JPH0695120B2 - Electronic component measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention surely fails as a measurement value overflow or an abnormal value of zero when contact failure occurs in any of four measurement terminals in four-terminal resistance measurement. The present invention relates to an electronic component measuring device for detecting.

2. Description of the Related Art FIG. 3 shows a measuring circuit of a conventional four-terminal resistance measuring device. This four-terminal resistance measuring circuit is often used as a means for eliminating the influence of the measuring terminal contact resistance on the measured value.

1 is a measured current source, 2 is a resistance to be measured, 3 and 4 are HI and LI terminals for supplying a current to the resistance to be measured 2, 5 and 6 are HVs for sensing the voltage across the resistance 2 to be measured, It is an LV terminal. H
The outputs appearing at the V terminal 5 and the LV terminal 6 are input to the differential amplifier 9 through the buffer amplifiers 7 and 8 having high input impedance, and the potential difference between HV and LV is connected to the differential amplifier 9 A /
Directly connected as a resistance value by the D converter 10. In the conventional measuring device, the measured value of the A / D converter 10 shows a true value only when the measuring terminals 3 to 6 are in contact with the resistance 2 to be measured. Although it becomes zero, the measured value cannot be determined when HV and LV have poor contact.

Problem to be Solved by the Invention Measured resistance 2 with measurement terminals 3 to 6 during resistance measurement
There is no guarantee that contact with the lead wire will always be maintained. Particularly, in an automatic resistance measuring / sorting machine using a high-speed machine or the like, a contact failure is likely to occur due to dirt on the machine-side measuring terminal and the terminal contact surface of the measured resistance 2, an oxide film or the like. When a contact failure occurs, the measured value greatly changes depending on which of the four terminals has the contact failure.

In Fig. 3, if either HI terminal 3 or LI terminal 4 has a poor contact, current does not flow, so the potentials of HV terminal 5 and LV terminal 6 become equal, and the measured value of A / D converter 10 is zero. Become. HV
If terminal 5 and LV terminal 6 are not in good contact, the buffer amplifier
Since 7,8 has a high input impedance of 10 ¹⁰ Ω or more,
The output levels of the buffer amplifiers 7 and 8 are not constant because they are easily induced by noise.

Therefore, in the automatic measurement and sorting machine, the measured resistance 2
Even if is a non-standard defective product, the measured value may show a value of a non-defective product and be classified as a non-defective product in some cases. This causes a serious problem that a defective product is mixed into a good product.

The present invention is such that the measured value shows a clear abnormal value (zero or overflow) regardless of which of the four terminals has poor contact.

Means for solving the problem A small capacity capacitor for charging is installed between the input of the HV and LV buffer amplifiers and the earth, and it is possible to measure at a timing not measured.
If the + V power supply voltage is charged to the HV side and the −V power supply voltage is charged to the LV side, and if the charge is turned off immediately before measurement, if the measured resistance is in contact with the HV and LV terminals, it will be instantly discharged and normal It becomes the measured voltage, and if there is poor contact, the charging voltage remains
The measurement value is configured to overflow.

Action With the above configuration, the measured value when the HV and LV measurement terminals have poor contact overflows due to the charging voltage of the charging capacitor, and no current flows when there is poor contact at the HI and LI measurement terminals, so no current flows. Since the measured value becomes an abnormal value in the case of any contact failure, it does not fall within the normal range of non-defective products of resistance, and it is possible to prevent an accident such as mixing of defective products into non-defective products due to poor contact of the measuring terminals.

Embodiment An embodiment of the present invention will be described below with reference to the block diagram of FIG.

In the drawing, 11 is a measured current source, 12 is a measured resistance, and 13 to
16 is a measurement terminal (HI, LI, HV, LV). 17,18 are HV and LV buffer amplifiers, 19 are differential amplifiers, 20 are A / D converters, 2
Reference numerals 1 and 22 are leads of the measured resistance 12. What is different from the conventional one is that switches 23 and 24 for charging the power supply voltage and small capacitors 25 and 26 of several tens of PF are added to the input of each buffer amplifier
Is added.

Until the measurement, as shown in the timing chart in Fig. 2, switch 23 and switch 24 are on, and capacitor 25
Is charged to the same voltage as the power supply voltage of the buffer amplifier 17, and the capacitor 26 is charged to-voltage. The switch 23 and the switch 24 are turned off by the signal of the measurement start. Measuring terminal 13
When 16 to 16 are in contact with the lead wires 21 and 22, they are instantly discharged by the measurement current source 11 and the resistance 12 to be measured, and normal measurement can be performed. If the HV measurement terminal 15 has a poor contact with the lead wire 21, the charging voltage of the capacitor 25 remains as it is and the differential amplifier
The output of 19 is a positive voltage overflow. LV measurement terminal
When 16 is in poor contact with the lead wire 22, the − voltage of the capacitor 26 remains as it is, enters the − input of the differential amplifier 19, and the output similarly overflows the + voltage.

In this way, the measured value can always be overflowed with respect to the contact failure between the HV, LV measurement terminals 15 and 16 and the lead wires 21 and 22 of the resistance 12 to be measured.

EFFECTS OF THE INVENTION As described above, according to the present invention, the measured value is made to be a clear abnormal value of overflow or zero for any contact failure of the measuring terminal by a relatively simple method without impairing the measurement accuracy, and a defective product is obtained. Can be prevented from being mixed into non-defective products. This is an important fail-safe function for ensuring the sorting quality of electronic component measuring and sorting machines.

Further, this method has a wide range of applications not only for resistance but also for other four-terminal measurement of a coil or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic component measuring apparatus according to the present invention, FIG. 2 is a measurement timing diagram of the present invention, and FIG. 3 is a block diagram of a conventional 4-terminal resistance measuring circuit. 11 …… Measurement current source, 12 …… Measured resistance, 13 …… HI measurement terminal, 14 …… LI measurement terminal, 15 …… HV measurement terminal, 16 …… LV measurement terminal, 17 …… HV buffer amplifier, 18 ...... LV buffer amplifier, 19
...... Differential amplifier, 20 …… A / D converter, 21,22 …… Lead wire, 23 …… Switch, 24 …… Switch, 25 …… Capacitor, 26 …… Capacitor.

Claims (1)

[Claims] 1. A capacitor is provided between a measurement terminal for measuring the voltage at both ends by applying a current to a part to be measured and the ground, and the capacitor is charged with a power supply voltage at a timing when no measurement is made. If so, this charging voltage remains during measurement, and the electronic component measuring device is configured so that the measured value becomes an abnormal value of overflow.