JPS6248194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a probe used in a highly sensitive voltage measuring instrument.

A highly sensitive voltage measuring instrument calibrates the ground potential by bringing the probe's ground contact terminal into contact with the input terminal wire contact before making a measurement by bringing the probe's contact into contact with the object to be measured. The potential of the object to be measured is measured with high precision using the ground potential as a reference. Highly sensitive voltage measuring instruments have become widely used with the development of electronic circuits.
There was a need for equipment and probes that could consistently and efficiently perform highly accurate voltage measurements.

The present invention has been made in view of the above points, and eliminates the need to calibrate the ground voltage by connecting the ground contact terminal of the probe to the contact of the input terminal line during calibration work. It is an object of the present invention to provide a probe which is always in a calibration state and whose signal terminal can be connected to a signal line by a simple button operation only during measurement.

That is, one aspect of the present invention is a probe that is connected to a voltage measuring device, which includes a contact that comes into contact with an object to be measured, a ground contact terminal that comes into contact with the ground potential of the object to be measured, and a contactor that is connected to a voltage measuring device. An input terminal wire connects the terminal and the voltage measuring device, a grounding wire connects the grounding contact terminal and the grounding terminal in the voltage measuring device, and a common terminal is provided in the middle of the input terminal wire. A changeover switch that is connected to the input terminal wire on the measuring instrument side, one of the normally closed contact and the normally open contact is connected to the input terminal wire on the contactor side, and the other is connected to a part of the ground wire. Another invention is characterized in that it has the first invention as a main part, and also includes a signal contact of a switch signal detection circuit that detects the switching state of the changeover switch. It is something to do.

Next, a first embodiment of the probe according to the present invention will be described with reference to FIG. In the figure, 1 is a probe according to the present invention, and 2 is a voltage measuring device connected to this probe 1. The probe 1 has a cylindrical outer housing 3 made of an insulating material, and a contact 4 that comes into contact with the object to be measured is attached to the front end 3a of the outer housing 3. This contactor 4 is shaped like a needle, and its tip 4a protrudes further forward than the front end 3a of the outer casing 3, and the base side is buried in the front end 3a, and the base side end 4b is outside. It is exposed within the inner cavity 3b of the housing 3. In the inner space 3b of the outer casing 3, there is an input terminal wire 5 connecting the contact 4 and the voltage measuring device 2, and a connection between the ground contact terminal 6 and the grounding terminal 7 inside the voltage measuring device 2. An alligator clip is used as the ground contact terminal 6, and the ground wire 8 is inserted from the ground contact terminal 6 through the side wall of the outer casing 3 and into the inner cavity 3b. It is being Furthermore, a changeover switch S is provided in the middle of the input terminal wire 5 in the inner space 3b,
A reed switch is used as the changeover switch S, and the common contact CO of the changeover switch S is connected to the input terminal line 5a on the voltage measuring device 2 side, and the normally open contact NO is connected to the input terminal line on the contactor 4 side. 5b, and a normally closed contact NC is connected to a part of the ground wire 8. Further, a switch operation button mounting slit 9 is formed in the outer casing 3 at a location corresponding to the changeover switch S, and a switch operation button 10 is slidable along the mounting slit 9. The changeover switch S is energized and the common contact CO and the normally open contact NC of the changeover switch S are brought into contact with each other, and the common contact CO and the normally open contact are connected to the inner cavity 3b side of the switch operation button 10. A magnet M that switches to contact with NO is fixed. Also, in the middle of the input terminal line 5a on the side of the measuring instrument 2, a parallel circuit 11 consisting of a resistor R for the purpose of dividing the input voltage and a capacitor C for improving AC characteristics is provided.
has been inserted. The input terminal wire 5 and the ground wire 8 are led out from the rear end 3c of the outer casing 3 containing the changeover switch S and the parallel circuit 11, and each end is connected to the It is connected to the voltage measuring device 2. The ground wire 8 is connected to the ground terminal 7 in the voltage measuring device 2 via the connector 12b, and the input terminal line 5 is connected to the high input impedance circuit 14 made of FET 13 etc. via the connector 12a. The input impedance circuit 14 is connected to a potentiometer (not shown) or the like.

Next, the operation of the probe configured as described above will be explained.

First, input terminal wire 5 of probe 1 and ground wire 8
are connected to the voltage measuring device 2 through connectors 12a and 12b, and the ground contact terminal 6 is clamped at a location of the object to be measured that has a ground potential. This state is a standby state for measurement, and in this standby state, the ground potential from the ground contact terminal 6 is matched with the ground terminal 7 in the voltage measuring device 2, and the ground potential is equal to the normal voltage of the changeover switch S. It is connected to the high input impedance circuit 14 of the voltage measuring instrument 2 via the close contact NC, common contact CO, parallel circuit 11, and input terminal wire 5, thereby controlling the operation of the measuring circuit of the voltage measuring instrument shown in 2 in the figure. Calibration of one ground voltage is performed. Next, when the contactor 4 is brought into contact with the object to be measured and the switch operation button 10 is slid in the direction in which the magnet M approaches the changeover switch S, the switch S is energized and the normally closed contact NC and the common contact
Contact with CO is cut off, and contact is made between the normally open contact NO and the common contact CO. Therefore, the potential of the object to be measured is determined by the contact 4, the normally open contact NO of the changeover switch S, and the common contact.
The voltage is applied to the high input impedance circuit 14 of the voltage measuring device 2 via the NC, parallel circuit 11 and input terminal line 5, and the voltage is measured. In this way, since the calibration signal of the ground potential is always given to the measuring instrument during standby, it means that the calibration has been completed immediately before measurement, making it possible to perform highly accurate measurements. This eliminates the need for the trouble of connecting the contact terminal 6 to the contactor 4. Therefore, as shown in Figure 5, if you apply the conventional ground potential to the measuring instrument, calibrate the DC offset voltage inside the measuring instrument to 0V, then proceed to measurement and continue measurement, the DC inside the measuring instrument will increase due to temperature changes.
However, with the probe according to the present invention, the ground potential of the voltmeter is calibrated every time the switch operation button 10 is pressed, making it easier to measure multiple locations.
DC voltage calibration can be easily performed and efficient and highly accurate measurements can be performed.

Next, second, third, and fourth embodiments of the probe according to the present invention will be described with reference to FIGS. 2, 3, and 4, respectively. Note that the same parts as in the first embodiment described above are given the same reference numerals, and the explanation thereof will be omitted.

In the second embodiment shown in FIG. 2, in addition to the configuration of the first embodiment described above, a signal contact 20a of a switch signal detection circuit 20 for detecting the switching state of the changeover switch S is provided, and a signal contact 20a is provided on the voltage measuring device 2 side. The switching state of the changeover switch S can be recognized at the time of the changeover. A reed switch is provided in the probe 1 in close proximity to the changeover switch S, and the common contact CO' and normally open contact NO' of the reed switch are used as the signal contact 20a of the switch signal detection circuit 20, and the common contact CO' is connected to the switch signal detection circuit 20 in the voltage measuring device 2 via the detection line 21 and the connector 21d, and the normally open contact NO' is connected to the power line 22 and the connector 12c.
is connected to the power supply 23 in the voltage measuring device 2 via
The normally closed contact NC' is connected to a ground terminal 24 in the voltage measuring device 2 via a ground wire 23 and a connector 12e.

Since the probe according to the second embodiment has the above-described configuration, the signal contact 20a is operated in conjunction with the switching operation of the switch S, and thereby the power supply 2
3 to connector 12c, power line 22, normally open contact NO', common contact CO', detection line 21,
Current is supplied to the switch signal detection circuit 20 through the connector 21d, and the voltage measuring device 2 side recognizes that the switch S has been switched.
Therefore, by using this signal as a timing to switch between measurement and self-calibration operations within the measuring instrument, the calibration work can be automated, and by displaying the measured value each time a measurement is made (each time the switch 10 is pressed), the measurement can be performed. There is no risk of misreading of the value, and by using it as a recording timing signal when inputting the measured value to a recorder connected to the voltage measuring device, the measured value can be recorded each time the switch is pressed.

In the third embodiment shown in FIG. 3, a manually operated micro switch is used as the signal contact 20a shown in the second embodiment, and one of the signal contacts 20a is connected to the power line 22. and the other end is connected to the detection line 21. Further, a relay driving coil 30 is provided in the middle of the detection line 21, and this relay driving coil 30 is wound around a changeover switch S, which is a reed switch, to constitute a reed relay.

Since the probe according to the third embodiment has the above-described configuration, when the signal contact 20a is turned ON by manual operation, current is supplied to the relay drive coil 30 and the switch signal detection circuit 20.
When the changeover switch S is operated, the voltage measuring device 2 side recognizes that the changeover operation of the switch S has been performed in the same manner as in the second embodiment. The active circuit 31 in Fig. 3 is the parallel circuit 11 in Figs. 1 and 2 replaced with, for example, an amplifier, and the influence of DC offset voltage due to temperature changes when the active circuit 31 is mounted in the probe. The installation of the changeover switch of this embodiment is particularly effective when calibrating the.

In the fourth embodiment shown in FIG. 4, the switch operation button 10' is a push button type. It is attached to the outer casing 3 via a spring 40.

As explained above, according to the present invention, the probe is provided with a changeover switch that switches between the ground contact terminal and the contact and connects it to the input terminal line. This has the effect of providing a 0V signal for DC calibration to the DC calibration, which allows calibration to be performed immediately before measurement, resulting in highly accurate measurements. Therefore, there is no need to go to the trouble of connecting the ground contact terminal to the contactor for calibration work, and even when measuring multiple points one after another, 0V is measured every time.
This has the effect of being able to perform measurements while being calibrated, and therefore enables highly accurate measurements even if the voltage measuring device using this probe is inexpensive and has a large DC drift.

Further, in the present invention, if a switch signal detection circuit for detecting the switching state of the changeover switch is provided, the calibration work can be automated by using the signal as a timing signal, and the operation switch can be pressed. By displaying the measured value each time, there is no risk of incorrect reading of the measured value, and when inputting data into the recorder, the measured value at the time of measurement is recorded, making it easier to confirm after the fact. There is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the probe according to the present invention, FIG. 2 is a circuit diagram showing the second embodiment, and FIG. 3 is a circuit diagram showing the third embodiment. FIG. 4 is an explanatory diagram showing the surroundings of the changeover switch in the fourth embodiment, and FIG. 5 is a timing chart explanatory diagram showing the time relationship between switch operation, self-calibration, and measurement in the second and third embodiments. It is. 1... Probe, 2... Voltage measuring device, 4... Contact, 5... Input terminal wire, 6... Ground contact terminal, 7... Earth terminal, 8... Earth wire, 20...
...Switch signal detection circuit, 20a...Signal contact,
S...Selector switch, CO...Common contact, NO...
…Normally open contact, NC…Normally closed contact.

Claims (1)

[Claims] 1. A probe connected to a voltage measuring device,
A contact that comes into contact with the object to be measured, a ground contact terminal that comes into contact with the ground potential of the object to be measured, an input terminal wire that connects the contact and the voltage measuring device, and a voltage between the ground contact terminal and the voltage measuring device. A ground wire connecting the earth terminal inside the measuring instrument and the above input terminal wire are provided in the middle, and the common contact is connected to the input terminal wire on the voltage measuring instrument side, as well as a normally closed contact and a normally open contact. a changeover switch, one of which is connected to the input terminal line on the contact side, and the other of which is connected to a part of the ground wire. 2 A probe connected to a voltage measuring device,
A contact that comes into contact with the object to be measured, a ground contact terminal that comes into contact with the ground potential of the object to be measured, an input terminal wire that connects the contact and the voltage measuring device, and a voltage between the ground contact terminal and the voltage measuring device. A ground wire connecting the earth terminal inside the measuring instrument and the input terminal wire are provided in the middle, and the common contact is connected to the input terminal wire on the voltage measuring instrument side, as well as a normally closed contact and a normally open contact. a changeover switch, one of which is connected to the input terminal line on the contact side and the other connected to a part of the ground wire, and a switch signal detection device that detects the switching state of the changeover switch. A probe characterized by comprising a signal contact of a circuit.