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Types of Current Sensors and Their Features


Nowadays, in industrial equipment, current detection usually requires isolation measures. There are many different current sensor suppliers that manufacture the current sensor by various methods. The methods include shunt resistance + isolation op amp/isolation ADC method (shunt resistor+isolation amplifier/isolation ADC), core current sensor method (open-loop, close-loop, fluxgate) and coreless current sensor method (general coreless, AKM).

This page will provide an overview of the various current sensing methods and what we offer as experienced current sensor manufacturer.

1. Shunt resistance + isolation op amp/isolation ADC method

The shunt resistance + isolation op amp/isolation ADC method is to flow the measured current through a known resistor, and calculate the current value according to the drop voltage value of the resistor. Insulation measures need to be implemented by using edge amplifiers or ADCs in the back-end. This is one of the methods used by some of current sensor suppliers.

This method is a wide-used current detection method and is suitable for detecting small currents that do not need to worry about heating. However, in applications in which large currents (10A or more), the following disadvantages are more pronounced:

1) As there are many components on the primary side (high voltage side) such as isolated power supplies and bipolar power supplies, the design takes time and effort.

2) As the heat generation is proportional to the resistance value, the heat generation is several times to several tens of times of other methods, which makes the heat dissipation design difficult.

3) Due to the large number of parts, wiring is difficult and the mounting area increases.

There is a way to work around the shortcomings of the shunt resistor + isolating amplifier/isolating ADC approach described above, named a magnetic current sensor.

2.Magnetic Current Sensor

Magnetic current sensor detects the amount of current by using a magnetic sensor to detect a magnetic field generated around an energized current line.

Unlike the shunt resistance method, the magnetic current sensor has an insulating structure inside, so there is no need to install an insulating amplifier or an isolated ADC in the rear stage.

In addition, as there is no need to change the resistance value according to the amount of current, it is an excellent solution that can solve the disadvantage of the shunt resistance method that can only detect the current with a low resistance resistance. This is also a wide-used method by current sensor suppliers.

2.1 Coreless Current Sensor

The coreless current sensor is a current sensor with a very simple structure that does not use a magnetic core to detect the magnetic field generated by the energized current of the primary conductor, but directly detects it by a Hall element and amplifies and corrects its output voltage by an IC, which used by some of the current sensor suppliers.

It can solve the problems caused by the magnetic core while maintaining the advantages of current sensors with a core, and has been used since 2010 in applications that emphasize size miniaturization.

However, silicon Hall elements have low sensitivity, so for compensation, some measures must be taken, such as thinning the primary conductor to increase the magnetic field strength, or increasing the gain of the correction IC. There are several advantages and disadvantages.

2.1.1 Advantages

1) As there is no magnetic core, the height can be reduced. Simple internal structure, easy to reduce cost;

2) There is no magnetic core, so there is no hysteresis error;

3) Low current consumption

2.1.2 Disadvantages

1) Since the primary conductor becomes thinner and the resistance value becomes higher, it is easy to generate heat. Large currents cannot be measured;

2) The sensitivity of the Hall element is low, and the frequency band is designed to be narrow in order to obtain sufficient resolution. Therefore, the response time becomes longer;

3) Increasing the gain of the correction IC also amplifies the offset of the Hall element, making it difficult to improve accuracy.

The solution to the above shortcomings of the coreless current sensor is to use a cored current sensor which is what we offer as current sensor supplier.

2.2 Cored Current Sensor – what we offer as experienced current sensor manufacturer

In magnetic current sensors, sensors that use a magnetic core to collect and detect the magnetic field around the current line are called cored current sensors.

Core current sensors can be divided into three categories: 1) Open-loop type, 2) Closed-loop type, 3) Fluxgate type, which is what we offer as experienced current sensor manufacturer.

2.2.1 Open-loop Type Current Sensor

Open-loop Type Current Sensor consists of three main components: an accurate low temperature drift linear hall sensor, a flux collector, and a current transformer. It offers markedly low resistance, reducing power loss and temperature drift to deliver exceptional performance.

2.2.2 Closed-loop Type Current Sensor

Closed-loop Type Current Sensor is a current sensor which operates on the principle of magnetic compensation. It measures DC, AC or pulse currents and their combinations, with galvanic isolation techniques used to separate the primary and secondary circuits.

2.2.3 Fluxgate Type Current Sensor

A fluxgate type current sensor incorporates dynamic fluxgate detection technology. Its design is simple and practical, with the ability to inhibit high temperature drift. Fluxgate technology makes use of the phenomenon of magnetic core saturation to modulate the measured magnetic field, transforming it into an electric field and thus, completing the magnetic field measurement process.

2.2.4 Comparison

Price from low to high: Open-loop type < Closed-loop type < Fluxgate type

Accuracy from low to high: Open-loop type < Closed-loop type < Fluxgate type

2.2.5 Disadvantages and Advantages


1) As there is magnetic core material inside the cored current sensor, it is difficult to reduce the height and the installation position is limited;

(But Luksens can produce compact size current sensors as experienced current sensor manufacturer)

2) Since the core has hysteresis in principle, the sensor output (bias voltage) at zero current changes before and after applying a large magnetic field, which causes errors.

(But Luksens makes it nearly zero as experienced current sensor manufacturer)

Advantages (what we offer as experienced current sensor manufacturer)

1) Large currents can be measured;

2) Output voltage proportional to carried current;

3) Compact size for PCB mount;

4) Accurately measures AC, DC and pulse currents;

5) Nearly zero offset voltage;

6) High frequency bandwidth;

7) Rapid response; minimal noise output;

8) Superior temperature stability and linearity;

9) No insertion losses;

10) Nearly zero magnetic hysteresis;

11) Excellent current overload capacity.

2.2.6 Applications

Our current sensors can be applied on many areas as experienced current sensor manufacturer, such as Automotive Battery Management, EV Chargers, Automotive Motion Control, Smart Grid, Welding, Automation, Drives, Power Supplies, Renewable Energies etc..

1) For example, in terms of renewable energies, as the use of power electronics is a must to drive and control energy from renewable sources in the most energy-efficient way. Modern systems require precise coordination between the power semiconductors, the system controller, mechanics and the feedback sensors. Current sensors provide the necessary information from the load to fulfil that function.

Hence, current sensors is a indispensable parts in many areas. And Luksens is your specialist for current sensor solutions. We are an experienced current sensor manufacture.