GB2193590A

GB2193590A - Environmental abnormality alarm apparatus

Info

Publication number: GB2193590A
Application number: GB08716834A
Authority: GB
Inventors: Tetsuo Kimura
Original assignee: Nittan Co Ltd
Current assignee: Nittan Co Ltd
Priority date: 1986-07-17
Filing date: 1987-07-16
Publication date: 1988-02-10
Anticipated expiration: 2007-07-16
Also published as: GB8716834D0; GB2193590B; JPS6324394A; JPH0470676B2

Abstract

An environmental abnormality alarm apparatus includes a plurality of analog sensors e.g. 26 for detecting environmental abnormalities such as a fire or gas leakage. A central monitor device receives the sensor outputs (digitised) and processes the data and generates an alarm if an abnormality is present. Variations in the characteristics of the analog sensors are corrected by the central monitor device in accordance with respective inherent analog output parameters supplied from memories A1...An at the sensors, or digitised from variable resistors there, or keyed in at the central monitor device. <IMAGE>

Description

SPECIFICATION Environmental abnormality alarm apparatus This invention relates to an environmental abnormality alarm apparatus for detecting environmental abnormalities such as a fire or gas leakage.

In a conventional alarm system, an analog sensor is identified by sn address and detects analog values such as smoke concentration or a temperature change upon occurrence of a fire or a gas concentration change caused by gas leakage. A central monitor device receives the analog values by address polling and executes arithmetic processing to determine whether to generate an alarm.

However, since the analog output characteristics of the analog sensors used in such a conventional analog sensor system may vary from sensor to sensor, the sensitivity of each analog sensor must be controlled to obtain substantially uniform outputs.

For example, referring to Figures 4 and 5 of the accompanying drawings, the variation of an analog output (y) with respect to smoke concentration (x) for the ionized analog sensor illustrated in Figure 4 is shown in the graph of Figure 5. The straight lines A, B and C shown in the graph of Figure 5 represent variations in three analog sensors.

Referring to Figure 4, the sensor comprises an ion chamber 1 for detecting smoke concentration, a FET amplifier 2, a monitor level control zener diode 3, sensitivity control resistors 5 and 6; and analog output terminals A, and A,.

As shown in Figure 5, in such an analog sensor, a normal monitor level is set corresponding to output level Y0, and when the normal monitor level is below Y0, a malfunction alarm is generated. In addition, an alarm level is set corresponding to output level Yn and when the smoke concentration x reaches a predetermined value (e.g., xO) the alarm level Yn is reached and an alarm is generated.

Therefore, each analog sensor needs to be controlled to obtain. the characteristics as represented by the straight line D of the graph in Figure 5. It should be noted that the characteristics of the respective sensors are represented in Figure 5 by the straight lines A, B and C; but they may often be represented by curves. Such an analog output may be represented by the following approximation: =Z a., x.

O11 However, when an analog sensor is used within a limited narrow range of an output characteristic, like a fire or gas leakage sensor, the analog output is substantially linear and hence can be represented by the following approximation: Y = a0 + alx An analog sensor having such a linear analog output need only be controlled to obtain the substantially fixed constants a0 and a, of the above approximation. This control is performed by the zener diode 3 and the variable resistor 6 in the circuit as shown in Figure 4.

The conventional sensitivity control as described above requires two control elements for controlling an initial value (aO) and a gradient value (a,) independently. In addition, when one of the above values is varied, the other value (constant) is affected and varies. Therefore, it is very difficult and troublesome to control, analog sensors having variations, for example, as represented by the straight lines A, B and C of the graph in Figure 5 with respect to the reference characteristic (that is the straight line D of the graph in Figure 5).

According to one aspect of this invention, there is provided an environmental abnormality alarm apparatus comprising: a plurality of analog sensors for detecting environmental abnormalities such as a fire or gas leakage and for outputting data representative of the detected abnormality; a central monitor device for receiving the data output from said sensors and processing it to generate an abnormality alarm if the detected environmental abnormality exceeds a preset limit, said central monitor device including setting means for setting inherent analog output parameters of said sensors and operating/evaluating means for operating/evaluating analog outputs from said sensors in accordance with the analog respective output parameters, whereby variations in the characteristics of said analog sensors are corrected by said central monitor device.

According to another aspect of this invention, there is provided an environmental abnormality alarm apparatus comprising: a plurality of analog sensors for detecting environmental abnormalities such as a fire or gas leakage and for outputting data representative of the detected abnormality, a central monitor device for receiving the data output from said sensors and processing it to generate an abnormality alarm if the detected abnormality exceeds a preset limit, said central monitor device including setting means for setting inherent analog output parameters of said sensors and operating/revaluating means for operating/evaluating analog outputs from said sensors in accordance with the respective analog output parameters, whereby variations in the characteristics of said analog sensors are corrected by said central monitor device, and said analog sensors are provided with parameter memories for storing the inherent analog output parameters.

The embodiment of the present invention described herein provides an environmental abnormality alarm apparatus wherein variations in characteristics of analog sensors can be corrected.

The described embodiment also provides an environmental abnormality alarm apparatus wherein analog sensors can be easily and accurately controlled at low cost.

The invention will now be described by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a block diagram of an overall system according to an embodiment of the present invention; Figure 2 is a block diagram of an analog sensor according to an embodiment of the present invention; Figure 3 is a flow chart illustrating the operation of the apparatus according to an embodiment of the present invention; Figure 4 is a circuit diagram of a conventional analog sensor; Figure 5 is a graph showing an output characteristic of a conventional analog sensor; and Figure 6 is a block diagram of an analog sensor according to another embodiment of the present invention.

Figure 1 is a block diagram of an overall system using an embodiment of apparatus of the present invention as a fire alarm. A plurality of analog sensors D, to DN are connected along a transmission line I extending from a central monitor device R and each is assigned a respective inherent address.

The transmission line I is. also connected to a CPU 10 through a transmitter 13 and an interface 11 contained withinthe central monitor device R so as to sequentially and circularly access the sensors D, to Dn by address signals. An accessed sensor D supplies an analog value of, e.g., smoke concentration to the central monitor device R, and the CPU 10 compares the supplied analog value with a reference value. If the CPU determines that a fire has occurred, it displays a fire display at a display 14 and generates a fire alarm. A con troi panel 15 includes a keyboard and the like and is used to input a predetermined command to access a specific sensor D, or to change the data stored in a memory 16 or an inherent analog output parameter of each sensor D.The memory 16 stores various data for determining a fire or program data for calculation.

Figure 2 is a block diagram of an embodiment of the analog sensor D used in the apparatus of the present invention. The analog sensor D includes: a transmission circuit 21 for inputting/outputting signals through the transmission line I connected to the transmitter 13 of the central monitor device R; a preset address memory 23; an address comparator 22 for executing address comparison with respect to the preset address memory 23; a command discriminator 24 for causing an A/D converter 25 to convert analog values detected by a detector 26 for detecting, e.g., smoke concentration, into digital values and for supplying them to the transmission circuit 21 in accordance with address coincidence signals from the address comparator 22; a switch S which is switched in accordance with signals from the command discriminator 24; and parameter memories A, to At connected to the switch S, and storing coefficients of the inherent parameters of the sensors D.

when an inherent parameter is subjected to address polling, it is supplied from one of the parameter memories A, to An to the central monitor device R through the transmission circuit 21 before an analog value is supplied.

A processing routine of the CPU 10 of the alarm apparatus having the above arrangement is shown in Figure 3. This processing example is represented by a linear function (straight line).

First, initial values a0 of the inherent parameters of the sensors D, to Dn are fetched in steps S1 to S3. Then, coefficients a, of the sensors D, to Dn are fetched in steps S4 to S6. The coefficients a, correspond to gradients of the graph (lines A to D) in Figure 5. If the lines are straight, a single coefficient may be used for the respective sensors D, to Dn.

However, if the lines are curved, the greater the number of fetched coefficients of a quadratic or higher function, the more accurately the judgement is performed. In this case, a selected number of coefficients are prestored in the parameter memories A, to An shown in Figure 2. It should be noted that the processing flow shown in steps SI to S6 does not need to be performed after an initial performance during installation of the apparatus unless data or the like is changed. The fetched data is stored in the memory 16.

In steps S7 to S14, the analog outputs of the sensors D, to Dn are sequentially fetched and arithmetically processed in accordance with the parameters already fetched in steps S1 to S6, thereby executing processing of the output data of the sensors to determine for example whether a fire has occurred (steps S10) or whether a sensor is malfunctioning (step S12).

In the above embodiment, the preset coefficient values are converted into digital values and then stored in the parameter memories A, to An shown in Figure 2. However, Figure 6 shows another embodiment wherein a switch S, which can be switched by the command discriminator 24, is provided before the A/D converter 25. In this embodiment, as for the initial value aO, the inherent initial value of the analog sensor D is preset by a voltage divider consisting of a series circuit including a variable resistor R, and a resistor R2. Similarly, the respective coefficient values are set by voltage dividers consisting of variable resistors R3 1 to R3-n and resistors R4.1 to R4-n Then, these values are sequentially supplied to the central monitor device R through the A/D converter 25.

Furthermore, a label, on which the coefficient of the sensor D is written, may be adhered to a predetermined position of the sensor D, and during installation of the spparatus, the above coefficient may be input by a key-in operation on the keyboard of the control panel 15 of the central monitor device R, thereby setting parameters. However, parameter setting methods are not limited to the above examples.

According to the alarm apparatus described above, variations in parameters of analog sensors need not be controlled to obtain a constant characteristic snd can be corrected more accurately with respect to the reference characteristic so as to judge abnormalities, thereby monitoring with high accuracy and a large decrease in cost.

Claims

1. An environmental abnormality alarm apparatus comprising: a plurality of analog sensors for detecting environmental abnormalities such as a fire or gas leakage and for outputting data representative of the detected abnormality; a central monitor device for receiving the data output from said sensors and processing it to generate an abnormality alarm if the detected environmental abnormality exceeds a preset limit; said central monitor device including setting means for setting inherent analog output parameters of said sensors and operating/evaluating means for operating/evaluating analog outputs from said sensors in accordance with the analog respective output parameters, whereby variations in the characteristics of said analog sensors are corrected by said central monitor device,

2.Apparatus according to claim 1, wherein the analog output parameter is stored in the form of a digital value.

3. An environmental abnormality alarm apparatus comprising: a plurality of analog sensors for detecting environmental abnormalities such as a fire or gas leakage and for outputting dats representative of the detected abnormality; a central monitor device for receiving the data output from said sensors and processing it to generate an abnormality alarm if the detected abnormality exceeds a preset limit, said central monitor device including setting means for setting inherent analog output parameters of said sensors and operating/evaluating means for operating/evaluating analog outputs from said sensors in accordance with the respective analog output parameters, whereby variations in the characteristics of said analog sensors are corrected by said central monitor device, and said analog sensors are provided with parameter memories for storing the inherent analog output parameters.

4. Apparatus according to claim 3, wherein said parameter memory includes a voltage divider comprising a variable resistor and a resistor, and the analog output parameter is set in the form of an analog value.

5. Apparatus according to claim 4, wherein the inherent analog output parameter is indicated on a label attached to said analog sensor.

6. Apparatus according to claim 3, wherein said parameter memory includes a voltage divider consisting of at least one variable resistor and at least one resistor and an A/D converter for converting an output therefrom into a digital signal, and the analog output parameter is set in the form of a digital value.

7. Apparatus according to claim 6, wherein the inherent analog output parameter is indicated on a label attached to said analog sensor.

8. Apparatus according to any of the preceeding claims wherein said analog sensor outputs data in the form of continuous values.

9. Apparatus according to any of the preceeding claims wherein said analog sensor outputs data in the form of quantitized values.

10. An environmental abnormality alarm apparatus substantially as hereinbefore described with reference to and as illustrated in, any of Figures 1 to 3, 5 and 6 of the accompanying drawings.

11. Any and all combinations and subcombinations of novel features disclosed herein.