Current (Irms) spike when turning on device or adc adjusting?

Hi, I am trying to measure the Irms and the apparent power using the EmonLib. When i turn on a light bulb, I see that the first current reading is higher than what the device is supposed to draw and from the second reading, it shows the nominal values. The snippet from the output is:

P(apparent)  Irms
43.19           0.36
27.37           0.23
27.96           0.23

The load is a 28 watt electric bulb. I want to know if the  first Irms value is the spike due to the starting of the bulb of if it is just because of the ADC adjusting to read the value?

I am also not sure if this comes under software or hardware. Therefore posting in both the forums. Sorry for the duplication.

Bill Thomson's picture

Re: Current (Irms) spike when turning on device or adc adjusting?

Duplicate post deleted.
Please don't double post.

Moderator

Robert Wall's picture

Re: Current (Irms) spike when turning on device or adc adjusting?

What you're seeing there is only the averaged inrush. In a typical tungsten lamp, the peak current in the first half-cycle can be up to 15 times the running rms current.

dBC's picture

Re: Current (Irms) spike when turning on device or adc adjusting?

I'm impressed you're able to reliably pick it up at all with an energy monitor.  My monitor does continuous sampling and produces an average power every 10 seconds.  The first reading I get when I turn a tungsten bulb on is invariably lower than the following  readings because even though it picks up the massive inrush current, it also picks up all the zero readings before the switch was thrown, and there's typically way more of them than there is inrush.

Had you set up some fancy s/w trigger to only start your averaging after you saw the first non-zero reading?

rseshadr's picture

Re: Current (Irms) spike when turning on device or adc adjusting?

I did not setup any fancy s/w trigger. I used the basic code which measures only the current from the github and multiplied by 120 to get the power. Although, when I use the code to measure all the variables, It doesnt detect this inrush. I just started using this a couple of days ago so I was not really sure if it was the inrush measured by the ADC. 

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.