CN212622765U - High-precision broadband digital display millivoltmeter based on STC89C52 - Google Patents
High-precision broadband digital display millivoltmeter based on STC89C52 Download PDFInfo
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- CN212622765U CN212622765U CN202020253431.XU CN202020253431U CN212622765U CN 212622765 U CN212622765 U CN 212622765U CN 202020253431 U CN202020253431 U CN 202020253431U CN 212622765 U CN212622765 U CN 212622765U
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Abstract
The utility model discloses a high accuracy broadband digital display millivoltmeter based on STC89C52 relates to and measures technical field, contains signal source, gain amplifier, range converter, RMS-DC converter, analog to digital converter, microcontroller, LCD display, the input of gain amplifier is connected to the output of signal source, the input of RMS-DC converter is connected to the output of gain amplifier, analog to digital converter's input is connected to the output of RMS-DC converter, microcontroller's input is connected to analog to digital converter's output, microcontroller's output passes through the range converter and connects the input of gain amplifier, the input of LCD display is connected to microcontroller's output. The utility model discloses a digital alternating-current millivoltmeter has measuring frequency bandwidth, precision height, response speed is fast, input impedance is high, frequency influence error is little, easy operation, use advantage such as convenient, sexual valence ratio is higher to have functions such as range automatic switching, overrange warning.
Description
Technical Field
The utility model relates to a measure technical field, especially relate to a high accuracy broadband digital display millivoltmeter based on STC89C 52.
Background
In the measurement of the electrical quantity, the voltage, the current and the frequency are the most basic three measured quantities, of which the measurement of the voltage quantity is the most common. With the development of electronic technology, it is necessary to measure weak voltage signals, so that a millivolt voltmeter becomes an indispensable measuring instrument. The digital display millivoltmeter adopts a singlechip control technology, integrates an analog technology and a digital technology, is a universal intelligent digital alternating current millivoltmeter, generally has an automatic/manual measurement function, can display a measuring range and a gear state, but has certain limitation on application due to narrow measurement frequency band, low precision and poor anti-interference capability.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve the technical problem that not enough to provide a high accuracy broadband digital display millivoltmeter based on STC89C52 to the background art, its voltage value with the signal source that awaits measuring is converted to RMS-DC converter input signal voltage within range through the gain amplifier, receives analog-to-digital converter's input with the output signal of RMS-DC converter again, and digital signal after the conversion inputs for microcontroller with serial mode, sends LCD display measurement result.
The utility model discloses a solve above-mentioned technical problem and adopt following technical scheme:
a high-precision broadband digital display millivoltmeter based on STC89C52 comprises a signal source, a gain amplifier, a range converter, an RMS-DC converter, an analog-to-digital converter, a microcontroller and an LCD display, wherein the output end of the signal source is connected with the input end of the gain amplifier, the output end of the gain amplifier is connected with the input end of the RMS-DC converter, the output end of the RMS-DC converter is connected with the input end of the analog-to-digital converter, the output end of the analog-to-digital converter is connected with the input end of the microcontroller, the output end of the microcontroller is connected with the input end of the gain amplifier through the range converter, and the output end of the microcontroller is connected with the;
the gain amplifier comprises a reference circuit for providing a suitable bias to the circuit and a bias circuit connected to the reference circuit,
The variable gain control circuit is characterized by comprising a transistor M6, a transistor M7 and a transistor M8 which are connected with each other, wherein a control voltage Vc is connected to the gate of the transistor M8 for enabling the transistor M8 to work in a saturation region and serve as a constant current source, and a control voltage Vc is connected to the gate of the transistor M7 for adjusting the gate of the transistor M7
The drain of the transistor M7 is connected with the resistor R1, and the gain and the bandwidth are controlled by adjusting the resistance of the resistor R1;
one end of the resistor R1 is coupled to the drain of the transistor M7 and then coupled to the dc power input terminal VDD, and the other end of the resistor R1 is coupled to the drain of the transistor M6 and then coupled to the output terminal Vout; the gate of the transistor M6 is connected to the reference circuit; the source of the transistor M6 and the source of the transistor M7 are coupled to the drain of the transistor M8, and the gate of the transistor M7 is coupled to the external control voltage terminal Vc; the source of the transistor M8 is coupled to the ground GND, and the gate of the transistor M8 is coupled to the voltage source Vbias;
the reference circuit comprises a transistor M1, a transistor M2, a transistor M3, a transistor M4 and a crystal which are connected with each other
The transistor M5 and the transistor M1 are used as load transistors of the input end differential pair; the gate of the transistor M5 is connected to a reference voltage source Vs, so that the transistor M5 operates in a saturation region and serves as a constant current source.
As a further preferred solution of the high-precision broadband digital display millivolt meter based on STC89C52 of the present invention, the source of the transistor M1 is coupled to the dc power input VDD after being coupled to the source of the transistor M2, and the gate of the transistor M1 is coupled to the drain of the transistor M1 and is coupled to the gate of the transistor M2 and the drain of the transistor M3; the gate of the transistor M3 is coupled to the input inp, and the source of the transistor M3 and the source of the transistor M4 are coupled to the drain of the transistor M5; the gate of the transistor M4 is coupled to the input terminal inn, the source of the transistor M5 is coupled to the ground GND, and the gate of the transistor M5 is coupled to the voltage source Vs.
As a further preferred scheme of high accuracy broadband digital display millivoltmeter based on STC89C52, microcontroller adopts STC89C52 singlechip.
As a further preferred scheme of high accuracy broadband digital display millivoltmeter based on STC89C52, the range converter adopts 8 passageway digital control analog electronic switch CD4051, and this device has 3 control input A, B, C and INH inputs, has low on-resistance and very low leakage current that ends.
As a further preferred scheme of the high accuracy broadband digital display millivoltmeter based on STC89C52 of the utility model, the RMS-DC converter has selected for use the RMS-DC conversion device AD637 of ADI company.
As a further preferred embodiment of the high-precision broadband digital display millivoltmeter based on STC89C52 of the utility model, the analog-to-digital conversion circuit adopts a 12-bit high-precision chip MAX187 released by the american MAXIM company.
As a further preferred scheme of the high accuracy broadband digital display millivoltmeter based on STC89C52 of the utility model, adopt LCD1602 LCD.
The utility model adopts the above technical scheme to compare with prior art, have following technological effect:
1. the utility model converts the voltage value of the signal source to be measured into the input signal voltage range of the RMS-DC converter through the gain amplifier, then connects the output signal of the RMS-DC converter to the input end of the analog-to-digital converter, inputs the converted digital signal to the microcontroller in a serial mode, and sends the digital signal to the liquid crystal display to display the measurement result after processing; if the voltage of the input signal to be measured is not in the proper measuring range, the microcontroller outputs a corresponding control signal after judgment, and the gain of the gain amplifier is adjusted through the measuring range converter so as to realize the function of automatically converting the measuring range of the millivoltmeter;
2. the digital AC millivoltmeter of the utility model has the advantages of wide measuring frequency band, high precision, fast response speed, high input impedance, small frequency influence error, simple operation, convenient use, high cost performance and the like, and has the functions of automatic range conversion, over-range alarming and the like; when voltage signals below 1000 mV are measured, the maximum resolution can reach 0.001 mV, the measurement requirement of weak signals can be met, and the method has wide market prospect and higher popularization and application values;
3. the utility model provides a pair of variable gain amplifier has realized a well low frequency variable gain amplifier, and this variable gain control circuit adopts analog circuit control structure, has realized the continuous adjustable of gain, and its gain adjustable range has reached 44dB, and the 3dB bandwidth is 0Hz to 600MHz, the biggest output noise-25 dB, and operating voltage 3.3V to possess fine linearity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following embodiments or prior arts will be described
While the drawings that are needed to be utilized in the description of the invention have been described briefly, it should be apparent that the drawings in the description that follows are illustrative of the invention
It will be apparent to one of ordinary skill in the art that the embodiments may be practiced without the use of the inventive faculty
From these figures further figures are obtained.
FIG. 1 is a schematic diagram of the system architecture of the present invention;
fig. 2 is a schematic circuit diagram of the present invention.
Detailed Description
The technical scheme of the utility model is further explained in detail with the attached drawings as follows:
the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
A high-precision broadband digital display millivoltmeter based on STC89C52 is shown in figure 1 and comprises a signal source, a gain amplifier, a range converter, an RMS-DC converter, an analog-to-digital converter, a microcontroller and an LCD display, wherein the output end of the signal source is connected with the input end of the gain amplifier, the output end of the gain amplifier is connected with the input end of the RMS-DC converter, the output end of the RMS-DC converter is connected with the input end of the analog-to-digital converter, the output end of the analog-to-digital converter is connected with the input end of the microcontroller, the output end of the microcontroller is connected with the input end of the gain amplifier through the range converter, and the output end of the microcontroller is connected;
firstly, the voltage value of a signal source to be measured is converted into the voltage range of an input signal of an RMS-DC converter through a gain amplifier, then an output signal of the RMS-DC converter is connected to the input end of an analog-to-digital converter, and a converted digital signal is input to a microcontroller in a serial mode and is sent to a liquid crystal display to display a measurement result after being processed by software. If the voltage of the input signal to be measured is not in the proper measuring range, the microcontroller outputs a corresponding control signal after judgment, and the gain of the gain amplifier is adjusted through the measuring range converter so as to realize the function of automatically converting the measuring range of the millivoltmeter.
As shown in fig. 2, the gain amplifier includes a reference circuit for providing a proper bias for the circuit and a variable gain control circuit connected to the reference circuit for controlling the gain of the regulating circuit, wherein the variable gain circuit includes a transistor M6, a transistor M7, and a transistor M8 connected to each other, a gate of the transistor M8 is connected to a control voltage Vc for operating the transistor M8 in a saturation region as a constant current source, a gate of the transistor M7 is connected to the control voltage Vc for adjusting the voltage value of the gate of the transistor M7, a drain of the transistor M7 is connected to a resistor R1, and the magnitude and bandwidth of the gain are controlled by adjusting the resistance value of the resistor R1;
one end of the resistor R1 is coupled to the drain of the transistor M7 and then coupled to the dc power input terminal VDD, and the other end of the resistor R1 is coupled to the drain of the transistor M6 and then coupled to the output terminal Vout; the gate of the transistor M6 is connected to the reference circuit; the source of the transistor M6 and the source of the transistor M7 are coupled to the drain of the transistor M8, and the gate of the transistor M7 is coupled to the external control voltage terminal Vc; the source of the transistor M8 is coupled to the ground GND, and the gate of the transistor M8 is coupled to the voltage source Vbias;
the reference circuit comprises a transistor M1, a transistor M2, a transistor M3, a transistor M4 and a crystal which are connected with each other
The transistor M5 and the transistor M1 are used as load transistors of the input end differential pair; the gate of the transistor M5 is connected to a reference voltage source Vs, so that the transistor M5 operates in a saturation region and serves as a constant current source.
A source of the transistor M1 and a source of the transistor M2 are coupled to the dc power input terminal VDD, and a gate of the transistor M1 and a drain of the transistor M1 are coupled to a gate of the transistor M2 and a drain of the transistor M3; the gate of the transistor M3 is coupled to the input inp, and the source of the transistor M3 and the source of the transistor M4 are coupled to the drain of the transistor M5; the gate of the transistor M4 is coupled to the input terminal inn, the source of the transistor M5 is coupled to the ground GND, and the gate of the transistor M5 is coupled to the voltage source Vs.
The microcontroller adopts an STC89C52 singlechip. The system adopts an STC89C52 single chip microcomputer as a system controller.
STC89C52 is a low power consumption, high performance CMOS 8-bit microcontroller that provides a highly flexible, super-efficient solution for many embedded control applications. The device is provided with a 1 KB RAM and a 64 KB on-chip Flash program memory; the system has the functions of application programming (IAP) and system programming (ISP); 3 16-bit timers/counters are provided, and a Programmable Counter Array (PCA) which can work independently without the participation of a CPU is additionally provided, so that the PWM capturing/comparing function is realized; 4 8-bit I/O ports; the system has the functions of programmable watchdog timer (WDT), power-down detection, low-power-consumption mode and the like. In addition, STC89C52 has increased a plurality of reset functions such as power-on reset, software reset, undervoltage detection and reset on 8051 basis to improve the interference killing feature of singlechip. Based on the performance and characteristics of the STC89C52 single chip microcomputer, an X1 and an X2 are externally connected with a 12MHz crystal oscillator, so that an internal oscillator oscillates according to the frequency of the quartz crystal oscillator to generate a clock signal; the RESET is externally connected with a RESET key, after RESET, ports P0-P3 are all set to be 1, pins are high level, and a program counter and a special function register SFR are all cleared. Connecting the P0 port with 8-bit data lines (D0-D7) of the LCD; pin1 to Pin3 in P1 mouth are connected to A/D conversion respectively
Clock Signals (SCLK), chip select signals (CS) and digital output signals (DOUT) of the circuit, wherein pins 4-Pin 6 are respectively connected with a data/command selection end (RS), a read/write selection end (R/W) and an enable signal (E) of the LCD display; the P2 ports Pin21~ Pin23 are connected to the 3 two-way control input ends A, B, C of the CD4051 multiplexer; the P3 port (Pin10~ Pin17) is an 8-bit bidirectional I/O port with internal pull-up resistor, and in the system design, the 8 pins are used for special secondary functions.
The range converter employs an 8-channel digitally controlled analog electronic switch CD4051 having 3 control inputs A, B, C and an INH input, with low on-resistance and very low off-leakage current. When INH =1, all channels are blocked. When CBA =000, the input end X0 is conducted, the input signal is amplified by 200 times, and the corresponding range is 0-10 mV; when CBA =001, the input end X1 is conducted, the input signal is amplified by 20 times, and the corresponding range is 10-100 mV; when CBA =010, the input end X2 is conducted, the input signal is amplified by 2 times, and the corresponding measuring range is 100-1000 mV. The output terminal (X) of CD4051 is connected with the input terminal (Vin) of RMS-DC converter
The RMS-DC converter adopts an RMS-DC conversion device AD637 of ADI company. Slave precision, bandwidth, power consumption, output
The RMS-DC conversion device AD637 of ADI company is selected by comprehensively considering factors such as signal level, crest factor, stable time and the like. AD637 belongs to a high-accuracy monolithic true-value/DC converter, and the frequency of input 1000 mV (RMS) reaches 5 MHz under the condition of +/-3 dB additional error. An independent buffer amplifier is arranged in the device, and the device can be used as an input buffer, and can also form an active filter to reduce ripples and improve the accuracy of measurement; the input end is provided with a voltage protection circuit, so that the chip can not be damaged generally even if Vin exceeds the power supply voltage.
The A/D converter circuit uses a 12-bit high-precision chip MAX187 from MAXIM, USA. The MAX187 serial 12-bit analog-to-digital converter can work under a single + 5V power supply, and the analog input voltage is 0-5V. MAX187 is a successive approximation ADC, fast sample/hold (1.5 μ s), on-chip clock, high speed 3-wire serial interface. The MAX187 power supply requires decoupling capacitance, using a 4.7 μ F capacitance in parallel with a 0.1 μ F. Pin4 is the reference terminal, connected to a 4.7 μ F capacitor, using an internal 4.096V reference voltage.
After 20ms after the power-up of MAX187, the capacitor connected to the reference voltage pin is charged completely, and the working state is entered. When the enable terminal CS is set to be at low level, the internal tracking/keeper (T/H) enters a holding state and starts conversion, and the DOUT outputs level after the conversion is finished. At this time, the shift pulse is input into the SCLK terminal to read out the 12-bit conversion result from the most significant bit to the least significant bit sequentially from the DOUT terminal. The CS terminal may be set low, a shift pulse may be sent 8.5 μ s later, the conversion result may be read, and the CS terminal may be set high after the entire 12-bit result is read.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Above embodiment only is for explaining the utility model discloses a technical thought can not be injectd with this the utility model discloses a protection scope, all according to the utility model provides a technical thought, any change of doing on technical scheme basis all falls into the utility model discloses within the protection scope. Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; go to
While the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: it is obvious that the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be modified
Performing equivalent replacement; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (7)
1. A high-precision broadband digital display millivoltmeter based on STC89C52 is characterized in that: the device comprises a signal source, a gain amplifier, a range converter, an RMS-DC converter, an analog-to-digital converter, a microcontroller and an LCD display, wherein the output end of the signal source is connected with the input end of the gain amplifier, the output end of the gain amplifier is connected with the input end of the RMS-DC converter, the output end of the RMS-DC converter is connected with the input end of the analog-to-digital converter, the output end of the analog-to-digital converter is connected with the input end of the microcontroller, the output end of the microcontroller is connected with the input end of the gain amplifier through the range converter, and the output end of the microcontroller is;
the gain amplifier comprises a reference circuit used for providing bias for the circuit and a variable gain control circuit which is connected with the reference circuit and used for controlling and adjusting the gain of the circuit, wherein the variable gain control circuit comprises a transistor M6, a transistor M7 and a transistor M8 which are connected with one another, a control voltage Vc is connected to the grid of the transistor M8 and used for enabling the transistor M8 to work in a saturation region and serve as a constant current source, the control voltage Vc is connected to the grid of the transistor M7 and used for adjusting the voltage value of the grid of the transistor M7, the drain of the transistor M7 is connected with a resistor R1, and the resistance value of a resistor R1 and the size and the bandwidth of the gain are controlled;
one end of the resistor R1 is coupled to the drain of the transistor M7 and then coupled to the dc power input terminal VDD, and the other end of the resistor R1 is coupled to the drain of the transistor M6 and then coupled to the output terminal Vout; the gate of the transistor M6 is connected to the reference circuit; the source of the transistor M6 and the source of the transistor M7 are coupled to the drain of the transistor M8, and the gate of the transistor M7 is coupled to the external control voltage terminal Vc; the source of the transistor M8 is coupled to the ground GND, and the gate of the transistor M8 is coupled to the voltage source Vbias;
the reference circuit comprises a transistor M1, a transistor M2, a transistor M3, a transistor M4 and a transistor M5 which are connected with each other, wherein the transistor M1 is used as a load tube of an input end differential pair; the gate of the transistor M5 is connected to a reference voltage source Vs, so that the transistor M5 operates in a saturation region and serves as a constant current source.
2. The STC89C 52-based high-precision broadband digital millivolt meter according to claim 1, wherein a source of a transistor M1 is coupled to a source of a transistor M2 and then coupled to a DC power input VDD, a gate of a transistor M1 is coupled to a drain of a transistor M1 and then coupled to a gate of a transistor M2 and a drain of a transistor M3; the gate of the transistor M3 is coupled to the input inp, and the source of the transistor M3 and the source of the transistor M4 are coupled to the drain of the transistor M5; the gate of the transistor M4 is coupled to the input terminal inn, the source of the transistor M5 is coupled to the ground GND, and the gate of the transistor M5 is coupled to the voltage source Vs.
3. The high-precision broadband digital millivoltmeter according to claim 1, wherein the broadband digital millivoltmeter is based on STC89C52, and is characterized in that: the microcontroller adopts an STC89C52 singlechip.
4. The high-precision broadband digital millivoltmeter according to claim 1, wherein the broadband digital millivoltmeter is based on STC89C52, and is characterized in that: the range converter employs an 8-channel digitally controlled analog electronic switch CD4051 having 3 control inputs A, B, C and an INH input, with low on-resistance and very low off-leakage current.
5. The high-precision broadband digital millivoltmeter according to claim 1, wherein the broadband digital millivoltmeter is based on STC89C52, and is characterized in that: the RMS-DC converter adopts an RMS-DC conversion device AD637 of ADI company.
6. The high-precision broadband digital millivoltmeter according to claim 1, wherein the broadband digital millivoltmeter is based on STC89C52, and is characterized in that: the analog-to-digital conversion circuit adopts a 12-bit high-precision chip MAX187 which is released by MAXIM.
7. The high-precision broadband digital millivoltmeter according to claim 1, wherein the broadband digital millivoltmeter is based on STC89C52, and is characterized in that: an LCD1602 liquid crystal display is used.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| RU2800397C1 (en) * | 2023-01-24 | 2023-07-21 | Акционерное общество "Научно-исследовательский институт "Полюс" им. М.Ф. Стельмаха" | Rms millivoltmeter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2800397C1 (en) * | 2023-01-24 | 2023-07-21 | Акционерное общество "Научно-исследовательский институт "Полюс" им. М.Ф. Стельмаха" | Rms millivoltmeter |
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