CN208000335U - A kind of digital multimeter - Google Patents

Abstract

The utility model is related to a kind of digital multimeter, including display screen, display drive circuit, MCU circuits, digital versatile watch circuit, voltage conversion and observation circuit and battery unit, it includes operating voltage Vdd terminal and dividing point ADC0 that voltage, which is converted with the output end of observation circuit, display screen, display drive circuit, MCU circuits and digital versatile watch circuit are sequentially connected with, and voltage conversion is separately connected the battery unit, MCU circuits and digital versatile watch circuit with observation circuit.The utility model has the advantage of:The utility model provides a kind of digital multimeter reminded with battery low-electricity quantity and can protect equipment itself; it is high that it samples accuracy; when the low digital multimeter of battery capacity can not provide accurate measurements; digital multimeter can be avoided impaired; and can make gauger that can not obtain there are large error or miss the measurement data surveyed completely, the danger that erroneous judgement is made to measured signal so as to avoid gauger or is injured.

Description

A kind of digital multimeter

Technical field

The utility model belongs to electronic measuring technology field, and in particular to a kind of digital multimeter.

Background technology

Existing digital multimeter is generally driven by display screen, display drive circuit, coding display circuit or MUC digital displays Circuit, digital versatile watch circuit, battery composition.The display driver circuit connection coding display circuit or MUC digital displays driving electricity Road;The coding display circuit or MUC digital display driving circuits connect digital versatile watch circuit;The battery connects digital multimeter Circuit and coding display circuit or MUC digital display driving circuits.When digital multimeter is tested, by measuring signal input number ten thousand With watch circuit, by digital multimeter circuit transformations at digital quantity, then will be surveyed by coding display circuit or MUC digital displays driving circuit Amount result is shown.However, in practical measurement process, when the cell voltage of digital multimeter declines to a certain extent, number Word multimeter can measure but will produce large error or accidentally survey completely, and gauger is caused to make erroneous judgement to measured signal, for example, In voltage measurement function, it is possible to will be considered that test line voltage is not powered, to make gauger come to harm, or survey Amount person is that foundation continues to measure other parameters with accidentally measured data, and digital multimeter may be caused impaired.Therefore, the utility model carries Go out a kind of digital multimeter, digital multimeter can be precisely controlled according to current voltage value, protect instrument and makes alarm prompt, Ensure gauger's personal safety.

The cell-monitoring circuit of the prior art, using divider resistance, analog-digital converter, processor and alarm realize, It when acquiring cell voltage, needs to open processor and analog-digital converter, directly be supplied from battery to processor and analog-digital converter Electricity, then digital quantity is converted battery voltage to by analog-digital converter, by processor according to the output of analog-digital converter to periphery Equipment is controlled.Since the electric current generated on processor and analog-digital converter can to generate pressure drop on battery, to influence The accuracy that the voltage acquisition and electricity of battery judge, thus existing technical solution can not solve the utility model proposes skill Art problem.

Publication No. CN106546920A, publication date are the utility model patent of 2017.3.29"Cell-monitoring circuit and it is System", it discloses a kind of cell-monitoring circuits, are divided to cell voltage by divider resistance, then comparator are used to use In the voltage for obtaining divider resistance, the input terminal of comparator connect with divider resistance, so use digital logic module with it is described The output end of comparator connects, the electricity for obtaining battery according to the output of comparator.The technical solution using comparator and The mode that digital logic module is combined obtains current battery charge, but due to its output valve, i.e. current battery charge, only An only single signal can only simply control peripheral equipment, such as:Control switch, control warning circuit is opened, single One output signal can not solve the utility model proposes the technical issues of --- prevent multimeter damage and control number ten thousand Alarm prompt is made with digital versatile watch circuit intrinsic inside table.

Utility model content

In order to solve the above-mentioned technical problem, the utility model provides a kind of digital multimeter, can monitor cell voltage, When battery is in low-pressure state, make gauger that can not obtain there are large error or miss the measurement data surveyed completely, and also Alarm prompt can be further made, the danger that erroneous judgement is made to measured signal so as to avoid gauger or is injured.

The technical solution of the utility model is as follows:

A kind of digital multimeter, including display screen, display drive circuit, digital versatile watch circuit and battery unit, The digital multimeter further includes MCU circuits, voltage conversion and observation circuit, the output end of the voltage conversion and observation circuit Including operating voltage Vdd terminal and dividing point ADC0, the display screen, display drive circuit, MCU circuits and digital multimeter Circuit is sequentially connected with, and the battery unit connects the voltage conversion and observation circuit, the MCU circuits and digital multimeter electricity The operating voltage Vdd terminal of the voltage conversion and observation circuit is accessed on road, and the MCU circuits are also connected with the voltage conversion and prison The dividing point ADC0 of slowdown monitoring circuit.

More preferably, voltage conversion and observation circuit include switch element, the first filter unit, voltage conversion unit, Second filter unit, third filter unit and partial pressure unit, the switch element, voltage conversion unit are series at battery unit Anode and cathode between, first filter unit is parallel to the input terminal and battery unit cathode of the voltage conversion unit Between, second filter unit is parallel between the output end of the voltage conversion unit and battery unit cathode, described point Pressure unit is series between the anode and cathode of the battery unit, and the third filter unit is parallel to the partial pressure unit Between dividing point ADC0 and battery unit cathode;Second filtering unit filters are passed through in the output of the voltage conversion unit Afterwards, the operating voltage Vdd terminal is provided, the Vdd terminal of the voltage conversion unit connects the digital versatile watch circuit and MCU electricity Road provides operating voltage for the digital versatile watch circuit and MCU circuits, and the dividing point ADC0 accesses the MCU circuits.

More preferably, the battery unit is a battery BAT1, and the switch element is diode D1, and first filtering is single Member includes capacitance C2 parallel with one another and capacitance C3, and the voltage conversion unit is voltage converter ic U4, and described second Filter unit includes capacitance C4 and capacitance C5 parallel with one another, and the third filter unit is capacitance C1, and the partial pressure unit is The resistance R5 and resistance R6 being serially connected;The anode of the battery BAT1 connects the anode of the diode D1, the diode The input terminal Vin, the capacitance C2 and C3 that the cathode of D1 connects the voltage converter ic U4 are parallel to the voltage turn It changes between the input terminal Vin of integrated circuit U4 and battery BAT1 cathode, the capacitance C4 and C5 is parallel to the voltage Transform Sets At between the output end vo ut and battery BAT1 cathode of circuit U 4, the resistance R5 and R6 is connected in series to the positive and negative of battery BAT1 Between pole, over resistor r 6, the capacitance C1 filters the dividing point ADC0 of resistance R5 and resistance R6 for the capacitance C1 parallel connections Wave, the dividing point ADC0 access the MCU circuits, the output of the voltage converter ic U4 by the capacitance C4 and The operating voltage Vdd terminal is provided after C5 filtering, the operating voltage Vdd terminal connects the digital versatile watch circuit and MCU electricity Road provides operating voltage for the digital versatile watch circuit and MCU circuits.

More preferably, the MCU circuits are microcontroller U1, and the display drive circuit is display driver chip U2, described Digital versatile watch circuit is digital multimeter integrated circuit U3;

Controlling switch CS, WR and data transmission pin DATA of the display driver chip U2 is connected respectively microcontroller I/O mouth PC5, PC6, PC7 of U1, when the voltage of battery unit is monitored drops to threshold value, microcontroller U1 passes through I/O mouthfuls described PC5, PC6, PC7 control the display driver chip U2, and using display screen prompting gauger, alerting pattern includes:1, it shows Screen shows bell character, does not show number;2, the display and extinguishing of the character regularity on display screen, realization screen flicker, 3, Display screen extinguishes, and closes display;

Controlling switch NCS, ALE, NWR, NRD and data transmission pin AD0 of the digital multimeter integrated circuit U3, AD1, AD2, AD3 are connected respectively I/O mouth PB0~PB7 of microcontroller U1, drop to threshold when the voltage of battery unit is monitored When value, microcontroller U1 controls the data transmission and net of the digital multimeter integrated circuit U3 by the I/O mouthfuls of PB0~PB7 Network access is arranged, and so that network path is arranged to safest measurement pattern and/or is closed corresponding input signal, with maximum limit The safety of degree protection instrument and gauger;

The power end of the microcontroller U1 and the power end of digital multimeter integrated circuit U3 are all connected with the voltage conversion With the operating voltage Vdd terminal of observation circuit, the I/O mouth PA6 connections divider node ADC0 of the microcontroller U1.

More preferably, the digital multimeter further includes a warning circuit, and the warning circuit is arbitrary in following circuits A kind of or following circuits arbitrary combination:Sound alarm circuit, indicator light warning circuit and vibrations warning circuit;The alarm Circuit accesses the MCU circuits.

More preferably, the sound alarm circuit includes resistance R1, resistance R2, triode Q1 and buzzer BUZ1, the electricity The MCU circuits are accessed in the one end for hindering R2, and the other end connects the poles B of the resistance R1 and triode Q1, and the resistance R1's is another The operating voltage Vdd terminal of the voltage conversion and observation circuit, the triode Q1 are accessed in one end and the poles E of the triode Q1 The poles C connect the buzzer BUZ1.

More preferably, the indicator light warning circuit includes resistance R3, resistance R4, Light-emitting diode LED 1 and triode The MCU circuits are accessed in one end of Q2, the resistance R4, and the other end connects the poles B of the triode Q2, the triode Q2's The poles C connect the cathode of the Light-emitting diode LED 1, and the anode of the Light-emitting diode LED 1 connects the resistance R3, the electricity The other end for hindering R3 accesses the voltage conversion and observation circuit operating voltage Vdd terminal.

More preferably, the vibrations warning circuit includes resistance R8, resistance R7, triode Q3 and vibration motor MG1, described The MCU circuits are accessed in one end of resistance R8, and the other end connects the poles B of the resistance R7 and triode Q3, the resistance R7's The voltage conversion and observation circuit operating voltage Vdd terminal, the triode Q3 are accessed in the poles E of the other end and the triode Q3 The poles C connect the vibration motor MG1.

The utility model has the advantages that:

1, the utility model provides stable work for the chip in digital multimeter by voltage conversion and observation circuit Voltage avoids current loss from generating interference to the monitoring of cell voltage, improves sampling accuracy;

2, the utility model carries out analog-to-digital conversion by MCU circuits to dividing point voltage, improves conversion accuracy, and pass through MCU circuit control digital multimeter integrated circuits, set digital versatile watch circuit to safest measurement pattern and/or closing Corresponding input signal, to protect the safety of instrument and gauger to greatest extent;Electricity is driven by MCU circuit control display screens Road makes display screen make alarm prompt;

3, the utility model further enhances low battery warning effect also by warning circuit, it is ensured that gauger can connect It receives digital multimeter and provides low battery feedback;

Therefore, the utility model provides a kind of number ten thousand reminded with battery low-electricity quantity and can protect equipment itself With table, sampling accuracy is high, when the low digital multimeter of battery capacity can not provide accurate measurements, can avoid number ten thousand It is impaired with table, and can make gauger that can not obtain there are large error or miss the measurement data surveyed completely, so as to avoid survey The danger that amount person makes erroneous judgement to measured signal or injured.Meanwhile the utility model realizes battery with simple circuit structure Electric power detection reduces cost.

Description of the drawings

Fig. 1 is a kind of structural schematic diagram of digital multimeter of the utility model;

Fig. 2 is voltage conversion and the observation circuit schematic diagram of a kind of digital multimeter of the utility model;

Fig. 3 is a kind of circuit diagram of digital multimeter of the utility model;

Fig. 4 is a kind of digital multimeter sound alarm circuit diagram of the utility model;

Fig. 5 is a kind of digital multimeter indicator light warning circuit schematic diagram of the utility model;

Fig. 6 is that a kind of digital multimeter of the utility model shakes warning circuit schematic diagram.

Reference numeral is expressed as in figure:

1- display screens, 2- display drive circuits, 3-MCU circuits, 4- digital versatiles watch circuit, the conversion of 5- voltages and monitoring Circuit, 6- battery units, 7- warning circuits.

Specific implementation mode

The utility model is described in detail in the following with reference to the drawings and specific embodiments.

Embodiment one

Referring to Fig. 1, a kind of digital multimeter, including display screen 1, display drive circuit 2, MCU circuits 3, number ten thousand With watch circuit 4, voltage conversion and observation circuit 5 and battery unit 6, the output end packet of the voltage conversion and observation circuit 5 Include operating voltage Vdd terminal and dividing point ADC0, the display screen 1, display drive circuit 2, MCU circuits 3 and digital versatile Watch circuit 4 is sequentially connected with, and the battery unit 6 connects the voltage conversion and observation circuit 5, the MCU circuits 3 and number ten thousand The operating voltage Vdd terminal of the voltage conversion and observation circuit 5 is accessed with watch circuit 4, the MCU circuits 3 are also connected with the electricity The dividing point ADC0 of pressure conversion and observation circuit 5.

Its operation principle is:It is obtained in digital multimeter needed for each modular circuit with observation circuit 5 by voltage conversion Operating voltage Vdd and dividing point ADC0(That is voltage monitoring point)Voltage.MCU circuits 3 are by the dividing point ADC0's received Voltage value is handled, is analyzed, and realizes the electric quantity monitoring to battery unit 6, when the electricity of battery unit 6 is monitored setting for decline When fixed value, by 3 outputting multiplex signals control display screen driving circuit 2 of MCU circuits and digital multimeter circuit 4, specifically, 1, It sets digital versatile watch circuit 4 to safest measurement pattern by MCU circuits 3 and/or closes corresponding input signal, with The safety of instrument and gauger is protected to greatest extent;2, by 3 control display screen driving circuit 2 of MCU circuits, display screen 1 is made to do Go out alarm prompt, mode includes:1,1 display alarm character of display screen, does not show number, for example, display screen utilizes liquid crystal display "" display of field composition "" bell character;2, screen is realized in the display and extinguishing of the character regularity on display screen 1 Curtain flicker, 3, display screen extinguish, close display;Above-mentioned three kinds of modes can arbitrarily select one kind, can also arbitrarily combine.

Embodiment two

In the present embodiment, to the voltage conversion specific embodiment is given with observation circuit 5:

The voltage conversion includes switch element, the first filter unit, voltage conversion unit, the second filter with observation circuit 5 Wave unit, third filter unit and partial pressure unit, the switch element, voltage conversion unit are being series at battery unit 6 just Between pole and cathode, first filter unit be parallel to the voltage conversion unit input terminal and 6 cathode of battery unit it Between, second filter unit is parallel between 6 cathode of output end and battery unit of the voltage conversion unit, the partial pressure Unit is series between the anode and cathode of the battery unit 6, and the third filter unit is parallel to the partial pressure unit Between 6 cathode of dividing point ADC0 and battery unit;Second filtering unit filters are passed through in the output of the voltage conversion unit Afterwards, the operating voltage Vdd terminal is provided, the Vdd terminal of the voltage conversion unit connects the digital versatile watch circuit 4 and MCU Circuit 3 provides operating voltage for the digital versatile watch circuit 4 and MCU circuits 3, and the dividing point ADC0 accesses the MCU electricity Road 3.

The switch element is for preventing battery polar reverse-connection damage digital multimeter;First filter unit is to described The input voltage of voltage conversion unit is filtered, and reduces input nonlinearities;Second filter unit converts the voltage single The output of member is filtered, and reduces output interference, and stable operating voltage is provided for MCU circuits 3 and digital multimeter circuit 4; The third filter unit is to dividing point ADC0(That is voltage monitoring point)Voltage be filtered, it is ensured that the samplings of MCU circuits 3 is accurate Really, and then ensure that the output precise control that MCU circuits 3 are made is errorless.

Embodiment two is expanded on further with reference to a specific implementation circuit:

Referring to Fig. 2, the battery unit 6 is a battery BAT1, the switch element is diode D1, first filter Wave unit includes capacitance C2 and capacitance C3 parallel with one another, and the voltage conversion unit is voltage converter ic U4, described Second filter unit includes capacitance C4 and capacitance C5 parallel with one another, and the third filter unit is capacitance C1, and the partial pressure is singly Member is the resistance R5 being serially connected and resistance R6;The anode of the battery BAT1 connects the anode of the diode D1, and described two The input terminal Vin, the capacitance C2 and C3 that the cathode of pole pipe D1 connects the voltage converter ic U4 are parallel to the electricity Between the input terminal Vin and battery BAT1 cathode that press converter ic U4, the capacitance C4 and C5 is parallel to the voltage and turns It changes between the output end vo ut of integrated circuit U4 and battery BAT1 cathode, the resistance R5 and R6 is connected in series to the anode of battery BAT1 Between cathode, the capacitance C1 parallel connections over resistor r 6, the capacitance C1 to the dividing point ADC0 of resistance R5 and resistance R6 into Row filtering, the dividing point ADC0 access the MCU circuits 3, and the electricity is passed through in the output of the voltage converter ic U4 The operating voltage Vdd terminal is provided after holding C4 and C5 filtering, the operating voltage Vdd terminal connects the digital versatile watch circuit 4 With MCU circuits 3, operating voltage is provided for the digital versatile watch circuit 4 and MCU circuits 3.

Embodiment three

The present embodiment three can be implemented in conjunction with the embodiments one or/and embodiment two, specific as follows:

Referring to Fig. 3, the MCU circuits 3 are microcontroller U1, the display drive circuit 2 is display driver chip U2, The digital versatile watch circuit 4 is digital multimeter integrated circuit U3;For example, the microcontroller U1 can select model STM8L052 chips, the display driver chip U2 can select GA1621 chips, and the digital multimeter integrated circuit U3 can To select FS9701 chips;

Controlling switch CS, WR and data transmission pin DATA of the display driver chip U2 is connected respectively microcontroller I/O mouth PC5, PC6, PC7 of U1, when the voltage of battery unit 6 is monitored drops to monitoring threshold, microcontroller U1 passes through described I/O mouthfuls of PC5, PC6, PC7 control the display driver chip U2, and using display screen prompting gauger, alerting pattern includes:1, 1 display alarm character of display screen, does not show number, for example, using liquid crystal display "" display of field composition "" alarm Character;2, the display and extinguishing of the character regularity on display screen 1, realize screen flicker, 3, display screen extinguish, close display. It should be noted that the output valve of I/O mouths PC5, PC6, PC7 of the microcontroller U1 are needed with display driver chip U2 data Handbook is foundation to the definition of controlling switch CS, WR and data transmission pin DATA, and those skilled in the art are refering to databook It can be realized, do not illustrate herein.

Controlling switch NCS, ALE, NWR, NRD and data transmission pin AD0 of the digital multimeter integrated circuit U3, AD1, AD2, AD3 are connected respectively I/O mouth PB0~PB7 of microcontroller U1, are dropped to when the voltage of battery unit 6 is monitored When monitoring threshold, the data that microcontroller U1 controls the digital multimeter integrated circuit U3 by the I/O mouthfuls of PB0~PB7 pass The setting of defeated and network path makes network path be arranged to safest measurement pattern and/or closes corresponding input signal, with The safety of instrument and gauger is protected to greatest extent;Specifically, monitoring threshold is dropped to when the voltage of battery unit 6 is monitored When, when digital multimeter is set as voltage, current measurement pattern, the network path of digital multimeter integrated circuit U3 is arranged to Maximum range measures shelves, reduces the partial pressure value of measuring signal to protect digital multimeter integrated circuit U3 internal conversion circuits;Number When word multimeter is set as resistance, capacitance, diode, temperature, frequency measurement pattern, the net of digital multimeter integrated circuit U3 Off-position is set in network access, forbids exporting test voltage signal and current signal, to protect external circuit-under-test, while The input of external signal is prohibited to protect digital multimeter integrated circuit U3 internal conversion circuits;

The power end of the microcontroller U1 and the power end of digital multimeter integrated circuit U3 are all connected with the voltage conversion With the operating voltage Vdd terminal of observation circuit 5, the I/O mouth PA6 connections divider node ADC0 of the microcontroller U1, described point Press the voltage value of node ADC0 by the analog-digital converter inside microcontroller U1 by the voltage transformation of dividing point ADC0 at digital quantity, The electric quantity monitoring to battery BAT1 is realized to digital quantity progress analyzing processing by microcontroller U1, it is further true by microcontroller U1 Protect the accuracy of the accuracy and output of conversion.

Example IV

Fig. 4 to fig. 6 is please referred to, the present embodiment four is compared with the distinguishing feature of embodiment one:The utility model is a kind of Digital multimeter further includes a warning circuit 7, and the warning circuit 7 is times of any one or following circuits in following circuits Meaning combination:Sound alarm circuit, indicator light warning circuit and vibrations warning circuit;The warning circuit 7 accesses the MCU electricity Road 3.The warning effect when warning circuit can further strengthen low battery prevents from having ignored low electricity because of the carelessness of gauger Amount warning, it is ensured that gauger can receive digital multimeter and provide low battery feedback.

One kind of sound alarm circuit, indicator light warning circuit and vibrations warning circuit is given individually below preferably Circuit implementations, but it is not limited to the circuit form provided in the present embodiment four.

Referring to Fig. 4, the sound alarm circuit includes resistance R1, resistance R2, triode Q1 and buzzer BUZ1, it is described The MCU circuits 3 are accessed in one end of resistance R2, and the other end connects the poles B of the resistance R1 and triode Q1, the resistance R1's The operating voltage Vdd terminal of the voltage conversion and observation circuit 5, three pole are accessed in the poles E of the other end and the triode Q1 The poles C of pipe Q1 connect the buzzer BUZ1.Specifically, the monolithic is accessed in one end of in conjunction with the embodiments three, the resistance R2 The I/O mouths PA0 of machine U1.

When the electricity of battery BAT1 drops to monitoring threshold, the I/O mouths PA0 of microcontroller U1 generates buzzer alert circuit Drive signal, buzzer BUZ1 send out the sound of rule to prompt gauger from the angle of the sense of hearing.

Referring to Fig. 5, the indicator light warning circuit includes resistance R3, resistance R4, Light-emitting diode LED 1 and three poles The MCU circuits 3 are accessed in one end of pipe Q2, the resistance R4, and the other end connects the poles B of the triode Q2, the triode The poles C of Q2 connect the cathode of the Light-emitting diode LED 1, and the anode of the Light-emitting diode LED 1 connects the resistance R3, institute The other end for stating resistance R3 accesses the voltage conversion and 5 operating voltage Vdd terminal of observation circuit.Specifically, in conjunction with the embodiments three, The I/O mouths PA7 of the microcontroller U1 is accessed in one end of the resistance R4.

When the electricity of battery BAT1 drops to monitoring threshold, the I/O mouths PA7 of microcontroller U1 generates indicator light warning circuit Drive signal, indicator light LED1 are regularly flickered to prompt gauger from the angle of vision.

Referring to Fig. 6, the vibrations warning circuit includes resistance R8, resistance R7, triode Q3 and vibration motor MG1, The MCU circuits 3 are accessed in one end of the resistance R8, and the other end connects the poles B of the resistance R7 and triode Q3, the resistance The poles E of the other end of R7 and the triode Q3 access voltage conversion and 5 operating voltage Vdd terminal of observation circuit, described three The poles C of pole pipe Q3 connect the vibration motor MG1.Specifically, the list is accessed in one end of in conjunction with the embodiments three, the resistance R8 The I/O mouths PF0 of piece machine U1.

When the electricity of battery BAT1 drops to monitoring threshold, the I/O mouths PF0 of microcontroller U1 generates vibrations warning circuit and drives Dynamic signal, vibration motor MG1 make the vibrations of rule to prompt gauger from the angle of tactile.

The above description is only the embodiments of the present invention, and it does not limit the scope of the patent of the present invention, every Equivalent structure or equivalent flow shift made based on the specification and figures of the utility model, is applied directly or indirectly in Other related technical areas are equally included in the patent within the scope of the utility model.

Claims (8)

1. a kind of digital multimeter, including display screen (1), display drive circuit (2), digital versatile watch circuit (4) and electricity Pool unit (6), it is characterised in that:The digital multimeter further includes MCU circuits (3) and voltage conversion and observation circuit (5), institute The output end for stating voltage conversion and observation circuit (5) includes operating voltage Vdd terminal and dividing point ADC0, and the display screen (1) shows Display screen driving circuit (2), MCU circuits (3) and digital versatile watch circuit (4) are sequentially connected with, and the battery unit (6) connects institute Voltage conversion and observation circuit (5) are stated, the MCU circuits (3) and digital multimeter circuit (4) access the voltage conversion and prison The operating voltage Vdd terminal of slowdown monitoring circuit (5), the MCU circuits (3) are also connected with the partial pressure of the voltage conversion and observation circuit (5) Point ADC0;

The voltage conversion and observation circuit (5) include a partial pressure unit and third filter unit, and the partial pressure unit is series at Between the anode and cathode of the battery unit (6), the third filter unit is parallel to the dividing point of the partial pressure unit Between ADC0 and battery unit (6) cathode;The dividing point ADC0 accesses the MCU circuits (3), specifically, the third filter Wave unit is capacitance C1, and the partial pressure unit is the resistance R5 being serially connected and resistance R6;The resistance R5 and R6 is connected in series to electricity Between the anode and cathode of pond BAT1, over resistor r 6, the capacitance C1 is to resistance R5's and resistance R6 for the capacitance C1 parallel connections Dividing point ADC0 is filtered, and the dividing point ADC0 accesses the MCU circuits (3).

2. a kind of digital multimeter according to claim 1, it is characterised in that:The voltage conversion and observation circuit (5) Further include switch element, the first filter unit, voltage conversion unit and the second filter unit, the switch element, voltage turn It changes unit to be series between the anode and cathode of battery unit (6), it is single that first filter unit is parallel to the voltage conversion Between the input terminal and battery unit (6) cathode of member, second filter unit is parallel to the output of the voltage conversion unit Between end and battery unit (6) cathode, the output of the voltage conversion unit provides after second filtering unit filters The Vdd terminal of the operating voltage Vdd terminal, the voltage conversion unit connects the digital versatile watch circuit (4) and MCU circuits (3), it is that the digital versatile watch circuit (4) and MCU circuits (3) provide operating voltage.

3. a kind of digital multimeter according to claim 2, it is characterised in that:The battery unit (6) is a battery BAT1, the switch element are diode D1, and first filter unit includes capacitance C2 parallel with one another and capacitance C3, described Voltage conversion unit is voltage converter ic U4, and second filter unit includes capacitance C4 and capacitance parallel with one another C5;The anode of the battery BAT1 connects the anode of the diode D1, and the cathode of the diode D1 connects the voltage and turns The input terminal Vin, the capacitance C2 and C3 for changing integrated circuit U4 are parallel to the input terminal Vin of the voltage converter ic U4 Between battery BAT1 cathode, the capacitance C4 and C5 is parallel to the output end vo ut and electricity of the voltage converter ic U4 Between the BAT1 cathode of pond, the output of the voltage converter ic U4 provides the work after the capacitance C4 and C5 filtering Make voltage Vdd terminal, the operating voltage Vdd terminal connects the digital versatile watch circuit (4) and MCU circuits (3), is the number General-purpose watch circuit (4) and MCU circuits (3) provide operating voltage.

4. a kind of digital multimeter according to claim 1, it is characterised in that:The MCU circuits 3 are microcontroller U1, institute It is display driver chip U2 to state display drive circuit (2), and the digital versatile watch circuit (4) is digital multimeter integrated circuit U3;

Controlling switch CS, WR and data transmission pin DATA of the display driver chip U2 is connected respectively microcontroller U1's I/O mouthfuls of PC5, PC6, PC7, when the voltage of battery unit (6) is monitored drops to threshold value, microcontroller U1 passes through I/O mouthfuls described PC5, PC6, PC7 control the display driver chip U2, and using display screen prompting gauger, alerting pattern includes:

One, display screen (1) display alarm character, does not show number;

Two, screen flicker is realized in the display and extinguishing of the character regularity on display screen (1);

Three, display screen (1) extinguishes, and closes display;

Controlling switch NCS, ALE, NWR, NRD and data transmission pin AD0, AD1 of the digital multimeter integrated circuit U3, AD2, AD3 are connected respectively I/O mouth PB0~PB7 of microcontroller U1, drop to threshold when the voltage of battery unit (6) is monitored When value, microcontroller U1 controls the data transmission and net of the digital multimeter integrated circuit U3 by the I/O mouthfuls of PB0~PB7 Network access is arranged, and so that network path is arranged to safest measurement pattern and/or is closed corresponding input signal, with maximum limit The safety of degree protection instrument and gauger;

The power end of the microcontroller U1 and the power end of digital multimeter integrated circuit U3 are all connected with the voltage conversion and prison The operating voltage Vdd terminal of slowdown monitoring circuit (5), the I/O mouth PA6 connections divider node ADC0 of the microcontroller U1.

5. a kind of digital multimeter according to claim 1, it is characterised in that:Further include a warning circuit (7), the announcement Alert circuit (7) is the arbitrary combination of any one or following circuits in following circuits:Sound alarm circuit, indicator light alarm electricity Road and vibrations warning circuit;The warning circuit (7) accesses the MCU circuits (3).

6. a kind of digital multimeter according to claim 5, it is characterised in that:The sound alarm circuit includes resistance One end access MCU circuits (3) of R1, resistance R2, triode Q1 and buzzer BUZ1, the resistance R2, other end connection The poles E of the poles B of the resistance R1 and triode Q1, the other end of the resistance R1 and the triode Q1 are accessed the voltage and are turned It changes and connects the buzzer BUZ1 with the operating voltage Vdd terminal of observation circuit (5), the poles C of the triode Q1.

7. a kind of digital multimeter according to claim 5, it is characterised in that:The indicator light warning circuit includes resistance One end access MCU circuits (3) of R3, resistance R4, Light-emitting diode LED 1 and triode Q2, the resistance R4 are another End connects the poles B of the triode Q2, and the poles C of the triode Q2 connect the cathode of the Light-emitting diode LED 1, the hair The anode of optical diode LED1 connects the resistance R3, and the other end of the resistance R3 accesses the voltage conversion and observation circuit (5) operating voltage Vdd terminal.

8. a kind of digital multimeter according to claim 5, it is characterised in that:The vibrations warning circuit includes resistance One end access MCU circuits (3) of R8, resistance R7, triode Q3 and vibration motor MG1, the resistance R8, the other end connect Connect the poles B of the resistance R7 and triode Q3, the poles the E access voltage of the other end of the resistance R7 and the triode Q3 The poles C of conversion and observation circuit (5) operating voltage Vdd terminal, the triode Q3 connect the vibration motor MG1.