CN207937545U - A kind of blown fuse suggestion device of digital multimeter - Google Patents

Abstract

The utility model is related to a kind of blown fuse suggestion devices of digital multimeter, including current measurement circuit and programmable digital multimeter chip；The current measurement circuit includes testing current anode, testing current negative terminal and fuse, and described fuse one end is connect through pull-up resistor R1 with power supply and testing current anode, and the sampled resistance R0 of the other end is connect with signal ground and testing current negative terminal；The programmable digital multimeter chip includes the MCU and analog switch array module being connect with the MCU, A/D modules and LCD drive modules；The sample resistance R0 is connect through input resistance R3 with the analog switch array module with the junction of the fuse, and the fuse is connect through input resistance R2 with the analog switch array module with the junction of pull-up resistor R1；The analog switch array module output end connects the A/D modules；The LCD drive modules are connect with a LCD display.

Description

A kind of blown fuse suggestion device of digital multimeter

Technical field

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

Background technology

It is well known that the current measurement function of current digital multimeter in the market generally uses fuse（Also known as Fuse）As overcurrent protection, when electric current is more than that it provides parameter value, its own fusing is to make circuit disconnect, to prevent Measuring circuit damage is caused because maloperation or electric current are excessive, important devices the serious consequences such as burns in control device.Work as guarantor When the fusing of dangerous silk, current gear cannot measure, and need replacing the current measurement function that digital multimeter could be used after fuse, but Many users do not know such case, it is believed that are that multimeter has damaged, cannot be used continuously, result in waste of resources.

User can not be directly displayed or reminded when existing digital multimeter blown fuse, it is often necessary to user or dimension Repair personnel and detected using professional tool and judge equipment cannot work whether be caused by blown fuse, or even accidentally with There are other failures to deactivate or send to repair, cause unnecessary waste to be equipment under test.

Application No. is a kind of utility model patent " blown fuse warning device " of " 201220244434.2 " application is right Problem above is solved, but the prior art in digital multimeter with when have the following disadvantages：

1. since digital multimeter generally uses battery powered, working power voltage smaller（Usually 3V）, examine simultaneously Consider the comparative level 0.5V+ after operating dynamic range R3, R4 partial pressure of comparator（About 1.5V）.But there is this in fuse The contact resistance of body resistance and fuse holder finds that measurement high current is big because of fuse pressure drop sometimes in practical applications, It is more than comparison voltage to cause Vc, and instrument erroneous judgement is made to generate alarm, and the measurement for influencing instrument uses；

2. if input reverse current（Current direction is opposite with diagram）, Vc voltages are negative value, that is, blow a fuse ratio It is also low level compared with device output, can not alarms；

3. it is a warning circuit, needs to increase digital versatile watch circuit, could play a role in multimeter, Circuit is complicated, of high cost.

In conclusion whether the fuse that the prior art can not only access device in booting tested loop state melts It is disconnected to be judged, and it is very low to the blown fuse status monitoring correctness during use behind the tested circuit of access, it drops significantly Low the practicality.

Utility model content

In order to solve above-mentioned problems of the prior art, the utility model provides, and the utility model provides a kind of number The blown fuse suggestion device of word multimeter is measured back by monitoring current simultaneously using programmable digital multimeter application-specific integrated circuit Whether road and digital multimeter input terminal voltage are fused and are alarmed judging fuse by its internal MCU, solve above-mentioned technology Defect and simplify circuit.

The technical solution of the utility model is as follows：

A kind of blown fuse suggestion device of digital multimeter, including current measurement circuit and programmable digital multimeter Chip；The current measurement circuit includes testing current anode, testing current negative terminal and fuse, and described fuse one end is through upper Pull-up resistor R1 is connect with power supply and testing current anode, and the sampled resistance R0 of the other end connects with signal ground and testing current negative terminal It connects；The programmable digital multimeter chip include MCU and the analog switch array module being connect with the MCU, A/D modules and LCD drive modules；The junction of the sample resistance R0 and the fuse is through input resistance R3 and the analog switch array Module connects to it and exports electric signal, and the junction of the fuse and pull-up resistor R1 is opened through input resistance R2 and the simulation Array module is closed to connect to its output electric signal；It is defeated to its that the analog switch array module output end connects the A/D modules Go out analog signal, the output end of the A/D modules connects the MCU to its output digit signals；The LCD drive modules and one LCD display connects, and the LCD drive modules receive the electric signal that the MCU is sent out and drive the LCD display.

Further, further include a buzzer, connect with the MCU and receive its electric signal sent out.

Further, further include a function setting module, connect with the MCU, and be circumscribed with functional switch；The work( It can switch and electric signal is sent to the MCU by the function setting module.

The utility model has the advantages that：

1, the blown fuse suggestion device of a kind of digital multimeter of the utility model, it is special using programmable digital multimeter With IC simultaneously by monitoring current measuring loop and digital multimeter input terminal voltage, fuse is judged by its internal MCU Whether fuse and alarm, can be not only monitored to whether digital multimeter fuse fuses in booting, it can also be to using Blown fuse is monitored in the process, is reached and is carried out overall process monitoring, alarm, side to digital multimeter inside fuse Just user；

2, the blown fuse suggestion device of a kind of digital multimeter of the utility model solves and measures high current sometimes Because fuse pressure drop is big, it is more than comparison voltage to cause Vc, and instrument erroneous judgement is made to generate alarm；

3, fuse alarm is integrated by processing in programmable digital multimeter chip by the utility model, by may be programmed Digital multimeter chip is completed, and circuit is simple, reliability is high, at low cost.

Description of the drawings

Fig. 1 is the utility model principle figure.

Reference numeral is expressed as in figure：

11, testing current anode；12, testing current negative terminal；13, fuse；2, programmable digital multimeter chip；21、 MCU；22, analog switch array module；23, A/D modules；24, LCD drive modules；3, LCD display；4, buzzer；50, work( It can setup module；51, functional switch.

Specific implementation mode

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

Referring to Fig. 1, a kind of blown fuse suggestion device of digital multimeter, including current measurement circuit and programmable number Word multimeter chip 2；The current measurement circuit includes testing current anode 11, testing current negative terminal 12 and fuse 13, institute It states 13 one end of fuse to connect with power supply and testing current anode 11 through pull-up resistor R1, the sampled resistance R0 of the other end and signal Ground and testing current negative terminal 12 connect；The programmable digital multimeter chip 2 includes MCU21 and is connect with the MCU21 Analog switch array module 22, A/D modules 23 and LCD drive modules 24；The company of the sample resistance R0 and the fuse 13 The place of connecing connect to it with the analog switch array module 22 through input resistance R3 and exports electric signal, the fuse 13 and pull-up The junction of resistance R1 connect to it with the analog switch array module 22 through input resistance R2 and exports electric signal；The simulation 22 output end of switch array module connects the A/D modules 23 and exports analog signal to it, and the output end of the A/D modules 23 connects The MCU21 is met to its output digit signals；The LCD drive modules 24 are connect with a LCD display 3, and the LCD drives mould Block 24 receives the electric signal that the MCU21 is sent out and drives the LCD display 3.

Further, further include a buzzer 4, connect with the MCU21 and receive its electric signal sent out, buzzer 4 As warning device.

Further, further include a function setting module 50, connect with the MCU21, and be circumscribed with functional switch 51； The functional switch 51 sends electric signal by the function setting module 50 to the MCU21；It is inputted by functional switch 51 To the function setting module 50, MCU21 is arranged multimeter and is in the functions such as measurement voltage, resistance or electric current signal；MCU21 is controlled Make the analog switch array module 22 according to function by the input of multimeter connect into measure function required by circuit.

The operation principle of the utility model is as follows：

Each resistance selects R1, R2, R3>>R0+Rf (Rf is the resistance of fuse 13 itself)；When measuring electric current, electricity Stream Ii, it is inputted by testing current anode 11, circuit-under-test, electricity is returned through fuse 13, sample resistance R0, testing current negative terminal 12 The size for the pressure drop Vi reflection electric currents Ii that stream Ii is formed on sample resistance R0, Vi is through input resistance R3 by programmable digital general-purpose The analog switch array module 22 of watch core piece 2 inputs, and MCU21 is inputed to after being converted into digital signal by A/D modules 23, MCU21 drives LCD display 3 to directly display current value by LCD drive modules 24.

When instrument input terminal open circuit or fuse 13 fuse, sample resistance R0 no currents flow through, Vi=0, LCD display 3 Show that current value is 0；

So as Vi ≠ 0, it is normal to show that sample resistance R0 has electric current, fuse 13, solves measurement high current Sometimes because 13 pressure drop of fuse is big, it is more than comparison voltage to cause Vc, and instrument erroneous judgement is made to generate alarm；

As Vi=0, start fuse monitoring program；（It is anti-interference to increase, and prevent zero of A/D converter in IC Point tolerance, the absolute value that Vi is arranged in actual track start fuse monitoring program when being less than the 1% of range）；From fuse 13 with it is upper Read the numerical value of voltage Vc in the junction of pull-up resistor R1；By Vc numerical value input programmable digital multimeter chip 2, through A/D modules It is sent into MCU21 after 23 conversions；In the case that testing current end is without external be tested, if fuse 13 fuses, Vc=V+；If by In digital multimeter, fuse 13 fuses in testing current course, and pull-up resistor R1 resistance values are bigger, test testing current end There is connection to be tested under loop case, Vc is approximately equal to the open-circuit voltage in tested circuit, is Vo maximum voltage values under normal conditions at this time Several times more than, it is possible to Vc absolute value data │ Vc │ are set>0.5V+ just illustrates that (Vi is actually arranged in the fusing of fuse 13 Absolute value be less than range 1% when start fuse monitoring program, in the case that fuse 13 without fuse, the electricity of 1% range It is also very small to flow the voltage formed on fuse 13<<0.5V+ will not cause to judge by accident).

As described above, the fusing of fuse 13 is judged by Vc absolute value datas, it is avoided that application No. is The utility model patent of " 201220244434.2 " input reverse current, Vc voltages be negative value, comparator export low level and The defect that can not be alarmed.

After MCU21 judges fuse 13 for fusing, show that " FUSE " is prompted using seven sections of strokes of LCD, buzzer 4 is sent out Audible alarm prompts user to replace the fuse 13 being blown, to ensure current instruments or control electronic circuit Normal use.

The utility model influences can be ignored on the measurement accuracy of measuring instrumentss, is described as follows：To measuring and controlling essence The influence of degree, on sample resistance R0 voltage U0 be measure needed for voltage, increased R1 pull-up resistors, R2 current limliting buffer resistances pair The influence situation of U0：

The electric current of the sampled resistance R0 of V+ power flows is IV+=V ÷（R0 + R1）, in order not to shadow when usual current measurement Circuit-under-test is rung, the sample resistance R0 for measuring electric current is low resistance, and R1 pull-up resistor values are larger, to flow through pull-up Influence of the electric current to sampling of resistance R1, sample resistance R04 control within the scope of required precision.

For example it is usually 0.01 Ω to measure the sample resistance of 10A electric currents in multimeter, if the utility model circuit is added, If V+=3V, R1=2M Ω, IV+=3 ÷（0.01+2000000）The μ A of=1.5 × 10-6A=1.5, this electric current is for measuring 10A The electric current of range influences only to be less than ten a ten thousandths, and for general multimeter, 10A measurement accuracy is 1% or more, institute It is negligible with this error；Similarly, if R2>>When R0, R2 errors caused by the shunting of input current are also that can ignore 's.

The utility model programmable digital multimeter chip 2 is preferably programmable automatic range digital multimeter special chip SD7890 series, FS98O24 series.

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 (3)

1. a kind of blown fuse suggestion device of digital multimeter, including current measurement circuit and programmable digital general-purpose watch core Piece（2）；The current measurement circuit includes testing current anode（11）, testing current negative terminal（12）And fuse（13）, described Fuse（13）One end is through pull-up resistor R1 and power supply and testing current anode（11）Connection, the sampled resistance R0 of the other end and letter Number ground and testing current negative terminal（12）Connection；It is characterized in that：The programmable digital multimeter chip（2）Including MCU（21） With with the MCU（21）The analog switch array module of connection（22）, A/D modules（23）With LCD drive modules（24）；It is described to take Sample resistance R0 and the fuse（13）Junction through input resistance R3 and the analog switch array module（22）Connect to It exports electric signal, the fuse（13）Junction with pull-up resistor R1 is through input resistance R2 and the analog switch array Module（22）It connects to it and exports electric signal；The analog switch array module（22）Output end connects the A/D modules（23） Analog signal, the A/D modules are exported to it（23）Output end connect the MCU（21）To its output digit signals；It is described LCD drive modules（24）With a LCD display（3）Connection, the LCD drive modules（24）Receive the MCU（21）It sends out Electric signal simultaneously drives the LCD display（3）.

2. a kind of blown fuse suggestion device of digital multimeter according to claim 1, it is characterised in that：Further include One buzzer（4）, with the MCU（21）Connection receives its electric signal sent out.

3. a kind of blown fuse suggestion device of digital multimeter according to claim 1, it is characterised in that：Further include One function setting module（50）, with the MCU（21）Connection, and it is circumscribed with functional switch（51）；The functional switch（51） Pass through the function setting module（50）To the MCU（21）Send electric signal.