JP3969468B2 - Portable gas detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable gas detection device having a concentration display based on a signal from a gas sensor and a function for triggering an alarm.
[0002]
[Prior art]
The portable gas detection device takes the atmospheric air from the suction nozzle into the chamber using the battery as a power source, converts the concentration of the target gas into an electrical signal by a gas sensor such as a hot-wire semiconductor gas sensor, and displays it on the display. When the alarm level is exceeded, it is configured to sound a notification means such as a buzzer. Depending on the application, it is required to reliably measure and notify a gas in a very wide concentration range from several tens of ppm to a percentage order. ing.
[0003]
[Problems to be solved by the invention]
For this reason, when the purpose is to detect high-concentration gas, an extremely low-concentration gas that does not cause a problem is detected, and if the alarm level is accidentally set to a low value, an alarm is issued. There are problems such as cutting attention.
In order to solve such a problem, it is conceivable to shift the alarm level to a higher concentration side, but there is a problem that an alarm error occurs due to forgetting to reset the alarm level.
The present invention has been made in view of such a problem, and its purpose is to detect a portable gas that can prevent the activation of an unnecessary alarm without requiring adjustment of the alarm level. Is to provide a device.
[0004]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, a gas detection means for outputting a detection signal corresponding to the gas concentration of the fluid taken in by the suction means as a voltage signal, and a voltage signal matching the selected level are provided. A dead zone level generating means for outputting, a difference detecting means for outputting a difference between the detection signal and the voltage signal, an analog-digital converting means for converting a signal from the difference detecting means into a digital signal, and the digital signal Means for displaying and alarm means for issuing an alarm when the detection signal exceeds a set level are provided.
[0005]
[Action]
Since the detection signal below the dead zone level is canceled, the alarm means is not activated even if the alarm level is exceeded.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows an embodiment of the present invention. A case 1 is configured by providing a panel 2 at a position that is easy to see when the case 1 is gripped, and a gas inlet 3 at the upper end. The panel 2 is provided with a display 4 for displaying the gas concentration on one side, and a power switch 5, a dead zone selection switch 6 that also serves as a buzzer ringing stop command switch, and a zero adjustment command switch 7 on the other side.
The display 4 has eight light emitting elements L1 to L8 arranged in a vertical direction so as to correspond to a plurality of levels, eight levels of density display in this embodiment, and light emitting elements L1 ′ to display the selected alarm density. L8 'and the selected dead band level In this embodiment, light emitting elements L9 and L10 for displaying 30 ppm and 150 ppm are provided.
[0007]
FIG. 2 is a block diagram showing an embodiment of the present invention. A chamber 10 is connected to a suction port 3 and a suction pump 11 and contains a hot-wire semiconductor gas sensor 12 therein. The suction pump 11 and the hot-wire semiconductor gas sensor 12 are supplied with electric power from a booster 15 connected to a battery 14 via a switch 13.
[0008]
The detection terminal 12 a of the hot wire type semiconductor gas sensor 12 is connected to the inverting terminal of the operational amplifier 16. The operational amplifier 16 has a zero-point coarse adjustment variable resistor 17 connected to its non-inverting terminal and a span adjustment variable resistor 18 connected to the return path so as to have a zero-point coarse adjustment function and a span adjustment function. It is configured.
[0009]
The dead level adjusting circuit 19 is configured to output a voltage at which the output of the differential amplifier 20 becomes zero in response to a command from the microcomputer 30 described later.
[0010]
The microcomputer 30 processes the gas detection signal output from the analog-digital conversion means 31 based on the control program and setting data of the storage means 31, and sets the dead zone level to a predetermined default value when the power is turned on. Is set to 150 ppm, and the display panel 4 connected via the interface 32 and the buzzer 33 as alarm means are operated based on the detection signal from the gas sensor 12.
[0011]
In the figure, reference numeral 34 denotes a stable power supply circuit for supplying operating power to the microcomputer 30, and 35 and 36 denote switch lamps.
[0012]
In this embodiment, when the power switch 5 is pressed, the microcomputer 3 wakes up, turns on the switch 13, operates the pump 11 by the booster circuit 15 to scavenge the chamber, and sets the hot wire semiconductor gas sensor 12 to the remaining heat. To do.
[0013]
At the same time, the light emitting elements L1 to L8 of the display panel 4 are operated in a different state, for example, moving blinking, to inform the user that warming up is in progress.
[0014]
When the predetermined time has elapsed and the movement and blinking of the light emitting elements L1 to L8 is completed and the measurement is possible, the microcomputer 30 performs zero point adjustment with the air taken into the chamber 10 as zero concentration, In addition, a voltage signal necessary for setting a predetermined dead band level of 150 ppm is output from the dead level generation circuit 19, and the corresponding light emitting element L4 or L4 'is lit in a different form at all times, and the dead band in the future measurement is measured. Let the user confirm the level.
[0015]
At this stage, each time the user presses the dead zone selection switch 6, the dead zone level increases one step at a time, and when it reaches the maximum value, it changes cyclically to become the lowest dead zone level. The light emitting elements L1 to L8 or L1 ′ to L8 ′ having the corresponding concentrations are turned on so as to be different from usual.
[0016]
The microcomputer 30 outputs a voltage signal necessary for setting the selected dead band level by outputting a signal to the dead level generation circuit 19 in order to generate the dead band level selected by the user.
[0017]
When such preparation is completed, when the tip of a nozzle (not shown) connected to the gas inlet 3 is brought close to the measurement area, the atmosphere here is sucked into the pump 11 and flows into the chamber 10.
[0018]
The signal from the gas sensor 12 is subjected to span adjustment and zero point adjustment by the operational amplifier 16 and is input to the differential amplifier 20, and the difference from the voltage signal from the dead level generation circuit 19 is taken to obtain analog-digital conversion means. 31.
[0019]
As a result, the detection signal below the dead zone level is not subjected to analog-digital conversion. Therefore, even when the detection signal from the gas sensor 12 exceeds the alarm level, the buzzer does not sound and is useless. Alarm notification can be prevented.
[0020]
On the other hand, when a gas having a concentration exceeding the dead zone level and exceeding the alarm level is detected, the microcomputer 30 sounds a buzzer 33 to issue an alarm to the user. When the user presses the dead zone selection switch 6 after confirmation, the microcomputer 30 stops the ringing of the buzzer 33 instead of performing the function of changing the dead zone level because the buzzer 33 is ringing.
[0021]
By the way, depending on the environment to be inspected, there is a case where the noise is so loud that the alarm cannot be recognized by the buzzer.
FIG. 3 shows a second embodiment of the present invention that can cope with such a problem. This embodiment is a dead zone selection switch that also serves as a buzzer ringing stop command switch in the above-described embodiment. 6 is further provided with an alarm form selection function.
[0022]
In addition to the buzzer 33 described above as a warning means, a vibration body 37, in this embodiment a vibration motor having an eccentric weight attached to the rotating shaft of the micromotor, is provided. When one of them is actuated and an alarm is issued, the dead zone selection switch 6 is pressed, so that the other alarm means, that is, the buzzer 33 is activated, the vibrator 37 and the vibrator The buzzer 33 is configured to operate in a state in which 37 is operating.
[0023]
In this embodiment, when a gas having a concentration exceeding the alarm level is detected (FIG. 4 Step A), the microcomputer 30 sounds the first alarm means, for example, the buzzer 33, and issues an alarm to the user (FIG. 4). Step b). However, when the environmental noise is high and it is difficult to hear the sound from the buzzer 33, when the dead zone selection switch 6 is pressed (step C in FIG. 4), the buzzer 33 stops ringing and the vibrator 37 operates ( Fig. 4 Step D). The microcomputer 30 notifies the user of the current gas concentration by rotating the vibrator 37 at a rotational speed corresponding to the detected gas concentration.
[0024]
Accordingly, it is possible to accurately know that the gas concentration has exceeded the alarm level even in a noisy environment, and it is possible to prevent the battery from being consumed due to unnecessary buzzing of the buzzer 33. After the user confirms, the dead zone selection switch 6 is pressed (step E in the figure), or when the gas concentration falls below the alarm level (step F in FIG. 4), the microcomputer 30 stops the operation of the vibrator 37 (see FIG. 4). Figure 4 Step).
[0025]
When the alarm is stopped while the alarm is sufficiently known by the buzzer 33, if the dead zone selection switch 6 is pressed twice in succession, so-called double-clicking, the vibrator 37 has inertia. The alarm operation can be stopped without operating the vibrator 37.
[0026]
In this embodiment, the buzzer 33 is operated first during the alarm operation, but the vibrator 37 is operated first, and the buzzer is operated when the dead zone selection switch 6 is operated. May be.
[0027]
Further, in the above-described embodiment, an example is described in which a hot-wire semiconductor is used as the gas detection means, but the present invention is applied to an apparatus using another type of gas detection means such as an electrochemical gas sensor. It is clear that there is a similar effect.
[0028]
【The invention's effect】
As described above, in the present invention, the gas detection means for outputting the detection signal corresponding to the gas concentration of the fluid taken in by the suction means as the voltage signal, and the dead zone for outputting the voltage signal corresponding to the selected level. Level generation means, difference detection means for outputting the difference between the detection signal and the voltage signal, analog-digital conversion means for converting the signal from the difference detection means into a digital signal, means for displaying the digital signal, and detection signal Alarm means that issues an alarm when the level exceeds the set level, so that the detection signal below the dead band level can be offset, and the need to adjust the alarm level can be prevented, preventing unnecessary alarms from being triggered. it can.
[Brief description of the drawings]
FIGS. 1A and 1B are a front view and a side view, respectively, showing an enlarged structure in the vicinity of a panel according to an embodiment of the portable gas detection device of the present invention.
FIG. 2 is a block diagram showing an embodiment of the apparatus.
FIG. 3 is a block diagram showing another embodiment of the present invention.
FIG. 4 is a flowchart showing an alarm operation of the apparatus.
[Explanation of symbols]
2 Panel 3 Gas inlet 4 Display panel 5 Power switch 6 Dead zone selection switch 7 Zero adjustment switch 10 Chamber 12 Hot wire semiconductor gas sensor 33 Buzzer

Claims (4)

Gas detection means for outputting a detection signal corresponding to the gas concentration of the fluid taken in by the suction means as a voltage signal, dead zone level generation means for outputting a voltage signal matching the selected level, the detection signal and the voltage Difference detection means for outputting a difference from the signal, analog-digital conversion means for converting the signal from the difference detection means into a digital signal, means for displaying the digital signal, and the detection signal exceeds a set level A portable gas detection device comprising alarm means for issuing an alarm.   2. The portable gas detection device according to claim 1, wherein the dead zone level setting means and the alarm stop means are constituted by the same switch. Gas detection means for outputting a detection signal corresponding to the gas concentration of the fluid taken in by the suction means as a voltage signal, dead zone level generation means for outputting a voltage signal matching the selected level, the detection signal and the voltage Difference detection means for outputting a difference from the signal, analog-digital conversion means for converting the signal from the difference detection means into a digital signal, means for displaying the digital signal, and the detection signal exceeds a set level Alarm means for issuing an alarm, and the alarm means is composed of a sounding means and a vibration generating means, the sounding means is activated at the time of alarm, and the dead zone level setting means is activated during the operation of the sounding means. When operated, the sounding means stops operating, the vibration generating means operates, and then the dead zone level setting means is operated. Portable gas detection apparatus broadcast operation is stopped.   The portable gas detection device according to claim 3, wherein the alarm operation is stopped when the dead zone level setting means is operated twice in succession during the operation of the sound generation means.

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