JPH073352Y2 - Measuring device equipped with an AC voltage source having a waveform control function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a measuring device provided with an AC voltage source such as an in-circuit tester.

2. Description of the Related Art Conventionally, in order to measure the electrical characteristics of an object to be measured such as an electric component, an appropriate measuring device must be used. For example, an in-circuit tester is used to judge the quality of a mounting board, that is, a printed board on which an electric component is soldered. The in-circuit tester includes a general type that measures electrical characteristics of components mounted on the board and inspects them, and a visual type that includes a camera to inspect from the appearance of the mounting board. Furthermore, due to the difference in the mounting method of the mounting board to the tester at the time of measurement for the general type, the mounting board is placed on a fixture (probe pin board) that is an inspection jig, and a large number of presser bars project downward. There are a press type in which the mounting board is lowered from above and clamped and fixed, and a vacuum type in which the mounting substrate is sucked and fixed on the fixture. Therefore, depending on the type of mounting board to be inspected,
Those testers will be used properly. However, the visual type tester cannot inspect the electrical characteristics of parts.

Such a general type in-circuit tester has a structure as shown in FIG. 4, and the switch 10 is closed at the time of measurement,
A constant sinusoidal AC voltage is applied from the AC voltage source 12 to the DUT 14, and the measurement current flowing there is converted into a voltage by the I / V conversion base 16. After removing the direct current component of this voltage by the coupling capacitor 18, the alternating current component is detected by the resistor 20, and the operational amplifier 22
Amplify with and put in the rectifier circuit 24. Therefore, the AC voltage corresponding to the measured current is converted to DC, and the A / D converter 2
After being converted from an analog value to a digital value by 6, the microcomputer 28 is entered. In this computer 28, the AC voltage value applied to the DUT is known, and the measured current value flowing therethrough is known from the analog value input from the A / D converter 26, so by computing them,
The electrical characteristic values such as the resistance (R), the electrostatic capacitance (C) and the inductance (L) can be calculated.

Problems to be Solved by the Invention However, in such a measuring device, a coupling capacitor is used.
Since a transient phenomenon appears under the influence of the charging current with respect to 18, it takes time to stabilize when the DUT 14 has a capacitance or an inductance. Moreover, the in-circuit tester requires high-speed measurement, and the measured object such as each electric component must be measured in several msec, so that the transient phenomenon cannot be ignored. Incidentally, a normal tester does not need to perform such high-speed measurement, so there is not much problem.

The present invention has been made by paying attention to such conventional problems, and provides a measuring device equipped with an AC voltage source having a waveform control function capable of performing accurate high-speed measurement without the influence of transient phenomena. The purpose is to do.

Means for Solving the Problems Means for achieving the above object will be described below with reference to FIG. 1 corresponding to the embodiment.

The measuring apparatus provided with an AC voltage source having this waveform control function is an AC voltage source that generates a sine wave AC voltage, and a current that flows when the sine wave AC voltage is applied to the DUT 40. / V converter 44, a coupling capacitor 46 that removes the DC component from the converted voltage, a detection resistor 48 that detects the AC component, and a voltage amplifier 50 that amplifies the detected AC voltage.
A rectifier circuit 52 for converting the amplified voltage to direct current, an A / D converter 54 for converting the rectified voltage from an analog value to a digital value, and a current flowing through the DUT 40 by receiving the digital value. However, according to the measurement device consisting of the value and the known AC voltage value applied thereto, the arithmetic unit 56 having a CPU 58 for calculating electrical characteristic values such as resistance, capacitance, and inductance. As a source, a memory 30 for storing sine wave data, an address counter 32 for designating an address at which the data to be read is stored for the memory 30, and a clock 34 for generating a pulse for advancing the address counter 32, When applying the sine wave AC voltage to the DUT 40 and the D / A converter 36 that converts the sine wave data read from the memory 30 into a sine wave AC voltage represented by an analog value from the digital value. An arithmetic unit 56 having a buffer amplifier 38 for amplifying the flowing current and having a CPU 58 according to the type of the DUT 40 is used so that the AC voltage corresponding to the measured current entering the rectifier circuit 52 rises from zero. The counter 32 is initialized and the clock 34 is controlled to generate a pulse for advancing the address counter 32.

Operation With the above configuration, the address counter 32 is initialized by the arithmetic unit 56 having the CPU 58, and the generation cycle of the pulse entering the address counter 32 from the clock 34 is controlled. , The sine wave data stored in the specified address is sequentially stored in the memory 30.
Since it goes out through the D / A converter 36, the phase and frequency of the sinusoidal AC voltage can be freely selected and added to the DUT 40. Therefore, depending on the type of the DUT 40, the phase and frequency of the sinusoidal AC voltage applied thereto are appropriately determined, and the I / V converter 44, the coupling capacitor 46, the detection resistor 4
8. If the AC voltage corresponding to the measured current entering the rectifier circuit 52 is made to rise from zero via the voltage amplifier 50 and the like, the rectified waveform will be stabilized more quickly.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a measuring device equipped with an AC voltage source having a waveform control function, such as an in-circuit tester to which the present invention is applied. In the figure, 30 stores sine wave data
Memory such as ROM (read-only memory) or RAM (read / write memory), 32 is an address counter that specifies the address where the data to be read is stored in memory 30, 34 is a pulse that advances address counter 32 36, a D / A converter 36 for converting the sine wave data read from the memory 30 into a sine wave AC voltage indicated by an analog value from the digital value, and 38 a sine wave AC voltage for the DUT 40.
It is a buffer amplifier that amplifies the current that flows when it is applied to. A switch 42 for opening and closing the circuit is interposed between the buffer amplifier 38 and the DUT 40. Further, 44 is an I / V converter for converting the measured current into a voltage, 46 is a coupling capacitor for removing the DC component from the converted voltage, 48 is a detection resistor for detecting the AC component of the converted voltage, and 50 is the detected AC voltage. It is a voltage amplifier such as an operational amplifier that amplifies. Further, 52 is a rectifier circuit that converts the amplified voltage into DC, and 54 is an A / D converter that converts the rectified voltage from an analog value to a digital value. Further, reference numeral 56 initializes the address counter 32 so that the AC voltage corresponding to the measured current entering the rectifying circuit 52 rises from zero according to the type of the DUT 40, and for the clock 34, the address counter 32 is set. Controls the generation cycle of the pulse that advances the pulse, receives the digital value from the A / D converter 54, detects the current flowing through the DUT 40, and detects the resistance from the value and the known AC voltage value applied to it. An arithmetic unit having a CPU for calculating electric characteristic values such as capacitance, inductance and the like. By the initial setting of the address counter 32, the storage address of the sine wave data that is first read from the memory 30 can be selected and specified. Further, every time one pulse is put into the address counter 32 by controlling the generation cycle of the clock pulse, the designated address is advanced by one address, and the sine wave data corresponding to the address is sequentially transferred from the memory 30 to the D / A. Since it goes out via the converter 38, the frequency of the sinusoidal alternating voltage can be freely determined.

The arithmetic unit 56 equipped with this CPU includes, for example, a CPU (central processing unit) 58, ROM 60, RAM 62, input / output port 64, bus line 66.
A microcomputer composed of the above is used.
The CPU 58 corresponds to a central brain portion of a microcomputer, executes control over the whole according to instructions of a program, performs arithmetic and logical operations, and temporarily stores the result. It also controls peripheral devices. The ROM 60 stores a control program for controlling the entire recorder, a measurement processing program, and the like. Further, the RAM 62 stores the data of the result calculated by the CPU 58 and the like. The input / output port 64 is connected with an address counter 32, a clock 34, an A / D converter 54, and the like, as well as a recording device, a display device, operation switches, etc. (none of which are shown). Further, the bus line 66 includes an address bus line, a data bus line, a control bus line, etc. for connecting them.

Next, the operation of this embodiment will be described.

First, referring to FIG. 2, a sine wave AC voltage e = Emsin (ω) from the D / A converter 36 to a series circuit composed of a coupling capacitor (its electrostatic capacity C) 46 and a detection resistor (its resistance value R) 48.
Consider the current flowing in the circuit when t + θ) is suddenly added. Therefore, if the current after t (sec) from the moment when the switch 42 is closed is i, the differential equation is as follows.

Ri + 1 / C∫idt = Emsin (ωt + θ) (1) This current i is composed of two parts, a steady state (steady state current) is and a transient term (transient current) it. That is, i = is + it (2) And this steady-state current is is = Isin (ωt + θ + φ) (3) φ = tan ⁻¹ 1 / ωcR Next, the transient term it is a solution of Rit + 1 / C∫itdt = 0 or a derivative of Rdit / dt + it / C = O. That is, the general solution of this differential equation is it = Ae- ^{t / CR} (A is a constant) (4) Therefore, i = is + it = Isin (ωt + θ + φ) + Ae- ^{t / CR} (5) As an initial condition, at t = 0, i = 0, O = Isin
(Θ + φ) + A and A = −Isin (θ + φ).

Therefore, i = I {sin (ωt + θ + φ) -e- ^{t / CR} sin (θ + φ)}
(5) 'Normally, the time constant of CR is set to φ = 0 by making C large so that the applied voltage e appears at both ends of R as it is.

Therefore, i = I {sin (ωt + θ) −e ^{−t / CR} sin θ} (5) ″ In order to eliminate the influence of the transient term, it is si
It is sufficient if nθ = 0, that is, θ = 0. So I / V converter
Assuming that there is no phase shift in 44, the DUT 40
It suffices if the phase θ of the current i flowing through is 0 degree.

A sinusoidal AC voltage e for generating such a current i
Is as follows depending on the type of the object 40 to be measured.

In the resistance (R), e = Emsinωt (6) At this time, the current iR is in phase.

In the electrostatic capacitance (C), e = Emsin (ωt−90 °) (7) At this time, the current iC advances by 90 ° as shown in FIG.

In the case of the inductance (L), e = Emsin (ωt + 90 °) (8) At this time, the current iL is delayed by 90 ° as shown in Fig. 3 (b).

In this way, if the waveform of the applied voltage e is controlled so that the waveform of the AC voltage corresponding to the measured current i entering the rectifier circuit 52 rises from zero according to the type of the DUT 40, the rectified waveform becomes faster. Stable high speed measurement is possible.

Also, when the waveform is stopped, if it is stopped at the point where the current value i is zero, the residual charge in the DUT 40 is reduced, which is convenient.

Effect of the Invention According to the present invention described above, it is possible to measure the electrical characteristic value of the object to be measured accurately and at high speed by eliminating the influence of the transient phenomenon that appears in the measurement current.

[Brief description of drawings]

FIG. 1 is a block diagram showing a measurement position provided with an AC voltage source having a waveform control function to which the present invention is applied. FIG. 2 is a circuit diagram for explaining a part of the operation of the measuring device, FIG. 3 is a waveform diagram showing the relationship between voltage and current when the DUT is interposed in the circuit, and FIG. The object to be measured is capacitance, and the object to be measured is inductance in (b). FIG. 4 is a block diagram showing a conventional measuring device equipped with an AC voltage source. 30 …… Memory, 32 …… Address counter, 34 …… Clock, 36 …… D / A converter, 38 …… Buffer amplifier, 40
…… DUT, 44 …… I / V converter, 46 …… Coupling capacitor, 48 …… Detecting resistor, 50 …… Voltage amplifier, 52 …… Rectifier circuit, 54 …… A / D converter, 56 …… Arithmetic device with CPU58

Claims (1)

[Scope of utility model registration request] 1. An AC voltage source for generating a sinusoidal AC voltage,
An I / V converter that converts the current that flows when the sine wave AC voltage is applied to the DUT, a coupling capacitor that removes the DC component from the converted voltage, and a detection resistor that detects the AC component, A voltage amplifier that amplifies the detected AC voltage, a rectifier circuit that converts the amplified voltage to DC, an A / D converter that converts the rectified voltage from an analog value to a digital value, and the digital value to be measured. In a measuring device consisting of a current flowing through an object and a calculation device having a CPU for calculating an electrical characteristic value from the value and a known AC voltage value applied thereto, a sine wave is used as the AC voltage source. A memory that stores data, an address counter that specifies the address where the data to be read is stored, a clock that generates a pulse that advances the address counter, and A D / A converter that converts the sine wave data read from the memory into a sine wave AC voltage indicated by an analog value, and a buffer amplifier that amplifies the current that flows when the sine wave AC voltage is applied to the DUT. Depending on the type of object to be measured, an arithmetic unit equipped with a CPU initializes the address counter so that the AC voltage corresponding to the measurement current entering the rectifier circuit rises from zero, and enters the address counter from the clock. A measuring apparatus provided with an AC voltage source having a waveform control function, characterized by controlling a pulse generation period.