CN104038162B - The signal amplification circuit of transformer station's gas concentration detection system - Google Patents

Abstract

The invention discloses a signal amplifying circuit of a substation gas concentration detection system, comprising a primary amplifying circuit, a band-pass filter circuit, a secondary amplifying circuit and an amplified signal output circuit, the primary amplifying circuit comprises a first amplifier, and a third resistor of the band-pass filtering circuit The two ends are respectively connected to the output terminal of the first amplifier and the eighth capacitor, and the other end of the eighth capacitor connected to the third resistor terminal is connected to the non-inverting input terminal of the second amplifier, and one end of the fourth resistor is connected to the third resistor and the eighth capacitor. On the line between the capacitors, the other end of the fourth resistor is connected to the inverting input end of the second amplifier. The noninverting input terminal of the third amplifier of the secondary amplifying circuit is connected with the output terminal of the second amplifier, and the two ends of the second adjustable resistance are respectively connected with the inverting input terminal and the output terminal of the third amplifier, and the output terminal of the third amplifier is connected with the amplified signal output line connection. When the present invention is applied, through two stages of amplification and filtering, it can ensure that the detection signal can be displayed accurately in the follow-up.

Description

Signal Amplifying Circuit of Substation Gas Concentration Detection System

technical field

The invention relates to the field of substation safety protection, in particular to a signal amplifying circuit of a substation gas concentration detection system.

Background technique

The substation is in a closed state for a long time, and the air in it is in a non-flowing state, and a large amount of high molecular weight gas is easy to deposit in the substation. Therefore, it is particularly important to regularly detect the gas concentration in the substation. In order to detect the gas concentration in the substation, a gas concentration detection system for the substation has been designed, which includes a sensor, a DC regulated power supply, an analog-to-digital conversion circuit and a digital display circuit. When the detection system is applied, the DC regulated power supply supplies power for the entire system. , the sensor converts the detected gas concentration signal into a voltage signal, and after being converted by an analog-to-digital conversion circuit, the gas concentration value is displayed through a digital display circuit. Among them, when the system is applied, the signal detected by the sensor is weak, and the signal will be attenuated and absorbed during the transmission process. The digital display circuit cannot accurately reflect the gas concentration in the substation. In this way, it will mislead the operators and pose a safety hazard.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a signal amplifying circuit of a substation gas concentration detection system capable of amplifying the detection signal of a sensor so as to visually display the gas concentration in the substation.

The present invention solves the above problems mainly through the following technical solutions: the signal amplifying circuit of the substation gas concentration detection system includes a primary amplifying circuit, a band-pass filter circuit, a secondary amplifying circuit and an amplified signal output circuit, and the primary amplifying circuit includes a first amplifier, the bandpass filter circuit includes a second amplifier, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh capacitor, and an eighth capacitor, and the two ends of the third resistor are respectively connected to the output of the first amplifier The terminal is connected to the eighth capacitor, the other end of the eighth capacitor opposite to the third resistor terminal is connected to the non-inverting input terminal of the second amplifier, one end of the fourth resistor is connected to the line between the third resistor and the eighth capacitor, and the other end Connected to the inverting input terminal of the second amplifier, the seventh capacitor, the fifth resistor and the sixth resistor are all connected to the ground, and the other end of the seventh capacitor is connected to the line between the third resistor and the eighth capacitor opposite to the ground terminal On the ground, the other end of the fifth resistor is connected to the line between the eighth capacitor and the non-inverting input of the second amplifier, and the other end of the sixth resistor is connected to the inverting input of the fourth resistor and the second amplifier. on the line between the terminals; the secondary amplifying circuit includes a third amplifier, a second adjustable resistor, a seventh resistor and an eighth resistor, the non-inverting input of the third amplifier is connected to the output of the second amplifier, and the second Both ends of the adjustable resistor are respectively connected to the inverting input terminal and output terminal of the third amplifier, one end of the seventh resistor is connected to the line between the inverting input terminal of the third amplifier and the second adjustable resistor, and the other end is grounded, so Both ends of the eighth resistor are respectively connected to the output terminal of the third amplifier and the output line of the amplified signal. When the present invention is applied, the signal detected by the sensor is input by the non-inverting input terminal and the inverting input terminal of the first amplifier, after the primary amplification by the first amplifier, it is filtered by the band-pass filter circuit, and then amplified again by the secondary amplifier circuit Then it is output by the amplified signal output line.

Because the AD620 is a differential special-purpose instrument operational amplifier integrated with three precision operational amplifiers, it has the characteristics of low offset, high gain, and high common-to-analog ratio. Further, the first amplifier adopts the AD620 chip.

Further, the primary amplifying circuit further includes a first adjustable resistor, and the two ends of the first adjustable resistor are respectively connected to the first pin and the eighth pin of the first amplifier.

In order to prevent noise from the power supply end from being coupled into the first amplifier, further, the primary amplifying circuit further includes a first magnetic bead, a second magnetic bead, a third capacitor, a fourth capacitor, a fifth capacitor, and a sixth capacitor, the Both ends of the first magnetic bead are respectively connected to the positive pole of the power supply and the seventh pin of the first amplifier, and one end of the parallel branch formed by the parallel connection of the third capacitor and the fourth capacitor is connected to the line between the first magnetic bead and the first amplifier The other end of the bead is connected to the ground; the two ends of the second magnetic bead are respectively connected to the negative pole of the power supply and the fourth pin of the first amplifier. On the line between the bead and the first amplifier, the other end of it is grounded. In this way, in the present invention, each power supply pin of the first amplifier is connected with two capacitors to the ground, and a magnetic bead is connected in series to decouple the power supply.

Further, the signal amplification circuit of the substation gas concentration detection system further includes a ninth resistor, one end of which is connected to the amplified signal output line, and the other end of which is connected to an external power supply.

Because the OP777 chip is an ultra-precise low-noise operational amplifier with extremely low voltage and current offsets and high gain stability, further, the second amplifier and the third amplifier both use the OP777 chip.

Further, the primary amplifying circuit also includes a first capacitor, a second capacitor, a first resistor and a second resistor, one end of the first capacitor is connected to the inverting input end of the first amplifier, and one end of the second capacitor is connected to the first The non-inverting input terminal of the amplifier is connected, both the first resistor and the second resistor are grounded, and the other end of the first resistor opposite to its grounding terminal is connected on the line between the first capacitor and the inverting input terminal of the first amplifier, and the second The other end of the resistor opposite to its grounding end is connected to the line between the second capacitor and the non-inverting input end of the first amplifier. In this way, when the present invention is applied, AC coupling input is performed through the first capacitor and the second capacitor. The first capacitor and the first resistor form a high-pass filter, and the second capacitor and the second resistor form a high-pass filter. The present invention uses the first capacitor, The high-pass filter formed by the second capacitor, the first resistor and the second resistor is used to reduce low-frequency interference in the environment.

In summary, the present invention has the following beneficial effects: (1) The present invention includes a primary amplifier circuit, a band-pass filter circuit, a secondary amplifier circuit and an amplified signal output circuit, the primary amplifier circuit includes a first amplifier, and the band-pass filter circuit includes The second amplifier, the third resistor, the fourth resistor, the fifth resistor, the sixth resistor, the seventh capacitor and the eighth capacitor, the secondary amplifier circuit includes the third amplifier, the second adjustable resistor, the seventh resistor and the eighth resistor , the non-inverting input terminal of the third amplifier is connected to the output terminal of the second amplifier, and the two ends of the second adjustable resistor are respectively connected to the inverting input terminal and output terminal of the third amplifier. The present invention adopts the above-mentioned structure, and the overall structure is simple and easy to realize. When the invention is applied, the sensor detection signal is input and amplified by the first amplifier, and then filtered by the band-pass filter circuit and then input to the secondary amplifying circuit for re-amplification. After the sensor detection signal is amplified, the digital display circuit can accurately reflect the gas concentration in the substation. In this way, the potential safety hazards of inaccurate detection can be eliminated.

(2) When the present invention is re-amplified, the band-pass filter circuit is used for filtering, and the band-pass filter circuit can filter out the noise generated by the components in the circuit, so that the signal can be guaranteed to have high enough precision after re-amplification.

Description of drawings

Fig. 1 is a structural schematic diagram of a specific embodiment of the present invention.

The names corresponding to the reference signs in the drawings are: R1, the first resistor, R2, the second resistor, R3, the third resistor, R4, the fourth resistor, R5, the fifth resistor, R6, the sixth resistor, R7, The seventh resistor, R8, the eighth resistor, R9, the ninth resistor, RW1, the first adjustable resistor, RW2, the second adjustable resistor, C1, the first capacitor, C2, the second capacitor, C3, the third capacitor, C4, the fourth capacitor, C5, the fifth capacitor, C6, the sixth capacitor, C7, the seventh capacitor, C8, the eighth capacitor, A1, the first amplifier, A2, the second amplifier, A3, the third amplifier, L1, The first magnetic bead, L2, the second magnetic bead.

detailed description

The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example:

As shown in Figure 1, the signal amplifying circuit of the substation gas concentration detection system includes a primary amplifying circuit, a band-pass filter circuit, a secondary amplifying circuit, and an amplified signal output circuit, wherein the primary amplifying circuit includes a first amplifier A1, a first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the first resistor R1, the second resistor R2, the first magnetic bead L1, the second magnetic bead L2 and the An adjustable resistor RW1, the first amplifier A1 of this embodiment adopts the AD620 chip, the two ends of the first adjustable resistor RW1 are respectively connected to the first pin and the eighth pin of the first amplifier A1, and one end of the first capacitor C1 It is connected to the inverting input terminal of the first amplifier A1, one end of the second capacitor C2 is connected to the non-inverting input terminal of the first amplifier A1, both ends of the first resistor R1 and the second resistor R2 are grounded, and the first resistor R1 is opposite to the ground The other end of the second resistor R2 is connected to the line between the first capacitor C1 and the inverting input end of the first amplifier A1, and the other end of the second resistor R2 opposite to its grounding end is connected between the second capacitor C2 and the non-inverting input end of the first amplifier A1 on the line. Both ends of the first magnetic bead L1 are respectively connected to the positive pole of the power supply and the seventh pin of the first amplifier A1, and one end of the parallel branch formed by the parallel connection of the third capacitor C3 and the fourth capacitor C4 is connected between the first magnetic bead L1 and the first amplifier A1 On the line between them, the other end is grounded. Both ends of the second magnetic bead L2 are respectively connected to the negative pole of the power supply and the fourth pin of the first amplifier A1, and one end of the parallel branch formed by the parallel connection of the fifth capacitor C5 and the sixth capacitor C6 is connected between the second magnetic bead L2 and the first amplifier A1 On the line between them, the other end is grounded.

The bandpass filter circuit of this embodiment includes a second amplifier A2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh capacitor C7 and an eighth capacitor C8, wherein the second amplifier A2 The OP777 chip is adopted, the power supply pin of the second amplifier A2 is connected to an external power supply and ground, the two ends of the third resistor R3 are respectively connected to the output terminal of the first amplifier A1 and the eighth capacitor C8, and the eighth capacitor C8 is relatively connected to the other terminal of the third resistor R3 One end is connected to the non-inverting input end of the second amplifier A2, one end of the fourth resistor R4 is connected to the line between the third resistor R3 and the eighth capacitor C8, and the other end is connected to the inverting input end of the second amplifier A2. The seventh capacitor C7, the fifth resistor R5 and the sixth resistor R6 are grounded at one end, and the other end of the seventh capacitor C7 is connected to the line between the third resistor R3 and the eighth capacitor C8. The other end of the ground end is connected to the line between the eighth capacitor C8 and the non-inverting input end of the second amplifier A2, and the other end of the sixth resistor R6 opposite to its ground end is connected between the fourth resistor R4 and the inverting input end of the second amplifier A2 on the line between.

The secondary amplifying circuit of this embodiment includes a third amplifier A3, a second adjustable resistor RW2, a seventh resistor R7 and an eighth resistor R8, wherein the third amplifier A3 also uses an OP777 chip, and the power supply pin of the third amplifier A3 is externally connected to The positive and negative poles of the power supply, the non-inverting input terminal of the third amplifier A3 is connected to the output terminal of the second amplifier A2, the two ends of the second adjustable resistor RW2 are respectively connected to the inverting input terminal and output terminal of the third amplifier A3, and one end of the seventh resistor R7 is connected to On the line between the inverting input terminal of the third amplifier A3 and the second adjustable resistor RW2, the other end thereof is grounded, and both ends of the eighth resistor R8 are respectively connected to the output terminal of the third amplifier A3 and the amplified signal output line. This embodiment also includes a ninth resistor R9, one end of the ninth resistor R9 is connected to the amplified signal output line, and the other end of the ninth resistor R9 is connected to an external power supply. In the specific application of this embodiment, the first amplifier A1 , the second amplifier A2 and the third amplifier A3 are all powered by a 5V power supply.

In this embodiment, the resistance values of the first resistor R1 and the second resistor R2 are both 24.7 KΩ, the resistance value of the third resistor R3 is 10 KΩ, the resistance value of the fourth resistor R4 is 28 KΩ, and the resistance value of the fifth resistor R5 is is 20 KΩ, the resistance values of the sixth resistor R6 and the seventh resistor R7 are both 10 KΩ, the resistance values of the eighth resistor R8 and the ninth resistor R9 are both 20 KΩ, and the resistance value of the first adjustable resistor RW1 is adjustable The resistance value of the second adjustable resistor RW2 is adjustable from 0 to 200 KΩ. In this embodiment, the first capacitor C1, the second capacitor C2, the third capacitor C3, the sixth capacitor C6, and the seventh capacitor Both the capacitor C7 and the eighth capacitor C8 have a capacitance of 0.1 μF, and both the fourth capacitor C4 and the fifth capacitor C5 are polarized tantalum capacitors with a capacitance of 10 μF.

When this embodiment is applied, the signal detected by the sensor is input by the other end of the first capacitor C1 and the second capacitor C2 that is connected to the first amplifier A1, and is input by the first capacitor C1, the second capacitor C2, the first resistor R1 and the second The high-pass filter circuit composed of resistor R2 filters out low-frequency interference, adjusts the gain of the primary amplification by adjusting the resistance value of the first adjustable resistor RW1, and then filters through the band-pass filter circuit after primary amplification to ensure that the secondary amplification To stabilize the input signal, the gain of the secondary amplification is adjusted by adjusting the resistance value of the second adjustable resistor RW2, and the signal after the secondary amplification is output from the amplified signal input line.

As described above, the present invention can be preferably carried out.

Claims (5)

1. The signal amplifying circuit of the substation gas concentration detection system is characterized in that it includes a primary amplifying circuit, a band-pass filter circuit, a secondary amplifying circuit and an amplified signal output circuit, and the primary amplifying circuit includes a first amplifier (A1). The band-pass filter circuit includes the second amplifier (A2), the third resistor (R3), the fourth resistor (R4), the fifth resistor (R5), the sixth resistor (R6), the seventh capacitor (C7) and the eighth A capacitor (C8), the two ends of the third resistor (R3) are respectively connected to the output terminal of the first amplifier (A1) and the eighth capacitor (C8), and the eighth capacitor (C8) is relatively connected to the other end of the third resistor (R3) One end is connected to the non-inverting input end of the second amplifier (A2), one end of the fourth resistor (R4) is connected to the line between the third resistor (R3) and the eighth capacitor (C8), and the other end is connected to the second amplifier ( The inverting input terminal of A2) is connected, the seventh capacitor (C7), the fifth resistor (R5) and the sixth resistor (R6) are all grounded, and the other end of the seventh capacitor (C7) is connected to the ground terminal On the line between the third resistor (R3) and the eighth capacitor (C8), the other end of the fifth resistor (R5) opposite to its grounding terminal is connected between the eighth capacitor (C8) and the non-inverting input terminal of the second amplifier (A2) On the line, the other end of the sixth resistor (R6) opposite to its grounding terminal is connected on the line between the fourth resistor (R4) and the inverting input terminal of the second amplifier (A2); the secondary amplifier circuit includes the third An amplifier (A3), a second adjustable resistor (RW2), a seventh resistor (R7) and an eighth resistor (R8), the non-inverting input terminal of the third amplifier (A3) is connected to the output terminal of the second amplifier (A2), Both ends of the second adjustable resistor (RW2) are respectively connected to the inverting input terminal and output terminal of the third amplifier (A3), and one end of the seventh resistor (R7) is connected to the inverting input terminal of the third amplifier (A3) and the second adjustable resistor. The other end of the eighth resistor (R8) is connected to the output terminal of the third amplifier (A3) and the output line of the amplified signal respectively; The first amplifier (A1) adopts AD620 chip; A ninth resistor (R9) is also included, one end of the ninth resistor (R9) is connected to the amplified signal output line, and the other end of the ninth resistor (R9) is connected to an external power supply. 2. The signal amplifying circuit of the substation gas concentration detection system according to claim 1, characterized in that the primary amplifying circuit further includes a first adjustable resistor (RW1), and the two ends of the first adjustable resistor (RW1) They are respectively connected to the first pin and the eighth pin of the first amplifier (A1). 3. The signal amplification circuit of the substation gas concentration detection system according to claim 1, characterized in that, the primary amplification circuit also includes a first magnetic bead (L1), a second magnetic bead (L2), a third capacitor ( C3), the fourth capacitor (C4), the fifth capacitor (C5) and the sixth capacitor (C6), the two ends of the first magnetic bead (L1) are respectively connected to the positive pole of the power supply and the seventh tube of the first amplifier (A1) One end of the parallel branch formed by the parallel connection of the third capacitor (C3) and the fourth capacitor (C4) is connected to the line between the first magnetic bead (L1) and the first amplifier (A1), and the other end is grounded ; Both ends of the second magnetic bead (L2) are respectively connected to the negative pole of the power supply and the fourth pin of the first amplifier (A1), and the fifth capacitor (C5) and the sixth capacitor (C6) are connected in parallel to form a parallel branch One end is connected to the line between the second magnetic bead (L2) and the first amplifier (A1), and the other end is grounded. 4. The signal amplification circuit of the substation gas concentration detection system according to claim 1, characterized in that, both the second amplifier (A2) and the third amplifier (A3) use OP777 chips. 5. The signal amplifying circuit of the substation gas concentration detection system according to any one of claims 1 to 4, characterized in that the primary amplifying circuit further includes a first capacitor (C1), a second capacitor (C2), The first resistor (R1) and the second resistor (R2), one end of the first capacitor (C1) is connected to the inverting input end of the first amplifier (A1), and one end of the second capacitor (C2) is connected to the first amplifier (A1) ), the first resistor (R1) and the second resistor (R2) are both grounded at one end, and the other end of the first resistor (R1) opposite to its grounding end is connected between the first capacitor (C1) and the first amplifier On the line between the inverting input terminals of (A1), the other end of the second resistor (R2) opposite to its grounding terminal is connected on the line between the second capacitor (C2) and the non-inverting input terminal of the first amplifier (A1).