JPH08128851A - Sensor output signal-processing circuit - Google Patents

Abstract

PURPOSE: To correct a background value (detection level) after installation by providing a storage part for retaining a non-signal reference value corresponding to the background value outputted by an input part amplifier. CONSTITUTION: When a signal is fed to a periodical inspection instruction terminal CAL of a digital controller 17 on periodical inspection, the controller 17 samples the output signal from an input part amplifier 10 for a specific number of times. Then, after averaging processing, a signal level value (corresponding to a background value) is written in a non-signal reference value (EEPROM) storage 14 as a non-signal reference value on inspection. At the time of shipment, the signal level value is written in a non-signal reference value storage 13 on manufacture. The controller 17 monitors an input signal from a sensor 8 at normal operation and compares an input value with the non-signal reference value on inspection. When the difference between the output value of an A/D converter 12 and the non-signal reference value on inspection is equal to or more than a specific value at least for a specific number of times, it is judged that a target to be detected exists and a detection signal is outputted to an output part 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor output signal processing circuit for processing a sensor output signal.

[0002]

2. Description of the Related Art An example of a conventional sensor system will be described with reference to FIG. FIG. 5 is a configuration diagram showing a configuration around a smoke sensor of a smoke sensor system that optically detects smoke caused by a fire. In the figure, 1 is a smoke sensor, 2 is an LED arranged inside the smoke sensor 1, 3 is a light receiving element arranged inside the smoke sensor 1, and 4 is a sensor output signal processing circuit. The light emitted from the LED 2 is configured so as not to directly enter the light receiving element 3.

In the smoke sensor system configured as shown in FIG. 5, when smoke 5 enters the smoke sensor 1, LE
The light emitted from D2 and diffusely reflected by the smoke 5 enters the light receiving element 3. The light receiving element 3 inputs an electric signal corresponding to the incident light to the input section amplifier 6 provided in the first stage of the sensor output signal processing circuit 4. After that, processing such as noise removal is performed, and the signal is output from the sensor output signal processing circuit 4.

The voltage level output from the input amplifier 6,
The relationship between the threshold voltage level serving as a reference for detecting the detection target and the voltage level output by the input amplifier 6 when the detection target does not exist will be described with reference to FIG. In the figure, A
Is a voltage signal output from the input amplifier 6 when there is no diffused reflection of the emitted light of the LED 2 inside the smoke sensor 1 and no incident light to the light receiving element 3, and B is a threshold voltage. When a fire occurs and smoke 5 having a predetermined concentration or higher enters the smoke sensor 1, the level of the voltage signal A exceeds the level of the threshold voltage B. This causes the smoke sensor system to output a signal indicating that a fire has occurred to the external circuit. The level of the voltage signal A and the level of the threshold voltage B are adjusted at the time of shipment by adjusting the variable resistance and the like provided in the sensor output signal processing circuit 4 together with the level adjustment of the maximum output voltage value of the input amplifier 6. It was set.

[0005]

In the smoke sensor system described above, due to the structure of the smoke sensor 1, the smoke 5 to be detected is caused to adhere to the inside of the smoke sensor 1 due to the attachment of dust 7 and the like to the inside of the smoke sensor 1. Even if it does not exist, the level of the voltage signal output from the smoke sensor 1 to the sensor output signal processing circuit 4 may change. That is, even if the smoke 5 does not exist inside the smoke sensor 1, the light emitted from the LED 2 is diffusely reflected by the dust 7 and is incident on the light receiving element 3, so that the voltage signal when there is no incident light on the light receiving element 3. A voltage signal having a higher level than the level A (for example, the voltage signal C shown in FIG. 2) may be output from the input amplifier 6. This causes a problem that the smoke detection level of the smoke sensor system substantially changes after the smoke sensor 1 is installed.

The present invention has been made in view of the above circumstances.
It is an object of the invention to provide a structure of a sensor output signal processing circuit capable of correcting the background value after installation.

[0007]

In order to achieve the above object, the sensor output signal processing circuit according to claim 1 is a sensor output signal processing circuit for processing an output signal of the sensor, and a voltage output by the sensor. An input amplifier for amplifying a signal is provided, and a manufacturing no-signal reference value corresponding to a manufacturing background value output by the input amplifier in response to an output of the sensor when there is no detection target is held. A non-signal reference value storage part for manufacturing and a no-signal reference value storage part for inspection that holds a no-signal reference value for inspection corresponding to the background value at the time of inspection, and the no-signal reference value for inspection Is updated to correct the detection level of the sensor and, at the same time, the manufacturing no-signal reference value is compared with the inspection no-signal reference value, and the difference between these values is equal to or more than a predetermined value. If it becomes, it is characterized in that for outputting a signal indicating that effect.

A sensor output signal processing circuit according to a second aspect of the present invention is a sensor output signal processing circuit for processing an output signal of a sensor, comprising a reference power source and an input amplifier for amplifying a voltage signal output by the sensor. When the power supply is turned on or at the time of inspection, the reference voltage output by the reference power supply is read, and the no-signal reference value corresponding to the background value output by the input amplifier when there is no detection target is the reference voltage. The output voltage of the input amplifier is adjusted so as to be equal to, and the detection level of the sensor is corrected.

A sensor output signal processing circuit according to claim 3 is a sensor output signal processing circuit for processing an output signal of a sensor, wherein an input amplifier for amplifying a voltage signal output by the sensor, and the input amplifier. And a digital controller for inputting the output signal from the digital signal as a digital signal, and the minimum output voltage value set in advance corresponding to the voltage signal output by the sensor when the detection target does not exist from the sensor output signal processing circuit. So that the input output amplifier is saturated, and a maximum output voltage value preset corresponding to the saturated output voltage signal of the input amplifier is output from the sensor output signal processing circuit. It is characterized in that the detection level of the sensor is corrected by associating with the digital controller.

[0010]

The sensor output signal processing circuit according to claim 1
There is a manufacturing no-signal reference value storage unit that holds the manufacturing no-signal reference value corresponding to the background value output by the sensor during manufacturing, and an inspection no-signal reference value corresponding to the background value output by the sensor during inspection. An inspection-time no-signal reference value storage section is provided, and a manufacturing no-signal reference value is stored in advance in the manufacturing no-signal reference value storage section. With this configuration, the detection level of the sensor system can be corrected by updating the no-signal reference value during inspection during inspection. Further, since the no-signal reference value during manufacturing and the no-signal reference value during inspection are held, a change in the no-signal reference value during inspection can be detected by comparing them.

A sensor output signal processing circuit according to a second aspect of the present invention comprises a reference power source and an input amplifier for amplifying a voltage signal output by the sensor, and outputs the reference voltage output by the reference power source at the time of power-on or inspection. The offset voltage is added by the input amplifier so that the reference voltage and the no-signal reference value corresponding to the voltage output from the input amplifier when there is no detection target are read, and the input amplifier is read. Is configured to adjust the output voltage of the.
With this configuration, it is possible to correct the output voltage of the input amplifier when there is no signal. In this case, it is not necessary to store the background value at the time of shipping.

According to a third aspect of the present invention, there is provided a sensor output signal processing circuit, which is provided with an input amplifier for amplifying a voltage signal output from the sensor, and a digital controller for inputting an output signal from the input amplifier as a digital signal. Depending on the voltage signal output by the sensor when there is no detection target, the sensor output signal processing circuit outputs the preset minimum output voltage value, and the input amplifier is saturated to saturate the input voltage. The digital controller performs the correspondence so that the maximum output voltage value preset corresponding to the voltage signal output from the local amplifier is output from the sensor output signal processing circuit. With this configuration, the minimum output value of the sensor output signal processing circuit can be kept constant even if the sensor output changes with time. Moreover, since the preset maximum output voltage value of the sensor output signal processing circuit is associated with the voltage signal output from the saturated input amplifier, it is not necessary to adjust the maximum output voltage value of the sensor output signal processing circuit.

For example, a digital controller for inputting the analog output voltage of the input amplifier as a digital value and a D / A converter for inputting a digital value of a predetermined digit output from the digital controller and outputting an analog voltage are provided. The output voltage of the input amplifier when there is no signal, the maximum output voltage of the input amplifier (the output voltage of the saturated input amplifier) is the digital value of the predetermined digit output from the digital controller. It is configured to correspond to the minimum and maximum values.
As a result, the minimum analog output value of the D / A converter,
The maximum values correspond to the output voltage of the input amplifier and the maximum output voltage of the input amplifier (the output voltage of the saturated input amplifier) when there is no signal, respectively. That is, even when the voltage signal of the sensor when there is no signal changes with time, the output of the input amplifier when there is no signal is associated with the minimum value of the digital value of a predetermined digit output by the digital controller.

When it is necessary to guarantee the maximum value of the output voltage of the D / A converter (the output voltage of the D / A converter is
In the case where it is limited by the upper limit of the input voltage of the circuit subsequent to the D / A converter), it can be dealt with by setting the power supply voltage of the D / A converter to its maximum value.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the sensor output signal processing circuit of the present invention will be described with reference to FIG. In the figure, 8 is a sensor, and 9 is a sensor output signal processing circuit for processing the output signal of the sensor 8. The sensor output signal processing circuit 9 is
An input amplifier 10 for amplifying the sensor output, a filter 11 for removing noise of an output signal of the input amplifier 10,
An A / D converter 12 that incorporates a sample-and-hold circuit and converts the output of the filter 11 into a digital value, and holds a no-signal reference value during manufacturing corresponding to the output (background value) of the input amplifier 10 during manufacturing. Manufacturing EEPROM storage unit 13 (manufacturing no-signal reference value storage unit) and inspection EEPROM storage unit 14 that holds an inspection no-signal reference value corresponding to the background value at the time of inspection (no-signal reference value storage at inspection) Section), an output section 16, a digital value output from the A / D converter 12, a value exchange with the storage section 15, a value comparison by a built-in comparator, and an output section 16. It is composed of a digital controller 17 for outputting a digital value and a power-on reset circuit 18.

When a signal is input to the regular inspection instruction terminal CAL provided in the digital controller 17 at the time of shipment or at the time of regular inspection, the digital controller 17 outputs the output signal from the input section amplifier 10 one or more times. After sampling a predetermined number of times and averaging, the signal level value is written in the EEPROM memory 14 for inspection as a no-signal reference value for inspection. At the time of manufacturing and shipping, the signal level value is also written in the manufacturing EEPROM memory 13 as a manufacturing no-signal reference value. The inspection non-signal reference value written in the inspection EEPROM memory 14 is updated at the time of periodic inspection or when the power-on reset circuit 18 operates.

Further, the digital controller 17 monitors the input signal from the sensor 8 during the normal operation and compares the input value with the no-signal reference value during inspection. The output value of the A / D converter 12 corresponding to the output of the sensor 8,
If a difference from the no-signal reference value during inspection is taken and it is confirmed that the difference is a predetermined value or more a predetermined number of times or more, it is determined that a detection target exists, and a detection signal is output from the output terminal to the output terminal 16. Order to do.

Further, when the in-manufacturing no-signal reference value written in the in-manufacturing EEPROM memory 13 has changed by more than a predetermined value from the in-manufacturing no-signal reference value, an alarm signal is output from an alarm terminal provided in the output section 16. A warning can be issued by outputting it.

The EEPROM memory device for inspection 14 may be composed of an EEPROM or a volatile memory such as SRAM. However,
In the case of the volatile memory, when the power down occurs and the power-on reset circuit 18 operates, it is necessary to perform the circuit operation at the time of regular inspection before performing the normal operation.

In the case of the present embodiment, the no-signal reference value during inspection corresponding to the output (background value) of the input section amplifier 10 when there is no signal is updated at the time of periodic inspection or the operation of the power-on reset circuit 18. Therefore, it is possible to correct the detection level in consideration of the change with time of the sensor 8 and peripheral circuits. Further, by outputting an alarm signal from the alarm terminal, it is possible to detect a remarkable deterioration of the sensor system and to give an instruction of the replacement time.

A different embodiment of the sensor output signal processing circuit of the present invention will be described with reference to FIG. The same components as those shown in FIG. 1 are designated by the same reference numerals.
In the figure, 8 is a sensor, and 9 is a sensor output signal processing circuit for processing the output signal of the sensor 8. The sensor output signal processing circuit 9 includes an input amplifier 10 that amplifies the output of the sensor 8, a filter 11 that removes noise in the output signal of the input amplifier 10, an output of the filter 11 that includes a sample and hold circuit, or as described below. The A / D converter 12 for converting the reference voltage output from the reference power source into a digital value, the output unit 16, the input of the digital value output by the A / D converter 12, the value exchange with the storage unit described later, and the built-in A digital controller 17 for performing a value comparison in a comparator, a digital value output to the output unit 16, etc., a power-on reset circuit 18,
A selector 20 for switching the input to the reference power source 19 and the A / D converter 12 to the output of the filter 11 or the output of the reference power source 19, and an EEPROM that holds a no-signal reference value corresponding to the background value at the time of inspection. , SRAM, a flip-flop, and the like, and a storage unit 21.

The sensor output signal processing circuit 9 shown in FIG.
At the time of regular inspection or power down, the digital controller 17 receives the CAL terminal signal applied to the regular inspection instruction terminal CAL or the signal generated by the power-on reset circuit 18 and receives no input signal. Output signal is read a predetermined number of times and averaged, and is once written in the storage unit 21 as a no-signal reference value. Next, the selector 20 is controlled to refer to the reference voltage output from the reference power source 19, this value is compared with the no-signal reference value stored in the storage unit 21, and the OFFSET circuit 22 is controlled to Adjustment is performed so that the OFFSET circuit 22 outputs a voltage that is a difference between the signal reference value and the reference voltage value. At this time, the control value of the output voltage of the OFFSET circuit 22 is controlled by the digital value stored in the storage unit 21. Therefore, the storage unit 21 stores the difference between the no-signal reference value corresponding to the output output from the input unit amplifier 10 when there is no signal and the difference for controlling the offset circuit 22 to output a constant no-signal reference value. Two types of values are stored.

After the background value correction operation described above is completed, the normal sensing mode is entered, and the digital controller 1
7 monitors the output value of the sensor 8 at regular intervals,
At this time, when the difference from the no-signal reference value is a certain value or more, or when the difference occurs more than a predetermined number of times in succession, a signal indicating that the detection target is detected is sent to the output unit and the detection signal is output. Further, similarly to the configuration shown in FIG. 1, a value for controlling the OFFSET circuit 22 at the time of manufacturing is stored in the storage unit 21 and compared with the updated value for the OFFSET control, and a difference of a predetermined value or more occurs. If it does, an alarm signal can be output.

In the case of the present embodiment, the output (background value) of the input amplification circuit is kept constant when there is no signal, so that the noise margin level of the detection level of the sensor is kept at a constant value. It is possible to improve detection reliability and prolong product life.

A different embodiment of the sensor output signal processing circuit of the present invention will be described with reference to FIG. In the figure, 23 is a sensor, and 24 is a sensor output signal processing circuit that processes the output signal of the sensor 23. The sensor output signal processing circuit 24 incorporates an input amplifier 25 that amplifies the output of the sensor 23, a filter 26 that removes noise in the output signal of the input amplifier 25, and a sample-and-hold circuit, and outputs the output of the filter 26 to a digital value. An A / D converter 27 for conversion, a digital controller 28 for inputting a digital value output from the A / D converter 27, exchanging a value with a storage unit described later, outputting a digital value to an output unit, and a reference power supply 29 , A selector 30 that switches the input to the input amplifier 25 to the output of the sensor 23 or the output of the reference power supply 29, the storage unit 31, the digital value output from the digital controller 28 is input, and the analog voltage is output D The A / A converter 32 and the output unit 33 that buffers the output of the D / A converter 32.

Before entering the normal sensing mode, the output voltage range of the input amplifier 25 is automatically adjusted.
The minimum value of the output of the input section amplifier 25 is set to the output (background value) of the input section amplifier 25 when there is no signal, which is stored in the storage section 31 in advance, and this value is the output of the digital controller 28. Associated with the minimum digital value.

Next, a method for setting the maximum value of the output of the input amplifier 25 will be described. First, the digital controller 28
By controlling the selector 30, the input of the input amplifier 25 is switched to the output of the saturation reference voltage of the reference voltage 29. The saturation reference voltage is set to a voltage at which the input amplifier 25 saturates. A saturation reference voltage is supplied from the reference power supply 29 to saturate the input amplifier 25, and the output voltage of the input amplifier 25 at that time is read by the digital controller 28 as the maximum value of the output of the input amplifier 25 and stored. Part 3
Save it in 1. The maximum output value of the input amplifier 25 is associated with the maximum digital value output by the digital controller 28.

Further, regarding the input value between the maximum value and the minimum value of the input section amplifier 25 set as described above, the digital controller 28 causes, for example, a linear relationship as shown in FIG. Correspond with the functional expression of. FIG.
FIG. 4 is a diagram showing the relationship between the input of the input section amplifier 25 and the output of the D / A converter 32 (output of the output section 33). In the figure, the horizontal axis represents the input of the input amplifier 25,
The vertical axis represents the output of the D / A converter 32 (output of the output unit 33)
Is represented. However, the functional expression is not limited to the embodiment. In this way, when the analog output value is required, the range of the output voltage (output of the output unit 33) is automatically set. Can be reduced.

When it is necessary to guarantee the maximum value of the output voltage of the D / A converter 28 (the output voltage of the D / A converter 28 is less than the input voltage of the circuit subsequent to the D / A converter 28). D / A converter 2 if limited by the upper limit)
This can be dealt with by setting the power supply voltage of No. 8 to its maximum value.

[0030]

According to the sensor output signal processing circuit of the first aspect, the detection level of the sensor system can be corrected by updating the no-signal reference value during inspection during inspection. Further, since the no-signal reference value during manufacturing and the no-signal reference value during inspection are held, a change in the no-signal reference value during inspection can be detected by comparing them.

Since the sensor output signal processing circuit according to the second aspect can correct the output voltage of the input amplifier when there is no signal, the noise margin can be kept constant and the detection reliability can be improved. . In this case, it is not necessary to store the background value at the time of shipping.

In the sensor output signal processing circuit according to the third aspect, the minimum output value of the sensor output signal processing circuit can be kept constant even if the background value changes with time. Moreover, since the preset maximum output voltage value of the sensor output signal processing circuit is associated with the voltage signal output from the saturated input amplifier, it is not necessary to adjust the maximum output voltage value of the sensor output signal processing circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a sensor output signal processing circuit of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the sensor output signal processing circuit of the present invention.

FIG. 3 is a circuit diagram showing still another embodiment of the sensor output signal processing circuit of the present invention.

FIG. 4 is a diagram showing the relationship between the output of the input section amplifier and the output of the output section of the sensor output signal processing circuit of the present invention.

FIG. 5 is a configuration diagram showing an example of a configuration of a sensor system.

FIG. 6 is a diagram showing a relationship between a voltage level output from an input amplifier and a threshold voltage level serving as a reference for detecting a detection target.

[Explanation of symbols]

8,23 Sensor 9,24 Sensor output signal processing circuit 10,25 Input amplifier 13 Manufacturing EEPROM memory (manufacturing no-signal reference value memory) 14 Inspection EEPROM memory (no-signal reference value memory) 19 Reference power supply 28 Digital controller

Claims (3)

[Claims] 1. A sensor output signal processing circuit for processing an output signal of a sensor, comprising an input amplifier for amplifying a voltage signal output by the sensor, and receiving an output of the sensor when there is no detection target. And a no-manufacturing signal reference value storage unit that holds a no-manufacturing signal reference value corresponding to the manufacturing background value output by the input amplifier, and a no-in-test value corresponding to the background value at the time of inspection. An inspection-time no-signal reference value storage unit that holds a signal reference value, and updates the inspection-time no-signal reference value at the time of inspection to correct the detection level of the sensor. The sensor output signal processing is characterized in that a value is compared with the reference value for no signal during inspection, and when the difference between these values exceeds a predetermined value, a signal to that effect is output. Logic circuit. 2. A sensor output signal processing circuit for processing an output signal of a sensor, comprising a reference power supply and an input amplifier for amplifying a voltage signal output by the sensor,
At power-on or inspection, the reference voltage output by the reference power source is read, and the no-signal reference value corresponding to the background value output by the input amplifier when there is no detection target is equal to the reference voltage. The output voltage of the input amplifier is adjusted so that the detection level of the sensor is corrected. 3. A sensor output signal processing circuit for processing an output signal of a sensor, wherein an input amplifier for amplifying a voltage signal output by the sensor, and an output signal from the input amplifier are inputted as digital signals. A digital controller, wherein the sensor output signal processing circuit outputs a preset minimum output voltage value corresponding to the voltage signal output by the sensor when there is no detection target, and the input Saturating the partial amplifier, the maximum output voltage value preset corresponding to the voltage signal output from the saturated input amplifier is associated with the digital controller so as to be output from the sensor output signal processing circuit, A sensor output signal processing circuit, which corrects a detection level of the sensor.