different amps cause sensor variable to be different in TMP35 ?

hi,
i just started to play around with my arduino uno board and i configuration it as show below:

const int sensorpin = A0;
const float baselinetemp = 30.0;

void setup(){
Serial.begin(9600);
for (int pinno = 2; pinno <6; pinno++){
pinMode(pinno,OUTPUT);
digitalWrite(pinno,LOW);
}
}

void loop(){
int senval = analogRead(sensorpin);
Serial.print(senval);
Serial.print("ADC, “);
float volt = (senval/1024.0) * 5.0;
Serial.print(volt);
Serial.print(” volt, “);
float temp = (volt - .5) *100;
Serial.println(temp);
Serial.print(”, degress C: ");

if (temp < baselinetemp){
digitalWrite(2,HIGH);
digitalWrite(3,LOW);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}else if (temp >=baselinetemp && temp < baselinetemp +2){
digitalWrite(2,LOW);
digitalWrite(3,HIGH);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}else if (temp >= baselinetemp +2 && temp < baselinetemp+4){
digitalWrite(2,LOW);
digitalWrite(3,LOW);
digitalWrite(4,HIGH);
digitalWrite(5,LOW);
}else if( temp >= baselinetemp +5) {
digitalWrite(2,LOW);
digitalWrite(3,LOW);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}
delay (50);
}

Q1: when i power my arduino uno with my laptop usb i getting “temp >=baselinetemp && temp < baselinetemp +2” but when i plug in wall plug usb charger i getting “temp < baselinetemp”, i do try to change capture what is the sensor value, by replacing it to this
if (senval < 164){
digitalWrite(2,HIGH);
digitalWrite(3,LOW);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}else if (senval >=164 && senval < 166){
digitalWrite(2,LOW);
digitalWrite(3,HIGH);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}else if (senval >=166 && senval < 168){
digitalWrite(2,LOW);
digitalWrite(3,LOW);
digitalWrite(4,HIGH);
digitalWrite(5,LOW);
}else if( senval >=168) {
digitalWrite(2,LOW);
digitalWrite(3,LOW);
digitalWrite(4,LOW);
digitalWrite(5,LOW);
}

and i found out, when i plug in the wall plug usb i getting sensor below 164 while with usb laptop to power up my ardunio i getting sensor value around 164-166. i also found out my usb are providing 100ma and my usb wall charge are providing 2A. So does amps do influence the output of the sensor value?

my usb wall charge are providing 2A

I'm pretty sure that means the maximum it can supply, not that it will always supply. Devices draw the current they need; it's not that the power source "forces" the maximum current into the device.

So you are saying, you get a slightly different temperature reading , depending on how you power your Arduino ?

Perhaps the actual temperature changed a bit ?

What actual temperature difference does the difference between 164 and 164-166 actually represent ?

Measure the voltages of both supplies - they are likely to differ somewhat, this could account for the difference. Without a precision voltage reference feeding the AREF pin you are at the mercy of the actual supply voltage for analog readings. Standard tolerances for a 5V logic supply is 4.75..5.25V

Hi, The temp change around 2 C for different power source i apply to arduino uno board. I understand using different source can result a different reading, so i wonder was the different of volt and current apply to the arduino board will influence adc sensor reading from the TMP35?

Hi Guys, manage to resolve the issue, by using 3.3v i manage to get a consistent reading either from the usb from laptop or usb from wall plug. Was it 5v causing a lot noise as compare with 3.3v ? as mention in http://learn.adafruit.com/tmp36-temperature-sensor/using-a-temp-sensor but what does the noise mean as mention in the url link?