CN209606499U - A kind of double impedance input multimeters - Google Patents

Abstract

The utility model relates to a kind of double impedances to input multimeter, including input terminal, gear switch switch, power supply circuit, double impedance measuring circuits, ADC converter, DSP digital processing unit and LCD display；The gear switch switch is for switching the range of multimeter measurement；The power supply circuit provides operating voltage for multimeter；The electric signal transmission that double impedance measuring circuits measure input terminal is to the ADC converter；The output end of the ADC converter is electrically connected with the input terminal of the DSP digital processing unit, and the electric signal of input is converted to digital signal and is delivered to the DSP digital processing unit；The output end of the DSP digital processing unit is electrically connected with the LCD display, and the DSP digital processing unit converts digital signals into the driving signal of the LCD display, and the LCD display is driven to show corresponding data.

Description

A kind of double impedance input multimeters

Technical field

The utility model relates to a kind of double impedances to input multimeter, be related to digital multimeter technical field.

Background technique

Digital multimeter voltage measurement has the higher feature of input impedance, is essentially all 10M Ω, and also some are measured manually The small table of journey gear shift is using 1M Ω, it means that when digital multimeter is placed in measured in circuit when, it is to circuit The influence that can be generated is minimum, this is for most of voltage measurements using required effect, however, some are to the interference of electromagnetic field Compare sensitive circuit, or also have in the measurements from apart from close electrified wire and being not powered on conducting wire, because conducting wire it Between there are distribution capacity, when being measured with the multimeter of high impedance, just have a false voltage and pass through distribution capacity It is coupled in measured instrument, to obtain a wrong reading, these false voltages can achieve sometimes " to be connect firmly The 80 ~ 85% of line " voltage will be consumed if do not come out them as false voltage identification in the investigation to fault Take additional time and efforts, if the low-impedance voltage measurement shelves that an input impedance only has 1K to tens K Ω are arranged, Low ESR It can make false loss of voltage, keep the reading of multimeter truer, can meet from fundamental voltage and test to sensitive electronic circuits The measurement of malfunction elimination needs, currently, the digital multimeter of commercial type, in addition to expensive individual product, consumer is It is difficult to buy the product with double impedance voltage measurements.

For digital multimeter as a kind of common electric instrument, being carried to outdoor or field work is common occurrence Feelings, during the work time when tester has found that the supplying cell electricity of instrument will be exhausted or exhausted, and not for more The battery changed, it may be said that be a kind of very intractable thing, many products are when supplying cell electricity ratio is lower, some test functions Power consumption it is smaller can also normal use, and the bigger such as antapex of some function power consumptions is bright, when buzzer alert, because of supplying cell Remaining electricity wretched insufficiency, can not normal use, all digital multimeter are without exception all using electricity currently on the market Pond electricity will exhaust just there is low-voltage prompt on LCD, inevitably makes troubles, realizes to the normal use of user It is a kind of to seem necessary to the power consumption of instrument supplying cell progress real-time monitoring itself.

Utility model content

In order to solve above-mentioned problems of the prior art, the utility model provides a kind of double impedance input multimeters, High input impedance circuit and low input impedance circuit are set, is switched by gear switch and is connect with ADC converter, solve existing skill The problem of only setting high input impedance is unable to satisfy multimeter measurement demand in art.

The technical solution of the utility model is as follows:

A kind of double impedance input multimeters, including input terminal, gear switch switch, power supply circuit, double impedance measurements electricity Road, ADC converter, DSP digital processing unit and LCD display；The gear switch switch is for switching multimeter measurement Range；The power supply circuit includes battery, provides operating voltage for multimeter；Double impedance measuring circuits include high input resistance Reactive circuit and low input impedance circuit, the input terminal of the high input impedance circuit are electrically connected with the input terminal, output end It is switched by gear switch and is electrically connected with the ADC converter, the input terminal and the input terminal of the low input impedance circuit Son electrical connection, output end are switched by gear switch and are electrically connected with the ADC converter, and double impedance measuring circuits will input The electric signal transmission of terminal measurement is to the ADC converter；The output end of the ADC converter and the DSP digital processing unit Input terminal electrical connection, the electric signal of input is converted into digital signal and is delivered to the DSP digital processing unit；The DSP number The output end of word processing device is electrically connected with the LCD display, and the DSP digital processing unit converts digital signals into described The driving signal of LCD display drives the LCD display to show corresponding data.

Further, the gear switch switch includes plural groups golden finger contact chip.

Further, the high input impedance circuit includes a high resistance measurement, described high resistance measurement one end and input Terminal electrical connection, the other end are electrically connected with the input terminal of the ADC converter；The low input impedance circuit includes a plurality of resistances Be worth different low resistance resistance, one end of each low resistance resistance is electrically connected with the input terminal, the other end respectively with Golden finger contact chip electrical connection described in each group on the gear switch switch, it is right after golden finger contact chip described in one group is connected The low resistance resistance answered is in parallel with the high resistance measurement.

Further, the power supply circuit includes a regulated power supply chip, and the input terminal of the regulated power supply chip passes through Golden finger contact chip described in one group is connect with the anode of the battery, ground terminal and the battery of the regulated power supply chip Cathode connection, the output end of the regulated power supply chip provide operating voltage for the electricity consumption device in multimeter.

It further, further include a battery flowmeter charge circle comprising divider resistance R4 and divider resistance R20, it is described The one end divider resistance R4 is connect with the input terminal of the regulated power supply chip, and one end of the other end and the divider resistance R20 connect It connects, the other end of the divider resistance R20 is connect with the ground terminal of the regulated power supply chip；The divider resistance R4 and partial pressure The node of resistance R20 connection is electrically connected with the input terminal of the ADC converter, transmits battery voltage signal to it, the ADC turns Parallel operation is delivered to the DSP digital processing unit after battery voltage signal is converted to digital signal, and the DSP digital processing unit drives It moves the LCD display and shows battery capacity.

Further, the ADC converter and the DSP digital processing unit integrate and a multimeter auto-shifted measurement core In piece IC1.

The utility model has the following beneficial effects:

1, a kind of double impedances of the present invention input multimeter, and high input impedance circuit and low input impedance circuit is arranged, passes through Gear switch switch is connect with ADC converter, and only setting high input impedance is unable to satisfy multimeter measurement in the prior art for solution The problem of demand.

2, a kind of double impedances of the present invention input multimeter, are provided with battery flowmeter charge circle, can monitor multimeter Battery capacity.

3, a kind of double impedances of the present invention input multimeters, wherein low input impedance circuit is provided with different low of multiple resistance values Valued resistor keeps measurement result more accurate to be adapted to the object under test of various different sizes.

Detailed description of the invention

Fig. 1 is the circuit block diagram of the utility model embodiment one；

Fig. 2 is the circuit diagram of the utility model embodiment one.

Appended drawing reference indicates in figure are as follows:

1, input terminal；2, gear switch switchs；3, power supply circuit；4, double impedance measuring circuits；41, high input impedance electricity Road；42, low input impedance circuit；5, ADC converter；6, DSP digital processing unit；7, LCD display；8, monitoring cell electricity quantity electricity Road.

Specific embodiment

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

Referring to Fig. 1 and Fig. 2, a kind of double impedances input multimeter, including input terminal 1, gear switch switch 2, power supply electricity Road 3, double impedance measuring circuits 4, ADC converter 5, DSP digital processing unit 6 and LCD display 7；The gear switch switch 2 For switching the range of multimeter measurement；The power supply circuit 3 includes battery, provides operating voltage for multimeter；Double resistances Anti- measuring circuit 4 includes high input impedance circuit 41 and low input impedance circuit 42, the input of the high input impedance circuit 41 End is electrically connected with the input terminal 1, and output end is electrically connected by gear switch switch 2 with the ADC converter 5, described low The input terminal of input impedance circuit 42 is electrically connected with the input terminal 1, and output end passes through gear switch switch 2 and the ADC Converter 5 is electrically connected, the electric signal transmission that double impedance measuring circuits 4 measure input terminal 1 to the ADC converter 5； The output end of the ADC converter 5 is electrically connected with the input terminal of the DSP digital processing unit 6, and the electric signal of input is converted to Digital signal is delivered to the DSP digital processing unit 6；7 electricity of the output end of the DSP digital processing unit 6 and the LCD display Connection, the DSP digital processing unit 6 convert digital signals into the driving signal of the LCD display 7, drive the LCD aobvious Display screen 7 shows corresponding data.

Further, the gear switch switch 2 includes plural groups golden finger contact chip；Referring specifically to Fig. 2, S1 in figure, S2, S3, S4, S5, S6, S7, S8, S9, S10 and S11 are each golden finger contact chip；In the present embodiment, the shelves of gear switch switch 2 Measurement when position includes AC/DC/BAT(high impedance combined-voltage and battery zero load) shelves, L (BAT/AC/DC) (low-power consumption battery And low input impedance voltage measurement) shelves, M (BAT) (medium power consumption battery) shelves, H (BAT) (high power consumption battery) shelves and OHM(resistance Measurement) shelves.

Further, the high input impedance circuit 41 includes that (high resistance measurement of the present embodiment is a high resistance measurement R25 in Fig. 2, R25 be 10M Ω precision resistance), described high resistance measurement one end is electrically connected with input terminal 1, the other end and The input terminal of the ADC converter 5 is electrically connected；The low input impedance circuit 42 includes the different low resistance electricity of a plurality of resistance values It hinders, in the present embodiment, low resistance resistance includes thermistor PTC1, PTC2 and PTC3, and the resistance value of PTC1 is 1K Ω, the resistance of PTC2 Value is 150 Ω, and the resistance value of PTC3 is 27 Ω；The one end PTC1 and the end INPUT of input terminal connect, the other end and metal contact chip S1 connection, metal contact chip S1 and metal contact chip S3 are one group, and the other end of metal contact chip S3 is grounded；One end of PTC3 with The end INPUT of input terminal connects, and the other end is connect with metal contact chip S10, and metal contact chip S10 is with metal contact chip S3 One group；One end of PTC2 is connected to the node that PTC3 is connect with metal contact chip S10, and the other end is connect with metal contact chip S2, Metal contact chip S2 and metal contact chip S3 is one group；When metal contact chip S1 and metal contact chip S3 is connected, double impedances are surveyed The equivalent circuit for measuring circuit 4 is that PTC1 is in parallel with resistance R25；When metal contact chip S1 and metal contact chip S10 is connected, double resistances The equivalent circuit of anti-measuring circuit 4 is that PTC3 is in parallel with resistance R25；When metal contact chip S1 and metal contact chip S2 is connected, The equivalent circuit of double impedance measuring circuits 4 is in parallel with resistance R25 again after PTC2 connects with PTC3.

Further, the power supply circuit 3 includes a regulated power supply chip (U2 in Fig. 2), the regulated power supply chip Input terminal V+ connect with metal contact chip S8, metal contact chip S8 with mono- group of metal contact chip S9, metal contact chip S9 and institute The anode connection of battery is stated, the ground terminal V- of the regulated power supply chip is connect with the cathode of the battery, the regulated power supply The output end VDD of chip provides operating voltage for the electricity consumption device in multimeter.

It further, further include a battery flowmeter charge circle 8 comprising divider resistance R4 and divider resistance R20, it is described The one end divider resistance R4 is connect with the input terminal V+ of the regulated power supply chip, one end of the other end and the divider resistance R20 Connection, the other end of the divider resistance R20 are connect with the ground terminal V- of the regulated power supply chip；The divider resistance R4 and The node of divider resistance R20 connection is electrically connected with the input terminal of the ADC converter 5, transmits battery voltage signal, battery to it Voltage through resistance R4, resistance R20 partial pressure after obtain, size are as follows: V+*R20/ (R4+R20), this voltage is through DSP digital processing unit After 6 calculation process, driving LCD display 7 finally shows the electricity of battery.

Further, the ADC converter 5 integrates and a multimeter auto-shifted measurement with the DSP digital processing unit 6 In chip IC 1, multimeter auto-shifted measurement chip IC 1 uses the chip of SD7830 model.

In the present embodiment, when the gear of gear switch switch 2 is beaten in AC/DC/BAT(high impedance combined-voltage and battery Measurement when unloaded) shelves when, the end INPUT of input terminal 1 is connect with one end of resistance R25, and the other end of resistance R25 is connected to Multimeter auto-shifted measurement chip IC 1, resistance R25 is as input impedance, so the input impedance of high input impedance circuit is 10MΩ；When the gear of gear switch switch 2 is beaten in L (BAT/AC/DC) (low-power consumption battery and low input impedance voltage measurement) shelves When, metal contact chip S1 is connected with metal contact chip S3, the end INPUT of input terminal 1 respectively with one end of resistance R25 and resistance One end of PTC1 connects, and the other end of resistance R25 is connected to multimeter auto-shifted measurement chip IC 1, another termination of PTC1 Ground, input impedance are equivalent to the parallel value of resistance R25 and PTC1, because the resistance value of resistance R25 is much larger than PTC1, L (BAT/ AC/DC) input impedance of shelves is the resistance value 1K Ω of PTC1；When the gear of gear switch switch 2 is beaten in M (BAT) (medium power consumption Battery) shelves when, metal contact chip S2 is connected with metal contact chip S3, the end INPUT respectively with one end of resistance R25 and resistance PTC3 One end connection, the other end of resistance R25 is connected to multimeter auto-shifted measurement chip IC 1, the other end and PTC2 of PTC3 One end connection, the other end of PTC2 is grounded by metal contact chip S2 and metal contact chip S3, and input impedance is equivalent to PTC3 The parallel value of R and resistance 25 after connecting with PTC2, because the resistance value of resistance R25 is much larger than PTC2 and PTC3, M (BAT) shelves Input impedance be PTC2 and PTC3 the Ω of series value 150+27=177；When the gear of gear switch switch 2 is beaten in H (BAT) (height Power consumption battery) shelves when, metal contact chip S10 is connected with metal contact chip S3, the end INPUT of input terminal 1 respectively with resistance R25 One end connected with one end of resistance PTC3, the other end of resistance R25 is connected to multimeter auto-shifted measurement chip IC 1, The other end of PTC3 is grounded through metal contact chip S10 and metal contact chip S3, input impedance be equivalent to resistance R25 and PTC3's and Connection value, because the resistance value of resistance R25 is much larger than PTC3, the input impedance of H (BAT) shelves is 27 Ω of resistance value of PTC3；When 2 dozens, gear switch switch in OHM(resistance measurement) shelves when, metal contact chip S4 and metal contact chip S5 are connected, metal contact chip S6 and metal contact chip S7 is connected；The end INPUT of input terminal 1 is connect with one end of one end of PTC1 and resistance R59 respectively, The one end and three of the other end of PTC1 through metal contact chip S1, metal contact chip S4 and metal contact chip S5 Yu resistance R30 The emitter of pole pipe Q4 connects, and the other end of resistance R30 is connected to multimeter auto-shifted measurement chip IC 1, and resistance R59's is another One end is connected to multimeter auto-shifted measurement chip IC 1 through metal contact chip S6 and metal contact chip S7, measures resistance markers Quasi- voltage is issued the both ends for being added to measured resistance by PTC1 through resistance R30 by multimeter auto-shifted measurement chip IC 1, is tested electricity The voltage drop at resistance both ends is added to multimeter auto-shifted measurement chip IC 1 through resistance R59, by multimeter auto-shifted measurement chip After IC1 carries out data processing, driving LCD display 7 shows measurement result；PTC1 and Q4, Q5 are that resistance grade protects circuit, when It shields after one voltage signal of input terminal erroneous input to circuit.

The above description is only the embodiments of the present invention, and therefore it does not limit the scope of the patent of the utility model, all 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 also included in the patent protection scope of the utility model.

Claims (6)

1. a kind of double impedances input multimeter, it is characterised in that: including input terminal (1), gear switch switch (2), power supply electricity Road (3), double impedance measuring circuits (4), ADC converter (5), DSP digital processing unit (6) and LCD display (7)；The shelves Position switching switch (2) is used to switch the range of multimeter measurement；The power supply circuit (3) includes battery, provides work for multimeter Make voltage；Double impedance measuring circuits (4) include high input impedance circuit (41) and low input impedance circuit (42), the height The input terminal of input impedance circuit (41) is electrically connected with the input terminal (1), and output end passes through gear switch switch (2) and institute ADC converter (5) electrical connection is stated, the input terminal of the low input impedance circuit (42) is electrically connected with the input terminal (1), defeated Outlet is electrically connected by gear switch switch (2) with the ADC converter (5), and double impedance measuring circuits (4) are by input terminal The electric signal transmission of sub (1) measurement is to the ADC converter (5)；The output end of the ADC converter (5) and DSP number The input terminal of processor (6) is electrically connected, and the electric signal of input is converted to digital signal and is delivered to the DSP digital processing unit (6)；The output end of the DSP digital processing unit (6) is electrically connected with the LCD display (7), the DSP digital processing unit (6) The driving signal for converting digital signals into the LCD display (7) drives the LCD display (7) to show corresponding data.

2. a kind of double impedances according to claim 1 input multimeter, it is characterised in that: the gear switch switchs (2) Including plural groups golden finger contact chip.

3. a kind of double impedances according to claim 2 input multimeter, it is characterised in that: the high input impedance circuit It (41) include a high resistance measurement, described high resistance measurement one end is electrically connected with input terminal (1), and the other end and the ADC turn The input terminal of parallel operation (5) is electrically connected；The low input impedance circuit (42) includes the different low resistance resistance of a plurality of resistance values, respectively One end of the low resistance resistance is electrically connected with the input terminal (1), and the other end switchs (2) with the gear switch respectively On each group described in the electrical connection of golden finger contact chip, after golden finger contact chip described in one group is connected, corresponding low resistance electricity It hinders in parallel with the high resistance measurement.

4. a kind of double impedances according to claim 2 input multimeters, it is characterised in that: the power supply circuit (3) includes One regulated power supply chip, the input terminal of the regulated power supply chip by golden finger contact chip and the battery described in one group just Pole connection, the ground terminal of the regulated power supply chip are connect with the cathode of the battery, the output end of the regulated power supply chip Operating voltage is provided for the electricity consumption device in multimeter.

5. a kind of double impedances according to claim 4 input multimeter, it is characterised in that: further include a monitoring cell electricity quantity Circuit (8) comprising divider resistance R4 and divider resistance R20, the one end the divider resistance R4 and the regulated power supply chip Input terminal connection, the other end connect with one end of the divider resistance R20, the other end of the divider resistance R20 with it is described surely The ground terminal of piezoelectricity source chip connects；The divider resistance R4 and the node of divider resistance R20 connection and the ADC converter (5) input terminal electrical connection, transmits battery voltage signal to it, battery voltage signal is converted to number by the ADC converter (5) The DSP digital processing unit (6) is delivered to after word signal, the DSP digital processing unit (6) drives the LCD display (7) aobvious Show battery capacity.

6. a kind of double impedances according to claim 5 input multimeter, it is characterised in that: the ADC converter (5) and institute State DSP digital processing unit (6) it is integrated in a multimeter auto-shifted measurement chip IC 1.