CN87201296U

CN87201296U - Ac digital tong-type ammeter

Info

Publication number: CN87201296U
Application number: CN 87201296
Authority: CN
Inventors: 张安钢
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-28
Filing date: 1987-04-28
Publication date: 1988-02-03

Abstract

The utility model relates to an AC digital tong-type ammeter, belonging to the technical field of automatic digital display measuring instrument for electricity quantity. A microswitch and a plug socket are adopted to realize the switching of the measuring objects which comprise resistance, voltage and current; the automatic range conversion can be obtained by utilizing an R-S bistable trigger; the digital display locking can be realized by an A/D converter and a Not gate circuit; a current transformer is lachrymiform and has the convenient operation. The utility model can be used for measuring AC current on line.

Description

AC digital tong-type ammeter

The utility model relates to the electrical measurement instrument, is a kind of automatic pincerlike meter of ac digital formula of measuring online exchange electric current, alternating voltage and resistance that is exclusively used in.

Pincerlike meter has pointer-type, non-automatic digital and automatic digital three kinds of pincerlike meters both at home and abroad at present.Pointer-type pincerlike meter anti-vibration performance is poor, and its display easily rolls table, and reading accuracy is hanged down and the non-metering locking device, promptly leaves on-the-spot back and measures also disappearance thereupon of numerical value, and range conversion and measuring object conversion all are easy to generate misoperation.

Fig. 1 is existing pincerlike meter outside drawing.

As shown in Figure 1, forcipated mutual-inductor (1) is exclusively used in measures the online exchange electric current, and jack (3), (5) can be measured alternating voltage and resistance respectively after inserting prod, switch (2) can be realized measuring object conversion and range conversion, when measuring the online exchange electric current, the range retaining of the retaining of the A in the switch (2) must be aimed at tip, use forcipated mutual-inductor (1) to vise tested lead subsequently.When measuring alternating voltage, the range retaining of the retaining of the V in the switch (2) must be aimed at tip, subsequently one of two prod are inserted jack (3), go measuring voltage with the other end.When measuring resistance, the range retaining of the retaining of the Ω in the switch (2) must be aimed at tip, subsequently one of two prod are inserted jack (5), remove measuring resistance with the other end.Therefore very easily misoperation taking place and damages instrument.Gauge outfit (4) is done to show and is used.Existing in addition pincerlike meter contour structures is inconvenient operation when the electric current of measuring near the lead on the wallboard bus-bar.

Non-automatic digital pincerlike meter, range conversion and measuring object switch are got wrong easily, and are easy to generate misoperation.

Existing automatic digitizing pincerlike meter has only a kind of measurement range to change automatically, also is easy to generate misoperation.

The purpose of this utility model designs and a kind ofly has automatic numeral and show that automatic range conversion and measuring object conversion are arranged again, and does not have a kind of pincerlike meter of misoperation generation, simultaneously, make it have the lock function of measuring numerical value, easy to operate during measurement, measuring accuracy is higher than 2.5 grades.

The technical scheme that the utility model solves: a. electric current, voltage, resistance three road incoming lines are to switch by circuit, being added to A/D converter as required switches, do not adopt traditional rotary switch, but adopt two-pin plug to promote the interior microswitch of socket, thereby realize that measuring object automaticallyes switch.B. the R-S trigger is adopted in the range automatic switchover, the R termination is subjected to the digital spill over UR output automatic switching signal auto of LCD display, the non-spill over OR that the S termination is subjected to LCD display exports the high range that non-automatic control signal is come Control current, voltage, resistance incoming line.C. the number lock of measured value is extremely important to pincerlike meter.The number lock function is generally made main part with the 7116A/D converter chip, and 7116A/D converter chip manufacturing technique requirent height, price is expensive, the utility model adopts eight CMOS and five resistance, an electric capacity replaces the 7116A/D converter chip, have identical effect, thereby reach the number lock function.D. low to supply voltage processing, the threshold level of employing cmos circuit, the sign on the control liquid crystal display LCD shows.

Fig. 2 is the automatic pincerlike off-balancesheet shape figure of ac digital formula.

Fig. 3 is a theory diagram

Fig. 4 is machine line figure

Fig. 5 is a measuring object switching device shifter structural drawing

Fig. 6 is a measuring object switching device shifter wiring diagram

The utility model embodiment: electric current incoming line in the incoming line part, as shown in Figure 3 and Figure 4, when tested alternating current produces pressure drop through forcipated mutual-inductor on resistance R 1, R2 and R3 form the dividing potential drop circuit, by integrated analog switch IC1, resistance R 4, potentiometer W1 and R-S trigger realize that range automaticallyes switch, when R-S trigger output auto signal is low level, not conducting of integrated analog switch IC1, this loop disconnects inoperative, at this moment be lower range, when R-S trigger output auto signal is high level, integrated analog switch IC1 conducting,, at this moment be high range then to 3 shunting actions of resistance R.Resistance R 3, potentiometer W1, resistance R 4, the input impedance that integrated analog switch IC1 forms, consequent alternating voltage is through resistance R 5 and R13, diode D1 and D2, resistance R 6, the linear rectification circuit rectification that potentiometer W2 and amplifier F1 form, at A point output dc voltage, voltage on the A point is again via resistance R 7, capacitor C 1, resistance R 8, the secondary resistance capacitance low-pass filtering that capacitor C 2 is formed, the last DC voltage that is entered as direct ratio with alternating current of exporting on B point resistance R 9 is delivered to the 7106A/D converter through the measuring object switching device shifter of being made up of three microswitches.Potentiometer W3, resistance R 11 and R10, operational amplifier F2 and F3, resistance R 12, diode D3 form the voltage stabilization and current stabilization circuit, stablize operational amplifier F1 in-phase end, i.e. anode.

Voltage input line road in the incoming line part, as shown in Figure 3 and Figure 4, alternating voltage is through the input terminal, through resistance R 14 step-downs, form half-wave rectification through diode D4 and D5, through resistance R 15 and capacitor C 3 low-pass filtering, produce voltage drop in resistance R 16, integrated analog switch IC2, resistance R 17, potentiometer W3 and R-S trigger composition range are changed automatically, when R-S trigger output auto signal is low level, and not conducting of integrated analog switch IC2, this loop disconnects, at this moment be in lower range, when R-S trigger output auto signal is high level, integrated IC2 conducting, shunting action is played to R16 in this loop, at this moment be in high range, the D point produces the DC voltage that is entered as direct ratio with voltage, delivers to the 7106A/D converter through the measuring object switching device shifter of being made up of three microswitches.

Resistance incoming line in the incoming line part, as shown in Figure 3 and Figure 4, input resistance R λ is in parallel with stabilivolt D6 and resistance R 21 between tested A2, the B2.Fet 3DJ6 produces constant current and acts on the stabilivolt D6, makes it produce the voltage stabilizing value, and the effect of this voltage of voltage regulation is when making measured resistance be input as ∞, and the two ends input terminal voltage that transfers to the 7106A/D converter is not higher.It is I that operational amplifier F4, resistance R 18 and R19, potentiometer W4 produce the necessary continuous current of metering circuit, and resistance R 20, potentiometer W5, integrated analog switch IC3 form the feedback resistance R of operational amplifier _InsteadIf regulator potentiometer W4 makes the in-phase end of operational amplifier F4, i.e. anode is V to the COM terminal potential of 7106A/D converter, and input resistance is R λ, then according to following calculating the resistance measurement process can be described,

The input measurement voltage that the 7106A/D converter is accepted:

Vλ＝Rλ·I （1）

Because the amplification coefficient of operational amplifier F4 is enough big, can think end of oppisite phase current potential and in-phase end, promptly positive terminal potential is identical to be V, then flows through feedback resistance R _InsteadElectric current be:

I=(V)/(R _Instead) (2)

Comprehensive above-mentioned two formula R _Instead=(V λ)/(V) R _Instead(3)

Because the utility model resistance range has 0～200 Ω and 0～2000 Ω two retaining ranges, V λ is 100mV to 2V concerning the 7106A/D converter, can appoint to get a value and fix, and the V value can fix by regulator potentiometer W4, so as long as get two R _InsteadValue is switched the requirement that just can satisfy 200 Ω and the conversion of 2000 Ω ranges, works as R _InsteadWhen being 200 Ω ranges, integrated analog switch IC3 conducting, resistance R 20 is in parallel with potentiometer W5, and when R λ=2000 Ω, integrated analog switch IC3 disconnects, and feedback resistance has only R20.

The measuring object switching device shifter is the automatic conversion that is used for resistance, voltage, three kinds of measuring objects of electric current, be maximum characteristics of the present utility model, adopt two-wire socket and plug to promote the other microswitch of side, as Fig. 5 and shown in Figure 6, the DC voltage that the circuit that microswitch (16), (17) are formed comes the convert resistance incoming line, the DC voltage that the circuit that microswitch (18) is formed comes the switched voltage incoming line.Wherein microswitch (16), (17) and socket (15), the protruding core of socket (14), joint A and B have formed resistance input socket (9) as shown in Figure 2.Microswitch (18) and socket (15), the protruding core of socket (14) joint A1 and B1, formed as Fig. 2 shown in voltage input socket (10).Plug loam cake (11), plug lower cover (13), the recessed core of plug (12), one two lead of prod is welded on (12), has formed the prod plug.

As shown in Figure 6, when the prod plug inserts resistance input socket (9), microswitch (16) joint H communicates with joint G, microswitch (17) joint E communicates with joint D, the DC voltage of resistance incoming line is promptly sent the 7106A/D converter like this, if at this moment the input of alternating current or alternating voltage is arranged, the DC voltage after the incoming line rectification, electric current all can not be sent into the 7106A/D converter, and can only record resistance value this moment.When the no plug of resistance input socket (9) inserts, and plug is when inserting voltage input socket (10), the joint H1 of microswitch (18) communicates with G1, and microswitch (16) joint H communicates with joint F, microswitch (17) joint E communicates with joint C, like this, the DC voltage on voltage input line road is promptly sent the 7106A/D converter, and this moment could measuring voltage.All not having plug when socket (9) and (10) inserts, then microswitch (17) joint E communicates with joint C, microswitch (16) joint H communicates with joint F, microswitch (18) joint H1 communicates with joint F1, like this, the DC voltage of electric current incoming line is promptly sent the 7106A/D converter, and this moment is with regard to the energy measurement electric current.

Adopt above-mentioned resistance, voltage, electric current successively to arrange switching, pincerlike meter does not have any line that drags when both guaranteeing to measure alternating current, other input quantity is inoperative when guarantee measuring a certain amount again, if just in case when having two plugs to insert socket (9) and (10) simultaneously, guarantee only resistance measurement to be played response, and the voltage measurement input of danger is isolated, and guaranteed the safety of instrument.

The automatic range circuit switched as shown in Figure 4, it is to adopt to have the R-S trigger that keeps level signal, it is by integrated NAND gate circuit IC4, IC5, resistance R 22 and R23, capacitor C 4, C5 forms, the R termination of R-S trigger is subjected to the digital spill over UR of LCD LCD, output is conversion auto signal automatically, control produces the high range on electric current incoming line and voltage input line road, the other end S end of R-S trigger, accept the non-spill over OR of LCD, export non-automatic conversion auto signal, control the high range of the incoming line that has a resistance.

Numeral of the present utility model shows locking control, be to adopt as shown in Figure 2 that functional switch (7) is the manual signal of K among Fig. 4, produce artificial locking digital displaying signal, make the OS1 end of 7106A/D converter connect the TEST end by integrated analog switch IC6 conducting, so vibration stops, be that 7106A/D converter B/P waveform disappears, external oscillator is by integrated Sheffer stroke gate IC9 simultaneously, IC10, resistance R 26, R27, capacitor C 6 is formed, because integrated analog switch IC8 ends and starting of oscillation, produce the EXB/P waveform signal, level after this signal and 7106A/D converter B/P waveform disappear is controlled integrated partial sum gate one end of IC16～IC37 by integrated analog switch IC13 after distance, its other end is then still controlled by the digital output end of 7106A/D converter, because being into distance, the level behind the digital output level of 7106A/D converter itself and the 7106A/D converter B/P waveform failure of oscillation concerns, and the EXB/P waveform signal becomes the distance relation with level behind the 7106A/D converter B/P waveform failure of oscillation, thereby EXB/P waveform signal and 7106A/D converting digital output level are by after IC16～IC37 distance, still normally starter liquid crystal display, because 7106A/D converter B/P waveform failure of oscillation, and 7106A/D converter digital output level is constant, so the LCD displayed value is also constant, realized the function of locking.

Supply voltage is low to be the threshold level that adopts cmos nand gate IC circuit 38, making V+ according to resistance R 29, R30 dividing potential drop is about 7.5V, make the upset of NAND gate circuit IC38 volt attitude, the polarity of utilizing the state of NAND gate circuit IC38 and IC39 to control the LCDB/P waveform by integrated analog switch IC circuit 40, IC41 is led to the low symbol end of supply voltage of LCD again, make its starter or extinguish, thereby make the low symbol of supply voltage on the LCD blip facility occur.

Forcipated mutual-inductor of the present utility model (8) as shown in Figure 2, profile is made the mutual inductor of " tear " pattern, can clamp the lead on the bus-bar of firm nearly wallboard easily.

Claims

1, a kind of have electric current, voltage, resistance input and range conversion, measuring object and cut the automatic pincerlike meter of ac digital formula that commentaries on classics, digital indicator, A/D converter, split core type current transformer are formed, and it is characterized in that:

A. electric current input measurement loop is made up of tear type current transformer [8] and electric current incoming line with automatic range conversion;

B. voltage input measurement loop is made up of socket [10], prod plug and voltage input line road with automatic range conversion;

C. resistance input measurement loop is made up of socket [9], prod plug and resistance incoming line with automatic range conversion;

D. the measuring object switching device shifter is made up of socket [9], [10] and microswitch [16], [17], [18];

E. automatic range switching signal device is made up of digital indicator circuit and automatic range switching signal circuit;

F. numeral shows that locking device shows that by functional switch [7] and numeral locking operation circuit forms;

G. the low controller of supply voltage is made up of digital indicator circuit and detection supply voltage threshold value control circuit;

2, the automatic pincerlike meter of ac digital formula according to claim 1, the electric current incoming line that it is characterized in that the conversion of tear type current transformer automatic range, be that employing has operational amplifier F1, the diode D1 of in-phase end current potential stabilization control circuit and the linear rectification circuit that D2, potentiometer W2, resistance R 5, R13, R6 form, and form the executive circuit of automatic range circuit switched with potentiometer W1, resistance R 4, integrated analog switch IC1 and R-S trigger.

3, the automatic pincerlike meter of ac digital formula according to claim 1, the voltage input line road that it is characterized in that the automatic range conversion are the executive circuits that adopts the automatic range circuit switched of half-wave rectifying circuit and potentiometer W3, R17, integrated analog switch IC2 and R-S trigger composition.

4, the automatic pincerlike meter of ac digital formula according to claim 1, the resistance input circuit that it is characterized in that automatic range conversion is to adopt input resistance R λ and stabilivolt D6, resistance R 21 in parallel, fet 3DJ6 produces continuous current and acts on stabilivolt D6 generation voltage stabilizing value, and is made of the executive circuit of automatic range circuit switched potentiometer W5, resistance R 20, integrated analog switch IC circuit 3, operational amplifier F4.

5, the automatic pincerlike meter of ac digital formula according to claim 1, it is characterized in that the measuring object switching device shifter, formed by the prod plug that microswitch (16), (17), (18), socket (9) and (10), the protruding core of plug (14), plug loam cake (11), lower cover (13), the recessed core of plug are formed.

6, the automatic pincerlike meter of ac digital formula according to claim 1 is characterized in that automatic range switching signal device, and R-S trigger flip-flop of being made up of integrated circuit (IC) 4, IC5 and resistance R 22, R23, capacitor C 4, C5 are constituted.

7, the automatic pincerlike meter of ac digital formula according to claim 1, it is characterized in that numeral shows lock controller, adopt 7106A/D converter and NAND gate circuit IC9, IC10, IC11, resistance R 24, R25, R26, R27 integrated analog switch IC circuit 6, IC7, IC8, IC13, IC14, IC15 NOR gate circuit IC12, IC16～IC37 to form.

8, the automatic pincerlike meter of ac digital formula according to claim 1, it is characterized in that the low circuit of supply voltage is made up of the NAND gate circuit IC38 that utilizes its threshold level, integrated analog switch IC40 and IC41, thereby make the low symbol of supply voltage on the LCD sign occur.