CN1009030B - Induction type ammeter with measuring head - Google Patents

Abstract

The present invention relates to an induction type ammeter with a measuring head, which belongs to direct reading electric instruments. The present invention solves the technical problems of low sensitivity and narrow measuring range of alternating current/direct current on-line measurement. The ammeter is composed of a measuring head and a display unit. Two magnetic saturation coils wound around an iron core made of a high magnetic conducting material in the measuring head converts magnetic field signals around a current carrying conducting wire into voltage signals, and the voltage signals push a meter head to display a measuring result after being converted by a circuit of a display unit part. The present invention is suitable for measurement and maintenance in electric appliance trades.

Description

Induction type ammeter with measuring head

The induction type current table that has gauge head belongs to the direct-reading electric instrument.

Existing ac and dc current table generally is contact instrument, need be concatenated in the circuit and can measure as multimeter and laboratory instrument, and trouble, time-consuming increases measuring error, just can't carry out when especially needing on-line measurement.Though pincerlike meter can carry out on-line measurement, sensitivity is low.It is difficult that tested electric current is differentiated less than 1 ampere-hour, generally is applicable to ac current measurement.Pincerlike meter with AC/DC function, its sensitivity is lower, can only measure the big electric current more than tens amperes.

In order to measure conveniently, reduce measuring error, solve the on-line measurement of AC and DC milliampere level electric current, invented the induction type current table that has gauge head.

Design concept of the present invention is: according to the law of electromagnetic induction is ultimate principle, change the field signal around the current carrying conductor into voltage signal with special gauge head, voltage signal is measured the size of current in the lead after the circuit conversion work of display unit part thus.Reometer is made up of gauge head and display unit.Display unit comprise square-wave signal source, pulse, detection, amplification, power amplifier, regularly, mu balanced circuit and battery supply, range selector, function conversion (AC and DC, supply voltage) switch, gauge outfit, panel, meter case etc.There are two on the gauge head around high permeability material (initial magnetic permeability mu _i＞0.025 henry/rice), be placed on symmetrically in the left and right sides slit of U-shaped housing for the magnetic saturation line of iron core encloses.Tension disk will place the tested current carrying conductor in the U-shaped housing groove to be fixedly clamped under spring action during measurement.Each saturation coil has field winding and output winding.Field winding has square hole around the center, has been formed on the iron core of two yokes.Winding constitutes the closed-loop path around the magnetic flux in two yokes after should guaranteeing galvanization.The output winding is containing two yokes around the outside of whole iron core.Saturation coil is made differential mode and is connected.Square-wave signal source by display unit during instrumentation is a field winding output square wave pulsed current, is zero at T1 moment pulse current amplitude, and field winding does not have electric current.Then two yokes in have a constant magnetic flux if there is stable external magnetic field to exist this moment, no-voltage signal in the output winding.When T2 arrives constantly, suddenly pass to permanent amplitude electric current in field winding, the magnetic flux of generation makes yoke saturated, thereby the magnetic flux of external magnetic field in iron core will sharply weaken, because the magnetic flux in the iron core sharply changes, in the output winding, will induce a positive spike pulse voltage.In like manner induce a negative spike pulse voltage constantly at T3.Induction electromotive force e=k * △ φ/△ t, K-are that constant is by core material and the full coil winding number of turn decision of magnetic.Flux change rate △ φ/△ t size depends on that external magnetic field intensity, yoke saturation depth and yoke are by state of saturation and unsaturated state transit time of co-conversion mutually.Wherein the yoke saturation depth is by the amplitude decision of exciting curent, and fringe time is by the rising edge time t of exciting curent _aWith negative edge time t _bDecision.Therefore when excitatory pulse current amplitude and waveform are constant, export then that winding internal induction voltage signal is big or small to be directly proportional with external magnetic field intensity.The magnetic field intensity that forms because of carrying flow direct conducting wire is directly proportional with electric current again, is inversely proportional to distance.Keep the distance between interior two saturation coils of tested lead and gauge head constant during measurement, voltage signal amplitude direct ratio of responding in the gauge head and the strength of current in the tested lead.The ac current measurement principle is identical with direct current.Difference is the amplitude difference of gauge head output waveform, because the magnetic field intensity that exchanges around the lead becomes cyclical variation with direction, so the voltage signal amplitude of gauge head internal induction also becomes cyclical variation with phase place.In order to realize that small current measurement also can guarantee the linearity, at the exciting curent power amplifier of display unit

Be connected in series a compensator between circuit and the gauge head.Its winding construction principle is identical with saturation coil in the gauge head, parallelly on the length direction of this external this saturable inductor iron core put into a small magnet, when the compensator field winding is connected with excitatory pulse current, because the existence of small magnet, produce very high pulse voltage signal in compensator output winding, its amplitude surpasses diode D ₁The knot pressure drop, the voltage signal that this voltage signal and gauge head are produced is superposition mutually, again through D ₁Just solved the nonlinear distortion when small-signal subtracts ripple after the detection.

Advantage of the present invention is: 1. AC/DC, measuring accuracy is ± 5%.Measurement range is wide, pacifies hundreds ofs from several milliamperes to tens and pacifies equal energy measurement.2. can on-line measurement, easy to use, reduce Measuring Time.For do not allow to provide sensitivity higher means of testing the occasion that tested lead is pulled down from circuit.3. eliminated because of reometer and be serially connected in the circuit-under-test by the interior group of error of bringing.Be widely used in the measurement and the maintenance of aspects such as electrical equipment, motor, instrument and equipment, power transmission and transformation line.

Figure of description:

Fig. 1: gauge head general structure synoptic diagram.

Fig. 2: gauge head tension disk work synoptic diagram.

Fig. 3: core structure synoptic diagram.

Fig. 4: field winding synoptic diagram.

Fig. 5: output winding stone intention.

Fig. 6-1: excitatory square wave pulsed current oscillogram.

Fig. 6-2: excitatory square wave pulsed current rising edge and negative edge time stone intention.

Fig. 6-3: the spike pulse voltage oscillogram of output winding induction.

Fig. 7-1: gauge head output waveform during direct current measurement.

Fig. 7-2: gauge head output waveform during AC measurment.

Fig. 7-3: AC magnetic field waveform.

Fig. 8: the differential mode of saturation coil connects schematic diagram.

Fig. 9: suppress terrestrial magnetic field interference principle synoptic diagram.

Figure 10: circuit principle structure block scheme.

Figure 11: display unit electrical schematic.

Figure 12: compensator structure synoptic diagram.

Figure 13: display unit schematic appearance.

Embodiments of the invention: two saturation coils (Fig. 1), 2 symmetries in the gauge head are placed in the left and right sides slit of U-shaped housing 3 centering position CH ₃₁4 encapsulation of type epoxy quality glue are fixing.Coil lead AF0.1 type hookup wire is drawn, and connects with gauge head feeder line 9 by conduit 7.With screw 10 feeder line 9 is fixed on the afterbody sleeve pipe 8, prevents that feeder line is loosening.Tension disk 5 reciprocatingly slides on conduit 7, during measurement with tested lead directly in the groove of U-shaped housing 3, tension disk 5 fastens wire clamp (Fig. 2) under the effect of spring 6.Conduit, afterbody sleeve pipe, tension disk all form with bakelite car system.Housing is made of electrical pure iron or other permeability magnetic material die casting or cold working.Feeder line adopts two single-core shielding lines, and the spring external diameter is 16 millimeters, adopts 0.8 millimeter spring steel wire of φ to make around 8 circles by the 4mm pitch.The core material of saturation coil adopt 1J79,1J85,1J88 all can, thickness is 0.05 millimeter, makes its chip center have square hole through stamping-out or etching process, forms two yoke a ₁, a ₂, (Fig. 3),, reach initial permeability μ again through magnetic property thermal treatment ₁＞0.025 henry/rice.Getting four repeatedly neat backs is adhesively fixed with 502.The field winding of saturation coil (Fig. 4) WA adopts φ 0.1mm enameled wire manual wearing around 15 circles on two yokes of iron core respectively, plays end and respectively reserves 30 millimeters in lead-in wire (the preceding mylar of bag one deck 0.01 millimeters thick on iron core earlier of coiling).Direction of winding will guarantee that the magnetic flux in latter two yoke of galvanization becomes closed-loop path (Fig. 4).Bread one deck mylar outside the field winding that winds.Output winding (Fig. 5) WB is close around 250 circles in the iron core outside with φ 0.06mm enameled wire, in field winding is included in.Top stays 30 millimeters in lead-in wire, and end stays 60 millimeters in lead-in wire.Two saturation coils in the gauge head are made differential mode and are connected (Fig. 8) output winding WB ₁WB ₂End of the same name as output signal G, F.The terrestrial magnetic field is at iron core B ₁B ₂The middle flow direction identical (Fig. 9) that produces is at WB ₁WB ₂In the voltage signal that induces be the same-phase common-mode signal, cancel each other, suppressed the terrestrial magnetic field interference.Current carrying conductor (Fig. 9) A surrounding magnetic field is at iron core B ₁B ₂In flow direction opposite.At WB ₁WB ₂In the voltage signal that induces be anti-phase difference mode signal, superposition has improved measurement sensitivity mutually.The iron core of compensator, winding construction, parameter, material implementing process are identical with saturation coil in the gauge head.Small magnet is to be cut into the long segment of 6～8mm with sewing-needle, is put into to make after magnetizing on the magnetite.Parallel with saturation coil core length direction is placed in the magnetic recording head shell, according to schematic diagram (Figure 11) wiring.The μ A of (Figure 13) table model is CI-A on the display unit panel, and full scale is 100 μ A.Range selector K ₁, function switch K ₃(interchange, direct current, supply voltage) is three to throw waver.The multiplying power K switch ₂Power switch K ₄Be the small capacity double double-pole double throw switch.Zero potentiometer R ₁₅4.7K Ω.Power supply is 9 volts of laminated batteries.Meter case phenolic moulding powder die casting.Display unit electrical schematic (Figure 11) Schmidt trigger adopts integrated of CH40106.Constitute the square-wave signal source of 4KC, through BG ₂BG ₃, multiple and pipe emitter-base bandgap grading output square wave pulsed current (Fig. 6) 1 is for the gauge head field winding provides exciting curent.Its rising edge time is t _a, the negative edge time is t _b(Fig. 6) 2, induce pointed pulse voltage (Fig. 6) 3 at the output winding.Voltage signal (Fig. 7) 1,2 that current-carrying diatom surrounding magnetic field is responded in gauge head is through D ₁Detection, R ₄R ₅R ₆C ₃Filtering.Field effect transistor BG ₃Amplify BG ₅BG ₆Promote microampere meter behind the power amplifier and show measurement result.The microampere meter reference voltage is by BG ₇Emitter-base bandgap grading output.BG ₈, C ₄, R ₂₅Constitute mu balanced circuit.For testing circuit provides stable power voltage.Guarantee measuring accuracy.Schmidt trigger a ₅, BG ₉, R ₂₆, R ₂₇, C ₆Form timing switch circuit, save power supply.After being welded on the bar printing wiring board, insert electric elements in the circuit diagram integrated of CH40106 again.Wiring board is screwed in meter housing.Testing and measuring technology: 1. K ₄Put " opening ", regulate R ₂₁Make BG ₇, emitter voltage be 2.6V.2. K ₃Put: " II ", K ₁Put " 100mA ", K ₂Put: " * 1 ", with the debugging usefulness wire clamp on gauge head, socket on gauge head plug and the meter housing (Figure 14) J joins.3. use zero potentiometer R ₁₅Make the meter pointer zero set.4. with R ₁₈Be transferred to the resistance maximum position, on the debugging lead, pass to the 100mA DC current, regulate R ₁₂Make meter pointer aim at full scale.Do not transfer R again if reach ₁₈To full scale.5. checking disconnection debugging current instrument pointer returns zero, connects 100mA debugging electric current, and instrument reaches full scale.Otherwise repeat 3. 4..6. as debugging electric current range switch K when being respectively 1A, 10A, 50A ₁K ₂Insert the relevant position, regulate R respectively ₇R ₈R ₁₀, make the demonstration of the gauge pointer requirement in reaching 5..7. with function switch K ₃Put " I ", other switch is put the optional position, takes off the 9V battery, replaces battery to insert appliance circuit with standard 9V direct supply.Regulate R ₂₃Make indicator aim at scale " 9 ", instrument instructed voltage value is used for detecting at any time cell voltage.When reducing to 7V, voltage to change battery.8. with K ₃Put " III " and be AC measurment, adjustment method is as follows: with K ₁Put " 1A " shelves, on the debugging lead, pass to the 1A alternating current, regulate R ₂₈, reach the requirement in the direct current debugging 5. at last.After these shelves were regulated, other each grade range promptly mixed up thereupon, must not debug separately.If measurement range needs to enlarge, then change the gauge head groove size.

Claims (1)

1, has the induction type current table of gauge head, form by gauge head and display unit.Display unit by square-wave signal source, pulse, detection, amplification, power amplification, regularly, mu balanced circuit and power supply (battery), range selector, function switch, gauge outfit, panel, tool housing etc. form.The invention is characterized in that instrument head is to be placed on symmetrically in the left and right sides slit of U shell body by two saturation coils on the special iron core to constitute, and between the current amplifier circuit of gauge head and display unit, be connected in series a compensator.The iron core of saturation coil adopts high permeability material (initial permeability μ _i＞0.025 henry/rice) center of making has the rectangular metal sheet of square hole, and each saturation coil is made up of field winding and output winding, and two saturation coils are made differential mode and connected.Compensator is packed into together by a saturation coil and a small magnet with the parallel placement of saturation coil core length direction and is constituted in the magnetic recording head shell.

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