def get_colormap_range(df_list):
    """Set default range for colormap based on number of sensors

    The range is normalized to between zero and one (0.0, 1.0)


    Args:
        df_list (list): Sensor datasets.

    Returns:
        cmap_range (tuple): Tuple of length 2 containing the lower and upper
        bounds for the normalized colormap range.

    """
    if len(df_list) < 4:
        cmap_range = (0, 0.4)
    else:
        cmap_range = (0, 1)

    return cmap_range