CN2840056Y

CN2840056Y - The multimeter alarm protecting apparatus

Info

Publication number: CN2840056Y
Application number: CN 200520104724
Authority: CN
Inventors: 郭文信
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-11-21
Filing date: 2005-11-21
Publication date: 2006-11-22
Anticipated expiration: 2015-11-21

Abstract

The utility model provides a kind of alarm and protection and indicating device of multimeter; this device can be when red test pencil and black meter pen touch object being measured; disconnect the DATA REASONING circuit earlier by a change-over switch control; be introduced into warning circuit; thereby judge whether object being measured is charged,, can also judge that object being measured has alternating current, or direct current if charged; the person also can judge its positive-negative polarity to have the direct current, utilizes luminotron to show and the warning of sounding.Remind the user to note, thereby make the user check whether multimeter pushes correct gear, and whether plug is inserted into correct jack, the danger of having avoided short trouble and having burnt multimeter.When the user checked that multimeter gear and jack are correct, the user can press change-over switch, connected multimeter DATA REASONING circuit and carried out DATA REASONING and reading.

Description

The multimeter alarm protecting apparatus

Technical field

The utility model relates to a kind of device that is used to measure curtage, is specially a kind of protective device of multimeter.

Background technology

Multimeter commonly used at present is divided into pointer indication type and digital display type two big classes, their weak point is, when the user measures with multimeter,, keep off or resistance ohm retaining measuring voltage as milliampere, microampere with multimeter because operator's error is often dialed the wrong number the range gear on-off; Or with the test pencil plug wrong plug jack of multimeter, common when also being inserted in the electric current jack as the test pencil plug, be used for surveying voltage, to making the situation that multimeter in measuring process, often occurs burning.Sometimes also serious short trouble can occur, cause the infringement of the equipment or the person.There is the people to design a kind of multimeter in the prior art with Machine guarding, it adopts gear on-off rotating disk and jack catch interlock protection, and promptly gear on-off is when voltage or power block, and voltage and resistance jack are opened, the electric current jack is closed, and makes the test pencil plug can only insert voltage and resistance jack; When gear on-off kept off at electric current, the electric current jack was opened, and voltage and resistance jack are closed, and made the test pencil plug can only insert the electric current jack.But the damage of multimeter, be mostly after the operator measures resistance or electric current, gear on-off and jack be also in former corresponding position, and gear on-off is not adjusted to suitable voltage gear, or test pencil is not inserted into suitable voltage jack, burn with regard to going direct measuring voltage.So the Machine guarding of gear on-off rotating disk and the interlock of jack catch can not be protected multimeter well.

Summary of the invention

The utility model has designed a kind of multimeter alarm protecting apparatus at the deficiency that above-mentioned prior art exists, and this device can remind the multimeter operator to notice checking whether the multimeter measuring contacts is inserted into correct jack, and whether gear is correct when operation.If testee is charged, then can show this object charged character or galvanic polarity.

A kind of multimeter alarm protecting apparatus of the present invention, comprise switch, socket and warning circuit, one three change-over switch is installed in a body of the public test pencil of multimeter, public test pencil line tail end has five core plugs that are connected with above-mentioned three change-over switches, five core sockets that mate with five core plugs are arranged on the multimeter dial plate, and the alarm and protection circuit is installed in the multimeter table body; Normally closed interlock b in described three change-over switches links to each other with an end of alarm and protection circuit, and the DATA REASONING circuit that the normally open contact c corresponding with normally closed interlock b and the public test pencil of multimeter are corresponding links to each other; Normally closed interlock e in described three change-over switches is connected with red test pencil voltage resistance jack A, and link to each other with the alarm and protection circuit other end, the moving contact d corresponding with normally closed interlock e is connected with the little electric current jack of the red test pencil B of multimeter, and is connected with the small current measurement circuit of the red test pencil jack of multimeter correspondence; Normally closed interlock h in the described change-over switch is connected with normally closed interlock e and is connected with red test pencil voltage resistance jack A, and the moving contact g corresponding with normally closed interlock h is connected with the big electric current jack of the red test pencil G of multimeter, and is connected with multimeter Super-Current Measurement circuit.

Described multimeter alarm protecting apparatus, alarm and protection circuit wherein is made up of following circuit: the full-bridge input circuit that diode D1, D2, D3, D4 constitute; The positive pole that two luminous component D5 in dichromatic LED D5 are green and D5 is red respectively with above-mentioned full-bridge input circuit in the negative pole of D3 and D4 connect and compose luminous warning circuit, the green and voltage characteristic indicating circuit of the red formation of D5 of D5 in parallel; Constitute the audible alarm circuit by audio generating circuit, loudspeaker or hummer; Wherein the negative electrode of dichromatic LED D5 is connected with the positive pole of capacitor C 1 in audio generating circuit and the voltage stabilizing divided current circuit thereof, and the positive pole of D1, D2 is connected with the negative pole of C1 in the full-bridge input circuit.The positive pole of diode D4 is connected with red test pencil voltage resistance jack A and multimeter voltage resistance metering circuit; Simultaneously the positive pole of D4 also is connected with normally closed interlock e, h in three change-over switches, and by normally closed interlock e and moving contact d, normally closed interlock h and moving contact g respectively with the little electric current jack of red test pencil B, electric current jack G and the red test pencil jack of multimeter are corresponding greatly DATA REASONING circuit is connected.

Described multimeter alarm protecting apparatus, wherein green, red protective resistance R2 and the R3 of being in series with respectively of D5 of two light emitting diode D5 among the dichromatic LED D5 is parallel with the overvoltage crowbar that is composed in series by diode D6, D7, D8 on the series circuit of R2 and the green formation of D5; On the series circuit of R3 and the red formation of D5, be parallel with the overvoltage crowbar that is composed in series by diode D9, D10, D11.

Described multimeter alarm protecting apparatus; audio generating circuit front portion wherein is connected with a voltage stabilizing divided current circuit; described voltage stabilizing divided current circuit is by filter capacitor C1; triode T1; T2 and be connected to T1; current-limiting resistance R4 on the T2 collector; R5; the voltage stabilizing diode DW1 that links to each other with triode T2 emitter; the divider resistance R6 of T2 base stage; R7; W1 forms; wherein the collector of triode T2 links to each other with the T1 base stage by resistance R 5; the emitter of T1 connects the positive pole of capacitor C 1; collector connects the negative pole of capacitor C 1 by resistance R 4, and the negative pole of DW1 connects the T2 emitter, and the positive pole of DW1 connects the negative pole of capacitor C 1.

Multimeter alarm protecting apparatus of the present utility model; because normally closed contact is linked to each other with the alarm and protection circuit; make before measuring operation or can remind the operator to notice checking whether jack and gear be correct, avoided misoperation to cause that the situation of damage table occurs in the operating process.In circuit, be provided with different holding circuits, make protective device can in use not damage, cause false alarm or do not report to the police.Make multimeter when carrying out DATA REASONING by change-over switch, can disconnect the line between three jacks of red test pencil, so can not influence measuring accuracy.

Multimeter alarm protecting apparatus of the present utility model; input circuit wherein adopts diode D1; D2; D3, the full-bridge circuit that D4 and indication diode D5 form is in order to guarantee that the multimeter test pencil touches object being measured and no matter has alternating current or direct current and can both enter the alarm and protection circuit and indicate and report to the police.

Description of drawings

Fig. 1 is the public test pencil structural representation of multimeter

Shown in the figure, the installation site of change-over switch 3 and with five core plug annexations.

Fig. 2 is the schematic diagram of change-over switch 3

D-moving contact e-normally closed interlock f-normally open contact among the switch 3-1 among the figure

A-moving contact b-normally closed interlock c-normally open contact among the switch 3-2

G-moving contact h-normally closed interlock i-normally open contact among the switch 3-3

Just often a-b, d-e, g-h closure, a-c, d-f, g-i disconnect; When the finger Push switch, a-b, d-e, g-h disconnect a-c, d-f, g-i closure; When finger unclamped, switch automatically reset.

Fig. 3 is five core plugs

Fig. 4 is five core sockets

Fig. 5 is a multimeter protective device circuit diagram

The public test pencil of 1-multimeter (black meter pen) 2-test pencil pin 3-change-over switch among the figure

The 4-recess 5-five core lead 6-e lead 7-d lead 8-b lead 9-c lead 10-g lead 11-test pencil plug 12a-pilot hole 12b-plug-socket electrode b 12c-plug-socket electrode c 12d-plug-socket electrode d 12e-plug-socket electrode e 12g-plug-socket electrode g13-five core socket 14a-socket positioning convex part 14b-five core socket b electrode 14c-five core socket c electrode 14d-five core socket d electrode 14e-five core socket e electrode 14g-five core socket g electrodes that hold a pen

Annexation with reference to accompanying drawing 1-5 explanation each several part circuit:

The luminous warning circuit that input circuit that the diode full-bridge circuit constitutes and dichromatic LED constitute and the annexation of testee voltage characteristic indicating circuit each several part.

R1 is connected with the D1 negative pole and is connected with the D3 utmost point, and the D3 negative pole is connected with R2, and R2 is connected with the green positive pole of D5, and D6, D7, D8 series connection back positive pole are connected with the D3 negative pole, and D6, D7, D8 series connection back negative pole are connected with the green negative pole of D5, and the green negative pole of D5 is connected with C1 is anodal.The positive pole of D1 is connected with the positive pole of D2 again and is connected with the negative pole of C1, the negative pole of D2 is connected with the positive pole of D4, the negative pole of D4 is connected with R3, the other end of R3 is connected with the red positive pole of D5, the negative pole that D5 is red is connected with the positive pole of C1, D9, D10, D11 series connection back positive pole are connected with the D4 negative pole, and D9, D10, D11 series connection back negative pole are connected with the red negative pole of D5.The positive pole of D4 is connected with the red test pencil voltage resistance jack A of place, and is connected with the voltage resistance metering circuit of the red test pencil jack of multimeter correspondence.The positive pole of D4 is connected with the normally closed interlock e of switch (3-1), and the moving contact d of switch (3-1) is connected with the little electric current jack B of place of the red test pencil of multimeter, and is connected with the small current measurement circuit of the red test pencil jack of multimeter correspondence.The positive pole of D4 is connected with the normally closed interlock h of switch (3-3), and the moving contact g of switch (3-3) is connected with the big electric current jack G of place of the red test pencil of multimeter, and is connected with the Super-Current Measurement circuit of the red test pencil jack of multimeter correspondence.

The annexation of protective circuit of voltage regulation:

The positive pole of C1 is received the negative electrode of D5, and the negative pole of C1 is received the positive pole of D1, D2

The emitter of T1 is received the positive pole of C1, and collector meets R4, the negative pole of another termination C1 of R4.

The base stage of T1 meets R5, the collector of another termination T2 of R5,

The emitter of T2 connects the negative pole of DW1, and the positive pole of DW1 connects the negative pole of C1.

The base stage of T2 meets R6, the positive pole of another termination C1 of R6,

The base stage of T2 connects the end of W1 simultaneously, and the slip pin of the other end of W1 and W1 is connected together, and is connected with R7 again, and the other end of R7 is connected with the negative pole of C1,

The annexation of audio generating circuit:

Audio generating circuit is by resistance R 8, R9 triode T3, T4 capacitor C 2, inductance L 1, and loudspeaker or hummer YD form.Its annexation is:

R8 is connected with C1 is anodal, and the other end of R8 is connected with the T3 base stage,

The T3 emitter is connected with the negative pole of C1, and the T3 collector is connected with the T4 base stage,

The T4 emitter connects the positive pole of C1, and the T4 collector is connected with L1 with YD,

The other end of YD is connected with the negative pole of C1.

The other end of L1 is connected with the negative pole of C1.

The end of R9 is connected with T3 base stage place with R8, and the other end of R9 is connected with C2, and the other end of C2 is connected with the T4 collector.

Embodiment

Because in a lot of multimeters, more than one of the jack of red test pencil often is voltage, resistance jack, little electric current jack, big electric current jack.This instructions mainly is divided into the voltage resistance jack with the jack of red test pencil, little electric current jack, and the multimeter of big electric current jack illustrates the use of apparatus of the present invention, but the utility model is equally applicable in other multimeter.

As shown in Figure 5, R1 is the current limliting protective resistance, and D1, D2, D3, D4, D5 are that diode is formed full-bridge circuit, and D5 is a dichromatic LED, is installed in multimeter panel full position.D5 is green to be the green emitting part, and D5 is red to be the emitting red light part.R2, R3 are the protective resistance of D5, series diode D6, and D7, D8 forms the green holding circuit of D5.Same series diode D9, D10, D11 are the red holding circuit of D5.C1 is a filter capacitor, and T1 is the PNP triode, and T2 is the NPN triode, and DW1 is a voltage stabilizing diode, and R4 is the current-limiting resistance of T1, and R5 is the current-limiting resistance of T2.R6, R7, W1 are the divider resistance of T2.YD is loudspeaker or hummer or other sound-producing device.T3 is the NPN triode, and T4 is the PNP triode, and R8 is the biasing resistor of T3, and R9 is a feedback resistance, and C2 is a feedback capacity.L1 is the telefault that has magnetic core.

Above-mentioned circuit shown in Figure 5 is contained in the multimeter, and D5 is installed in multimeter panel full position.

13 is five core sockets of the public test pencil black meter pen of multimeter among Fig. 4, is contained on the multimeter.In three change-over switches 3 shown in Figure 1, the normally closed contact b of switch 3-2 is connected with b lead 8 in the five core leads 5, b lead 8 is connected with 12b electrode in the five core test pencil plugs 11, when plug 11 inserts socket shown in Figure 4, the 12b electrode is connected with socket electrode 14b shown in Figure 4,14b socket electrode is connected with s point resistance R 1 shown in Figure 5, and the t point connects corresponding with the red test pencil jack of multimeter again DATA REASONING circuit with red test pencil socket voltage resistance jack A and is connected among Fig. 5.Normally opened contact c is connected with c lead 9 in the five core leads 5 among the switch 3-2, c lead 9 is connected with electrode 12c in the five core test pencil plugs 11, when test pencil plug 11 inserts five core sockets shown in Figure 4, the 12c electrode is connected with socket electrode 14c shown in Figure 4, and 14c socket electrode is connected with former black meter pen DATA REASONING circuit in the multimeter.The normally closed contact e of switch 3-1 is connected with e lead 6 in the five core leads 5, e lead 6 is connected with 12e electrode in the five core test pencil plugs 11, when plug 11 inserts among Fig. 4 socket, the 12e electrode is connected with socket electrode 14e shown in Figure 4, and socket electrode 14e is connected with red test pencil socket voltage resistance jack A.Switch 3-1 moving contact d is connected with d lead 7 in the five core leads 5, d lead 7 is connected with 12d electrode in the five core test pencil plugs 11, when plug 11 inserted socket shown in Figure 4, the 12d electrode was connected with socket electrode 14d, and socket electrode 14d is connected with the little electric current jack of red test pencil socket B.The normally closed contact h of switch 3-3 is connected with the normally closed contact e point of switch 3-1, switch 3-3 moving contact g is connected with g lead 10 in the five core leads 5, g lead 10 is connected with 12g electrode in the five core test pencil plugs 11, when plug 11 inserts socket shown in Figure 4, the 12g electrode is connected with socket electrode 14g, and socket electrode 14g is connected with the big electric current jack of red test pencil socket G.

Shown in Fig. 1-5, change-over switch 3 is installed in the test pencil body of the public test pencil black meter pen of multimeter, and the recess 4 that holds a pen is arranged near the change-over switch 3, change-over switch 3 has a bit of distance from the recess 4 that holds a pen, when the user when using multimeter, user's thumb, forefinger, middle finger are caught the recess 4 that holds a pen in the multimeter test pencil body naturally, because change-over switch 3 has a bit of distance from the recess 4 that holds a pen, so the user can not be not intended to press change-over switch 3.When two test pencils when touching circuit-under-test, if voltage is arranged in the circuit-under-test, then when two test pencils have just touched circuit-under-test; because change-over switch 3 is not pressed, the a-b point is closed, and tested electric current can be from test pencil pin 2; switch a point b point, the b lead 8 in the five core leads 5, the 12b electrode in the test pencil plug 11; socket electrode 14b in the socket 13, current-limiting protection resistance R 1, commutation diode D1; D2; D3, the protective resistance R2 of D4 and dichromatic LED D5 and D5, R3; protection diode D6; D7, D8, D9; D10; D11, filter capacitor C1 flows through by triode T1; T2; voltage stabilizing diode DW1; resistance R 4; R5; R6; R7; the voltage stabilizing divided current circuit that W1 forms enters audio generating circuit, and audio generating circuit is by resistance R 8; R9; capacitor C 2; inductance L 1, triode T3; T4 forms, again by loudspeaker or the hummer YD warning of sounding.Electric current, is flowed out by red test pencil when hot test pencil is inserted in the voltage resistance jack through the t point; When hot test pencil was inserted in little electric current jack, electric current was flowed out by red test pencil through switch 3-1 normally closed contact e moving contact d; When hot test pencil was inserted in big electric current jack, electric current was flowed out by red test pencil through switch 3-3 normally closed contact h moving contact g.Warning circuit is reported to the police immediately, reminds the user to check whether the multimeter gear on-off is correct, and whether the test pencil plug is inserted into correct jack.

When the user determines when errorless, change-over switch 3 press...withes one's finger down, a-b, d-e, g-h point disconnect, a-c, d-f, g-i point closure, electric current is from test pencil pin 2, the a-c point of flowing through, through the c lead 9 in the five core leads 5, electrode 12c in the test pencil plug 11, socket electrode 14c in the five core sockets shown in Figure 4 enters in the multimeter black meter pen DATA REASONING circuit and measures, because the disconnection of d-e, g-h point, in the time of can making the multimeter DATA REASONING, disconnect the line between three jacks of red test pencil, so can not influence measuring accuracy.

When two test pencils of multimeter touch alive circuit, can divide following three kinds of situations.

(1) when the multimeter test pencil touches testee and has alternating current

Tested electric current can be from test pencil pin 2, switch a point b point, the b lead 8 in the five core leads 5; electrode 12b in the plug 11, the socket electrode 14b in the socket 13, current-limiting protection resistance R 1; commutation diode D1; D2, D3, D4; dichromatic LED D5 flows through; at this moment D5 is red alternately lights with D5 is green, sends orange light, and expression detects alternating voltage.The protective resistance of flowing through then R2, R3, protection diode D6; D7, D8 and D9, D10; D11, filter capacitor C1 flows through by triode T1, T2; voltage stabilizing diode DW1, the voltage stabilizing divided current circuit that resistance R 4, R5, R6, R7, W1 form enters by resistance R 8, R9; capacitor C 2; inductance L 1, the audio generating circuit that triode T3, T4 form is again by loudspeaker or the hummer YD warning of sounding.

(2) testee has direct current and red test pencil is run into high level when the multimeter test pencil touches, when black meter pen is run into low level:

Tested electric current can (when being inserted in the little electric current jack of red test pencil jack as the arnotto test pencil, electric current can pass through normally closed some d-e of switch 3-1, when being inserted in the big electric current jack of red test pencil jack as the arnotto test pencil from red test pencil pin, electric current can pass through normally closed some g-h point of switch 3-3), commutation diode D4, resistance R 3, diode D9, D10, D11, the D5 of dichromatic LED D5 is red to be flow through, this moment, D5 was red lights, and sends red light, and expression detects DC voltage, red test pencil is a high level, and black meter pen is a low level.Flow through then by triode T1, T2; voltage stabilizing diode DW1; the voltage stabilizing divided current circuit that resistance R 4, R5, R6, R7, W1 form; enter by resistance R 8, R9; capacitor C 2; inductance L 1; the audio generating circuit that triode T3, T4 form, by loudspeaker or the hummer YD warning of sounding, D1 again flows through; current-limiting protection resistance R 1; flow through socket electrode 14b in the socket 13, the electrode 12b in the plug 11, the b lead 8 in the five core leads 5; the b point a point of switch 3-2 in the pushbutton switch 3, test pencil pin 2 flows out.

(3) testee has direct current and red test pencil is run into low level when the multimeter test pencil touches, when black meter pen is run into high level:

Tested electric current can be from test pencil pin 2, switch a point b point, the b lead 8 in the five core leads 5; electrode 12b in the plug 11, the socket electrode 14b in the socket 13, current-limiting protection resistance R 1; commutation diode D3, resistance R 2, diode D6; D7, D8, dichromatic LED D5 is green to be flow through; this moment, D5 was green lights, and sends green light, and expression detects DC voltage; red test pencil is a low level, and black meter pen is a high level.Flow to by triode T1, T2 voltage stabilizing diode DW1, the voltage stabilizing divided current circuit that resistance R 4, R5, R6, R7, W1 form then; enter by resistance R 8, R9 capacitor C 2, inductance L 1; the audio generating circuit that triode T3, T4 form is by loudspeaker or the hummer YD warning of sounding.

Triode T1, T2; voltage stabilizing diode DW1; the principle of work of the voltage stabilizing divided current circuit that resistance R 4, R5, R6, R7, W1 form; when the test pencil input voltage is excessive; the voltage at C1 two ends can raise, and the both end voltage of audio generating circuit can increase, through R6; R7; the dividing potential drop of W1, the base voltage of T2 can raise, and base current can increase; collector current can increase; the electric current of T1 can increase, and the voltage at R1 two ends can raise, because the increase of the shunting action of T1; the both end voltage of audio generating circuit can reduce, and plays the effect of voltage stabilizing.When the test pencil input voltage was too small, the voltage at C1 two ends can reduce, and the both end voltage of audio generating circuit can reduce, through R6, R7, the dividing potential drop of W1, the base voltage of T2 can reduce, base current can reduce, and collector current can reduce, and the electric current of T1 can reduce, the voltage at R1 two ends can reduce, because the shunting action of T1 reduces, the both end voltage of audio generating circuit can increase, and plays the effect of voltage stabilizing.Because triode T1, T2, voltage stabilizing diode DW1, the voltage stabilizing divided current circuit voltage stabilizing shunting action that resistance R 4, R5, R6, R7, W1 form will make input voltage in very wide scope, and audio generating circuit can operate as normal, can not damage.

R2, R3 is the protective resistance of D5, D6; D7, D8, D9, D10; D11 is the protection diode of D5, and its principle of work is, when the voltage that enters when test pencil is excessive; the electric current that D5 is green can rise, and the electric current that flows through R2 can rise, and the voltage at R2 two ends can rise, and the voltage when R2 and the green two ends of D5 rises to D6; D7, during the forward voltage of D8 series connection, D6, D7; the D8 conducting, the voltage at R2 two ends no longer raises, and the electric current that D5 is green no longer raises, D5 is green not to be burnt out thereby protected.In like manner, R3 and D9, D10, D11 have protected also that D5 is red not to be burnt out.

Because in a lot of multimeters, more than one of the jack of red test pencil often is voltage, resistance jack, little electric current jack, big electric current jack.Switch 3-1 in the described public test pencil, the handoff functionality of 3-2 can guarantee no matter red test pencil is inserted in can realize in that jack reporting to the police, and can not influence the measurement of these several jack functions.Several jacks for red test pencil are not the multimeters of distinguishing with voltage resistance jack, little electric current jack, big electric current jack, switch 3-1, the contact of 3-2 can be linked into two jacks of red test pencil respectively, jack as the arnotto test pencil is not three jacks, can increase and decrease the contact number of pushbutton switch accordingly, the core number of corresponding lead, the core number of corresponding plugs and sockets.Can realize in that jack reporting to the police to guarantee no matter red test pencil is inserted in, when pressing the button switch, connect metering circuit, the disjunction warning circuit, the line between several jacks of the red test pencil of disjunction is so can not influence the measurement of these several jack functions.

Claims

1, a kind of multimeter alarm protecting apparatus, comprise switch, socket and warning circuit, interior one three change-over switch (3) of installing of a body that it is characterized in that the public test pencil of multimeter (1), public test pencil line tail end has five core plugs (11) that are connected with above-mentioned three change-over switches (3), five core sockets (13) that mate with five core plugs (11) are arranged on the multimeter dial plate, and the alarm and protection circuit is installed in the multimeter table body; The normally closed interlock b of (3-2) links to each other with an end of alarm and protection circuit in described three change-over switches, and the DATA REASONING circuit that the normally open contact c corresponding with normally closed interlock b and the public test pencil of multimeter are corresponding links to each other; The normally closed interlock e of (3-1) is connected with red test pencil voltage resistance jack A in described three change-over switches, and link to each other with the alarm and protection circuit other end, the moving contact d corresponding with normally closed interlock e is connected with the little electric current jack of the red test pencil B of multimeter, and is connected with the small current measurement circuit of the red test pencil jack of multimeter correspondence; The normally closed interlock h of (3-3) is connected with red test pencil voltage resistance jack A in the described change-over switch, and the moving contact g corresponding with normally closed interlock h is connected with the big electric current jack of the red test pencil G of multimeter, and is connected with multimeter Super-Current Measurement circuit.

2, according to the multimeter alarm protecting apparatus of claim 1, it is characterized in that described alarm and protection circuit is made up of following circuit: the full-bridge input circuit that diode D1, D2, D3, D4 constitute; Two luminous component D5 that dichromatic LED D5 is interior _GreenWith D5 _RedPositive pole respectively with above-mentioned full-bridge input circuit in the negative pole of D3 and D4 connect and compose luminous warning circuit, and the D5 that connects _GreenWith D5 _RedConstitute a voltage characteristic indicating circuit; Constitute the audible alarm circuit by audio generating circuit, loudspeaker or hummer; Wherein the negative electrode of dichromatic LED D5 is connected with the positive pole of capacitor C 1 in audio generating circuit and the voltage stabilizing divided current circuit thereof, and the positive pole of D1, D2 is connected with the negative pole of C1 in the full-bridge input circuit.The positive pole of diode D4 is connected with red test pencil voltage resistance jack A and multimeter voltage resistance metering circuit; Simultaneously the positive pole of D4 also is connected with normally closed interlock e, h in three change-over switches, and by normally closed interlock e and moving contact d, normally closed interlock h and moving contact g respectively with the little electric current jack of red test pencil B, electric current jack G and the red test pencil jack of multimeter are corresponding greatly DATA REASONING circuit is connected.

3,, it is characterized in that two light emitting diode D5 among the dichromatic LED D5 according to the multimeter alarm protecting apparatus of claim 2 _Green, D5 _RedBe in series with protective resistance R2 and R3 respectively, at R2 and D5 _GreenBe parallel with the overvoltage crowbar that is composed in series by diode D6, D7, D8 on the series circuit that constitutes; At R3 and D5 _RedBe parallel with the overvoltage crowbar that is composed in series by diode D9, D10, D11 on the series circuit that constitutes.

4; multimeter alarm protecting apparatus according to claim 2; it is characterized in that described audio generating circuit front portion is connected with a voltage stabilizing divided current circuit; described voltage stabilizing divided current circuit is by filter capacitor C1; triode T1; T2 and be connected to T1; current-limiting resistance R4 on the T2 collector; R5; the voltage stabilizing diode DW1 that links to each other with triode T2 emitter; the divider resistance R6 of T2 base stage; R7; W1 forms; wherein the collector of triode T2 links to each other with the T1 base stage by resistance R 5; the emitter of T1 connects the positive pole of capacitor C 1; collector connects the negative pole of capacitor C 1 by resistance R 4, and the negative pole of DW1 connects the T2 emitter, and the positive pole of DW1 connects the negative pole of capacitor C 1.