JPH08147031A - Instrumentation signal abnormality detecting device - Google Patents

Abstract

PURPOSE: To discriminate a detector which becomes abnormal by a two- measuring method which uses two detectors for reliability improvement. CONSTITUTION: First and second arithmetic circuits 2A and 2B, provided with a means which finds a moving average value of measured values (a) and (b) of 1st and 2nd detectors, a means which finds a 1st and a 2nd variation rate by differentiating the moving average value, a comparing means which judges that the 1st or 2nd detector is abnormal by comparing the 1st and 2nd variation rates with a set value (c), detect the abnormality of the 1st or 2nd detector. Further, a deviation alarm circuit 5 detects an abnormal increase in the deviation between the measured values (a) and (b) to confirm that one of the 1st and 2nd detectors becomes abnormal. Then AND circuits 7A and 7B output when abnormality detection signals (d) and (f) are inputted from the 1st and 2nd arithmetic circuits 2A and 2B on condition that there is a signal (f) from the deviation alarm circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to instrumentation equipment in water treatment plant equipment and the like, and detection in two measurements conducted by two detectors in order to improve the reliability of the measurement value at one measurement location. The present invention relates to an instrumentation signal abnormality detection device that detects an abnormality in a vessel.

[0002]

2. Description of the Related Art In instrumentation equipment, in the measurement by two measurements in which two detectors are used to improve the reliability of measured values, two detectors are provided in comparison circuits 11 and 12 as shown in FIG. The measured values a and b from A and B are input, and one of the two signals a and b is used as a reference value b, and the difference between the signals a and b is compared with the deviation signals + α and −α set externally. hand,
When ab <+ α or ab> −α, the upper or lower limit alarm output H or L is output.

[0003]

In the case of the above-mentioned two conventional measurements, it is possible to compare the measured values from the two detectors and detect the detector abnormality by the difference between the measured values, but the two detectors are used. It is not possible to determine which of them is the failure.

Therefore, when the measurement signal is used for automatic control, it is impossible to automatically disconnect the faulty detector and switch to the control using only the measurement signal from the normal detector. Therefore, proper operation of plant equipment cannot be performed.

In the measurement by three measurements using three detectors, the measurement values from the three detectors are compared and the majority detector can judge the failure detector. However, the measurement by three measurements is not common because the cost of the detector increases and there is a problem of installation space.

The present invention has been made in view of the problems of the prior art, and its object is to make an abnormal instrumentation signal capable of determining which of the two detectors in two measurements is abnormal. It is to provide a detection device.

[0007]

In order to achieve the above-mentioned object, the instrumentation signal abnormality detecting device according to the present invention uses the first and second measurement values from the first and second detectors in two measurements. First and second moving average value calculating means for obtaining a moving average value, first and second differentiating means for obtaining a rate of change of the first and second moving average values, and the first and second It is provided with first and second comparing means for ratioing the rate of change of the moving average value to the set rate of change and outputting a detector abnormality signal when the rate of change of the moving average value is large.

Further, a deviation alarm circuit for detecting a deviation between the first and second measured values and outputting when the deviation exceeds a predetermined value, and a signal from the deviation alarm circuit are inputted. Under the above condition, it is preferable to provide first and second AND circuits that output when the detector abnormality signal from the first and second comparing means is input.

[0009]

When the abnormality occurs in the detector, the output of the detector changes suddenly. The first and second moving average value calculating means calculate moving average values of the first and second detectors, and the first and second differentiating means calculate the rate of change of the first and second moving average values. Output. First, second
The comparing means compares the rate of change of the first and second moving average values with the set value, detects a sudden change in the detector output, and determines the abnormality of the first and second detectors.

When one of the first and second detectors becomes abnormal, the deviation between the first and second measured values increases. The deviation alarm circuit detects that the deviation exceeds a predetermined value and judges that a detector abnormality has occurred. The first and second AND circuits output the detector abnormality signal from the first and second comparing means on condition that the signal from the deviation warning circuit is input.
Therefore, the abnormal detector can be reliably detected.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an instrumentation signal abnormality detection device. Reference numeral 1 is the measured values a and b from two detectors A and B.
The input circuits 2A and 2B for input are the measured values a and b from the input circuit 1 and the set change rate c from the change rate setting device 4 (for example, in the case of a pump well water level, the change condition (10 (10 cm etc. in seconds) is set)
An arithmetic circuit for detecting an abnormality of the detector A or B and outputting an abnormality signal d or e, which is configured or functions as shown in FIG.

Reference numeral 5 is a deviation alarm circuit for outputting a signal f when the deviation between the measured values a and b exceeds a predetermined value, and 7A and 7B.
Is an alarm output g or h when the abnormal signal d or e from the arithmetic circuit 2A or 2B is input on condition that the signal f from the deviation alarm circuit 5 is input, or the detector B as shown in FIG. It is a logical product circuit that outputs a use instruction of the signal b of 1 or the signal a of detector A.

Next, the configuration and function of the arithmetic circuit 2A will be described with reference to FIG. First, in S1, the moving average value of the measured value a is obtained by the moving average value processing, and in S2, the change rate of the moving average value of the measured value a is obtained, and in S3, the change rate and the change rate setting unit 4 When the calculated change rate is larger than the set change rate c, the detector A is determined to be abnormal. If it is smaller, the process returns to S1.

When the measured value a is compared with the normal output current range (for example, 4 to 20 mA) or the output voltage range (for example, 1 to 5 V) of the detector A in S4, and the value is out of the normal output range, a validity error occurs. Determined to occur. S5 is an OR circuit, which outputs an abnormal signal d to the AND circuit 7A when the Y determination signal is input from S3 or S4.

The configuration or function of the arithmetic circuit 2B is shown in FIG.
As shown in (B), it is similar to the arithmetic circuit 2A (FIG. 2A).

Since the embodiment is constructed as described above, when the rate of change of the moving average value of the measured values a or b from the detectors A and B becomes large, or when the rated output current of the detector or If the output voltage is out of the rated output voltage range, it is judged that the detector A or B has failed on the condition that the deviation between the measured values a and b exceeds a predetermined value, and the signal b of the detector B or the detector A is detected. Since the use instruction of the signal a is output to the control circuit of the instrumentation device, it is possible to perform control using only the signal of the normal detector without using the signal of the defective detector.

Further, according to this embodiment, even if the detection abnormality cannot be detected in S1 to S3, the output of the abnormal detector is out of the normal output range of the detector from S4. It is safe because it is judged that a validity error has occurred and an abnormal signal is output.

[0018]

Since the present invention is configured as described above, it has the following effects.

(1) In the two-measurement method, since it is possible to perform abnormality diagnosis of individual detector signals, it is possible to judge which detector is abnormal.

(2) Since the error is output under the condition of the logical product with the deviation alarm setting, the reliability of the abnormality detecting device is high.

(3) Since it is not necessary to use the 3 measuring method, the initial cost and maintenance cost can be reduced as plant equipment cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an instrumentation signal abnormality detection apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating the configuration and operation of an arithmetic circuit.

FIG. 3 is an explanatory diagram of a configuration of a device output unit.

FIG. 4 is an explanatory diagram of a configuration of a conventional detector abnormality detection device.

[Explanation of symbols]

 2A, 2B ... Arithmetic circuit 4 ... Change rate setter 5 ... Deviation warning circuit 7A, 7B ... AND circuit 11, 12 ... Comparison circuit

Claims (3)

[Claims] 1. A first and second method of obtaining a moving average value of first and second measurement values from first and second detectors in two measurements.
Moving average value calculating means, first and second differentiating means for obtaining the changing rates of the first and second moving average values, and the changing rate of the first and second moving average values set. And a first and second comparing means for outputting a detector abnormality signal when the moving average value change rate is large. 2. A deviation warning circuit for detecting a deviation between the first and second measurement values and outputting when the deviation exceeds a predetermined value, and a condition that a signal from the deviation warning circuit is inputted. The instrumentation abnormality detection device according to claim 1, further comprising: a first and second AND circuit that outputs when the detector abnormality signal from the first and second comparison means is input to . 3. When the output current or voltage of the first and second detectors is compared with the normal output current or voltage range of the first and second detectors and the detector output is out of the normal range The instrumentation abnormality detecting device according to claim 1, further comprising third and fourth comparing means for outputting a detector abnormality signal.