Cumulocity Event Language (CEL): Computing the Total Energy Consumption from the Battery Level Signal

Question

My device registered on the Cumulocity IoT Platform has a signal for the current battery level: DLValues => battery_level

I want to compute the total energy consumption from this signal. The energy consumption between two battery level measurements can be computed with the following expression:

create expression double calcConsumedEnergy(prevBatteryLevel, newBatteryLevel) [
  var batteryCapacity = 100;
  var energyConsumption = 0;
  if(newBatteryLevel < prevBatteryLevel){
      energyConsumption = batteryCapacity * (prevBatteryLevel - newBatteryLevel) / 100;
  }
  energyConsumption;
];

My question is: How can I add up the delta between the battery level measurements?

If I create a new signal DLValuesCalc => energy_consumption, then initialy it will have no measurement at all, so I cannot use this signal conceptually in the following way:

DLValuesCalc.energy_consumption.value = DLValuesCalc.energy_consumption.value + delta

score 0 · Answer 1 · answered Apr 12 '18 at 14:30

Probably the built-in aggregation functions in esper will already solve this for you (http://esper.espertech.com/release-7.0.0/esper-reference/html/functionreference.html#epl-function-aggregation). There is a function sum() that will do the job for you (it handles also the initial null value). It just needs the return value of your expression as input.

Cumulocity Event Language (CEL): Computing the Total Energy Consumption from the Battery Level Signal

1 Answers1