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Introduction to closed loop Hall Effect Current Transducers


07.12.2018

Transducers with closed-loop system are designed to create a compensation current in the secondary coil. That allows to create special flux, which is measured by operation of Hall generator.

Principle of work

In such design, the primary and secondary currents create special flows that are equal in amplitude to each other, but move in different directions. This is the main difference from devices with open circuit.

Work in the mode under zero flow conditions eliminates changes in temperature gain.

In addition, the secondary winding will operate at high frequencies as a transducer. That will significantly reduce the converter`s respond time and expand the bandwidth. This feature makes such devices more efficient than open loop systems.

When the value of the magnetic flux parameter reaches to zero, the magnetic potential will be the same on both coils. For this case, following formula is valid: Np× Ip= Ns× Is. Hence, Is= Ip × N/ Ns . Consequently, the secondary current will be completely identical to the primary.

Closed loop transducers modes

In such systems, also a special measuring resistor is installed. Such device is connected in series to secondary coil. That allows system to create an output voltage, which is accurate display of the measured current.

The average number of turns in secondary coil is approximately Ns=1000…5000, and the current strength often has range Is=25…300 mA, but in some cases can reach even 2A. To obtain higher output current values, an output stage is required for producing the converter`s output current.

During operations at low frequencies, transducer is working with Hall generator. If it is necessary to operate on high values, the coil works as a current converter and provides output current. The value of this parameter is determined by ratio number of turns in coil and can be converted into voltage by using a measuring resistor.
Due to design uniqueness, the device is able to provide excellent bandwidth.

The main equipment`s goal is to provide a same rate of frequency throughout the entire circuit. This is especially necessary in places where both curves intersect. Such work will provide excellent response and accuracy of the output signals.