What Is a Current Sensor?
A current sensor is a device that measures the current flowing in a circuit. It is sometimes also referred to as a current sensor.
A current sensors is attached to a circuit or conductor through which current flows and monitors the amount and characteristics of the current passing through it. They are generally rugged in design and can be used for long periods of time.
They can also measure with high reliability when properly installed. Some current sensors are capable of non-contact current measurement and are unique in that they can measure currents at high voltages and in hazardous environments.
However, the appropriate current capacity must be selected according to the current range you wish to measure. This is because there may be cases where the sensor may be damaged if an overload or overcurrent occurs. It is important to check the allowable current range and design appropriately.
Uses of Current Sensors
Current sensors are mainly used in electrical circuits. The following are examples of applications of current sensors:
1. Power Control
Current is monitored and controlled in power suppliers and power converters. In photovoltaic and wind power generation systems, current sensors monitor the amount and characteristics of the generated current to ensure a stable power supply.
They are also used to protect circuits and equipment from overcurrents. In power supply equipment and power circuits, currents exceeding the rated current can be detected by current sensors to activate protective circuits. Overcurrent protection is important to ensure safety from equipment failure due to short circuits, etc.
2. Battery Control
Used in battery management systems to monitor the charging and discharging current of batteries. By measuring the current, it is possible to evaluate the condition of the battery and estimate the remaining capacity. Battery monitoring with current sensors is important in various applications such as electric vehicles and mobile devices.
3. Motor Control
Current sensors are important devices in motor drive control. It measures the motor current and feeds it back to the control algorithm to control the torque and speed of the motor. It is widely used in drives, mainly inverters.
Principle of Current Sensors
The principle of current sensors is to measure current based on Ampere’s law. Ampere’s law describes the relationship between the current passing through a conductor and the magnetic field around the conductor.
According to Ampere’s law, the current passing through a conductor is proportional to the strength of the magnetic field formed around it. Current sensors are capable of detecting the effect of this magnetic field or current and sensing it as a voltage or other signal. Depending on the specific current sensor principle, different methods are used.
Types of Current Sensors
Different types of current sensors exist, depending on the measurement principle. The following are examples of current sensor types.
1. Shunt Resistor Type Current Sensor
This type of current sensor measures the current value by connecting a shunt resistor in series with the circuit in which the current flows. The current flowing through the shunt resistor is calculated by the resistance value and the measured voltage drop according to Ohm’s law. The current can be measured by measuring the voltage at both ends of the shunt resistor whose resistance is known.
The shunt resistor type can measure current with high accuracy. In addition, its simple structure allows it to be manufactured at low cost. They are used on boards and in rectifier circuits for large currents.
2. Hall Effect Current Sensor
A Hall effect current sensor uses a Hall element to detect current. The Hall element is placed near a conductor through which a current flows, and a Hall voltage is generated by the magnetic field. By measuring this Hall voltage, the current is detected.
DC currents can be measured without contact. This type of sensor is used in portable clamp ammeters for DC.
3. Current Transformer Type Current Sensor
This is a current sensor that transforms and measures alternating current. It consists of a conductor that serves as the secondary winding and measures the secondary winding current, which varies according to the primary winding current. This allows the AC current to be calculated.
Because of its low cost and high measurement accuracy, it is widely used in industrial equipment. However, their heavy weight and large area for use are drawbacks.