresponding to the detected current and detected voltage before the gain, and the ratio of these count numbers is calculated. , determining whether the calculated ratio is within the predetermined range, switching the current detection resistor when it is not within the predetermined range, and determining the current current detection resistor to an optimal value when it is within the predetermined range;
A method for controlling an LCR measuring device, characterized in that the optimum measurement range for the object to be measured is set.