CN2622700Y - Array signal regulating circuit of gas sensor - Google Patents

Abstract

A circuit for conditioning gas sensor signals in a gas sensor array. The conditioning circuit includes a sensor signal program-controlled amplifying circuit and a filter circuit. It is characterized in that the amplifying circuit adopts a program-controlled amplification composed of a combination of a program-controlled multi-channel switch and an operational amplifier. For different sensor signals, the program-controlled switch is uniformly controlled by the computer, and different channels are selected to adjust the multiple of signal amplification; through the input and output of the operational amplifier A capacitor is added at the terminal to prevent high-frequency interference, and a filter circuit is added at the output of the operational amplifier to filter the signal to improve the detection accuracy of the sensor.

Description

Gas Sensor Array Signal Conditioning Circuit

Technical field

The utility model relates to a gas sensor signal processing circuit, in particular to a gas sensor array signal conditioning circuit when an array composed of a plurality of gas sensors is used to detect odors.

Background technique

At present, most gas detection devices use a single gas sensor, such as alcohol odor detection gas. Since a single sensor can usually only detect a certain gas, the detection range of this detection device is limited. Compared with a single gas sensor, the gas sensor array device has a wider detection range, and its sensitivity, reliability and repeatability are greatly improved. Therefore, the detection of gas using a gas sensor array is increasingly valued. However, since different objects have different odor concentrations volatilized, and different gas sensors produce different signals to different odors, and the signals are generally very weak, they should be adjusted before the A/D conversion is input to the computer for processing ( amplification and filtering, etc.). The existing gas sensor signal processing circuit cannot realize the function of conditioning simultaneously according to the different magnitudes of signals generated by different sensors in the sensor array.

Contents of the invention

In order to overcome the deficiencies of the prior art, the purpose of this utility model is to provide a gas sensor array signal conditioning circuit for conditioning according to the signals of different sensors in the gas sensor array.

The technical scheme of the utility model is:

The conditioning circuit is characterized in that it adopts a sensor signal program-controlled amplifying circuit composed of a program-controlled multi-way switch and an operational amplifier. For different sensor signals, the computer can control the program-controlled switch to select different paths according to the size of the signal to adjust the signal amplification factor.

Capacitors are added to the input and output terminals of the operational amplifier to prevent high-frequency interference, and a filter circuit is added to the output terminal of the operational amplifier to filter the signal to improve the detection accuracy of the sensor.

The utility model has the advantage that it can perform program-controlled amplification on the signals detected by different gas sensors in the sensor array, select a suitable amplification factor and filter form, and achieve the purpose of improving the detection accuracy of the gas sensor. Because when the gas sensor detects a relatively strong odor or the sensor is sensitive to the detected signal, the output signal is relatively large, and a channel with a relatively small magnification can be selected through the program-controlled switch, so that the sensor signal does not overflow during A/D conversion. The phenomenon. When the signal detected by the sensor is relatively weak, a channel with a relatively large amplification factor can be selected through the program-controlled switch, so that the signal cannot be detected due to the weak signal. Signal fluctuations can be reduced by using a filter circuit.

Description of drawings

Figure 1 Schematic diagram of gas sensor array detecting odor

Fig. 2 is an embodiment of the conditioning circuit (one circuit) of the gas sensor of the present invention.

Detailed ways

As shown in Figure 1, the signal generated by the sensor and the odor molecule must first be conditioned by the conditioning circuit, that is, amplification, filtering, etc., before it can be A/D converted and input to the computer. The computer adjusts the magnification of each sensor signal according to the size of the signal.

As shown in FIG. 2 , the gas sensor circuit is in the dotted line box, Sn is the nth gas sensor, and the output signal of the sensor is V _in . U ₁ is the OP-07 operational amplifier; U ₂ is the IC4051 program-controlled multi-way switch, and the pins 9, 10, 11 are respectively connected to the channel selection information sent by the computer. According to the difference of DO3, DO2, and DO1, the channels connected by IC4051 are different. . Table 1 shows the relationship between each channel and the signals on pins 9, 10, and 11.

Table 1 IC4051 Programmable Multiplexer A 0 0 0 0 1 1 1 1 B 0 0 1 1 0 0 1 1 C 0 1 0 1 0 1 0 1 gated pin X0 X1 X2 X3 X4 X5 X6 X7

For example, when x0 is selected, the resistor R15 (100 ohm) is connected to the channel, then the magnification of the whole circuit is:

${\mathrm{\β}}_1=\frac{100+10000}{10000}=1.01\≈1$ (Formula 1)

At this time, it can be understood that the voltage signal measured by the original gas sensor 1 is amplified to double the original meter and then output to the data acquisition card (ie output as it is). In the same way, the resistance value of each path can be properly selected, so that the gas sensor signal is amplified by a certain factor and then output. Of course, if the output is to the A/D data acquisition card, because the input signal voltage range of the general data acquisition card can be 0 to 10V or -5 to +5V, so when considering the magnification of the entire gas sensor conditioning circuit, it should be noted that its Within a certain range, see Table 2 for the relationship between the resistance of each path adopted by the utility model and the magnification of the entire gas sensor conditioning circuit. In this way, the highest output voltage of the entire conditioning circuit does not exceed 10V.

In order to prevent high-frequency interference from the signal terminal, capacitor C7 can be added to the input and output terminals of the operational amplifier (U ₁ ), and a filter circuit composed of resistor R20 and capacitor C8 can be added to the output terminal of the operational amplifier.

The conditioning circuit shown in Figure 2 is used for each gas sensor circuit, and the channel selection is uniformly controlled by the computer, which can realize the comparison of sensor data collected when different magnifications are used, adjust in time, and select the most appropriate magnification. V _out conditioned output signal.

Table 2 The relationship between the resistance of each path and the magnification of the gas sensor conditioning circuit

Claims (3)

1. The gas sensor array signal conditioning circuit is characterized in that it adopts a sensor signal program-controlled amplifying circuit formed by a combination of a program-controlled multi-way switch and an operational amplifier. 2. The gas sensor array signal conditioning circuit according to claim 1, characterized in that a capacitor is added between the input and output terminals of the operational amplifier to prevent high-frequency interference. 3. The gas sensor array signal conditioning circuit according to claim 1, characterized in that a filter circuit is added at the output end of the operational amplifier to filter the signal.

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