What Is a Current Sensor and How to Choose the Right One?

Current sensors, also commonly called current transformers or CTs, measure the current flowing through a wire by detecting it and producing a proportional output. They work for both alternating and direct currents, allowing us to measure current passively without any interruptive interference in the circuit. They are positioned around the conductor in which current needs to be measured, and are generally used for proof-of-operation, monitoring, and logging applications. With the basics in order, let us now learn more about current sensors in detail.

How do Current Sensors Work?

Current sensing is of two types: indirect and direct. Direct current sensing involves Ohm’s law, whereas indirect sensing uses the magnetic field induced around the conductor when current flows through it.

By measuring the voltage drop across a resistor, its current can be measured. Ohm’s law states that the current of a conductor is a ratio of the voltage to its resistance. The total observable current maintains the voltage drop and the induced loss to a minimum due to its own dissipation. However, since the voltage drop may be negligible over a short distance of the conductor, voltage amplification may be needed to overcome resistance.

Current sensors also often use Hall effect sensor technology, which can be either an open- or closed-loop. A closed-loop sensor consists of a coil that is effectively driven to generate a magnetic field that counteracts the field produced by the measured current. The Hall sensor is used as a null detector, and the output is proportional to the current induced in the coil.

Inductive technology is another often-used system, especially when the CT is specifically designed to measure an alternating current. Since alternating current has a constantly fluctuating potential, the magnetic field also fluctuates accordingly. In such sensors, the wire is usually wrapped around a core. The magnetic field generated by the current flowing through the conductor stimulates a proportional current in the current sensor. This measured voltage/current is then converted into a readable output on the device.

Types of Current Sensors

Apart from the closed-loop and open-loop current transducers that have already been discussed, provided below is a list of CTs most commonly in use today:

  • Solid-Core: These current transducers are complete circuits with no way of opening. That way, while connecting them, cables must be disconnected and placed through the CT during installation. This makes these CTs best-suited for brand new installations, offering highly accurate results.
  • Split-Core: These CTs can be snapped open and clipped around a conductor to make installation easier in pre-existing set-ups. While they may be less precise than solid-core sensors, they are still helpful for all practical purposes. These CTs are deliberately designed for semi-permanent installation systems.
  • Rogowski Coils: These are flexible current transformers that provide many benefits in practical applications. To begin, they are less challenging to install than traditional current transformers. The thin coil of the part can quickly be wrapped around the conductor and snapped shut. Therefore, they are ideal for use in places where installation involving live wires might make the process complicated.

How to Find the Right Current Sensor?

Engineers designing powerful monitoring equipment need to pay special attention while choosing the appropriate current sensor for their needs based on the following criteria:

  1. Linearity: A sensor’s linearity refers to its stability over the entire operating range. High linearity of the analog sensing part is needed for a precise measurement of a wide variety of primary currents, specifically at low current levels. Many technologies provide great results over a narrow range of measurements, limiting the application area to relatively low or high currents.
  2. Drift: A sensor’s drift is associated with the long-term stability of the reading it generates, which is independent of the initial system calibration. Factors such as component-aging, fluctuations in the ambient temperature and humidity, well as other conditions may cause some changes in its characteristics. A low drift level is indicative of the high resistance of the sensor to such constraints.
  3. Accuracy: Taking into account the unique traits of every type of sensor enables the use of its most accurate operating mode while simultaneously mitigating variations among different types. For instance, a class 1 power meter will necessitate using current sensors with more than 1% accuracy, which itself will need expensive manufacturing processes and materials.

To Conclude

Now that you know why selecting only the most top-rated current sensors is necessary, allow Fulfillment 3Sixty to be of service. We at Fulfillment 3Sixty stock up on only the best-quality, thoroughly checked currents sensors for the utmost satisfaction of all our customers. As one of the leading distributors of the electronic parts industry, we go the extra mile to ensure the safe delivery of all top-class current sensors. Get a quote from our website today, and we would be more than glad to assist!


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October 21, 2020

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