JPS636469A - Wire breaking detection and warning system for sensor - Google Patents

Abstract

PURPOSE:To detect various wire breaking configurations of a sensor and to generate a warning by sending a specific output from an output converter when either the driving or signal output side of the sensor has impedance variation. CONSTITUTION:A Wheatstone type pressure sensor 10 is considered to have 30 kinds of wire breaking when all configurations of wire breaking are checked. In this invention, the 1st warning means 31 which detects the abnormality of the driving side of the sensor and sets the output signal of an output converter 15 to a specific value and the 2nd warning means 32 which detects the abnormality of the signal output side of the sensor and sets the output signal value to a specific value are provided. If the breaking of a wire occurs to the pressure sensor 10 to cause abnormality on the sensor driving side, the output of an operational amplifier 33 is at 15V and a warning device 30 is driven in response to the value. If the abnormality occurs to the sensor signal output side, an initial amplifier 17 gets saturated and the 15V output is obtained to drive the warning device 30.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a system for detecting a disconnection accident in a sensor, such as a pressure sensor, and issuing an alarm.

<Prior Art> For example, in the case of an extrusion molding machine, it is necessary to maintain the pressure of the processing resin at a predetermined value.

For this reason, conventionally, a pressure sensor is used to constantly detect the resin pressure, the value is compared with a set value, and the deviation is used to drive a control device on the extrusion molding machine to control the resin pressure.

Pressure sensors used in such control systems include:
For example, there is a Wheatstone bridge type sensor.As is well known, this sensor consists of a bridge section consisting of four resistance elements connected in a diamond shape, and four human/output leads connecting these elements. Consists of lines.

Since this sensor is used under conditions such as a high temperature environment, there is a good chance that the sensor itself will break.

<Problems to be Solved by the Invention> Therefore, if you do not notice such a sensor disconnection accident and continue to operate the control equipment on the extrusion molding machine, not only will normal extrusion not be possible, but sometimes problems may occur. This may lead to extremely serious accidents such as equipment damage.

The present invention has been made to prevent such a control system from running out of control.

First, prior to the invention, the inventor of the present invention conducted a thorough investigation of all forms of wire breakage in Wheatstone bridge pressure sensors.

For example, in the Wheatstone bridge type shown in Figure 5, the location where wire breakage occurs is the 4th part of the bridge.
Examples include resistance elements A to D and lead wires 1 to 4 on the input and output sides. To show the specific types of wire breakage, there are 4 types of lead wires that break individually, 6 types of lead wires that break at the same time, 4 types of cases where 3 wires break at the same time, and 4 types of lead wires that break at the same time. There is one type of disconnection, for a total of 15 types, and if there is a disconnection in each of the resistor elements A to D in the pre-fuji part, there are 15 types of disconnection, similar to the lead wire. In the end, a total of 30 U
Possible r-line polymorphism.

Tables 1 and 2 show examples of the types of wire breakage and changes in various parts.

In addition, in the case of this sensor, the applied voltage on the drive side is +5V on one side.
, the other is 15V, and the resistance values of resistance elements A to D are each 374Ω.

According to each of these tables, in each of the 30 types of disconnection, the impedance on either the drive side or the signal output side of the sensor changes, and correspondingly, the output on the output converter side changes as well. It can be seen that the output formats can be roughly divided into two types.

<Means for Solving the Problems> The present invention focuses on changes in impedance on the drive side or signal output side of such a sensor, and when this change occurs, in any case of disconnection, the output converter The output is set to reach a certain predetermined value, and the presence or absence of a sensor disconnection accident is detected from this predetermined value and an alarm is issued.

To describe this more specifically, the present invention provides a control system that inputs a sensor detection signal to an output converter and controls a controlled object using the converted output signal, when the sensor is disconnected. a first alarm means for detecting an abnormality on the drive side and setting the output signal value of the output converter to a predetermined value; and a first alarm means for detecting an abnormality on the signal output side of the sensor and setting the output signal value of the output converter to a predetermined value. I! of the sensor consisting of a second alarm means for It is in the Ir ray detection alarm system.

With this configuration, when the sensor is disconnected, if the impedance on the drive side changes due to the type of disconnection, the first alarm means is activated, or when the impedance on the signal output side changes, the second alarm means is activated. In either case, a predetermined output signal value is obtained from the output converter, so the presence or absence of a sensor disconnection is detected and an alarm is issued.

<Embodiment> FIG. 1 shows a case where a sensor disconnection detection alarm system according to the present invention is applied to an output converter.

In the figure, 10 is a Wheatstone bridge type pressure sensor, A to D are four resistance elements of the bridge part, 11
~14 is the input/output lead wire, ・15 is this sensor 10
This is an output converter in which the detection signal is input manually.

In this output converter 15, 16 is connected to the sensor 10 via output leads &'H3, 14, and the sensor 1
17 is a first-stage amplifier that amplifies the noise-cut sensor detection signal; 18 is a second-stage amplifier that inverts and amplifies the output polarity from the first-stage amplifier 17; 19; 20 is a full scale adjustment section connected in parallel to the output lines of the first stage amplifier 17 and the next stage amplifier 18 to set an output value corresponding to the rated pressure of the sensor 10, and 20 is a final stage that further amplifies the output from the next stage amplifier. Amplifiers, 21a-d are output terminals from which various required voltage levels or current levels can be taken out, 22a-b are voltage-to-voltage conversion circuits for the different level voltage terminals 21b-C, and 23 is for the current output terminal 21d. A voltage-current conversion circuit, 24 is a sensor zero point adjustment bias circuit connected to the first stage amplifier 17, 25 is a reference voltage setting section for the sensor drive voltage, and 26 is connected to this reference voltage setting section 25, and its output. Sensor 1 is at the end
The positive applied voltage generation circuit 27 connected to the lead 'fIAll of 0 is connected to the reference voltage setting section 25 via the polarity conversion inverting amplifier 28, and its output terminal is connected to the lead wire 12 of the sensor 10. 29 is a power supply circuit; 30 is a buzzer or lamp connected to each of the output terminals 21a to 21d, and set to be activated when a predetermined output is generated when the sensor is disconnected; This is an alarm device consisting of an indicator, etc.

The sensor disconnection detection alarm system of the present invention is added to this output converter 15, and when the sensor disconnects, a first alarm system detects an abnormality on the drive side of the sensor and sets the output signal value of the output converter 15 to a predetermined value. It consists of an alarm means 31 and a second alarm means 32 for detecting an abnormality on the signal output side of the sensor and adjusting the output signal value of the output converter 15 to a predetermined value.

This first alarm means 31 includes a comparator operational amplifier 3
3. N-channel FET34 and necessary resistance R8~,
The inverting input terminal of the operational amplifier 33 is connected to the positive power supply (+15 V), the non-inverting input terminal is connected to the collector side of the transistor Tl of the positive side applied voltage generation circuit 26, and the output terminal of the operational amplifier 33 is FET
34 to the non-inverting input terminal side of the final stage amplifier 20.

The second alarm means 32 is attached to both the non-inverting input terminal side and the reversing blade terminal side of the first stage amplifier 17, both of which are composed of resistors R5 to R8, the resistor R6 is a high resistance, and the - one is attached to the first stage amplifier 17. The other side is connected to the inverting input terminal side of the first stage amplifier 17, and the non-inverting input terminal side is connected to a positive power supply (+15 V), and the inverting input terminal side is connected to a negative power source. 5 (-1 sv) is applied to each.

In such a control system, when the pressure sensor 10 is working normally, for example, when trying to extract the maximum rated pressure (for example, 350 kg/cm2) of the sensor 10 using the IOV voltage, etc., as shown in the schematic diagram of FIG. The signal output (-7.5 mV, +7.5 mV) of the sensor 10 is input to the first stage amplifier 17, where it is amplified (-3 V), then inverted and amplified by the next stage amplifier 18 (8 V), and then the final It is amplified again by the stage amplifier 20 (IOV). This amplified output is
The control information is sent from each output terminal 21a-d to a control device such as an extrusion molding machine.

However, suppose that a disconnection accident occurs in this pressure sensor 10 and an abnormality occurs on the sensor drive side.

In the case of this output converter 15, the potential of the collector portion (X point) of the transistor T1 of the positive side applied voltage generation circuit 26 is normally 11°5V, but when the impedance becomes 748Ω due to a partial disconnection, Or, when it is completely open, it becomes 15V. This voltage is input to the non-inverting input terminal of the comparator operational amplifier 33.

The potential on the inverting input terminal side of this operational amplifier 330 is resistor R1
Since it is set to 12V by ~3, if the potential on the non-inverting input terminal side is 12V or more, the output of the operational amplifier 33 becomes 15V, turning on the FET 34. This FE
Due to the conduction of T34, the potential on the non-inverting input terminal side of the final stage amplifier 20 increases, and the output from this final stage amplifier 20 becomes 15V. This output is transmitted to each output terminal 21axd, and the alarm device 30 is driven by this value.

- On the other hand, if an abnormality occurs on the sensor signal output side, there will be no signal output to the non-inverting input terminal or the inverting input terminal of the first stage amplifier 17, or even to both terminals. Therefore, on the non-inverting input terminal side, current flows from the positive power supply (+15V) through the high resistance R5, resulting in +Q.

A potential of 5V is generated, and on the inverting input terminal side, a current flows from the negative power supply (-15V) through the high resistance R4, and a potential of -0.5V is generated. Therefore, in either case, the first stage amplifier 17 is saturated and an output of 15V is obtained, which is transmitted to each output terminal 21a to 21d through the next stage amplifier 18 and the final stage amplifier 20, and similarly to the above, the alarm device 3
o is driven.

In this embodiment, when the sensor is disconnected, the output converter 15
The output of the first alarm means 3 is configured to swing to the +15V side.
1 is connected between the next stage amplifier 18 and the final stage amplifier 20, but the present invention is not limited to this, and it is also possible to connect it to the inverting input terminal side of the first stage amplifier I7. Further, as shown in FIG. 3, the transistor T of the positive side applied voltage generation circuit 26 is connected to the inverting input terminal of the comparator operational amplifier 33.

Connect the collector side of the FET, connect the positive power supply (+15 V) to the non-inverting input terminal side, and
34", the first alarm means 31° can be connected between the first stage amplifier 17 and the next stage amplifier 18, or to the non-inverting input terminal side of the first stage amplifier 17. In both of the scheme 1 alarm means 31 and 31'' described above, the input voltage at the time of abnormality is brought from the collector side of the transistor T of the positive side applied voltage generation circuit 26, but the present invention is not limited to this. It is also possible to bring it from the emitter side (X° point) of the transistor T2 of the generating circuit 27.

Furthermore, in the above embodiment, when the sensor is disconnected, the output converter 1
Although the configuration was such that the output of No. 5 was made to swing to the +15V side, it is also possible to make the output swing to the -15V side in the present invention. Examples of such cases include, for example, when you want to control the pressure to maintain it above a certain level even if there is a disconnection, or when you want to monitor it only with an indicator without using it in the control loop. . If the voltage is to be swung to the -15V side, the first alarm means 31 and the first alarm means 31', which are constructed separately, may be installed in opposite positions. The second alarm means 32 on the signal output side is connected to a negative power supply (-15V) on the non-inverting input terminal side of the first stage amplifier 17, as shown in FIG.
), and the positive power supply (+15
V) may be connected to the second alarm means 32°.

(Effects of the Invention) As is clear from the above explanation, according to the sensor disconnection detection alarm system of the present invention, when incorporated into an output converter, etc. in a resin pressure control system of an extrusion molding machine, etc., when a sensor disconnection occurs, Since it outputs the predetermined output value that has been set, it is possible to quickly determine whether there is a disconnection.This prevents unnecessary defective products from occurring due to control system runaway, and also increases the safety of the control system. Can be done.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram showing an example of the case where the sensor disconnection detection alarm system according to the present invention is applied to an output converter, Fig. 2 is a schematic diagram showing the amplification state in each amplifier, and Fig. 3 is A wiring diagram showing another first alarm means according to the present invention, FIG. 4 is a wiring diagram showing another second alarm means according to the present invention, and FIG.
The figure is a wiring diagram showing a pressure sensor. In the figure, 10... Pressure sensor, A-D... Resistance element, 11-14... Input/output lead wire, 15... Output converter, 30... Alarm device, 31.31' ...first alarm means, 32.32'
...Second alarm means, patent applicant Rika Kogyo
Co., Ltd. Figure 2 Figure 3 Figure 31'\ Figure 4 Figure 5

Claims (1)

[Claims] In a control system that inputs the detection signal of a sensor to an output converter and controls a controlled object using the output converted signal, when the sensor is disconnected, an abnormality on the drive side of the sensor is detected and the output of the output converter is changed. A sensor comprising a first alarm means for setting a signal value to a predetermined value, and a second alarm means for detecting an abnormality on the signal output side of the sensor and setting the output signal value of the output converter to a predetermined value. Disconnection detection alarm system.