How to measure the current electrical current at the outlet?

[hrmi]

How to measure the current electrical current at the outlet?

Power on and off works fine.
Public Device1 As New TPLink.SmartHome.PlugWithEnergyMeterClient("192.168.10.114")

Device1.SetOutput(OutputState.On)
Device1.SetOutput(OutputState.Off)

But, prow measurement doesn't work.
Dim a As Decimal
a = Device1.GetConsumption.Current

reports an error: Value cannot be NULL.
Parameter name: value

Thanks.