# Signal quality annotations¶

In this tutorial you will learn how to perform signal quality annotations within the PhysioZoo Peak detection module and how to use these for your analysis in order to provide contextual information.

## Introduction¶

PhysioZoo allows you to annotate and load signal quality annotations, which contain time intervals with quality annotations made on the original electrophysiological signal time series. The annotations highlight parts of the RR time series which are not to be trusted because the underlying ECG was of bad quality and the peak detector might have failed in estimating the heart rate within these intervals or just because you want to exclude these segments because they correspond to some transition period during drug injection and so you decide to label these time periods as ‘bad quality’.

## Annotating signal quality¶

To annotate the quality of an electrophysiological signal time series, follow these steps:

1. Select the rabbit ECG example: File-> Open data file-> Rabbit_example.txt
2. Under the record panel, select Annotation -> Signal quality. See the red rectangle on the figure below.
3. Look for a segment with some bad quality data and draw a rectangle around it with the mouse. The background of the area you have selected will become red.

In PhysioZoo we define three levels of signal quality:

• A”: good quality signal where HRV and morphological analysis of the electrophysiological signal are possible. This means that the waveform is clean enough to detect the beats and to also study its morphology.
• B”: average quality signal where the beats can be detected and thus HRV analysis is possible but the signal quality is not good enough for morphological analysis.
• C”: bad quality signal. Neither HRV or morphological analysis is possible.