JPS5855533B2 - Failure diagnosis method for signal conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal conversion arrangement for converting a voltage signal corresponding to the operating state of an external contact, such as a plant contact, into a logic level signal, and in particular, the present invention relates to a signal conversion arrangement for converting a voltage signal corresponding to the operating state of an external contact, such as a plant contact, into a logic level signal, and in particular, for fault diagnosis of a signal conversion circuit, for system operation. This invention relates to a fault diagnosis method that can be performed online.

FIG. 1 is for explaining a conventional failure diagnosis method for a signal conversion circuit.

External contact 3a. One end of 3b is connected to input terminals 5a and 5b of signal conversion circuit A, respectively, and the other end is connected to ground terminal 5C.

Input signal terminal 5a is connected to power supply vB via resistor R1a, and further connected to the negative input terminal of comparator circuit 1a via resistor R28, a filter circuit consisting of capacitor C1a, and resistor R3a.

Similarly, the input signal terminal 5b is connected to the power supply VB via a resistor R1b, and is further connected to a resistor R2b and a capacitor C.
It is connected to the minus (→ input terminal) of the comparator circuit 1b via the filter circuit consisting of 1b and the resistor i1'tab.

A common reference voltage Es is applied to the positive (G) input terminals of the comparison circuits 1a, 1b, . . . , 1n.

Although FIG. 1 shows two external contacts 3a and 3b, in reality there may be several thousand or even several thousand external contacts.

In such a signal conversion circuit, for example, when the contact 3a is turned on, the input voltage e1a of the comparator circuit 1a becomes the low level voltage O.
(2), and in the off state, the high level voltage (3).

The reference voltage Es is between O■ and vB, for example, 1/2・■
3, and for low level input, comparator 1a
outputs a logic level "1", and in the case of a high level, outputs a logic level "0", and outputs a logic level signal corresponding to the operating state of each contact.

Conventionally, fault diagnosis of such a signal conversion circuit has been carried out when the system is in operation (online), once the system is stopped (offline), the input signal line is removed at the input signal terminal 5b and the ground terminal 5c, and a pseudo By connecting the contact 4 and manually turning the contact 4 on and off, a pseudo input signal is taken in and a failure diagnosis of the signal conversion circuit is performed.

For this reason, there were the following drawbacks.

(1) Online failure diagnosis is not possible.

(2) Manual operation and system downtime is a problem.

(3) Operation is troublesome.

The present invention was invented in view of the above points, and its purpose is to provide a novel fault diagnosis method that enables online fault diagnosis.

One object of the present invention is to perform fault diagnosis using a simple method.

A feature of the present invention is that by changing the reference voltage of the comparator circuit, a state equivalent to applying a pseudo input signal is created.

Other objects and features of the present invention will become apparent from the following description.

FIG. 2 is a circuit diagram of one embodiment of the present invention.

The major difference between FIG. 2 and FIG. 1 is that the reference voltage Es of the comparator circuits 1a, lb...1n can be changed by an external signal.
This is shown as a voltage variable setting circuit 100.

The voltage variable setting circuit 100 includes switch elements 17, 18,
The reference voltage Es of the comparator circuits 1a to 1n composed of an inverter 21 and resistors R5 and R6 is changed by a pseudo input setting signal 19DCK from a computer (not shown).

Resistors R7a and R8a1 are correction resistors, and r is equivalent to the DC resistance on the plant side.

Now, in FIG. 2, when performing a pseudo input setting equivalent to the ON state of the plant contact 3a, the pseudo input setting signal 1
9 is given logic "1", check signal 20CHEC
K turns on switch element 17, switch element 18
Turn off.

Here, the reference voltage EES of the comparison circuits 1a to 1n is normally set to an intermediate value, for example, VB/2, with respect to the input voltage Vi when the plant contacts 3a, 3b, . . . are in the on state or off state. The switch element 17.1
8 is turned off, and VB is divided by a resistor Rs t R6.

If R5=R6, the reference voltage ES becomes equal to B/2 when the switch elements 17 and 18 are in the off state.

When the check signal 20 is not present, the switch elements 17 and 18 are both off, and depending on the content of the pseudo input setting signal 19, one of them is turned on and the other is turned off.

Now, when the pseudo input setting signal 19 is logic "1", the switch element 17 is on and the switch element 18 is off, and if the reference voltage in this case is ESI, then the voltage drop when the switch element 17 is on is Letting VCES be, it becomes.

Here, the plant contact 3 input terminal ■i (0) is when a is in the off state, and the reference voltage ESI is the input voltage V i (0)
? ■For 1(1), E 81 > Vi(
.

), R31>■1 (1), and the output of the comparator circuit 1a is independent of the operating state of the plant contact 3a. When performing a pseudo-human setting equivalent to the OFF state of 3a, logic "0" is given to the pseudo-input setting signal 19, and the check signal 20 causes the switch element 17 to
is turned off, and the switch element 18 is turned on.

If the reference voltage in this case is 1Eso, becomes.

The resistor R7a is set so that vcEs 1 (1), and the reference voltage ESO is set to the input voltage 1 (1).
1) and ■1(o), respectively, ESo<■1(1)
, E8o x vi(o).

At this time, the output of the comparator circuit 1a operates equivalent to when the plant contact 3a is in the OFF state.

The above situation is shown in FIG.

In this way, the reference voltage Es is set to the higher voltage level signal ■i() of the two voltage level signals.

) By setting the voltage level ESO to a voltage level even lower than the voltage level ES1% lower than the voltage level signal V i (1), it is possible to set a pseudo input regardless of the operating state of the plant contacts, and diagnosis after the comparison circuit can be performed. This can be done online.

A simple example of fault diagnosis is shown in FIG.

In FIG. 4, B indicates a computer, and the check signal CHECK and pseudo input setting signal DCK are input from the computer B to the voltage variable setting circuit 100 of the signal conversion circuit A, and the comparison circuit output Dia"Din at this time is taken. It looks like this.

In FIG. 4, consider the case where the check signal CHECK and the pseudo-input setting signal DCK of logic "1" (pseudo-input "1" data pattern) are input to the signal conversion circuit A.

At this time, the setting signal is activated.

Output signal Di of signal conversion circuit A for logic “1” of K
a(1) to D i n (1) (these are collectively referred to as D i
It is shown as (1).

) is taken into computer B, and the pseudo input setting signal DCK (1
) compared to

Here, the logic of the pseudo input setting signal DCK (1) is "1".
However, there is a mismatch in the bit 0 data (logic "O").

This indicates that there is an abnormality in the circuit operation after the comparison circuit corresponding to bit O.

Similarly, when the signal conversion circuit A is given the logic "0" (pseudo input "0" data pattern) of the pseudo input setting signal DCK, the output signal Dia (of the signal conversion circuit A) is applied.

)~Din(o) (These are collectively referred to as Di(.

). ) and pseudo input setting signal DCK(
0) are compared in computer B.

Here, the logic of the pseudo input setting signal D CK (o) is
There is a discrepancy in the data of bit 1 for "O".

This indicates that there is an abnormality in the circuit operation after the comparison circuit corresponding to bit 1.

As described above, according to the present invention, since the pseudo input can be set regardless of the operating state of the external contact, it is possible to perform failure diagnosis of the signal conversion circuit in a simple manner without causing a system down even when the system is in operation. is possible.

Furthermore, according to the present invention, failure diagnosis (simulation operation) can be performed on a computer without modifying input signal terminals even when the system is started up and is not connected to a process.

Furthermore, according to the present invention, even in the event of a failure, it is possible to localize the failure location in a shorter time, and a significant reduction in system downtime can be expected.

Furthermore, the voltage variable setting circuit newly added according to the present invention can be realized with a simple configuration.

[Brief explanation of drawings]

Figure 1 is a circuit diagram for explaining a conventional signal conversion circuit and failure diagnosis, Figure 2 is a circuit diagram of an embodiment of the present invention, and Figure 3 is a circuit diagram for explaining a conventional signal conversion circuit and failure diagnosis.
2 is a timing chart showing the operation of FIG. 2, and FIG. 4 is a diagram showing an embodiment of the present invention for carrying out specific failure diagnosis. 19...Pseudo input setting signal, 20...
Check signal, 100... Voltage variable setting circuit.

Claims (1)

[Claims] 1. Two operating states of the external contact are input into one input terminal of the comparator as a voltage signal, and a reference set between the two voltage signals is input into the other input terminal. In a signal conversion circuit that applies a voltage and extracts the operating state of the external contact as a logic level signal from the comparator, the reference voltage of the comparator is switched to a voltage level different from a steady state, A fault diagnosis method for a signal conversion circuit, characterized in that a fault diagnosis is performed by comparing a comparator output at this time with preset data. 2. The voltage level different from the steady state as recited in claim 1 is a voltage level that is larger than the large voltage signal corresponding to one operating state of the external contact and a small voltage signal corresponding to the other operating state. A fault diagnosis method for a signal conversion circuit that uses a voltage level that is even smaller than a signal.