JPH0334595B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention particularly relates to process input/output devices (hereinafter referred to as PIOs).
digital input/output module (hereinafter referred to as DIO), which is used as a simulated sensor when testing or maintaining the digital input/output module (hereinafter referred to as DIO).
Regarding output testers.

[Problems with the technical background of the invention]

Conventionally, digital input devices (hereinafter referred to as DI)
or digital output device (hereinafter referred to as DO)
In order to perform this test, it was necessary to use a dedicated digital input tester or digital output tester that matched the type of device under test. However, DI and DO are generally modular.
Since these tests are often grouped together as DIO, the above two types of testers are always required for testing, which poses problems in terms of workability and economy.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to develop a digital input/output tester with excellent workability and economy that can be used for both DI (digital input device) and DO (digital output device) tests. Our goal is to provide the following.

[Summary of the invention]

In the present invention, a connector section is provided which has a pair of signal lines and a common line that can be connected to either a DI or a DO having a common arrangement of pairs of signal terminals and common terminals, and also includes a first fixed contact, a second fixed contact, and a A changeover switch having a movable contact, the movable contact being connected to the common line,
If this switch is switched to the first fixed contact side, it is possible to test the DO by supplying power to the signal line via the light emitting element, whereas the switch is switched to the second fixed contact side. If it has been switched, the common line is connected to the signal line via the changeover switch and bit switch, thereby making it possible to test the DI. Furthermore, in order to test DO, it is necessary to have low impedance between the first fixed contact and the ground, but in the present invention, the changeover switch is
If it is accidentally operated for DO testing,
In order to prevent overcurrent from flowing to the common line due to the power supply in the DI that is supplied to the common terminal of the DI, the impedance between the first fixed contact and the ground must be The impedance can be switched to either low impedance or high impedance depending on the voltage value.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a digital input/output tester 10.
This shows the configuration of 11 is DI ₂₀ and
A common connector terminal 12 is connected to a common terminal COM of a device under test such as DO ₃₀ , and a signal connector terminal 12 is also connected to a signal terminal S. 13 is a connector portion having a common connector terminal 11 and a signal connector terminal 12;
1. One ends of a common line 14 and a signal line 15 are connected to the signal connector terminal 12, respectively. A movable contact ₁₆₀ of a changeover switch 16 is connected to the other end of this common line 14. In addition, an impedance switching circuit 17 is connected to the fixed contact 16 ₁ (first fixed contact) of the changeover switch 16.
is connected. In this impedance switching circuit 17, R ₁ and R ₂ are resistors, Vz is a Zener diode, Tr ₁ and Tr ₂ are transistors, and PST is a power supply. The siener voltage of the siener diode Vz is PS _I , assuming that the internal power supply of DI20 is PS _I.
＞Vz＞PS Selected to satisfy _T. In this example, +15V, +24V, +48V are used as PS _I ,
+5V, which is a lower voltage than PS _I , is used as PS _T. Also, the Zener voltage (operating point) is +
A 6.3V Sienar diode Vz is used.
Furthermore, the resistors R ₁ and R ₂ are selected so as to satisfy R ₁ >>R ₂ 0 (Ω).

On the other hand, the fixed contact 16 ₂ (second
The other end of the signal line 15 is connected to the fixed contact of the signal line 15 via a bit switch 18. Also, between the other end of this signal line 15 and the power supply _PST , a resistor R ₃ , a light emitting diode D _L , and a switch 19 are connected.
is inserted, and when the switch 19 is turned on, the power source _PST is supplied to the signal line 15 via the light emitting diode _DL . This switch 19 responds to the switching operation of the changeover switch 16, and is turned on when the changeover switch 16 is switched to the fixed contact ₁₆₁ side, and turned off when the changeover switch 16 is switched to the fixed contact ₁₆₂ side. In addition, DI20
However, in general, there are multiple pairs of common terminals COM and signal terminals S of the device under test such as DO30, but in Figure 1, for convenience, one pair of common terminals COM,
The configuration corresponds to the signal terminal S.

Figure 2 shows the case where the digital input/output tester 10 in Figure 1 is connected to DI20.
At 20, PS _I is the internal power supply. 21 is a protective fuse in case of a short circuit on the tester 10 side, and the power source PS _I is supplied to the common terminal COM via the protective fuse 21. Reference numeral 22 denotes a photocoupler, which is activated when a valid signal is input to the signal terminal S, and performs input to the inside.

Figure 3 shows the case where the digital input/output tester 10 of Figure 1 is connected to the DO30.
In the DO 30, Tr ₃ is, for example, an NPN type output transistor. The collector of the transistor _Tr3 is connected to the signal terminal S, and the emitter is connected to the common terminal COM.

Next, the operation of one embodiment of the present invention will be explained. First, connect the digital input/output tester 10 to DI20.
We will explain the case where the DI20 is tested by connecting it to the DI20. In this case, it is necessary to switch the changeover switch 16 (the movable contact 16 ₀ ) to the fixed contact 16 ₂ side as shown by the solid line in FIG. However,
Protective fuse 21, common terminal COM, common connector terminal 11 of connector section 13, common line 14, changeover switch 16, bit switch 18,
A power supply (digital input) supply path consisting of the signal line 15, the signal connector terminal 12 of the connector section 13, and the signal terminal S is formed, and the DI
The internal power supply PS _I of 20 is supplied to the photocoupler 22 as a simulated digital input when the bit switch 18 is turned on. As a result, the photocoupler 22 is activated and a signal is input into the DI 20.

Next, connect the digital input/output tester 10 to DO3.
The case of testing DO30 by connecting it to 0 will be explained. In this case, it is necessary to switch (the movable contact 16 ₀ of) the changeover switch 16 to the fixed contact 16 ₁ side as shown in FIG. When the changeover switch 16 is switched to the fixed contact ₁₆₁ side, the switch 19 is turned on in response. Therefore, the power supply P _T in the tester 10 is connected to the light emitting diode D _L , the resistor R ₃ , the signal line 15, the signal connector terminal 12 of the connector section 13, and the DO
It is supplied to the collector of the output transistor Tr ₃ in the DO 30 via the signal terminal S of the DO 30. The power supply _PST is +5V, so the potential of the emitter of the transistor _Tr3 is lower than +5V. At this time, the emitter is the common terminal COM, the common connector part 11 of the connector part 13, and the common line 1.
4. It is connected to the impedance switching circuit 17 via the movable contact 16 ₀ and the fixed contact 16 ₁ of the changeover switch 16. DO30 as mentioned above
The potential of the emitter of output transistor Tr ₃ in
Since it is lower than 5V, the Zener diode Vz (in the impedance switching circuit 17) whose Zener voltage is +6.3V does not conduct. Therefore, no base current is supplied to the transistor Tr ₁ , and the transistor Tr ₁ is in an off state. Since the transistor Tr ₁ is in the off state, the power supply _PST supplies base current to the transistor Tr ₂ , and the transistor Tr ₂ is in the on state. Therefore, the on-resistance of transistor Tr ₂ is
Assuming R _pN , the impedance seen from the common terminal COM to the tester 10 side is R ₂ +R _pN +V _CE (SAT)
0 (Ω), and the common terminal COM, that is, DO3
The emitter of the output transistor Tr ₃ in 0 is almost grounded. As a result, the transistor Tr ₃ operates normally on/off. During the on-operation period of the transistor _Tr3 , the light emitting diode _DL in the tester 10 is turned on by the power supply _PST applied to the anode of the diode _DL , indicating that there is a digital output.

Next, using the digital input/output tester 10,
When testing DI20, the changeover switch 16 in the tester 10 is switched to the fixed contact ₁₆₁ side as shown by the broken line in FIG. 2, that is, the changeover switch 16 is switched to the DO30 test. A case will be described in which the connector section 13 is connected to the DI 20 in a state where the In this case, at the moment when the connector section 13 is connected to the DI 20, the internal power supply PS _I of the DI 20 is connected to the protective fuse 21, the common terminal COM, the common connector terminal 11 of the connector section 13, the common line 14, and the movable contact 16 of the changeover switch 16. ₀ and is supplied to the impedance switching circuit 17 via the fixed contact 16 ₁ . Above power supply
As mentioned above, PS _I is generally larger than the power supply PS _T (+5V) in the tester 10, such as +15V, +24V, +48V. Further, the Zener voltage of the Zener diode Vz in the impedance switching circuit 17 is +6.3V, which is sufficiently smaller than +15V even if the base-emitter forward voltage V _BE (0.7V) of the transistor Tr ₁ is added. Therefore, the Zener diode Vz becomes conductive the moment the connector section 13 is connected to the DI 20, thereby supplying the base current to the transistor _Tr1 . As a result, the transistor Tr ₁ is turned on, and as the transistor Tr ₁ is turned on, the transistor Tr ₂ is turned off. Therefore,
The impedance seen from the common terminal COM to the tester 10 side is different from that in the test for DO30, and is R ₁ × {PS _I / (PS _I − Vz − V _BE )}≫R ₂ , that is, high impedance. For this reason, when the changeover switch 16 is set to test DO30, the connector part is
Even if the user erroneously connects the terminal 3 to the DI 20, no overcurrent will flow through the common line 14, that is, the protective fuse 21, and there is no risk of the fuse blowing. Note that if the impedance switching circuit 17 is not provided and the fixed contact ₁₆₁ side of the changeover switch 16 is fixedly set in a low impedance state (by switching the changeover switch 16, the common tester can be used with the DI20 as in the previous embodiment). Although testing for DO30 can be performed), there may be errors in the operation of the changeover switch,
If the wrong connection is made (as in the previous example, when it should have been connected to DO30 but was connected to DI20), an overcurrent will flow through the common line 14, causing problems such as blown fuses. It turns out.

It should be noted that the impedance switching circuit is not limited to the above-mentioned embodiment, but may be one that compares the potential of the fixed contact ₁₆₁ of the changeover switch 16 with a reference potential using a comparator, and switches the impedance according to the comparison result. But that's fine.

〔Effect of the invention〕

As detailed above, according to the present invention, one unit can
It is possible to provide a digital input/output tester that can perform both DI (digital input device) and DO (digital output device) tests, and is free from inconveniences caused by operational errors, and has excellent workability and economic efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the digital input/output tester of the present invention, and FIGS.
The figure shows a case where the tester of the above embodiment is connected to a digital input device and a digital output device, respectively. DESCRIPTION OF SYMBOLS 10... Digital input/output tester, 13... Connector part, 14... Common line, 15... Signal line, 16... Changeover switch, 17... Impedance switching circuit, 18... Bit switch, 20... Digital input device (DI), 21... Hughes, 30...
Digital output device (DO), D _L ...Light emitting diode.

Claims (1)

[Claims] 1. A connector portion having a pair of signal lines and a common line that can be connected to either a digital input device or a digital output device having a common arrangement of pairs of signal terminals and common terminals, first and second fixed contacts, and A changeover switch has a movable contact and the movable contact is connected to the common line, and when the changeover switch is switched to the first fixed contact side, a power source is connected to the signal line via a light emitting element. means for connecting the common line to the signal line via the changeover switch and a bit switch when the changeover switch is switched to the second fixed contact side; A digital input/output characterized by comprising a first fixed contact and a means for switching the impedance between the first fixed contact and ground to either low impedance or high impedance depending on the voltage between the first fixed contact and ground. tester.