When should you worry about interference affecting the analog input? I made something that uploads the measured current to Thingspeak. Everything works, but i did not place the DC to DC converter on the board because i was worried that it would interfere with the analog input. Also the ESP8266 is very close to the Arduino Pro Mini. Could it affect the reading?
Could i have put the DC to DC converter on the board without any problem?



230VAC to 12VDC adapter(not on the picture) --> 12VDC to 3,3VDC(on the picture)-->the prototype board

Sensor: SCT-013-030 30A = 1V
Noise reduction involving Analog to Digital Conversions can be done in many ways.  Common software solutions involve averaging multiple conversions.  Exponential smoothing is one such method.  One advantage of exponential smoothing is that it can be applied to an endless stream of conversions.