CN210720563U

CN210720563U - Current sampling device

Info

Publication number: CN210720563U
Application number: CN201921614856.2U
Authority: CN
Inventors: 付鹏; 范小远; 王晋硕; 刘骞; 郝至健; 刘许杨; 孙立平
Original assignee: Yantai Dongfang Wisdom Electric Co Ltd
Current assignee: Yantai Dongfang Wisdom Electric Co Ltd
Priority date: 2019-09-26
Filing date: 2019-09-26
Publication date: 2020-06-09
Anticipated expiration: 2029-09-26

Abstract

The utility model discloses a current sampling device, which comprises a load resistor, a signal conditioning circuit, an AD sampling module connected with the output end of the signal conditioning circuit, and a current transformer; the current transformer comprises an iron core, a primary side winding and a secondary side winding, wherein the primary side winding and the secondary side winding are respectively wound on the iron core; one end of the primary side winding is used for connecting a Hall current sensor, and the other end of the primary side winding is connected to a grounding end through the load resistor; and the secondary side winding is connected with the input end of the signal conditioning circuit. The utility model discloses a hall current sensor improves the fail safe nature and the interference killing feature of product with the isolation of sampling module, has still reduced the lectotype requirement of load resistance in the aspect of precision and temperature coefficient simultaneously for conditioning circuit's design is more free.

Description

Current sampling device

Technical Field

The utility model relates to a device of acquisition electric current.

Background

As shown in fig. 5, the conventional current collection method is: the Hall current sensor will generate a primary side alternating current I_PConverted into current signal I in equal proportion_SCurrent I of_SVia a load resistor R_MConverted into a voltage signal U_MVoltage signal U_MAnd the signal enters an AD sampling module through a signal conditioning circuit for sampling. The defects are as follows: (1) the Hall current sensor and the AD sampling module are not isolated, and the safety reliability and the anti-interference capability of the product are poor; (2) due to R_MThe current ratio of (A) is large, the heating is serious, the temperature drift is large, the sampling precision is greatly influenced by the current temperature rise, and R_MThe resistor has to be a high-power high-precision resistor, and the type selection is difficult; (3) the input impedance of the rear-stage signal conditioning circuit is greater than R_MMore than 100 times, otherwise, the precision is affected, the design limitation of the post-stage conditioning circuit is large, and the design cost is high.

SUMMERY OF THE UTILITY MODEL

The utility model provides a current sampling device, its purpose: (1) the isolation between the Hall current sensor and the sampling module is realized, and the safety reliability and the anti-interference capability of the product are improved; (2) the model selection requirements of the load resistor on the aspects of precision and temperature coefficient are reduced; (3) the design limitation of the conditioning circuit is reduced, and the design cost is reduced.

The utility model discloses technical scheme as follows:

a current sampling device comprises a load resistor, a signal conditioning circuit, an AD sampling module and a current transformer, wherein the AD sampling module is connected with the output end of the signal conditioning circuit;

the current transformer comprises an iron core, a primary side winding and a secondary side winding, wherein the primary side winding and the secondary side winding are respectively wound on the iron core; the primary side winding and the load resistor are connected in series between the output end of the secondary side of the Hall current sensor and the grounding end; and the secondary side winding is connected with the input end of the signal conditioning circuit.

As a further improvement of the device: the device also comprises a CPU module used for processing the signals collected by the AD sampling module.

As a further improvement of the device: the signal conditioning circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a capacitor C2;

one end of a secondary side winding of the current transformer is connected with the other end of the secondary side winding through a resistor R1 and a resistor R2 which are connected in series, and a connection point between the resistor R1 and the resistor R2 is grounded; one end of a secondary side winding of the current transformer is connected with the other end of the secondary side winding through a resistor R3, a capacitor C1, a capacitor C2 and a resistor R4 which are sequentially connected in series, and a connection point between the capacitor C1 and the capacitor C2 is grounded; the connecting point between the resistor R3 and the capacitor C1 is connected with the first input end of the AD sampling module, and the connecting point between the resistor R4 and the capacitor C2 is connected with the second input end of the AD sampling module.

As a further improvement of the device: the current transformer is arranged in the shell;

the shell is provided with two terminals which are respectively connected with two ends of a primary side winding of the current transformer;

the shell is internally provided with a plurality of resistance elements, and the shell is provided with terminals which are respectively connected with two ends of each resistance element in a one-to-one correspondence manner;

the resistance element is connected with each other through a terminal and a lead to form the load resistor, and is connected with the primary side winding through the terminal and the lead.

Compared with the prior art, the utility model discloses following positive effect has: (1) the utility model adopts the current transformer to electrically isolate the output signal of the Hall current sensor from the rear-stage AD sampling module, thereby improving the safety, reliability and anti-interference capability; (2) after the current transformer is used for isolation, the sampling precision and the load resistor R are obtained_MThe resistance value, the temperature and the voltage are not related any more, so that the type selection requirement of the load resistor is reduced, and the sampling precision is higherHigh; (3) internal resistance and load resistance R of signal conditioning circuit_MThe isolation is realized, and the signal conditioning circuit has no input impedance requirement, so that the design of the signal conditioning circuit and the sampling module is more free, and the design cost is reduced; (4) the main parts are installed in the shell provided with the connecting terminals, so that the product can be conveniently produced in batch operation, flexible wiring can be realized, and different requirements on the site can be met.

Drawings

Fig. 1 is the structure diagram of the present invention connected to the hall current sensor.

Fig. 2 is a schematic structural diagram of the current transformer.

Fig. 3 is a schematic structural diagram of a signal conditioning circuit and an AD application module.

Fig. 4 is a schematic diagram of the connection between the current transformer and the resistive element.

Fig. 5 is a schematic diagram of A, B, C three-phase current collected by the scheme of the utility model.

Fig. 6 is a schematic structural diagram of the prior art.

Detailed Description

The technical scheme of the utility model is explained in detail below with the attached drawings:

example one

Referring to fig. 1, the current sampling device includes a current transformer 2, a load resistor 6, a signal conditioning circuit 3, an AD sampling module 4, and a CPU module 5.

As shown in fig. 2, the current transformer 2 includes an iron core 2-1, and further includes a primary winding 2-2 and a secondary winding 2-3 respectively wound around the iron core 2-1. Because the Hall current sensor 1 outputs a signal I_STypically tens or hundreds of milliamps, with a relatively small current. According to the characteristic that a primary side winding 2-2 and a secondary side winding 2-3 of the current transformer 2 have the same ampere turns, in the circuit design, a lead is wound in the core-through iron core 2-1 for a plurality of turns, and the secondary output current value of the current transformer 2 is amplified to be I_OThe sampling precision of the current under the small current can be improved.

As shown in fig. 1, one end of the primary winding 2-2 is used for connecting the hall current sensor 1, and the other end is connected to the ground terminal through the load resistor 6. And the secondary side windings 2-3 are connected with the input end of the signal conditioning circuit 3.

The load resistor 6 selects a resistance value according to the Hall load resistance value range, the resistance power meets the load current requirement, the resistance value precision and temperature coefficient requirements are low, the resistance value difference is a few ohms, the overall precision cannot be influenced, and the design requirement can be met by the conventional power wire-wound resistor.

As shown in fig. 3, the signal conditioning circuit 3 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, and a capacitor C2.

One end I of a secondary side winding 2-3 of the current transformer 2_O+ connected with the other end I of the secondary winding 2-3 through a resistor R1 and a resistor R2 in series_O-connected, the connection point between the resistor R1 and the resistor R2 being connected to ground; one end I of a secondary side winding 2-3 of the current transformer 2_O+ is connected with the other end I of the secondary side winding 2-3 through a resistor R3, a capacitor C1, a capacitor C2 and a resistor R4 which are connected in series in sequence_O-connected, the connection point between the capacitance C1 and the capacitance C2 being grounded; the connection point between the resistor R3 and the capacitor C1 is connected to the first input terminal of the AD sampling module 4, and the connection point between the resistor R4 and the capacitor C2 is connected to the second input terminal of the AD sampling module 4.

R1 and R2 are loads of secondary output signals of the current transformer 2, the current signals output by the current transformer 2 are converted into differential voltage signals, high-frequency interference signals are filtered by an RC anti-aliasing circuit consisting of R3, R4, C1 and C2, and then the signals are sent to the AD sampling module 4 for sampling and quantization.

The CPU module 5 is used for processing the signals collected by the AD sampling module 4, and quantizing the AD conversion value into a primary current value after being calibrated by a software coefficient to be displayed.

Further, the current transformer 2 is mounted in a housing, and the housing is provided with two terminals S1 and S2 connected to two ends of the primary winding 2-2 of the current transformer 2, respectively, as shown in fig. 1.

During batch production and inspection in an instrument factory, the serial connection of the numbers S1 and S2 of a plurality of instruments can be realized, the serial connection is connected with the current output of a standard current source (or a power source), and the errors of the current transformer 2 and the AD sampling module 4 are compensated in a software calibration mode, so that batch operation is realized. When the Hall current sensor is used on site, the output of the Hall current sensor 1 is connected with an S1 terminal, and an S4 terminal is connected with a Hall power ground, so that the Hall current sensor can be normally used.

Since the sampling accuracy is independent of the load resistor 6, it can be taken out of operation during calibration and verification.

Example two

The difference between the present embodiment and the first embodiment is: referring to fig. 4, a plurality of resistor elements are disposed in the housing, and terminals, such as S3, S4, … …, S2n +2, are disposed on the housing and connected to two ends of each resistor element in a one-to-one correspondence.

In this embodiment, the load resistor 6 is modified into a plurality of step resistance modes, and a plurality of resistors inside the meter are respectively led to the wiring terminals of the meter. When the Hall current sensor is used on site, the resistance elements are connected in series, in parallel and the like by using an external lead to form a resistance value within a required range of the Hall current sensor 1, and then the resistance value is connected with the primary side winding 2-2 by a terminal and a lead wire, so that the field application is more flexible.

EXAMPLE III

This embodiment differs from the first and second embodiments in that: three Hall current sensors 1 are used for respectively collecting A, B, C three-phase currents, three current transformers 2, a load resistor 6 and a signal conditioning circuit 3 are adopted in the instrument, and a group of AD adoption circuits and a CPU module 5 are shared.

The technical scheme can be applied to current loop sampling of instruments such as current measurement and power measurement, can realize electrical isolation of a Hall output loop and an instrument sampling loop, and can realize multi-path current sampling of one instrument with low cost.

Claims

1. The utility model provides a current sampling device, includes load resistance (6), signal conditioning circuit (3) and with AD sampling module (4) that signal conditioning circuit (3) output is connected, its characterized in that: the current transformer (2) is also included;

the current transformer (2) comprises an iron core (2-1), and further comprises a primary side winding (2-2) and a secondary side winding (2-3) which are respectively wound on the iron core (2-1); the primary side winding (2-2) and the load resistor (6) are connected in series between the secondary side output end and the grounding end of the Hall current sensor (1); the secondary side winding (2-3) is connected with the input end of the signal conditioning circuit (3).

2. The current sampling device of claim 1, wherein: the device also comprises a CPU module (5) used for processing the signals collected by the AD sampling module (4).

3. The current sampling device of claim 1, wherein: the signal conditioning circuit (3) comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a capacitor C2;

one end of a secondary side winding (2-3) of the current transformer (2) is connected with the other end of the secondary side winding (2-3) through a resistor R1 and a resistor R2 which are connected in series, and a connection point between the resistor R1 and the resistor R2 is grounded; one end of a secondary side winding (2-3) of the current transformer (2) is connected with the other end of the secondary side winding (2-3) through a resistor R3, a capacitor C1, a capacitor C2 and a resistor R4 which are sequentially connected in series, and a connection point between the capacitor C1 and the capacitor C2 is grounded; the connecting point between the resistor R3 and the capacitor C1 is connected with the first input end of the AD sampling module (4), and the connecting point between the resistor R4 and the capacitor C2 is connected with the second input end of the AD sampling module (4).

4. A current sampling device as claimed in any one of claims 1 to 3 wherein: the current transformer (2) is mounted in the shell;

the shell is provided with two terminals which are respectively connected with two ends of a primary side winding (2-2) of the current transformer (2);

the resistance elements are connected with each other through terminals and leads to form the load resistor (6), and the connection with the primary side winding (2-2) is realized through the terminals and the leads.