CN205785606U - Digital pressure measuring instrument circuit - Google Patents

Abstract

The utility model discloses a circuit of a digital pressure measuring instrument, which comprises a piezoresistive sensor, which outputs a voltage signal proportional to the pressure by sensing external pressure; an operational amplifier circuit, which amplifies the voltage signal in phase; The voltage signal is analyzed and processed, and then the bit strobe signal and BCD code data are output. If there is an over-range situation in the BCD code, the over-range signal is output; the decoder converts the BCD code output by the analog-to-digital converter into seven segments signal; the digital tube display, which digitally displays the seven-segment signal output by the decoder; the driver, which receives the bit strobe signal, drives the digital tube display for display; the trigger, receives the over-range signal output by the analog-to-digital converter, and uses the data In the latch mode, the digital tube is controlled by the decoder to flash and display.

Description

Digital Pressure Measuring Instrument Circuit

technical field

The utility model relates to the field of pressure measuring circuits, in particular to a digitally displayed pressure measuring instrument circuit.

Background technique

With the advancement of science and technology and the development of the electronic industry, various sensors, integrated sensors, large-scale integrated circuits (LSI) and very large-scale integrated circuits (VLSI) have been introduced at home and abroad, which provides a great opportunity for the development of various digital instruments and intelligent digital instruments. Provides great convenience. Adopting new technology and new technology, a large number of new digital instruments designed by sensors, LSI or VLSI and corresponding peripheral circuits have come out, marking a revolution in the field of electronic instruments and creating a precedent for electronic measurement. For example, on the basis of a digital voltmeter, coupled with temperature, force, pressure and other sensors (integrated sensors) and corresponding peripheral circuits, a digital thermometer (measuring instrument), force (measuring instrument), pressure gauge (measuring instrument) can be formed. instrument) and other new general-purpose and special-purpose digital instruments or measurement systems.

Utility model content

In order to make the reading of the pressure measuring instrument objective and accurate, conform to people's reading habits, and reduce visual fatigue, the utility model provides a digital pressure measuring instrument circuit.

The utility model adopts the following solutions to technical problems:

The digital pressure measuring instrument circuit is characterized in that it includes:

The piezoresistive sensor outputs a voltage signal proportional to the pressure by sensing the external pressure;

An operational amplifier circuit amplifies the voltage signal in phase;

An analog-to-digital converter analyzes and processes the voltage signal output by the operational amplifier circuit, and then outputs a bit strobe signal and BCD code data. If an over-range situation occurs in the BCD code, an over-range signal is output;

A decoder, converting the BCD code output by the analog-to-digital converter into seven-segment signals;

A nixie tube display digitally displays the seven-segment signals output by the decoder;

a driver, receiving the bit strobe signal, and driving the nixie tube display to display;

The flip-flop receives the over-range signal output by the analog-to-digital converter, and controls the digital tube to flash and display through the decoder in a data latch mode.

Optionally, the operational amplifier circuit includes an operational amplifier, a tenth potentiometer, an eleventh resistor and a twelfth resistor;

The eleventh resistor and the tenth potentiometer are connected in series between the negative phase input terminal of the operational amplifier and the output terminal of the operational amplifier, and the negative phase input terminal of the operational amplifier is electrically connected to the tenth potentiometer. Two resistors are connected to the negative voltage output terminal of the piezoresistive sensor, and the non-inverting input terminal of the operational amplifier is connected to the positive voltage output terminal of the piezoresistive sensor.

Further, the model of the operational amplifier is ICL7650.

Preferably, the clock pulse input port of the flip-flop is connected to the conversion period end flag bit output port of the analog-to-digital converter, and the data input port of the flip-flop and the inverted code output port of the flip-flop are connected to the output port of the flip-flop. The blanking control end of the decoder is connected, the reset end of the flip-flop is connected with the over-range flag bit end of the analog-to-digital converter, and the set end of the flip-flop is grounded.

Further, the model of the trigger is CD4013.

Preferably, the input terminal of the driver is connected to the bit strobe signal terminal of the analog-to-digital converter, and the output terminal of the driver is connected to the common cathode terminal of the nixie tube display.

Further, the model of the driver is MC1413.

Preferably, the measuring instrument circuit also includes a reading hold circuit, wherein,

The reading holding circuit includes a twenty-second resistor and a switch;

The conversion end flag output terminal of the analog-to-digital converter is electrically connected to the twenty-second resistor to the real-time output control terminal of the analog-to-digital converter, and the real-time output control terminal is electrically connected to the switch to the analog-to-digital converter. Negative Supply Port of Converter.

Preferably, the measuring instrument circuit also includes a high-frequency filter circuit, wherein,

The high-frequency filter circuit includes a twenty-first resistor and a twenty-first capacitor, the twenty-first capacitor is connected between the voltage input terminal of the analog-to-digital converter and the analog ground of the analog-to-digital converter, The voltage input terminal is connected to the twenty-first resistor to the output terminal of the operational amplifier, and the analog ground is grounded.

The utility model has the following beneficial technical effects:

It has the advantages of small size, reliable operation, simple circuit and convenient use;

Using advanced digital display technology, the measurement results are clear at a glance, which is more in line with people's reading habits;

It has the advantages of high accuracy, high resolution, and high cost performance.

Description of drawings

Fig. 1 is a circuit block diagram of a digital pressure measuring instrument provided by an embodiment of the utility model;

Fig. 2 is a schematic circuit diagram of a digital pressure measuring instrument provided by an embodiment of the present invention.

detailed description

The utility model will be further explained through specific embodiments below in conjunction with FIG. 1 and FIG. 2 .

Please refer to Figure 1 and Figure 2 comprehensively, the digital pressure measuring instrument circuit, including:

The piezoresistive sensor DYC-103 outputs a voltage signal proportional to the pressure by sensing the external pressure;

Constant current source, supply constant current to piezoresistive sensor DYC-103;

Stabilized power supply to provide stable voltage to the piezoresistive sensor DYC-103;

Operational amplifier circuit, amplifying the voltage signal in phase;

Negative power converter, providing negative voltage to the chopper amplifier circuit;

The analog-to-digital converter MC14433 analyzes and processes the voltage signal output by the operational amplifier circuit, and then outputs the bit strobe signal and BCD code data. If there is an over-range condition in the BCD code, the over-range signal is output;

The reference voltage source circuit provides a reference voltage to the analog-to-digital conversion driving circuit;

Decoder CD4511 converts the BCD code output by the analog-to-digital converter MC14433 into a seven-segment signal;

Nixie tube display, which digitally displays the seven-segment signal output by the decoder CD4511;

The driver MC1413 receives the bit strobe signal and drives the digital tube display for display;

The trigger CD4013 receives the over-range signal output by the analog-to-digital converter MC14433, and uses the data latch mode to control the digital tube to flash and display through the decoder CD4511.

The operational amplifier circuit includes an operational amplifier ICL7650, a tenth potentiometer RP10, an eleventh resistor R11 and a twelfth resistor R12;

The eleventh resistor R11 and the tenth potentiometer RP10 are connected in series between the negative input terminal of the operational amplifier ICL7650 and the output terminal of the operational amplifier ICL7650, and the negative input terminal of the operational amplifier ICL7650 is electrically connected to the twelfth resistor R12 to the piezoresistive The negative voltage output terminal of the sensor DYC-103, the non-inverting input terminal of the operational amplifier ICL7650 are connected with the positive voltage output terminal of the piezoresistive sensor DYC-103.

ICL7650 is a chopper-stabilized zero-type high-precision operational amplifier made by Intersil using dynamic zero-calibration technology and CMOS technology. Accurately amplify the weak voltage signal from 0 to 100mV to 1V, matching with the digital voltmeter DVM. ICL7650 adopts 14-pin dual-in-line package or 8-pin metal shell package. When using 14-pin dual-in-line package ICL7650, memory capacitors C1 and C2 should be connected to pins 1 and 2 respectively. The recommended value is 0.1 uf, the 8th pin is the common terminal of C1 and C2, and the accuracy of this level of operational amplifier is better than ±0.5%.

The clock pulse input port CP of the flip-flop CD4013 is connected with the conversion cycle end flag bit EOC of the analog-to-digital converter MC14433, the data input port D of the flip-flop CD4013 is connected with the inverted code output port of the flip-flop CD4013 With the blanking control terminal of the decoder CD4511 Connection, the reset terminal R of the flip-flop CD4013 and the over-range flag terminal of the analog-to-digital converter MC14433 Connection, the setting terminal S of the flip-flop CD4013 is grounded.

The input terminals I ₁ -I ₄ of the driver MC1413 are connected to the bit strobe signal terminals DS ₁ -DS ₄ of the analog-to-digital converter MC14433, and the output terminals O ₁ -O ₄ of the driver MC1413 are connected to the common cathode terminal of the digital tube display.

The digital pressure measuring instrument circuit also includes a reading hold circuit, wherein,

The reading holding circuit includes a twenty-second resistor R22 and a switch S;

The conversion cycle end flag EOC of the analog-to-digital converter MC14433 is electrically connected to the twenty-second resistor R22 to the real-time output control terminal DU of the analog-to-digital converter MC14433, and the real-time output control terminal DU is electrically connected to the switch S to the negative terminal of the analog-to-digital converter MC14433. Power supply port U _SS , when each analog-to-digital conversion cycle ends, a positive pulse is output from the EOC end of the conversion cycle end flag, and its pulse width is 1/2 of the clock signal cycle;

When the switch S is off, the analog-to-digital conversion results can be displayed normally, and the displayed value is continuously refreshed; when the switch S is closed. DU=0/, the analog-to-digital conversion result is kept for a long time, and the modulus is in the latched state at this time. The holding time is the closing time of the switch, and S is called the reading holding switch.

The digital pressure measuring instrument circuit also includes a high-frequency filter circuit, wherein,

The high-frequency filter circuit includes a twenty-first resistor R21 and a twenty-first capacitor C21, the voltage input terminal of the analog-to-digital converter MC14433 is connected to the analog ground of the analog-to-digital converter MC14433, and the twenty-first capacitor C21 is connected, and the voltage input terminal Connect the twenty-first resistor R21 to the output terminal of the operational amplifier ICL7650, and the analog ground U _AG is grounded.

The high-frequency filter has two functions: the first is to filter out high-frequency interference, eliminate the influence of external noise interference, and improve the signal-to-noise ratio of the instrument; the second is to use the current limiting function of R21 to prevent the Damage the chip and avoid breakdown of the input terminal due to the induction of instantaneous high voltage. In view of the role of the high-frequency filter, generally take R21 = 1MΩ, C21 = 0.1μF.

The reference voltage source circuit includes a voltage source MC1403 and a potentiometer RP. One end of the potentiometer RP is connected to the ground terminal of the voltage source MC1403, and the other end of the potentiometer RP is connected to the output end of the voltage source MC1403. The potentiometer RP is used to obtain The positive reference voltage is used as a reference voltage for the analog-to-digital conversion driving circuit.

MC14433 requires a positive reference voltage U _REF to be provided externally. If the DVM wants to achieve full-scale output, take U _M = 2v. According to the main performance characteristics of MC1443 above: the relationship between the reference voltage U _REF and the range is 1:1, so this design The stability of U _REF = U _M = 2VU _REF has a great influence on the accuracy of A/D conversion and the measurement accuracy of the whole system, so a high-precision voltage source should be used.

The working principle of the digital tube display:

The analog-to-digital converter MC14433 performs dynamic scanning through bit selection signals DS1~DS4, and the decoder CD4511 digitally realizes the dynamic scanning display of four-digit LED light-emitting digital tubes with the conversion result of the analog-to-digital converter MC14433. Bit selection signals DS1-DS4 output multiplex modulation strobe pulse signals. When the DS strobe pulse is high level, it means that the corresponding digit is strobed, and the data of this bit is output at the Q0~Q3 terminals at this time. The timing relationship between the bit selection signal DS and the conversion cycle end flag EOC is that after the conversion cycle end flag EOC pulse ends, DS1 immediately outputs a positive pulse. The following are bit selection signal DS2, bit selection signal DS3 and bit selection signal DS4 in sequence. During the strobe period corresponding to DS2, DS3 and DS4, Q0~Q3 output BCD full-bit data, that is, output corresponding numbers 0~9 in 8421 code mode. During DS1 gating period, Q0 ~ Q3 output the half-digit 0 or 1 of the thousand bit and over-range, under-range and polarity flag signals. The conversion cycle end flag bit EOC provides the clock pulse signal of the flip-flop CD4013, the setting terminal S is grounded, and the D-terminal number of the flip-flop CD4013 is latched to the Q-terminal, because the D-terminal and connected, the overrange flag bit In case of output low level, the The terminal outputs high and low levels in turn, and then controls the blanking control terminal of the decoder CD4511 Make the nixie tube display flicker.

The utility model has the following beneficial technical effects:

It has the advantages of small size, reliable operation, simple circuit and convenient use;

Using advanced digital display technology, the measurement results are clear at a glance, which is more in line with people's reading habits;

It has the advantages of high accuracy, high resolution, and high cost performance.

The above is only a preferred embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, and any person familiar with the technical field can easily think of All changes or replacements should fall within the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (9)

1. A digital pressure measuring instrument circuit, characterized in that it comprises: The piezoresistive sensor outputs a voltage signal proportional to the pressure by sensing the external pressure; An operational amplifier circuit amplifies the voltage signal in phase; An analog-to-digital converter analyzes and processes the voltage signal output by the operational amplifier circuit, and then outputs a bit strobe signal and BCD code data. If an over-range situation occurs in the BCD code, an over-range signal is output; A decoder, converting the BCD code output by the analog-to-digital converter into seven-segment signals; A nixie tube display digitally displays the seven-segment signals output by the decoder; a driver, receiving the bit strobe signal, and driving the nixie tube display to display; The flip-flop receives the over-range signal output by the analog-to-digital converter, and controls the digital tube to flash and display through the decoder in a data latch mode. 2. The digital pressure measuring instrument circuit according to claim 1, wherein the operational amplifier circuit comprises an operational amplifier, a tenth potentiometer, an eleventh resistor and a twelfth resistor; The eleventh resistor and the tenth potentiometer are connected in series between the negative phase input terminal of the operational amplifier and the output terminal of the operational amplifier, and the negative phase input terminal of the operational amplifier is electrically connected to the tenth potentiometer. Two resistors are connected to the negative voltage output terminal of the piezoresistive sensor, and the non-inverting input terminal of the operational amplifier is connected to the positive voltage output terminal of the piezoresistive sensor. 3. The digital pressure measuring instrument circuit according to claim 2, characterized in that: the model of the operational amplifier is ICL7650. 4. The digital pressure measuring instrument circuit according to claim 1, characterized in that: the clock pulse input port of the flip-flop is connected to the conversion cycle end flag bit output end of the analog-to-digital converter, and the flip-flop's The data input port and the inverse code output end of the flip-flop are connected to the blanking control end of the decoder, the reset end of the flip-flop is connected to the over-range flag bit end of the analog-to-digital converter, and the The set end of the flip-flop is grounded. 5. The digital pressure measuring instrument circuit according to claim 4, characterized in that: the model of the trigger is CD4013. 6. The digital pressure measuring instrument circuit according to claim 1, characterized in that: the input end of the driver is connected to the bit strobe signal end of the analog-to-digital converter, and the output end of the driver is connected to the digital tube display common cathode terminal connection. 7. The digital pressure measuring instrument circuit according to claim 6, characterized in that: the model of the driver is MC1413. 8. The digital pressure measuring instrument circuit according to claim 1, characterized in that, the measuring instrument circuit further comprises a reading hold circuit, wherein, The reading holding circuit includes a twenty-second resistor and a switch; The conversion end flag output terminal of the analog-to-digital converter is electrically connected to the twenty-second resistor to the real-time output control terminal of the analog-to-digital converter, and the real-time output control terminal is electrically connected to the switch to the analog-to-digital converter. Negative Supply Port of Converter. 9. The digital pressure measuring instrument circuit according to claim 1, wherein the measuring instrument circuit further comprises a high-frequency filter circuit, wherein, The high-frequency filter circuit includes a twenty-first resistor and a twenty-first capacitor, the twenty-first capacitor is connected between the voltage input terminal of the analog-to-digital converter and the analog ground of the analog-to-digital converter, The voltage input terminal is connected to the twenty-first resistor to the output terminal of the operational amplifier, and the analog ground is grounded.