def set_custom_data(name, value)
      unless @custom_data_labels.include?(name)
        PEROBS.log.fatal "Unknown custom data field #{name}"
      end

      @custom_data_values[@custom_data_labels.index(name)] = value
      write_header if @f
    end
def set_custom_data(name, value)
      unless @custom_data_labels.include?(name)
        PEROBS.log.fatal "Unknown custom data field #{name}"
      end

      @custom_data_values[@custom_data_labels.index(name)] = value
      write_header if @f
    end
Set the registered custom data field to the given value.
 @param name [String] Label of the offset
 @param value [Integer] Value