Storing data updates from firebase

I have a sensor object that can contain multiple sensors, each sensor have different parameters that are read. Here is the schema:

Sensors{
 sensor01{
  sensorId:value,
  sensorName: value,
  readings: 
   {
     timestamp: date/time
     firstParameter: value
     secondParameter: value
   }
 }
}

The readings array contains a list of parameters that the sensor will store. This parameter will change with time. How should I proceed with storing all the reading updates on firebase? Should i use an external database to store updates in the readins?