CN2265544Y

CN2265544Y - Essential safety type electronic megohm-meter

Info

Publication number: CN2265544Y
Application number: CN 96208700
Authority: CN
Inventors: 张若愚
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-10
Filing date: 1996-04-10
Publication date: 1997-10-22
Anticipated expiration: 2006-04-10

Abstract

The utility model discloses an essential safety type electronic megohm-meter, which can effectively reduce spark strength and prevent causing firedamp explosion when used in mines. The utility model adopts power transfer technique with which low-voltage provided by battery units is transformed into higher standard measurement voltage. The utility model is characterized in that a meter case, interior power supply units, fixed amplitude oscillating circuits, voltage boosting outputs components, and measuring accessory circuits arranged on the case body are provided with essential safety, namely the electric spark and thermal effect produced by internal circuits and external circuits can not ignite the methane in mines under the condition of normal operation or contingent faults to ensure the whole body of the essential safety type electronic megohm-meter is provided with explosion proof performance.

Description

Essential safe type electronics megohmmeter

The utility model relates to a kind of electrical instrument.

At present, the megohmmeter that uses in industrial enterprise has two types: a kind of is to utilize hand generator to take place to make the megohmmeter of measuring power supply than High Level DC Voltage; A kind of is that the low-voltage of utilizing the transistor supply convertor that electric battery is provided is transformed into higher pulse ac voltage, and after rectification and feedback regulation, output higher standard direct current measurement voltage is as the electronics megohmmeter of measuring power supply.These two kinds of megohmmeters electric spark energy under normal use and inner contingent failure condition is higher, uses easily to cause biogas (CH4) blast under coal mine, makes miner's personal safety and national wealth be subjected to serious threat.

The purpose of this utility model is that a kind of essential safe type electronics megohmmeter will be provided, it can effectively reduce megohmmeter in normal operating condition and the electric spark energy and the thermal effect that are produced under the contingent failure condition of internal circuit, cause blow-up thereby prevent to use in mine.

The purpose of this utility model is achieved in that the relevant regulations according to GB (GB3836-4-83 explosive atmosphere electrical apparatus for explosive atmospheres intrinsically safe circuit equipment " I "), in insulation shell with fire-retardant and electrostatic prevention characteristics, be provided with three and have the equal element circuit of essential safety characteristic, be power supply module, the fixed ampllitude oscillatory circuit and the output precision that boosts; The measurement accessory circuit that possesses the essential safety characteristic is set on housing.During circuit working, pushbutton switch AN inserts the fixed ampllitude oscillatory circuit to the power supply module output voltage in the accessory circuit by measuring, make it to be in the impulse hunting duty, at the higher pulse ac voltage of the secondary output of the output precision pulse transformer that boosts, through voltage multiplying rectifier, divide two-way output through current-limiting resistance again: the one tunnel be by current-limiting resistance RA or RB, the range selector K in measuring accessory circuit outputs to measurement terminal L, E again, as measuring power supply; Another road, is taken out feedback signal from RW and is sent operational amplifier YF (F0007) input end the fixed ampllitude oscillatory circuit back to the feedback regulation potentiometer RW that measures accessory circuit through current-limiting resistance RC.The conducting degree of YF output voltage control compound adjustment pipe BG2, BG3, thus the oscillation amplitude of adjustment oscillating tube BG1 realizes the fixed ampllitude vibration, makes the stable direct current measurement voltage of output precision output that boosts, to guarantee measuring accuracy.For fear of the discharge spark of the direct discharge generation danger of equipment under test distributed capacitance CX, an internal discharge loop of being connected by current-limiting resistance RF and pushbutton switch AN normally closed contact is set in measuring accessory circuit.Protect the safe and reliable discharge of CX for treadle-operated tilt hammer for hulling rice and also be furnished with the safety discharge test pencil that an inner string has current-limiting resistance Rf specially, do the secondary auxiliary discharge when finishing in order to measuring.

The utility model circuit structure is simple and reliable, can guarantee the electric spark energy that produces and the thermal effect safety value less than the GB regulation under various contingent failure conditions, thereby have reliable explosion-proof performance.

Below in conjunction with drawings and Examples the utility model is further specified.

Fig. 1 is the electrical schematic diagram according to the essential safe type electronics megohmmeter that the utility model proposes.

Fig. 2 is the structural drawing of annex of the present utility model-safety discharge test pencil.

The utility model is provided with power supply module (2), fixed ampllitude oscillatory circuit (3) and the output precision that boosts (4) in the insulation shell (1) with fire-retardant and electrostatic prevention; The input terminal I, the II that measure accessory circuit (5) and power supply module (2) is charged are set on housing (1).Wherein power supply module is made of the current-limiting resistance RO of No. 5 rechargeable batteries of 6 joints and inner serial connection, and the RO value should guarantee that assembly external short circuit electric current is less than allowing safety value.Whole assembly is with the tight sealing of insulating gel.The infallible component that current-limiting resistance RO can be considered between lead-in wire and resistive surface can not be short-circuited in the glue envelope.Glue is honored as a queen, even be short-circuited between internal battery, but spark do not expose, and do not reach outside damp, thereby whole assembly has the essential safety feature.Fixed ampllitude oscillatory circuit (3) is by operational amplifier YF (F007), generator triode BG1 and compound adjustment pipe BG2, BG3 and peripheral Resistor-Capacitor Unit formation.The short-circuit current that takes place owing to maximum possible in this circuit has been defined as by the current-limiting resistance RO in the power supply module (2) and has allowed below the safety value, as long as therefore guarantee that capacity cell C1C2C3 capacity is not more than 10 microfarads, the capacitor discharge spark energy is in the permission safety value, and then the fixed ampllitude oscillatory circuit also is an essential safety.Boost output precision (4) by the diode D6D7 capacitor C 4C5C6 in pulse transformer NB, the voltage doubling rectifing circuit, and current limliting output resistance RARBRC forms.The elementary winding of pulse transformer NB and feedback winding press on collector and the base stage of generator triode BG1 respectively, constitute a pulse oscillation circuit.Fixed ampllitude oscillatory circuit (3) constitutes a supply convertor jointly with the output precision (4) that boosts, and the low-voltage that power supply module is provided is stablized boosts.Electric clearance and creepage distance that NB level of the middle pulse transformer of the output precision (4) that boosts connect between component lead must not be less than 6 millimeters and 16 millimeters.Two windings of low-pressure side are owing to directly be connected to the fixed ampllitude oscillatory circuit, thus its inductance value should strictly be limited, should be greater than 0.4 milihenry, the spark energy when guaranteeing to connect outside wire break is less than the permission safety value.Because pulse transformer NB secondary winding inductance value is bigger, may produce dangerous break spark, the operating voltage of capacity cell C4C5C6 in the voltage doubling rectifing circuit is also higher, also may produce dangerous short circuit dischange spark, current-limiting resistance RARBRC such as resistance are chosen too small, or be short-circuited between lead-in wire, then the operate outside electric current also can surpass the permission safety value.The way that solves is that the current-limiting resistance value is wanted suitably, to limit the operate outside electric current serves as to allow in the safety value, the electric clearance of current-limiting resistance and creepage distance strengthen being not less than under 6 millimeters and the 16 millimeters situations as far as possible, on this basis, be one with diode D6D7, capacitor C 4C5C6 in pulse transformer NB, the voltage doubling rectifing circuit and current limliting output resistance RARBRC with the insulating gel sealing again.Can guarantee that the NB secondary winding opens circuit, the dangerous electric spark that the capacity cell short circuit causes does not expose contact biogas, between current-limiting resistance RARBRC can not go between yet or the fault of surperficial short circuit dischange, after taking these measures, the output precision that boosts (4) also is the reliable circuit unit with essential safety feature.Measuring accessory circuit (5) is made up of pushbutton switch AN, range selector K, discharge current-limiting resistance RF, measurement display gauge head M.Current limliting output resistance RARBRC in the boosted output precision of maximum short circuit current of this part circuit is defined as and allows below the safety value, also is essential safety so measure accessory circuit.

During measurement, press the button switch AN, the operating voltage of power supply module (2) output inserts the fixed ampllitude circuit that shakes through the normally opened contact of AN.The oscillatory circuit that pulse transformer NB in the triode BG1 in this circuit and the output precision (4) that boosts forms is started working, (the utility model is a series of products through 1000 volts of direct current measurement voltages of voltage multiplying rectifier output to go out pulse ac voltage about 400 volts at the NB secondary induction, the embodiment introduction be that electric pressure is 1000 volts a megohmmeter), this voltage divides two-way output: the one tunnel is connected to the range selector K that measures in the accessory circuit (5) through current limliting output resistance RA or RB outputs to measurement terminal LE, as measuring power supply; Another road is connected to the feedback regulation potentiometer RW that measures in the accessory circuit (5) through current-limiting resistance RC, takes out feedback signal from RW and sends operational amplifier YF input end the fixed ampllitude oscillatory circuit (3) back to.The conducting degree of YF output voltage control compound adjustment pipe BG2, BG3, thus the oscillation amplitude of adjustment oscillating tube BG1 makes the output measuring voltage be stable at 1000 volts.When measure finishing, do not take apart be connected to the lead-in wire of measured resistance RX by the LE terminal before, first release button switch AN, this moment, the distributed capacitance CX of equipment under test will be through inner current limliting discharge resistance RF, the normally closed contact of AN discharges automatically, after about two seconds, can remove measuring lead wire.In addition for guaranteeing safe and reliable to the CX discharge, prevent because the internal discharge loop is not switched on, this extra-has the discharge test pencil (6) that an inside is connected to discharge current-limiting resistance Rf specially, be used for when measuring end, equipment under test distributed capacitance CX being done secondary discharge, guarantee the safe reliability of discharging.Because the discharge current through inner current limliting discharge resistance and ascending part current limliting discharge resistance all is limited in below the permission safety value, so this part circuit also has the essential safety characteristic.

Claims

1, a kind of essential safe type electronics megohmmeter that possesses explosion-proof performance that can under coal mine, use, use the transistor power supply transducer, produce higher pulse ac voltage, after voltage multiplying rectifier and feedback regulation, export higher canonical measure voltage, the overall construction design and the circuit parameter that it is characterized in that instrument determine will guarantee gauge internal circuit and external circuit in normal operating conditions or under contingent malfunction that electric spark that is produced and thermal effect can not cause the biogas that exists in the mine and blast; Its=architectural feature is in the insulation shell (1) with fire-retardant and antistatic performance, setting has electric former assembly (2), fixed ampllitude oscillatory circuit (3) and the output precision that boosts (4) of essential safety performance, on housing (1), be provided with and measure accessory circuit (5), make it to have reliable explosion-proof performance on the whole.

2, essential safe type electronics megohmmeter according to claim 1, it is characterized in that power supply module (2) is to constitute at the inner serial connection of rechargeable battery pack current-limiting resistance R0, whole assembly is formed the circuit unit with essential safety characteristic with the tight sealing of insulation colloid.

3, essential safe type electronics megohmmeter according to claim 1 is characterized in that the capacity of used capacity cell C1C2C3 in the fixed ampllitude oscillatory circuit (3) must not be greater than 10 microfarads, and this circuit also is the circuit unit with essential safety feature like this.

4, intrinsic safety electro megohmmeter according to claim 1, the elementary winding electric sensibility reciprocal of pulse transformer NB that it is characterized in that boosting in the output precision (4) must not be greater than 0.4 milihenry, reach voltage doubling rectifing circuit between the secondary winding lead-in wire, electric clearance between each component lead, between current limliting output resistance lead-in wire must not be less than 6 millimeters, and creepage distance must not be less than 16 millimeters; Whole assembly also with the tight sealing of insulation colloid, constitutes the circuit unit with essential safety characteristic.

5, as wanting the essential safe type electronics megohmmeter of profit as described in requiring 1, it is characterized in that in measuring accessory circuit (5), a discharge loop that is made of discharge current-limiting resistance RF, pushbutton switch AN normally closed contact is set, for guaranteeing safe and reliable discharge to equipment under test distributed capacitance CX, the design also specially is equipped with a safety discharge test pencil (6), and whole measurement accessory circuit and safety discharge test pencil also possess the essential safety feature.