Cirrus Logic AN365 User Manual
An365
Copyright
Cirrus Logic, Inc. 2012
(All Rights Reserved)
Cirrus Logic, Inc.
Application Note
Using the CS5480/84/90 Energy Measurement IC
with Rogowski Coil Current Sensors
1. Introduction
Rogowski coil, or di/dt, current sensors have been increasingly implemented in AC power and energy measurement
applications because of their exceptional linearity, high current capacity and dynamic range, light weight, and
electrical isolation. The Cirrus Logic energy measurement ICs CS5480, CS5484 and CS5490 support various types
of Rogowski coils.
This application note presents accuracy results from testing the CS5480 with three different types of Rogowski coil
sensor. The CS5484 and CS5490 use the same core technology. Testing results of the CS5484 and CS5490 show
nearly identical results. Comparable power meters were constructed using the CS5480 and three Rogowski coils:
Pulse Electronics PA3202NL, TAEHWATRANS TR9L, and Sentec Mobius. Accuracy test results are presented that
demonstrate that the CS5480 can achieve an energy measurement accuracy of 0.1% over a 4000:1 dynamic range
when interfaced to a Rogowski coil.
2. Rogowski Coil Overview
A Rogowski coil current sensor is a helical coil of wire wrapped around an AC line conductor and used to measure
the flow of electric charge through the conductor. Since a Rogowski coil has an air core instead of an iron core, the
measurements show excellent linearity with practically no saturation problems. In addition, the Rogowski coil rates
highly for electrical isolation from the buss bar, and is light weight with low material cost. The Rogowski coil is
increasingly being implemented when measuring high-current AC power and energy.
A
v(t)
i(t)
R
Figure 1. Rogowski Coil Current Sensor
AN365
MAR’12
AN365REV1