CN102116801A - Circuit and device for measuring protective conductor - Google Patents

Abstract

The invention discloses a circuit and a device for measuring a protective conductor. The circuit comprises a current limiting resistor, a voltage dividing resistor, a sampling resistor, a current positive and negative switching relay and an analog-to-digital converter, wherein the current limiting resistor, the voltage dividing resistor and the sampling resistor are connected in series between a direct current stabilized voltage power supply and reference ground; one end of the current limiting resistor is connected with the direct current stabilized voltage power supply; one end of the sampling resistor is connected with the reference ground; a common end of the current limiting resistor and the voltage dividing resistor is connected with the current positive and negative switching relay; a common end of the voltage dividing resistor and the sampling resistor is connected with the analog-to-digital converter; and the current positive and negative switching relay is connected with a protective conductor connecting end and a shell grounding end of tested equipment. The circuit for measuring the protective conductor can more accurately measure resistance of the protective conductor.

Description

A kind of protection conductor metering circuit and measurement mechanism

Technical field

The present invention relates to the security appliance detection range, more particularly relate to a kind of protection conductor metering circuit and measurement mechanism.

Background technology

The protection conductor is called ground wire (PE, Protecting Earthing) again, and it is earthy to be used for electrical equipment shell etc., is because of electrical leakage human electric shock's accident to take place in order to prevent.The conductor that it is used for and the arbitrary part work of exposed conductive part, outside conductive part, main ground terminal, earthing pole, power ground point or artificial neutral point is electrically connected.

In order to guarantee that people use the security of electrical equipment, need to measure the resistance of protection conductor.Wherein in European patent PCT/GB2006/003395, mention a kind of metering circuit of protecting conductor, protect conductor by a pulsing circuit is loaded an electric capacity charging back, and the change in voltage of test protection conductor detects the resistance of protection conductor.

But when protecting the resistance of conductor with above test circuit test, along with the increase of protection conductor resistance, the strain of test errors meeting phase is big, and the resistance of the feasible like this protection conductor of testing is inaccurate.

Summary of the invention

In view of this, the invention provides a kind of protection conductor metering circuit and measurement mechanism, can measure the resistance of protection conductor more accurately.

For achieving the above object, the invention provides following technical scheme: a kind of metering circuit of protecting conductor comprises: current-limiting resistance, divider resistance, sample resistance, the positive and negative transfer relay of electric current and A/D converter;

Described current-limiting resistance, described divider resistance and described sample resistance are connected in series in D.C. regulated power supply and with reference between the ground, an end of wherein said current-limiting resistance links to each other with described D.C. regulated power supply, and an end of described sample resistance links to each other with reference ground;

The common port of described current-limiting resistance and described divider resistance links to each other with the positive and negative transfer relay of described electric current;

The common port of described divider resistance and described sampling resistor links to each other with described digital to analog converter;

The positive and negative relay of described electric current links to each other with earthing of casing end with the protection conductor terminals of equipment under test.

Preferably, the positive and negative transfer relay of described electric current comprises: first relay, second relay and the 3rd relay;

One port of described first relay links to each other another port ground connection with the common port of described current-limiting resistance and described divider resistance;

Described second relay links to each other with described electric appliance casing earth terminal;

Described the 3rd relay links to each other with described protection conductor earth terminal.

Preferably, the span of described current-limiting resistance is: the resistance＞200MA of the magnitude of voltage/current-limiting resistance of D.C. regulated power supply.

The present invention also provides a kind of protection conductor measurement mechanism, comprises the above protection conductor metering circuit.

From above-mentioned technical scheme as can be seen; current-limiting resistance, divider resistance, sample resistance, the positive and negative transfer relay of electric current and A/D converter have been comprised in a kind of protection conductor metering circuit provided by the invention; realize employing direct current bidirectional measurement technology by the positive and negative transfer relay of electric current, improved the precision of measuring protection conductor resistance.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is a kind of connection diagram of protecting the conductor metering circuit in the embodiment of the invention;

Fig. 2 is a kind of internal circuit connection diagram of protecting the positive and negative commutation circuit in the conductor metering circuit in the embodiment of the invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.

Referring to Fig. 1, be a kind of connection diagram of protecting the metering circuit of conductor that the embodiment of the invention provides, this circuit comprises: current-limiting resistance 1, divider resistance 2, sample resistance 3, the positive and negative transfer relay 4 of electric current and analog to digital converter (ADC) 5;

Described current-limiting resistance 1, described divider resistance 2 and described sample resistance 3 are connected in series in D.C. regulated power supply 6 and with reference between the ground, an end of wherein said current-limiting resistance 1 links to each other with described D.C. regulated power supply 6, and an end of described sample resistance 2 links to each other with reference ground;

The common port of described current-limiting resistance 1 and described divider resistance 2 links to each other with the positive and negative transfer relay 4 of described electric current;

The common port of described divider resistance 2 and described sampling resistor 3 links to each other with described digital to analog converter 4;

The positive and negative transfer relay 4 of described electric current links to each other with earthing of casing end with the protection conductor terminals of tested electric equipment 7.

Wherein, the positive and negative transfer relay of electric current comprises: first relay, second relay and the 3rd relay; referring to Fig. 2; be a kind of internal circuit connection diagram of protecting the positive and negative commutation circuit in the conductor metering circuit in the embodiment of the invention; the positive and negative transfer relay of electric current comprises first relay 41, second relay 42 and the 3rd relay 43; described first relay 41, second relay 42 and third phase relay 43 include eight ports

First port 411 of described first relay 41 is a positive terminal, the 8th port 418 is a negative terminals, the 4th port 414 links to each other with the common port of current-limiting resistance 1 with divider resistance 2, five-port 415 ground connection, the 3rd port 413 links to each other with the 6th port 436 with the 3rd port 433 of the 3rd relay 43 respectively with the 6th port 416.In addition, first relay 41 also comprises second port 412 and the 7th port 417.

First port 431 of the 3rd relay 43 is a positive terminal; the 8th port 438 is a negative terminals; second port 432 of the 3rd relay 43 is connected with its five-port 435; and with linked to each other by the protection conductor earth terminal of electricity measurer, the 4th port 434 of the 3rd relay 43 and the series connection of the 7th port 437 are connected in the 6th port 426 of second relay 42.

First port 421 of second relay 42 is a positive terminal, and the 8th port 428 is a negative terminals, and second port 422 of second relay 42 is connected with the 7th port 427, and with linked to each other by the earthing of casing end of electricity measurer.In addition, second relay 42 also comprises the 3rd port 423, the 4th port 424, five-port 425.

Protection conductor metering circuit of the present invention can realize direct current bidirectional measurement technology.Current direction during the bipolarity test is:

The electric current forward is measured: direct supply VCC---current-limiting resistance R1---first relay 41 (through the 4th, three ports)---the 3rd relay 43 (through the 3rd, two ports)---appliances power source line PE holds J1---electric appliance casing earth terminal J2---second relay (through the 7th, six ports)---the 3rd relay 43 (through the 7th, six ports)---first relay 41 (closing) (through the 6th, five-port)---ground;

Current reversal is measured: direct supply VCC---current-limiting resistance R1---the first relay R L1 (through the 4th, three ports)---the 3rd relay 43 (through third and fourth port)---second relay 42 (through the 6th, seven ports)---electric appliance casing earth terminal J2---appliances power source line PE holds J1---the 3rd relay 43 (through the 5th, six ports)---first relay 41 (through the 6th, five-port)---ground.

Wherein, the span of current-limiting resistance R1 is: the resistance R1＞200MA of the magnitude of voltage VCC/ current-limiting resistance of D.C. regulated power supply.

Wherein, the resistance of the resistance of described divider resistance R2 and described sample resistance R3 should be far longer than the resistance of current-limiting resistance R1, so that the partial pressure value of divider resistance R2 and sample resistance R3 can be ignored with respect to the partial pressure value of current-limiting resistance R1.And the ADC sampling voltage value (sampling in analog to digital converter) of sampling resistor R3 should be less than the reference voltage of ADC.

Protection conductor electricity is tried to achieve by following formula one:

(formula one)

Wherein, the resistance of protection conductor is Rx, and V1 is the dividing potential drop on the resistance R x of protection conductor, and the magnitude of voltage of V1 can read at analog to digital converter.

Dividing potential drop to divider resistance R2 and sample resistance R3 is ignored, and the dividing potential drop of R1 is VCC-V1, and formula one becomes following formula two so:

$\frac{R1}{R_x}=\frac{\mathrm{VCC}-V1}{V1}$ (formula two)

Above formula two can be converted into the computing formula of protection conductor resistance, following formula:

Rx=(the ÷ (VCC-V1) (formula three) of R1 * V1)

Circuit of the present invention adopts direct current bidirectional measurement technology by the positive and negative transfer relay of electric current, has improved the precision of measuring protection conductor resistance.

In addition, the invention provides a kind of protection conductor measurement mechanism, this device comprises aforesaid protection conductor metering circuit.

Each embodiment adopts the mode of going forward one by one to describe in this instructions, and what each embodiment stressed all is and the difference of other embodiment that identical similar part is mutually referring to getting final product between each embodiment.

To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the present invention.Multiple modification to these embodiment will be conspicuous concerning those skilled in the art, and defined herein General Principle can realize under the situation that does not break away from the spirit or scope of the present invention in other embodiments.Therefore, the present invention will can not be restricted to these embodiment shown in this article, but will meet and principle disclosed herein and features of novelty the wideest corresponding to scope.

Claims (4)

1. a metering circuit of protecting conductor is characterized in that, comprising: current-limiting resistance, divider resistance, sample resistance, the positive and negative transfer relay of electric current and analog to digital converter;

Described current-limiting resistance, described divider resistance and described sample resistance are connected in series in D.C. regulated power supply and with reference between the ground, an end of wherein said current-limiting resistance links to each other with described D.C. regulated power supply, and an end of described sample resistance links to each other with reference ground;

The common port of described current-limiting resistance and described divider resistance links to each other with the positive and negative transfer relay of described electric current;

The common port of described divider resistance and described sampling resistor links to each other with described digital to analog converter;

The positive and negative transfer relay of described electric current links to each other with earthing of casing end with the protection conductor terminals of equipment under test.

2. circuit according to claim 1 is characterized in that, the positive and negative transfer relay of described electric current comprises: first relay, second relay and the 3rd relay;

One port of described first relay links to each other another port ground connection with the common port of described current-limiting resistance and described divider resistance;

Described second relay links to each other with described electric appliance casing earth terminal;

Described the 3rd relay links to each other with described protection conductor earth terminal.

3. circuit according to claim 1 is characterized in that, the span of described current-limiting resistance is: the resistance＞200MA of the magnitude of voltage/current-limiting resistance of D.C. regulated power supply.

4. a protection conductor measurement mechanism is characterized in that, comprises the described circuit of claim 1 to 3.

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