US-20260126304-A1 - Sensor System

US20260126304A1US 20260126304 A1US20260126304 A1US 20260126304A1US-20260126304-A1

Abstract

A sensor system according to the present invention includes a sensor unit that is formed of a pair of a sensor and an electronic circuit unit for each of the sensors, switching circuits in the electronic circuit units are connected in series, and the electronic circuit units are configured such that, when outputs from all the sensors are normal, all the switching circuits are electrically connected in series.

Inventors

Dai KANEDA
Naoya Ishigaki

Assignees

HITACHI HIGH-TECH CORPORATION

Dates

Publication Date: 20260507
Application Date: 20250916
Priority Date: 20241105

Claims (8)

1 . A sensor system comprising a plurality of sensors, wherein a sensor unit that is formed of a pair of the sensor and an electronic circuit unit is provided for each of the sensors, each of the electronic circuit units includes a switching circuit, the switching circuits are connected in series, and the electronic circuit units are configured such that, when outputs from all the sensors are normal, all the switching circuits are electrically connected in series.
2 . The sensor system according to claim 1 , wherein the switching circuit includes a first input terminal, a second input terminal, and an output terminal, and is configured to be switched such that any of a signal input to the first input terminal or a signal input to the second input terminal is output from the output terminal, the output terminal in the switching circuit is connected to the first input terminal of the switching circuit in the electronic circuit unit of a next stage such that the switching circuits are connected in series, the second input terminal in the sensor unit is connected to an output of the sensor in the same sensor unit, and when the output from the sensor in the same sensor unit is normal, the switching circuit in the sensor unit is switched such that the input to the first input terminal is output from the output terminal.
3 . The sensor system according to claim 2 , wherein when the output from the sensor in the same sensor unit is abnormal, the switching circuit in the sensor unit is switched such that the input to the second input terminal is output from the output terminal.
4 . The sensor system according to claim 2 , wherein the electronic circuit unit includes a differential amplifier circuit configured to amplify and output a difference between the output from the sensor and a reference signal, an absolute value circuit configured to output an absolute value of the output signal from the differential amplifier circuit, and a comparator circuit configured to output a result of comparing the output signal from the absolute value circuit to a threshold voltage, wherein the electronic circuit unit switches the switching circuit based on the output signal from the comparator circuit.
5 . The sensor system according to claim 4 , wherein the comparator circuit switches the switching circuit such that, when the output signal from the absolute value circuit is the threshold voltage or lower, the first input terminal and the output terminal are connected, and when the output signal from the absolute value circuit is higher than the threshold voltage, the second input terminal and the output terminal are connected.
6 . The sensor system according to claim 1 , further comprising a line configured to connect the electronic circuit units in series to supply power to each of the electronic circuit units, wherein the line is provided separately from a line configured to connect the switching circuits in series.
7 . The sensor system according to claim 1 , wherein the electronic circuit unit includes an OR logic circuit, a first input terminal of the OR logic circuit receives a switching signal for switching the switching circuit, and an output terminal of the OR logic circuit is connected to a second input terminal of the OR logic circuit in the electronic circuit unit of a next stage such that the OR logic circuits are connected in series.
8 . The sensor system according to claim 7 , wherein the OR logic circuits are connected in series such that, when at least any of outputs of the sensors is abnormal, an output of the OR logic circuit of a final stage is configured to output a signal representing that at least any of the outputs of the sensors is abnormal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor system where a plurality of sensors are connected. 2. Description of Related Art A sensor system where a plurality of sensors are connected in parallel to one monitoring device can monitor each of the sensors without requiring a complicated algorithm, but has poor extensibility. In addition, as the scale of the system increases, the number of sensors required increases. In this environment, there is a problem such as an increase in the number of wirings or complication of a wiring path. In order to solve this problem, as a technique of improving extensibility, cost benefit, and maintenance, a technique where sensors are connected in series to a monitoring device is present. There are various connection methods between the monitoring device and the sensors, and one examples thereof is disclosed in JP2001-067575A. JP2001-067575A provides a sensor system where a plurality of sensors are connected in series assuming that the sensor that detects ON/OFF is mounted. Until now, in the system where a plurality of sensors are connected in series, it has been difficult to accurately detect the position of the sensor that executes the ON/OFF operation. The position detection herein refers to a technique of specifying the number of position where any sensor is positioned in the sensor system where a plurality of sensors are connected in series. JP-A-2001-067575 provides a solution by transmitting and receiving a pulse train using a central monitoring device. That is, by associating each of the sensors with a count value of the pulse train and processing a signal from the sensor in a time-division manner, the position detection of the sensor can be executed. However, the sensor system of JP2001-067575A is limited to application to the sensor that detects ON/OFF, and cannot be applied to an analog sensor that detects a physical change such as a temperature, a pressure, or a humidity and outputs a voltage signal proportional to the amount of change. The reason for this is that the output from the analog sensor is not a binary value such as ON/OFF. On the other hand, in the analog sensor system, for example, when a consistent process environment is required as in a semiconductor inspection device, it is very important to keep an environmental variable such as a temperature, a humidity, or a pressure constant, and a subtle change in environment condition directly affects the quality of a product. Under these circumstances, comprehensive monitoring is required for the inside of a device including an analog sensor that detects changes in various physical quantities such as temperature, a humidity, and a pressure in the device and outputs the detected changes as electric signals. Further, abnormality detection of one point on the sensor system may affect the entire process. Therefore, determination of the overall stability of the sensor system takes precedence over individual position specifying. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and an object thereof is to determine an overall state of a sensor system using an output of a signal terminal of one point in the sensor system where sensor units on which an analog sensor is mounted are connected in series. A sensor system according to the present invention includes a sensor unit that is formed of a pair of a sensor and an electronic circuit unit for each of the sensors, switching circuits in the electronic circuit units are connected in series, and the electronic circuit units are configured such that, when outputs from all the sensors are normal, all the switching circuits are electrically connected in series. With the sensor system according to the present invention, an overall state of the sensor system can be determined using an output of a signal terminal of one point in the sensor system where sensor units on which an analog sensor is mounted are connected in series. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a sensor system 10 according to a first embodiment; FIG. 2 is a block diagram illustrating a configuration of each sensor unit and connection between the sensor units; FIG. 3 is a block diagram illustrating a configuration of a switching circuit; FIG. 4 is a waveform chart illustrating a relationship between signals in the first embodiment; FIG. 5 is a block diagram illustrating a configuration of a switching circuit according to a second embodiment; and FIG. 6 is a waveform chart illustrating a relationship between signals in the second embodiment. DESCRIPTION OF EMBODIMENTS First Embodiment FIG. 1 is a block diagram illustrating a sensor system 10 according to a first embodiment of the present invention. The sensor system 10 is configured with a plurality of sensor units. Each of the sensor units is configured with a sensor (for example, analog sensor) and an electronic