# RMS Level of a Signal

The RMS level of a signal is the square root of the mean value of the squared signal. RMS measurements are always positive. Use RMS measurements when a representation of energy is needed. You usually acquire RMS measurements on dynamic signals—signals with relatively fast changes—such as noise or periodic signals.

The RMS level of a continuous signal V(t) from time t1 to time t2 is given by the following equation:

| (A)

where t2 – t1 is the integration time or measurement time.

The RMS level of a discrete signal Vi is given by the following equation.

| (B)

One difficulty is encountered when measuring the dynamic part of a signal using an instrument that does not offer an AC-coupling option. A true RMS measurement includes the DC part in the measurement, which is a measurement you might not want.