JPH0448400A - Alarm area setting device - Google Patents

Abstract

PURPOSE:To obtain an alarm circuit which secures the minimum safety operating state even when a preset value is set incorrectly by outputting an alarm signal by output from an alarm decision part which outputs an alarm decision signal by computing an alarm area by the output value of a comparator. CONSTITUTION:The alarm setting device is comprised of the alarm decision part 2 provided with the alarm area which outputs the alarm signal by inputting the preset value or a real value to decide an alarm, and an alarm part 3 which outputs the alarm decision signal. As the upper/lower limit values of the alarm of the real value for the preset value, a value computed based on the preset value at the lapse of time, and alarm setting of fixed value is performed on even the preset value. After a fixed alarm area is set, a process control value is inputted, and decision is performed by the alarm decision part 2, and when abnormality occurs, the alarm signal 3a is outputted from the alarm part 3. Thereby, an alarm area setting device operated safely can be obtained even when the preset value is set incorrectly due to unexecution in an arithmetic operation to decide an alarm setting value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an alarm area setting device in a process control device.

(Prior Art) In a conventional alarm setting circuit, when a set value (variable) is changed, the settings of the upper and lower limits of the alarm value are changed accordingly.

Generally, SV + between set value SV and process value Pv
If there is no relationship such as a≧pv>sv-β (α and β are upper and lower limit values), the circuit will sound an alarm.

(Problem to be solved by the invention) When the set value is fixed, the upper limit value and lower limit value can also be fixed and the alarm can be set, but if the set value changes over time, the upper limit value and lower limit value must also be changed. Since the alarm is set by calculating each time based on the set value, if the alarm set value loses reliability for some reason, there may be a situation where no alarm is issued even if the actual value becomes abnormal.

An object of the present invention is to provide an alarm circuit that can ensure a minimum safe driving condition even if the set value is incorrectly set by providing an absolute warning range for the set value with respect to the actual value.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a setting circuit that predetermines a set value for alarm or judgment, a comparison circuit that compares a set value signal from this setting circuit with an operating value, and a comparison circuit that compares a set value signal from this setting circuit with an operating value. This is an alarm area setting device that includes an alarm determination section that calculates an alarm area based on an output value and outputs an alarm determination signal, and an alarm section that outputs an alarm signal based on the output from the alarm determination section.

(Function) There is an absolute warning range that the set value or actual value must not exceed over time, and an alarm is issued when the set value or actual value exceeds it.

(Example) Next, an example of the present invention will be described. FIG. 1 shows a setting circuit 1 that predetermines a set value for alarm or judgment, a comparison circuit 4 that compares a set value signal 1a from this setting circuit 1 and an operating value 1b, and an output value of this comparison circuit 4. 4a and outputs an alarm determination signal 2a; and an alarm section 3 that outputs an alarm signal 3a based on the output from the alarm determination section 2. ing. That is, it is composed of an alarm judgment section 2 having an alarm area for outputting an alarm signal by inputting a set value or actual value for making an alarm judgment and a set value or actual value, and an alarm section 3 for outputting an alarm judgment signal. A set value for alarm judgment is input, and this set value is variable. and,
The alarm upper and lower limits of the actual value with respect to the set value are calculated by the above-mentioned formula Sv+α≧pv>sv−β based on the set value at the elapsed time, and this value is also variable, so the set value will be incorrect. It becomes unreliable.

From the above, consider the pattern of set values at elapsed times, set the minimum required alarm range to a fixed value, and set the alarm to a fixed value.Also set the set value to a fixed value.

After setting the above fixed alarm area, input the process control value and let the alarm judgment section make the judgment. As shown in FIG. 2, if there is an abnormality, the alarm section outputs an alarm signal.

In FIG. 2, 12 is an alarm area (upper limit), 11 is a set value (SV) pattern, and 13 is an alarm area (lower limit).

14 is the actual value.

In the present invention, an alarm is set for changes in set values due to the passage of time, but it can also be applied to other types of variables in addition to the passage of time.

〔Effect of the invention〕

According to the present invention, it is possible to provide an alarm area setting device that operates effectively even when the set value is different due to non-execution in the calculation for determining the alarm set value.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a setting device showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of FIG. 1. 1...Setting circuit 2...Alarm judgment section 3...Alarm section 4...Comparison circuit 4 Comparison circuit 2! Figure 2

Claims (1)

[Claims] a setting circuit that predetermines a set value for alarm or judgment;
A comparison circuit that compares the set value signal from this setting circuit with an operating value, an alarm judgment section that calculates an alarm area based on the output value of this comparison circuit and outputs an alarm judgment signal, and An alarm area setting device comprising an alarm section that outputs an alarm signal.