JPH0650077Y2 - Alarm setter - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to an alarm setting device, and more particularly, to a means for adjusting an alarm setting level.

B. Overview of the Invention The present invention is an alarm setting device that obtains a contact output to an output relay by comparing the alarm setting level and the input signal of the process amount, and confirms the process amount with an indicator while changing the setting level. Hold the output state of the output relay as a latch relay,
By disconnecting the comparison output from the latch relay, it is possible to prevent process status confirmation and erroneous output while temporarily stopping the process when changing the alarm setting level.

C. Prior art The alarm setter detects that the process amount has reached the alarm set level, and compares the process input with the alarm set level to obtain an on / off output.

FIG. 2 shows a conventional circuit diagram. The process quantity PV detected by the detector 1 is input to the comparators 2 and 3 as comparison inputs, and the comparators 2 and 3 have the upper limit set value and the lower limit set by the upper limit setter 4 and the lower limit setter 5 as a comparison reference. Given a set value,
Further, an upper limit hysteresis circuit 6 and a lower limit hysteresis circuit 7 for providing hysteresis in the comparison operation are provided to detect whether the process amount PV exceeds the upper limit set value or the lower limit set value. The result of this comparison is the drive transistors 8 and 9
The relays 10 and 11 are energized and deenergized by the relays, and the output of the relays 10 and 11 is turned on and off to obtain the setter output. Reference numeral 12 is a power supply circuit, which obtains a control power supply required for the comparators 2, 3 and the like.

D. Issues to be solved by the invention In the conventional alarm setting device, the alarm setting level is often changed depending on the process usage situation. When the alarm setting level is changed, the outputs of the comparators 2 and 3 may be spotted due to an error in the adjustment operation of the setting devices 4 and 5, and an incorrect output may be given to the monitoring device or the like. Therefore, conventionally, when changing the setting level, etc., the process is temporarily stopped, and adjustments and changes are made using a measuring instrument or the like.

Therefore, in the conventional apparatus, the process is temporarily stopped during the change of the set level, which makes continuous operation of the process difficult. This problem may be caused by temporarily disconnecting the detector and alarm setting device and changing the level, but in this case the contact output state of the output relay may change, and the process amount PV state may change during the change. There remains a problem that confirmation is not possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an alarm setting device capable of confirming the state of the process without requiring a temporary stop of the process when changing the alarm setting level and preventing an erroneous output.

E. Means and Actions for Solving the Problem In order to achieve the above object, the present invention provides an alarm setting device that obtains a contact output to an output relay by comparing the input signal of the process amount with an alarm setting level. Indicator for instructing the input signal, a latch relay that is driven by the comparison output of the process amount and the alarm setting level, and holds the contact output when the comparison output is cut off, and the comparison output while the alarm setting level is being changed. It is equipped with a push-button switch that shuts off between the latch relay and The output change of the latch relay is eliminated by keeping it in advance.

F. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. The process amount PV from the detector 1 is used as an instruction signal of the indicator 13 and also as a comparison input of the comparators 14-17. The comparator 14 compares the set value of the upper limit setter 4 with the process amount PV, and the comparator 15 compares the value obtained by subtracting the hysteresis width from the upper limit set value in the upper limit hysteresis circuit 6 with the process amount PV. Compare. Similarly, the comparator 16 compares the set value of the lower limit setting unit 5 with the process amount PV, and the comparator 17 compares the output of the lower limit hysteresis circuit 7 with the process amount PV.

The outputs of the comparators 14 to 17 drive the driver transistors 22 to 25 via the four circuit contacts 18 to 21 of the momentary operation type push button switch, respectively. Transistor 22 is a latch relay
The set drive of 26 is carried out, and the transistor 23 carries out the reset drive of the latch relay 26. Similarly, the transistor
24 drives the set of the latch relay 27, and the transistor 25 drives the reset of the latch relay 27. The upper limit output is obtained at the output contact of the latch relay 26, and the latch relay 27
Obtain the lower limit output at the output contact of.

In such a configuration, when changing the alarm setting level, the push button switch is operated without disconnecting the connection with the detector 1 and while keeping the process in the operating state.
Perform with 21 open. In this change, the change and the state of the process amount PV are confirmed by the indicator 13, and the contact 18 for the output change of the comparators 14 to 17 due to the adjustment of the setters 4 and 7.
By turning off ~ 21, the transistors 22 to 25 are turned off to disconnect the latch relay. The latch relays 26 and 27 retain the output contact state before the start of the change, and the output contact state does not change during the change. Further, when the operation of the push button switch is stopped due to the end of the change, the normal operation state is restored by the automatic return, and the inoperability due to forgetting the return operation of the push button switch is eliminated.

Although the embodiment shows an alarm setting device having an upper limit and a lower limit, this can be applied to a device having one of the upper limit and the lower limit.

G. Effects of the Invention As described above, according to the present invention, the process amount is confirmed by the indicator, the output state is held by the latch relay, and the comparison output by the pushbutton switch and the disconnection between the latch relay are performed. It is possible to change the alarm setting level without needing to stop the process once, and to check the process status and prevent erroneous output.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a conventional circuit diagram. 1 ... Detector, 4 ... Upper limit setter, 5 ... Lower limit setter,
6 ... Upper limit hysteresis circuit, 7 ... Lower limit hysteresis circuit, 13 ... Indicator, 14,17 ... Comparator, 18,21 ... Push button switch contacts, 26,27 ... Latch relay.

Claims (1)

[Scope of utility model registration request] 1. An alarm setter that obtains a contact output to an output relay by comparing the input signal of the process amount with an alarm setting level, and an indicator for indicating the input signal of the process amount, and the process amount and alarm setting. A latch relay that is driven by a comparison output with a level and holds a contact output when the comparison output is cut off; and a push button switch that cuts off between the comparison output and the latch relay while the alarm setting level is being changed. Alarm setting device characterized by.