Ask any electrical professional what the most important piece of equipment he or she carries and the answer you will almost certainly receive is their current sensor. There are different current sensors for DC current and for AC current, and this article will focus on the technology used for accurately assessing AC currents.
In any given current flow, there is a proportional magnetic field that is created around the conductor. It is the size of the magnetic field that is being measured rather than the current directly. For AC current, the most commonly used technology is inductive technology.
An inductive sensor uses a core that has a number of conductive coils of wire wrapped around it and includes a signal conditioner. The electrical current will be passed through the core in an effort to magnify the magnetic field that surrounds the current so that it can be measured. Because AC current is constantly changing potentials, flipping back and forth between positive and negative at a rate of around 50-60 Hz, the magnetic field that is created will be in constant flux, expanding and collapsing at the same rate in the windings. This secondary current is converted by the AC current sensor into a measurable voltage that has been conditioned by the signal conditioner.
Know Your Power
Every electrical professional will tell you that their Ac current sensors are indispensible when working with various currents. They can help monitor equipment status, detecting any sort of process variations and ultimately provide safety to those working closely with electricity.
AC sensors have the ability to provide real time feedback for electrically powered loads. They provide a much more reliable measurement than older technology such as pressure switches, optical sensors and even zero-speed sensors. Not only do they provide better measurements, they do so in a much more economical way that previous technology could provide.
Methods of Current Sensing
As mentioned previously, most AC current sensors use inductive technology to measure current.
In an inductive sensor arrangement, the current is passed through the sensor which contains a magnetically permeable core that is designed to magnify the magnetic field that is created by the current. Because the current passing through the core is constantly changing back and forth between positive and negative, the magnetic field that surrounds it is constantly expanding and collapsing. It is this expansion and collapsing that creates the voltage inside the sensor that is measured. It is the same principle that current transformers use to “step down” current.
Most inductive sensors are designed to measure currents between 20 and 100 Hz, though there are some specialty sensors that can operate at a much higher range.
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