The Main Sensor Types and What Each One Measures
Selecting sensors requires matching physical transduction principles to measurands while accounting for thermal drift, noise floor, and fab availability.
Rogowski Coils
Current Transduction
Air-cored toroidal windings provide a method for measuring alternating current without the risk of magnetic saturation. These Rogowski coils produce a voltage that is proportional to the rate of change of the current passing through the center of the loop. An integrator circuit is required to convert this derivative signal into a usable voltage proportional to the actual current.
The lack of a magnetic core allows for the measurement of extremely high currents without the device becoming heavy or bulky.
Mechanical Flexibility
The sensing element is often built as a flexible rope that can be wrapped around large or irregularly shaped conductors. Because Rogowski coils do not require a closed magnetic path made of iron, they can be opened and installed without disconnecting the primary circuit. This makes them ideal for temporary monitoring or for use in tight spaces within electrical cabinets.
The accuracy is influenced by the position of the conductor within the loop.
Linear Performance
Exceptional linearity across a wide dynamic range distinguishes these sensors from traditional current transformers. Rogowski coils do not suffer from hysteresis or DC saturation, allowing them to accurately capture transient events and large fault currents. The bandwidth typically extends from a few hertz to several megahertz.
Protection against external magnetic fields is achieved through precise winding techniques.
Output Sensitivity
Low signal levels produced by the coil require high-gain amplification and shielding to maintain a good signal to noise ratio.