CN219351711U

CN219351711U - Wide-range small-signal amplifying circuit and redox voltage measuring circuit

Info

Publication number: CN219351711U
Application number: CN202320047825.3U
Authority: CN
Inventors: 刘以祥; 梁毛鹞
Original assignee: Fucos Shenzhen Technology Co ltd
Current assignee: Fucos Shenzhen Technology Co ltd
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2023-07-14
Anticipated expiration: 2033-01-06

Abstract

The utility model provides a wide-range small-signal amplifying circuit, which relates to the technical field of signal amplification and comprises an analog signal terminal Vda, an operational amplifier U1A, an input resistor R1, a feedback resistor R2 and an output terminal Vout; the analog signal terminal Vda is connected with the input resistor R1, the other end of the input resistor R1 is connected with the feedback resistor R2, a first connection point is arranged between the input resistor R1 and the feedback resistor R2, the first connection point is connected with the negative input port of the operational amplifier U1A, and the positive input port of the operational amplifier U1A is connected with an input signal to be amplified; the other end of the feedback resistor R2 is connected with the output port of the operational amplifier U1A, a second connection point is arranged between the feedback resistor R2 and the output port of the operational amplifier U1A, the second connection point is connected with the output terminal Vout, and the output terminal Vout outputs amplified signals.

Description

Wide-range small-signal amplifying circuit and redox voltage measuring circuit

Technical Field

The utility model relates to the technical field of signal amplification, in particular to a wide-range small-signal amplification circuit and a redox voltage measurement circuit.

Background

Instruments and meters based on analog sensors are currently mainstream applications, but the current and voltage signals output by the sensors are very weak, for example, the signals of a pH value sensor and an ORP sensor are mV levels, and the current signals of a polarographic dissolved oxygen sensor are nA levels. Because the instrument and meter has higher requirement on sampling precision, the signals can be accurately sampled by an ADC chip or an ADC interface of the MCU by generally amplifying the signals or improving the resolution of the ADC by improving the amplification factor. However, increasing the amplification factor may cause the voltage range of the output signal to exceed the voltage range sampled by the ADC, and increasing the resolution of the ADC may result in a significant increase in cost. How to ensure the sampling precision without increasing the cost is a current problem to be solved.

Disclosure of Invention

In order to overcome the defects of the prior art, the utility model provides a wide-range small-signal amplifying circuit and a redox voltage measuring circuit.

The technical scheme adopted for solving the technical problems is as follows: in a wide range small signal amplification circuit, the improvement comprising: the circuit comprises an analog signal terminal Vda, an operational amplifier U1A, an input resistor R1, a feedback resistor R2 and an output terminal Vout;

the analog signal terminal Vda is connected with the input resistor R1, the other end of the input resistor R1 is connected with the feedback resistor R2, a first connection point is arranged between the input resistor R1 and the feedback resistor R2, the first connection point is connected with the negative input port of the operational amplifier U1A, and the positive input port of the operational amplifier U1A is connected with an input signal to be amplified;

the other end of the feedback resistor R2 is connected with the output port of the operational amplifier U1A, a second connection point is arranged between the feedback resistor R2 and the output port of the operational amplifier U1A, the second connection point is connected with the output terminal Vout, and the output terminal Vout outputs amplified signals.

The utility model also provides a redox voltage measurement circuit, which comprises the wide-range small-signal amplification circuit, an absolute value module and a zero-crossing detection module;

the absolute value module is connected with the positive input port of the operational amplifier U1A and is used for converting an input signal and outputting the converted input signal to the operational amplifier U1A;

the zero-crossing detection module is connected with the input signal to be amplified to judge the positive and negative of the input signal to be amplified.

The beneficial effects of the utility model are as follows: the method and the device realize the high precision of signal sampling while guaranteeing the wide-range signal input, and have low cost.

Drawings

Fig. 1 is a schematic circuit diagram of a wide-range small-signal amplifying circuit according to the present utility model.

Fig. 2 is a schematic circuit diagram of a redox voltage measurement circuit according to the present utility model.

Detailed Description

The utility model will be further described with reference to the drawings and examples.

The conception, specific structure, and technical effects produced by the present utility model will be clearly and completely described below with reference to the embodiments and the drawings to fully understand the objects, features, and effects of the present utility model. It is apparent that the described embodiments are only some embodiments of the present utility model, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present utility model based on the embodiments of the present utility model. In addition, all the coupling/connection relationships referred to in the patent are not direct connection of the single-finger members, but rather, it means that a better coupling structure can be formed by adding or subtracting coupling aids depending on the specific implementation. The technical features in the utility model can be interactively combined on the premise of no contradiction and conflict.

Referring to fig. 1, the present utility model provides a wide-range small-signal amplifying circuit including an analog signal terminal Vda, an operational amplifier U1A, an input resistor R1, a feedback resistor R2, and an output terminal Vout; the analog signal terminal Vda is connected with the input resistor R1, the other end of the input resistor R1 is connected with the feedback resistor R2, a first connection point 10 is arranged between the input resistor R1 and the feedback resistor R2, the first connection point 10 is connected with the negative input port of the operational amplifier U1A, and the positive input port of the operational amplifier U1A is connected with an input signal to be amplified; the other end of the feedback resistor R2 is connected with the output port of the operational amplifier U1A, a second connection point 20 is arranged between the feedback resistor R2 and the output port of the operational amplifier U1A, the second connection point 20 is connected with an output terminal Vout, and the output terminal Vout outputs amplified signals.

Referring to fig. 1, an input signal Vin is added to a positive input end of an operational amplifier U1A, the model of the operational amplifier U1A is COS8554SR, an analog output signal of the single-chip microcomputer is added to a negative input end of the operational amplifier U1A through an analog signal terminal Vda, and the amplified output signal is connected to an AD input end of the single-chip microcomputer through an output terminal Vout, and the three relations are calculated according to the formula: vin, (1+r2/R1) -Vda R2/r1=vout. The output signal Vout of the input signal Vin amplified by the amplifier is supplied to the AD detection port of the singlechip, if the singlechip program detects that the output signal Vout is saturated (approaching 3.3V power supply voltage or approaching 0V), the analog output voltage Vda is gradually regulated until the output is unsaturated, and the singlechip program specifically regulates the following processes: if the voltage of the output signal Vout is already close to 3.3V, which means that the input signal Vin is larger, the singlechip program gradually increases the analog output voltage Vda until the output voltage Vout of the amplifier is far smaller than 3.3V; if the voltage of the output signal Vout is already close to 0V, indicating that the input signal Vin is relatively small, the single-chip microcomputer program gradually decreases the analog output voltage Vda until the amplifier output voltage Vout is much greater than 0V. The single chip microcomputer program substitutes the known Vda voltage and the Vout voltage into the formula to calculate Vin, if R2=200K and R1=20K, the input signal Vin is amplified 11 times, the signal sampling error is reduced 11 times according to the Dulby noise reduction principle, if the data sampling of the single chip microcomputer is that the power supply of a 12-bit power supply is 3.3V, the CPU sampling precision is 3.3V/4096=0.8 mV, the input signal is amplified 11 times by utilizing the amplifying circuit, and the sampling precision of the whole system is 0.8 mV/11=73uV, which is equivalent to the precision of the single chip microcomputer without an amplifier for 16-bit AD sampling. The multiple of the amplifier can be arbitrarily increased, that is, the accuracy can be arbitrarily increased, but the reference voltage and the amplifier resistance are required to be accurate. The method and the device realize high precision of signal sampling while guaranteeing wide-range signal input, and have low cost.

The wide-range small-signal amplifying circuit has stronger anti-interference capability than a high-precision AD sampling chip and a singlechip, and is more stable in equipment. In general electronic products, certain interference signals exist, and according to the dolby noise reduction principle, the larger the useful signal is, the stronger the anti-interference capability is. However, if the signal is not amplified, the accuracy of the sampling chip is only improved, the theoretical accuracy is improved, but the accuracy is not actually improved, because the unit voltage signal is smaller when the resolution of the sampling chip is higher, and when the unit voltage signal is smaller than the interference signal, the unit voltage signal and the interference signal are not distinguished, so that the improvement of the accuracy does not exist. Only when the sampled signal is amplified without error so that it is far greater than the interference signal, the measured signal is truly stable and accurate.

Referring to fig. 2, the utility model further provides a redox voltage measurement circuit, which comprises the wide-range small-signal amplification circuit, an absolute value module and a zero-crossing detection module; the absolute value module is connected with the positive input port of the operational amplifier U1A and is used for converting an input signal and outputting the converted input signal to the operational amplifier U1A; the zero-crossing detection module is connected with an input signal to be amplified, converts the input signal into a signal which can be identified by the singlechip, and outputs the signal to the singlechip so as to judge the positive and negative of the input signal to be amplified (the specific structures of the absolute value module and the zero-crossing detection module are conventional knowledge in the technical field, so that the specific expressions of the absolute value module and the zero-crossing detection module are omitted here).

As shown in FIG. 2, the ORP signal measurement range of the redox voltage measurement circuit requires a measuring range of + -1999.9 mV and an accuracy of + -0.1 mV (similar products on the market have an accuracy of 1 mV), so that the problem that the measuring range and the accuracy are difficult to be compatible is faced, a 16-bit AD conversion chip with more than 4V for supplying power is used, or the level of + -1999.9 mV signal is converted into 0-3.3V, and then a 3.3V power is used for supplying 16-bit high-accuracy AD for sampling CPU. The 16-bit high-precision sampling chip and the CPU are not purchased at all in domestic markets, and are very expensive and unstable in source even if purchased. Therefore, by adopting the design of the redox voltage measurement circuit, an input + -1999.9 mV signal is converted into a positive 1999.9mV signal by an absolute value module and is represented by Vin, a singlechip program judges whether a signal is positive or negative by a zero-crossing detection module, and the signal is negative when the zero-crossing detection module outputs a low level, and positive when the zero-crossing detection module outputs a high level. Vin is added to the positive input end of the operational amplifier U1A, the analog output signal Vda of the single chip microcomputer is added to the negative input end of the operational amplifier U1A, the output signal Vout of the operational amplifier U1A is connected to the AD input end of the single chip microcomputer, and the relation between the three is calculated by the formula: vin (1+r2/R1) -Vda R2/r1=vout, an input signal is converted into Vin after passing through an absolute value module, the Vin is amplified by an amplifier, an output signal is set as Vout, if the singlechip detects that the output signal Vout is saturated (near 3.3V power supply voltage or near 0V), the singlechip program adjusts the analog output voltage Vda until the output is unsaturated, and then the known Vda voltage and Vout voltage are substituted into the formula to calculate Vin, so that the purpose of measuring the input signal is achieved, and the measurement process and the circuit are simple and easy to realize.

The wide-range small-signal amplifying circuit ensures the high precision of signal sampling while ensuring the input of a wide-range signal, has low cost and makes up the defects of the traditional ADC chip and MCU; the redox voltage measuring circuit achieves the purpose of measuring input signals, and the measuring process and the circuit are simple and easy to realize.

While the preferred embodiment of the present utility model has been described in detail, the present utility model is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model, and these equivalent modifications or substitutions are included in the scope of the present utility model as defined in the appended claims.

Claims

1. A wide-range small-signal amplification circuit, characterized in that: the circuit comprises an analog signal terminal Vda, an operational amplifier U1A, an input resistor R1, a feedback resistor R2 and an output terminal Vout;

2. A redox voltage measurement circuit, characterized by: the wide-range small-signal amplification circuit according to claim 1, further comprising an absolute value module and a zero-crossing detection module;